WorldWideScience

Sample records for gd-conjugated dendrimer nanoclusters

  1. Preparation of Cu Nanoclusters within Dendrimer Templates

    National Research Council Canada - National Science Library

    Zhao, M

    1998-01-01

    ... (16-atom Cu cluster in G4 and 64-atom Cu cluster in G6 dendrimers). The clusters remain trapped within the dendrimers for extended periods of time, do not agglomerate, and do not precipitate. The clusters can also be oxidized to yield dendrimer-encapsulated Cu(2+).

  2. UV luminescence of dendrimer-encapsulated gold nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Shim, Hyeong Seop; Kim, Jun Myung; Sohn, So Hyeong; Han, Noh Soo; Park, Seung Min [Dept. of Chemistry, Kyung Hee University, Seoul (Korea, Republic of)

    2016-10-15

    Size-dependent luminescence color is one of the interesting properties of metal nanocrystals, whose sizes are in the dimension of the Fermi wavelength of an electron. Despite the short Fermi wavelength of electrons in gold (-0.7 nm), luminescence of gold nanoclusters has been reported to range from the near-infrared to near-ultraviolet, depending on the number of atoms in the nanoclusters. The photoluminescence of G4-OH (Au) obtained by the excitation of 266 nm showed UV emission in addition to the well-known blue emission. The higher intensity and red-shifted emission of the gold nanoclusters was distinguished from the emission of dendrimers. The UV emission at 352 nm matched the emission energy of Au{sub 4} in the spherical jellium model, rather than the planar Au{sub 8}, which supported the emission of Au{sub 4} formed in G4-OH. Despite the change of [HAuCl{sub 4} ]/[G4-OH], the relative population between Au{sub 4} and Au{sub 8} was similar in G4-OH(Au), which indicated that the closed electronic and geometric structures stabilized the magic number of Au{sub 4}.

  3. Liquid-crystalline dendrimer Cu(II) complexes and Cu(0) nanoclusters based on the Cu(II) complexes: An electron paramagnetic resonance investigation

    Science.gov (United States)

    Domracheva, N. E.; Mirea, A.; Schwoerer, M.; Torre-Lorente, L.; Lattermann, G.

    2007-07-01

    New nanostructured materials, namely, the liquid-crystalline copper(II) complexes that contain poly(propylene imine) dendrimer ligands of the first (ligand 1) and second (ligand 2) generations and which have a columnar mesophase and different copper contents (x = Cu/L), are investigated by EPR spectroscopy. The influence of water molecules and nitrate counterions on the magnetic properties of complex 2 (x = 7.3) is studied. It is demonstrated that water molecules can extract some of the copper ions from dendrimer complexes and form hexaaqua copper complexes with free ions. The dimer spectra of fully hydrated complex 2 (x = 7.3) are observed at temperatures T dendrimer copper(II) complex. The temperature-induced valence tautomerism attended by electron transport is revealed for the first time in blue dendrimer complexes 1 (x = 1.9) with a dimer structure. The activation energy for electron transport is estimated to be 0.35 meV. The coordination of the copper ion site (NO4) and the structural arrangement of green complexes 1 (x = 1.9) in the columnar mesophase are determined. Complexes of this type form linear chains in which nitrate counterions serve as bridges between copper centers. It is revealed that green complexes 1 (x = 1.9) dissolved in isotropic inert solvents can be oriented in the magnetic field (B 0 = 8000 G). The degree of orientation of these complexes is rather high (S z = 0.76) and close to that of systems with a complete ordering (S z = 1) in the magnetic field. Copper(0) nanoclusters prepared by reduction of complex 2 (x = 7.3) in two reducing agents (NaBH4, N2H4 · H2O) are examined. A model is proposed for a possible location of Cu(0) nanoclusters in a dendrimer matrix.

  4. DFT investigation of the interaction of gold nanoclusters with poly(amidoamine) PAMAM G0 dendrimer

    Science.gov (United States)

    Camarada, M. B.

    2016-06-01

    The interaction between PAMAM G0 and gold nanoclusters Aun (n = 2, 4, 6, and 8) was studied theoretically at DFT level. Different coordination sites were explored, including internal and superficial coordination. All stable complexes exhibited external interaction with the amine or carbonyl site, while the core site coordination was not favored. The more stable binding of Aun was registered with the terminal amine group, while the binding at the amide site was relatively weaker. The vertical first ionization potential, electron affinity, Fermi level, and the HOMO-LUMO gap of PAMAM and Aun-PAMAM G0 complexes were also analyzed.

  5. DNA assisted self-assembly of PAMAM dendrimers.

    Science.gov (United States)

    Mandal, Taraknath; Kumar, Mattaparthi Venkata Satish; Maiti, Prabal K

    2014-10-09

    We report DNA assisted self-assembly of polyamidoamine (PAMAM) dendrimers using all atom Molecular Dynamics (MD) simulations and present a molecular level picture of a DNA-linked PAMAM dendrimer nanocluster, which was first experimentally reported by Choi et al. (Nano Lett., 2004, 4, 391-397). We have used single stranded DNA (ssDNA) to direct the self-assembly process. To explore the effect of pH on this mechanism, we have used both the protonated (low pH) and nonprotonated (high pH) dendrimers. In all cases studied here, we observe that the DNA strand on one dendrimer unit drives self-assembly as it binds to the complementary DNA strand present on the other dendrimer unit, leading to the formation of a DNA-linked dendrimer dimeric complex. However, this binding process strongly depends on the charge of the dendrimer and length of the ssDNA. We observe that the complex with a nonprotonated dendrimer can maintain a DNA length dependent inter-dendrimer distance. In contrast, for complexes with a protonated dendrimer, the inter-dendrimer distance is independent of the DNA length. We attribute this observation to the electrostatic complexation of a negatively charged DNA strand with the positively charged protonated dendrimer.

  6. Polyphenylene dendrimers

    International Nuclear Information System (INIS)

    Marek, T.

    2002-01-01

    Complete text of publication follows. The most attractive property of polyphenylene dendrimers is their rigidity. They retain the molecular symmetry and monodispersity of the usual, commercially available alyphatic dendrimers, while the composition of the dendritic branches makes them self-supporting. In solution flexible dendrimers usually form a globular 3D-structure in which the dendritic branches are evenly distributed over the whole molecular volume, however, it has been shown that, depending on the generation of the particular dendrimer, their peripheral groups tend to fold back into the interior of the molecule. Moreover, when being adsorbed on a surface (or by the removal of the solvent), they often tend to flatten out. In contrast to this behaviour, it has been shown that rigid dendrimers based on polyphenylenes have stiff branches and the backfolding in solutions is impossible. Furthermore, when polyphenylene dendrimers are absorbed on a mica substrate their original shape is retained. These features and their size, lying in the low nanometer scale, make these molecules attractive candidates for several applications such as supports for functional groups and as hosts for smaller guest molecules. We have studied the free volume in a series of rigid polyphenylene dendrimers by positron lifetime spectroscopy (PLTS) and molecular dynamics calculations, in order to assess the expected relationship between the size (number of generations, molecular weight) of these molecules and the intramolecular free volume. We have found that the size of these inner free volumes is stable, and increases with the increasing number generations

  7. Dendrimer Prodrugs

    Directory of Open Access Journals (Sweden)

    Soraya da Silva Santos

    2016-05-01

    Full Text Available The main objective of this review is to describe the importance of dendrimer prodrugs in the design of new drugs, presenting numerous applications of these nanocomposites in the pharmaceutical field. Therefore, the use of dendrimer prodrugs as carrier for drug delivery, to improve pharmacokinetic properties of prototype, to promote drug sustained-release, to increase selectivity and, consequently, to decrease toxicity, are just some examples of topics that have been extensively reported in the literature, especially in the last decade. The examples discussed here give a panel of the growing interest dendrimer prodrugs have been evoking in the scientific community.

  8. Peptide dendrimers

    Czech Academy of Sciences Publication Activity Database

    Niederhafner, Petr; Šebestík, Jaroslav; Ježek, Jan

    2005-01-01

    Roč. 11, - (2005), 757-788 ISSN 1075-2617 R&D Projects: GA ČR(CZ) GA203/03/1362 Institutional research plan: CEZ:AV0Z40550506 Keywords : multiple antigen peptides * peptide dendrimers * synthetic vaccine * multipleantigenic peptides Subject RIV: CC - Organic Chemistry Impact factor: 1.803, year: 2005

  9. Dendrimers for Drug Delivery

    Directory of Open Access Journals (Sweden)

    Abhay Singh Chauhan

    2018-04-01

    Full Text Available Dendrimers have come a long way in the last 25 years since their inception. Originally created as a wonder molecule of chemistry, dendrimer is now in the fourth class of polymers. Dr. Donald Tomalia first published his seminal work on Poly(amidoamine (PAMAM dendrimers in 1985. Application of dendrimers as a drug delivery system started in late 1990s. Dendrimers for drug delivery are employed using two approaches: (i formulation and (ii nanoconstruct. In the formulation approach, drugs are physically entrapped in a dendrimer using non-covalent interactions, whereas drugs are covalently coupled on dendrimers in the nanoconstruct approach. We have demonstrated the utility of PAMAM dendrimers for enhancing solubility, stability and oral bioavailability of various drugs. Drug entrapment and drug release from dendrimers can be controlled by modifying dendrimer surfaces and generations. PAMAM dendrimers are also shown to increase transdermal permeation and specific drug targeting. Dendrimer platforms can be engineered to attach targeting ligands and imaging molecules to create a nanodevice. Dendrimer nanotechnology, due to its multifunctional ability, has the potential to create next generation nanodevices.

  10. Optical absorption in dendrimers

    International Nuclear Information System (INIS)

    Supritz, C.; Engelmann, A.; Reineker, P.

    2004-01-01

    Dendrimers are highly branched molecules, which are expected to be useful, for example, as efficient artificial light harvesting systems in nano-technological applications. There are two different classes of dendrimers: compact dendrimers with constant distance between neighboring branching points throughout the macromolecule and extended dendrimers, where this distance increases from the system periphery to the center. We investigate the linear absorption spectra of these dendrimer types using the Frenkel exciton concept. The electron-phonon interaction is taken into account by introducing a heat bath that interacts with the exciton in a stochastic manner

  11. Glycopeptide dendrimers. Part I

    Czech Academy of Sciences Publication Activity Database

    Niederhafner, Petr; Šebestík, Jaroslav; Ježek, Jan

    2008-01-01

    Roč. 14, č. 1 (2008), s. 2-43 ISSN 1075-2617 R&D Projects: GA ČR GA203/03/1362; GA ČR GA203/06/1272; GA MZe QF3115; GA AV ČR KAN200520703 Institutional research plan: CEZ:AV0Z40550506 Keywords : artificial virus * calixarene dendrimers * carbopeptide dendrimers * glycopeptide dendrimers Subject RIV: CC - Organic Chemistry Impact factor: 1.654, year: 2008

  12. Energy transport in dendrimers

    International Nuclear Information System (INIS)

    Supritz, C.; Engelmann, A.; Reineker, P.

    2006-01-01

    Dendrimers are highly branched polymers which are expected to be useful, for example, as efficient artificial light harvesting systems in nano-technological applications. There are two different classes of dendrimers: compact dendrimers with constant distance between neighboring branching points throughout the macromolecule and extended dendrimers where this distance increases from the system periphery to the center. An open question is still whether energy transport (via Frenkel excitons) occurs in a coherent or incoherent manner. We model the hyperbranched dendrimer molecule as an arrangement of two-level systems and apply the Frenkel exciton concept. The two-level systems are interacting with each other via transfer integrals modeling the special spatial structure of dendrimers. To take into account the electron-phonon interaction we introduce a heat bath that interacts with the exciton in a stochastic manner. In this way we describe the coupled coherent and incoherent Frenkel exciton transport inside a dendrimer. In order to mimic the influence of an energy capturing reaction center (like in photosynthesis) on exciton transport, we attach a sink to the dendrimer core

  13. Energy transport in dendrimers

    Energy Technology Data Exchange (ETDEWEB)

    Supritz, C. [Abteilung Theoretische Physik, Universitaet Ulm, Albert-Einstein-Allee 11, 89069 Ulm (Germany)]. E-mail: christoph.supritz@uni-ulm.de; Engelmann, A. [Abteilung Theoretische Physik, Universitaet Ulm, Albert-Einstein-Allee 11, 89069 Ulm (Germany); Reineker, P. [Abteilung Theoretische Physik, Universitaet Ulm, Albert-Einstein-Allee 11, 89069 Ulm (Germany)

    2006-07-15

    Dendrimers are highly branched polymers which are expected to be useful, for example, as efficient artificial light harvesting systems in nano-technological applications. There are two different classes of dendrimers: compact dendrimers with constant distance between neighboring branching points throughout the macromolecule and extended dendrimers where this distance increases from the system periphery to the center. An open question is still whether energy transport (via Frenkel excitons) occurs in a coherent or incoherent manner. We model the hyperbranched dendrimer molecule as an arrangement of two-level systems and apply the Frenkel exciton concept. The two-level systems are interacting with each other via transfer integrals modeling the special spatial structure of dendrimers. To take into account the electron-phonon interaction we introduce a heat bath that interacts with the exciton in a stochastic manner. In this way we describe the coupled coherent and incoherent Frenkel exciton transport inside a dendrimer. In order to mimic the influence of an energy capturing reaction center (like in photosynthesis) on exciton transport, we attach a sink to the dendrimer core.

  14. Phosphorus dendrimers for nanomedicine.

    Science.gov (United States)

    Caminade, Anne-Marie

    2017-08-31

    From biomaterials to imaging, and from drug delivery to drugs by themselves, phosphorus-containing dendrimers offer a large palette of biological properties, depending essentially on their types of terminal functions. The most salient examples of phosphorus dendrimers used for the elaboration of bio-chips and of supports for cell cultures, for imaging biological events, and for carrying and delivering drugs or biomacromolecules are presented in this feature article. Several phosphorus dendrimers can be considered also as drugs per se (by themselves) in particular to fight against cancers, neurodegenerative diseases, and inflammation, both in vitro and in vivo. Toxicity assays are also reported.

  15. Dendrimers in drug research

    DEFF Research Database (Denmark)

    Boas, Ulrik; Heegaard, Peter M. H.

    2004-01-01

    and in vivo cytotoxicity, as well as biopermeability, biostability and immunogenicity. The review deals with numerous applications of dendrimers as tools for efficient multivalent presentation of biological ligands in biospecific recognition, inhibition and targeting. Dendrimers may be used as drugs...... for antibacterial and antiviral treatment and have found use as antitumor agents. The review highlights the use of dendrimers as drug or gene delivery devices in e.g. anticancer therapy, and the design of different host-guest binding motifs directed towards medical applications is described. Other specific examples...

  16. Dendrimers in Medicine

    DEFF Research Database (Denmark)

    Wu, Linping; Ficker, Mario; Christensen, Jørn Bolstad

    2015-01-01

    Dendrimers are three-dimensional macromolecular structures originating from a central core molecule and surrounded by successive addition of branching layers (generation). These structures exhibit a high degree of molecular uniformity, narrow molecular weight distribution, tunable size and shape ...

  17. Glycopeptide dendrimers. Part II

    Czech Academy of Sciences Publication Activity Database

    Niederhafner, Petr; Šebestík, Jaroslav; Ježek, Jan

    2008-01-01

    Roč. 14, č. 1 (2008), s. 44-65 ISSN 1075-2617 R&D Projects: GA ČR GA203/03/1362; GA ČR GA203/06/1272; GA MZe QF3115; GA AV ČR KAN200520703 Institutional research plan: CEZ:AV0Z40550506 Keywords : artificial virus * cascade-release dendrimers * glycopeptide dendrimers * glycoconjugate * glycopeptides Subject RIV: CC - Organic Chemistry Impact factor: 1.654, year: 2008

  18. Noncovalent synthesis of protein dendrimers

    NARCIS (Netherlands)

    Lempens, E.H.M.; Baal, van I.; Dongen, van J.L.J.; Hackeng, T.M.; Merkx, M.; Meijer, E.W.

    2009-01-01

    The covalent synthesis of complex biomolecular systems such as multivalent protein dendrimers often proceeds with low efficiency, thereby making alternative strategies based on noncovalent chemistry of high interest. Here, the synthesis of protein dendrimers using a strong but noncovalent

  19. Structure of Carbon Nanotube-dendrimer composite

    OpenAIRE

    Vasumathi, V.; Pramanik, Debabrata; Sood, A. K.; Maiti, Prabal K

    2012-01-01

    Using all atomistic molecular dynamics (MD) simulations we report the microscopic picture of the nanotube-dendrimer complex for PAMAM dendrimer of generation 2 to 4 and carbon nanotube of chirality (6,5). We find compact wrapping conformations of dendrimer onto the nanotube surface for all the three generations of PAMAM dendrimer. The degree of wrapping is more for non-protonated dendrimer compared to the protonated dendrimer. For comparison we also study the interaction of another dendrimer,...

  20. Preclinical studies of dendrimer prodrugs.

    Science.gov (United States)

    Kojima, Chie

    2015-01-01

    Dendrimers are synthetic macromolecules with well-defined structures bearing a wide variety of functional groups on their periphery. These groups can be used to conjugate bioactive molecules such as drugs, ligands and imaging agents. Dendrimer prodrugs can be used to improve the water solubility and pharmacokinetic properties of the corresponding free drugs. This article summarizes preclinical studies pertaining to the use of drug-dendrimer conjugates as dendrimer prodrugs for the treatments of various diseases, including cancer and inflammatory diseases. A wide range of anticancer drugs have been conjugated to dendrimers via biodegradable linkers. The side effects of the parent drugs can be markedly reduced using dendrimer prodrugs, with some drugs showing improved efficacy. Anti-inflammatory agents have also been conjugated to dendrimers and used to treat a number of inflammatory diseases. Drug-dendrimer conjugates are preferable to drug-dendrimer complexes, where the use of degradable linkers is critical to the release of the drug. Polyethylene glycol and/or ligands can be added to a dendrimer prodrug, which is useful for the targeting of affected tissues. Imaging probes can also be incorporated into dendrimer prodrugs for the simultaneous delivery of therapeutic and diagnostic agents as 'theranostics.'

  1. Dendrimers: new hope for cancer

    International Nuclear Information System (INIS)

    Ghosh, S.S.

    2010-01-01

    A class of nanomaterials called dendrimers have been found particularly useful in cancer treatment. Dendrimers have often been referred to as the Polymers of the 21st century. The name Dendrimer comes from the Greek dendron, meaning tree. They are nearly perfect monodisperse (a consistent size and form) macromolecules with a regular and highly branched three-dimensional architecture having an average size of around 5x10 -9 m, which can be artificially synthesized

  2. Synthesis and characterization of colloidal fluorescent silver nanoclusters.

    Science.gov (United States)

    Huang, Sherry; Pfeiffer, Christian; Hollmann, Jana; Friede, Sebastian; Chen, Justin Jin-Ching; Beyer, Andreas; Haas, Benedikt; Volz, Kerstin; Heimbrodt, Wolfram; Montenegro Martos, Jose Maria; Chang, Walter; Parak, Wolfgang J

    2012-06-19

    Ultrasmall water-soluble silver nanoclusters are synthesized, and their properties are investigated. The silver nanoclusters have high colloidal stability and show fluorescence in the red. This demonstrates that like gold nanoclusters also silver nanoclusters can be fluorescent.

  3. Dendrimer-protein interactions versus dendrimer-based nanomedicine.

    Science.gov (United States)

    Shcharbin, Dzmitry; Shcharbina, Natallia; Dzmitruk, Volha; Pedziwiatr-Werbicka, Elzbieta; Ionov, Maksim; Mignani, Serge; de la Mata, F Javier; Gómez, Rafael; Muñoz-Fernández, Maria Angeles; Majoral, Jean-Pierre; Bryszewska, Maria

    2017-04-01

    Dendrimers are hyperbranched polymers belonging to the huge class of nanomedical devices. Their wide application in biology and medicine requires understanding of the fundamental mechanisms of their interactions with biological systems. Summarizing, electrostatic force plays the predominant role in dendrimer-protein interactions, especially with charged dendrimers. Other kinds of interactions have been proven, such as H-bonding, van der Waals forces, and even hydrophobic interactions. These interactions depend on the characteristics of both participants: flexibility and surface charge of a dendrimer, rigidity of protein structure and the localization of charged amino acids at its surface. pH and ionic strength of solutions can significantly modulate interactions. Ligands and cofactors attached to a protein can also change dendrimer-protein interactions. Binding of dendrimers to a protein can change its secondary structure, conformation, intramolecular mobility and functional activity. However, this strongly depends on rigidity versus flexibility of a protein's structure. In addition, the potential applications of dendrimers to nanomedicine are reviwed related to dendrimer-protein interactions. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. DENDRIMER CONJUGATES FOR SELECTIVE OF PROTEIN AGGREGATES

    DEFF Research Database (Denmark)

    2004-01-01

    Dendrimer conjugates are presented, which are formed between a dendrimer and a protein solubilising substance. Such dendrimer conjugates are effective in the treatment of protein aggregate-related diseases (e.g. prion-related diseases). The protein solubilising substance and the dendrimer together...

  5. Computer simulations of dendrimer-polyelectrolyte complexes.

    Science.gov (United States)

    Pandav, Gunja; Ganesan, Venkat

    2014-08-28

    We carry out a systematic analysis of static properties of the clusters formed by complexation between charged dendrimers and linear polyelectrolyte (LPE) chains in a dilute solution under good solvent conditions. We use single chain in mean-field simulations and analyze the structure of the clusters through radial distribution functions of the dendrimer, cluster size, and charge distributions. The effects of LPE length, charge ratio between LPE and dendrimer, the influence of salt concentration, and the dendrimer generation number are examined. Systems with short LPEs showed a reduced propensity for aggregation with dendrimers, leading to formation of smaller clusters. In contrast, larger dendrimers and longer LPEs lead to larger clusters with significant bridging. Increasing salt concentration was seen to reduce aggregation between dendrimers as a result of screening of electrostatic interactions. Generally, maximum complexation was observed in systems with an equal amount of net dendrimer and LPE charges, whereas either excess LPE or dendrimer concentrations resulted in reduced clustering between dendrimers.

  6. Structure-skin permeability relationship of dendrimers.

    Science.gov (United States)

    Venuganti, Venkata Vamsi; Sahdev, Preety; Hildreth, Michael; Guan, Xiangming; Perumal, Omathanu

    2011-09-01

    To investigate skin penetration of poly (amidoamine) (PAMAM) dendrimers as a function of surface charge and molecular weight in presence and absence of iontophoresis. Dendrimers were labeled with fluoroisothiocynate (FITC); skin penetration of dendrimers was studied using excised porcine skin in-vitro. Skin penetration of FITC-labeled dendrimers was quantified using confocal laser scanning microscope (CLSM). G2-G6 NH(2), G3.5-COOH and G4-OH dendrimers were used. Cationic dendrimers showed higher skin penetration than neutral and anionic dendrimers. Skin penetration of cationic dendrimer increased linearly with increase in treatment time. Iontophoresis enhanced skin penetration of cationic and neutral dendrimers. Increase in current strength and current duration increased skin transport of dendrimers. Passive and iontophoretic skin penetration of cationic dendrimers was inversely related to their molecular weight. Dendrimer penetrated the skin through intercellular lipids and hair follicles. With iontophoresis, dendrimer was also found in localized skin regions. The study demonstrates that the physicochemical properties of dendrimers influence their skin transport. Findings can be used to design dendrimer-based nanocarriers for drug delivery to skin.

  7. Optical absorption in compact and extended dendrimers

    International Nuclear Information System (INIS)

    Supritz, C.; Engelmann, A.; Reineker, P.

    2005-01-01

    Dendrimers are highly branched molecules, which are expected to be useful, for example, as efficient artificial light harvesting systems, in nano-technological or in medical applications. There are two different classes of dendrimers: compact dendrimers with constant distance between neighboring branching points throughout the macromolecule and extended dendrimers, where this distance increases from the system periphery to the center. We investigate the linear optical absorption spectra of these dendrimer types using the Frenkel exciton concept. The electron-phonon interaction is taken into account by introducing a heat bath that interacts with the exciton in a stochastic manner. We discuss compact dendrimers with equal excitation energies at all molecules, dendrimers with a functionalized core as well as with a whole branch functionalized. Furthermore the line shape of a compact dendrimer is discussed when neighboring molecules at the periphery interact and when all molecules have randomly distributed excitation energies due to disorder. Finally, we discuss two models for extended dendrimers

  8. Which Dendrimer to Attain the Desired Properties? Focus on Phosphorhydrazone Dendrimers.

    Science.gov (United States)

    Caminade, Anne-Marie; Majoral, Jean-Pierre

    2018-03-09

    Among the six Critical Nanoscale Design Parameters (CNDPs) proposed by Prof. Donald A. Tomalia, this review illustrates the influence of the sixth one, which concerns the elemental composition, on the properties of dendrimers. After a large introduction that summarizes different types of dendrimers that have been compared with PolyAMidoAMine (PAMAM) dendrimers, this review will focus on the properties of positively and negatively charged phosphorhydrazone (PPH) dendrimers, especially in the field of biology, compared with other types of dendrimers, in particular PAMAM dendrimers, as well as polypropyleneimine (PPI), carbosilane, and p-Lysine dendrimers.

  9. Which Dendrimer to Attain the Desired Properties? Focus on Phosphorhydrazone Dendrimers

    Directory of Open Access Journals (Sweden)

    Anne-Marie Caminade

    2018-03-01

    Full Text Available Among the six Critical Nanoscale Design Parameters (CNDPs proposed by Prof. Donald A. Tomalia, this review illustrates the influence of the sixth one, which concerns the elemental composition, on the properties of dendrimers. After a large introduction that summarizes different types of dendrimers that have been compared with PolyAMidoAMine (PAMAM dendrimers, this review will focus on the properties of positively and negatively charged phosphorhydrazone (PPH dendrimers, especially in the field of biology, compared with other types of dendrimers, in particular PAMAM dendrimers, as well as polypropyleneimine (PPI, carbosilane, and p-Lysine dendrimers.

  10. Phosphorus dendrimers and photodynamic therapy. Spectroscopic studies on two dendrimer-photosensitizer complexes: Cationic phosphorus dendrimer with rose bengal and anionic phosphorus dendrimer with methylene blue.

    Science.gov (United States)

    Dabrzalska, Monika; Zablocka, Maria; Mignani, Serge; Majoral, Jean Pierre; Klajnert-Maculewicz, Barbara

    2015-08-15

    Dendrimers due to their unique architecture may play an important role in drug delivery systems including chemotherapy, gene therapy and recently, photodynamic therapy as well. We investigated two dendrimer-photosensitizer systems in context of potential use of these systems in photodynamic therapy. The mixtures of an anionic phosphorus dendrimer of the second generation and methylene blue were studied by UV-vis spectroscopy while that of a cationic phosphorus dendrimer (third generation) and rose bengal were investigated by spectrofluorimetric methods. Spectroscopic analysis of these two systems revealed the formation of dendrimer-photosensitizer complexes via electrostatic interactions as well as π stacking. The stoichiometry of the rose bengal-cationic dendrimer complex was estimated to be 7:1 and 9:1 for the methylene blue-anionic dendrimer complex. The results suggest that these polyanionic or polycationic phosphorus dendrimers can be promising candidates as carriers in photodynamic therapy. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Positron annihilation study of polyphenylene dendrimers

    International Nuclear Information System (INIS)

    Marek, T.; Suevegh, K.; Vertes, A.; Ernst, A.; Bauer, R.; Weil, T.; Wiesler, U.; Klapper, M.; Muellen, K.

    2003-01-01

    The free volume of a series of rigid polyphenylene dendrimers was studied by positron lifetime spectroscopy and the experimental data were compared with results from molecular dynamics calculations. Contrary to dendrimers containing flexible repeat units rigid polyphenylene dendrimers proved to contain large stable 'inner' voids of a distinct size between their dendritic branches. The size of the 'inner' cavities increases with the size of the dendrimer. Due to these voids, polyphenylene dendrimers are potentially attractive with respect to the selective incorporation of guest molecules

  12. [Dendrimers in biomedical sciences and nanotechnology].

    Science.gov (United States)

    Sekowski, Szymon; Miłowska, Katarzyna; Gabryelak, Teresa

    2008-12-30

    Dendrimers are relatively new, hyper-branched polymers that have many interesting abilities. Dendrimers could be used, for example, as drug or gene carriers, contrast agents, sensors for different metal ions, and in developing innovation technology. These spherical polymers are also characterized by pharmacological activity against different bacterial and viral diseases. Dendrimers are currently being intensively investigated as anti-prion and anti-amyloid fibril agents. They can be used to build specific dendrimer films to be applied in modern technology. This review describes different uses of dendrimer particles in biomedical sciences and nanotechnology and shows advantages of their application.

  13. Phenomenological model of nanocluster in polymer matrix

    International Nuclear Information System (INIS)

    Oksengendler, B.L.; Turaeva, N.N.; Azimov, J.; Rashidova, S.Sh.

    2010-01-01

    The phenomenological model of matrix nanoclusters is presented based on the Wood-Saxon potential used in nuclear physics. In frame of this model the following problems have been considered: calculation of width of diffusive layer between nanocluster and matrix, definition of Tamm surface electronic state taking into account the diffusive layer width, receiving the expression for specific magnetic moment of nanoclusters taking into account the interface width. (authors)

  14. Nanocluster production for solar cell applications

    International Nuclear Information System (INIS)

    Al Dosari, Haila M.; Ayesh, Ahmad I.

    2013-01-01

    This research focuses on the fabrication and characterization of silver (Ag) and silicon (Si) nanoclusters that might be used for solar cell applications. Silver and silicon nanoclusters have been synthesized by means of dc magnetron sputtering and inert gas condensation inside an ultra-high vacuum compatible system. We have found that nanocluster size distributions can be tuned by various source parameters, such as the sputtering discharge power, flow rate of argon inert gas, and aggregation length. Quadrupole mass filter and transmission electron microscopy were used to evaluate the size distribution of Ag and Si nanoclusters. Ag nanoclusters with average size in the range of 3.6–8.3 nm were synthesized (herein size refers to the nanocluster diameter), whereas Si nanoclusters' average size was controlled to range between 2.9 and 7.4 nm by controlling the source parameters. This work illustrates the ability of controlling the Si and Ag nanoclusters' sizes by proper optimization of the operation conditions. By controlling nanoclusters' sizes, one can alter their surface properties to suit the need to enhance solar cell efficiency. Herein, Ag nanoclusters were deposited on commercial polycrystalline solar cells. Short circuit current (I SC ), open circuit voltage (V OC ), fill factor, and efficiency (η) were obtained under light source with an intensity of 30 mW/cm 2 . A 22.7% enhancement in solar cell efficiency could be measured after deposition of Ag nanoclusters, which demonstrates that Ag nanoclusters generated in this work are useful to enhance solar cell efficiency

  15. Possibility of superradiance by magnetic nanoclusters

    International Nuclear Information System (INIS)

    Yukalov, V I; Yukalova, E P

    2011-01-01

    The possibility of realizing spin superradiance by an assembly of magnetic nanoclusters is analyzed. The known obstacles for realizing such a coherent radiation by magnetic nanoclusters are their large magnetic anisotropy, strong dephasing dipole interactions, and an essential nonuniformity of their sizes. In order to give a persuasive conclusion, a microscopic theory is developed, providing an accurate description of nanocluster spin dynamics. It is shown that, despite the obstacles, it is feasible to organize such a setup that magnetic nanoclusters would produce strong superradiant emission

  16. Ordered Layered Dendrimers Constructed from Two Known Dendrimer Families: Inheritance and Emergence of Properties.

    Science.gov (United States)

    Dib, Hanna; Rebout, Cyrille; Laurent, Régis; Mallet-Ladeira, Sonia; Sournia-Saquet, Alix; Sárosi, Menyhárt B; Hey-Hawkins, Evamarie; Majoral, Jean-Pierre; Delavaux-Nicot, Béatrice; Caminade, Anne-Marie

    2016-07-25

    A new concept is presented, namely the synthesis of dendrimers intrinsically composed in alternation of building blocks pertaining to two known families of dendrimers: phosphorhydrazone dendrimers and triazine-piperazine dendrimers. These mixed dendrimers with layered controlled architecture inherit their easy (31) P NMR characterization and their thermal stability from the phosphorhydrazone family, and their decreased solubility from the triazine-piperazine family. However, they have also their own and original characteristics. Both parent families are white powders, whereas the mixed dendrimers are yellow, orange, or red powders, depending on the generation. DFT calculations were carried out on model dendrons to understand these special color features. Remarkably, these dendrimers incorporating redox-active organic entities allow for the first time the monitoring of the growth of an organic dendrimer by electrochemistry while highlighting an even-odd generation behavior. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Perspective: Dendrimer drugs for infection and inflammation.

    Science.gov (United States)

    Shaunak, Sunil

    2015-12-18

    Biologists are dissecting complex biological pathways at breath taking speed. It is opening up new opportunities for the therapeutic evaluation of novel dendrimer drugs. This review focuses on studies of small dendrimers decorated with sulfate, phosphonate, N-acetyl-cysteine, glucosamine and mannose in animal model studies of infection and inflammation. It highlights those animal model studies which have demonstrated the most promising dendrimer drug constructs as potential new medicines. The issues relating to their analytical chemistry that are slowing the progress of dendrimer drugs into the clinic are highlighted. It should be possible to solve these with additional analytical expertise because it is small dendrimers with only 16-32 peripheral groups that make for the best infection and inflammation related medicines. Public-private partnerships are now needed to progress these dendrimer drugs into proof-of-concept clinical trials. Copyright © 2015 Elsevier Inc. All rights reserved.

  18. Review Dendrimer : Definisi, Sintesis, Aplikasi Dan Prospektif

    OpenAIRE

    Rahmi, Dwinna

    2013-01-01

    Dendrimer merupakan makrostruktur monodisperse dengan banyak cabang yang homogen dan degree of branching (DB) 100%. Dua cara sintesis dendrimer yaitu convergent dan divergent dilakukan. Convergent dilakukan dengan reaksi kovalen antara dua dan lebih monomer. Divergent dimulai dengan pembentukan inti dilanjutkan dengan pembentukan cabang yang merupakan group fungsional yang aktif. Sejauh ini dendrimer sudah banyak diterapkan pada bidang farmasi yaitu drug delivery dan non farmasi pada proses i...

  19. Dendrimer-based dynamic combinatorial libraries

    NARCIS (Netherlands)

    Chang, T.; Meijer, E.W.

    2005-01-01

    The aim of this project is to create water-sol. dynamic combinatorial libraries based upon dendrimer-guest complexes. The guest mols. are designed to bind to dendrimers using multiple secondary interactions, such as electrostatics and hydrogen bonding. We have been able to incorporate various guest

  20. Research progress on synthesis and characteristic about dendrimers

    Science.gov (United States)

    Tang, Zitao

    2017-12-01

    Dendrimers are hyper-branched polymers which have perfectly defined structures. Different from the common polymers, dendrimers are synthesized by a step-by-step iterative style, which starts from a central core and forms branching parts outward. The dendrimers also have different physical and chemical characteristics from common polymers. In this paper, contributions to dendrimer synthesis from different researchers with different scientific background, synthesis of different dendrimers, and applications of them will be reviewed.

  1. Dendrimers for siRNA Delivery

    Directory of Open Access Journals (Sweden)

    Swati Biswas

    2013-02-01

    Full Text Available Since the discovery of the “starburst polymer”, later renamed as dendrimer, this class of polymers has gained considerable attention for numerous biomedical applications, due mainly to the unique characteristics of this macromolecule, including its monodispersity, uniformity, and the presence of numerous functionalizable terminal groups. In recent years, dendrimers have been studied extensively for their potential application as carriers for nucleic acid therapeutics, which utilize the cationic charge of the dendrimers for effective dendrimer-nucleic acid condensation. siRNA is considered a promising, versatile tool among various RNAi-based therapeutics, which can effectively regulate gene expression if delivered successfully inside the cells. This review reports on the advancements in the development of dendrimers as siRNA carriers.

  2. Influence of dendrimer generation and polyethylene glycol length on the biodistribution of PEGylated dendrimers.

    Science.gov (United States)

    Kojima, Chie; Regino, Celeste; Umeda, Yasuhito; Kobayashi, Hisataka; Kono, Kenji

    2010-01-04

    Dendrimers are a potential drug carrier. Because modification with polyethylene glycol (PEG) is known to improve the blood retention, PEGylated dendrimers have been studied as a useful drug carrier. In this study, three types of PEGylated L-lysine-bearing polyamidoamine dendrimers (PEG2k-Lys-PAMAM (G4), PEG5k-Lys-PAMAM (G4), PEG2k-Lys-PAMAM (G5)) were synthesized, which are composed of a dendrimer of different generations (generations 4 and 5) and PEG chains with different molecular weights (2k and 5k). An acetylated L-lysine-bearing dendrimer was also synthesized as a non-PEGylated dendrimer. Bifunctional diethylenetriaminepentaacetic acid (pSCN-benzyl-DTPA) was bound to the epsilon -amino group of lysine in a dendrimer, to be labeled with radioactive indium-111. These PEGylayed dendrimers showed longer blood retention and lower accumulation in other normal organs such as the kidneys than the non-PEGylated dendrimer. The PEGylated dendrimers with the higher generation and the longer PEG led the greater blood retention.

  3. Nanoclusters a bridge across disciplines

    CERN Document Server

    Jena, Purusottam

    2010-01-01

    This comprehensive book on Nanoclusters comprises sixteen authoritative chapters written by leading researchers in the field. It provides insight into topics that are currently at the cutting edge of cluster science, with the main focus on metal and metal compound systems that are of particular interest in materials science, and also on aspects related to biology and medicine. While there are numerous books on clusters, the focus on clusters as a bridge across disciplines sets this book apart from others. Delivers cutting edge coverage of cluster science Covers a broad range of topics in

  4. Poly(amidoamine) dendrimers on lipid bilayers II: Effects of bilayer phase and dendrimer termination.

    Science.gov (United States)

    Kelly, Christopher V; Leroueil, Pascale R; Orr, Bradford G; Banaszak Holl, Mark M; Andricioaei, Ioan

    2008-08-07

    The molecular structures and enthalpy release of poly(amidoamine) (PAMAM) dendrimers binding to 1,2-dimyristoyl- sn-glycero-3-phosphocholine (DMPC) bilayers were explored through atomistic molecular dynamics. Three PAMAM dendrimer terminations were examined: protonated primary amine, neutral acetamide, and deprotonated carboxylic acid. Fluid and gel lipid phases were examined to extract the effects of lipid tail mobility on the binding of generation-3 dendrimers, which are directly relevant to the nanoparticle interactions involving lipid rafts, endocytosis, lipid removal, and/or membrane pores. Upon binding to gel phase lipids, dendrimers remained spherical, had a constant radius of gyration, and approximately one-quarter of the terminal groups were in close proximity to the lipids. In contrast, upon binding to fluid phase bilayers, dendrimers flattened out with a large increase in their asphericity and radii of gyration. Although over twice as many dendrimer-lipid contacts were formed on fluid versus gel phase lipids, the dendrimer-lipid interaction energy was only 20% stronger. The greatest enthalpy release upon binding was between the charged dendrimers and the lipid bilayer. However, the stronger binding to fluid versus gel phase lipids was driven by the hydrophobic interactions between the inner dendrimer and lipid tails.

  5. Positron confinement in embedded lithium nanoclusters

    Science.gov (United States)

    van Huis, M. A.; van Veen, A.; Schut, H.; Falub, C. V.; Eijt, S. W.; Mijnarends, P. E.; Kuriplach, J.

    2002-02-01

    Quantum confinement of positrons in nanoclusters offers the opportunity to obtain detailed information on the electronic structure of nanoclusters by application of positron annihilation spectroscopy techniques. In this work, positron confinement is investigated in lithium nanoclusters embedded in monocrystalline MgO. These nanoclusters were created by means of ion implantation and subsequent annealing. It was found from the results of Doppler broadening positron beam analysis that approximately 92% of the implanted positrons annihilate in lithium nanoclusters rather than in the embedding MgO, while the local fraction of lithium at the implantation depth is only 1.3 at. %. The results of two-dimensional angular correlation of annihilation radiation confirm the presence of crystalline bulk lithium. The confinement of positrons is ascribed to the difference in positron affinity between lithium and MgO. The nanocluster acts as a potential well for positrons, where the depth of the potential well is equal to the difference in the positron affinities of lithium and MgO. These affinities were calculated using the linear muffin-tin orbital atomic sphere approximation method. This yields a positronic potential step at the MgO||Li interface of 1.8 eV using the generalized gradient approximation and 2.8 eV using the insulator model.

  6. Tailoring Enzyme-Like Activities of Gold Nanoclusters by Polymeric Tertiary Amines for Protecting Neurons Against Oxidative Stress.

    Science.gov (United States)

    Liu, Ching-Ping; Wu, Te-Haw; Lin, Yu-Lung; Liu, Chia-Yeh; Wang, Sabrina; Lin, Shu-Yi

    2016-08-01

    The cytotoxicity of nanozymes has drawn much attention recently because their peroxidase-like activity can decompose hydrogen peroxide (H2 O2 ) to produce highly toxic hydroxyl radicals (•OH) under acidic conditions. Although catalytic activities of nanozymes are highly associated with their surface properties, little is known about the mechanism underlying the surface coating-mediated enzyme-like activities. Herein, it is reported for the first time that amine-terminated PAMAM dendrimer-entrapped gold nanoclusters (AuNCs-NH2 ) unexpectedly lose their peroxidase-like activity while still retaining their catalase-like activity in physiological conditions. Surprisingly, the methylated form of AuNCs-NH2 (i.e., MAuNCs-N(+) R3 , where R = H or CH3 ) results in a dramatic recovery of the intrinsic peroxidase-like activity while blocking most primary and tertiary amines (1°- and 3°-amines) of dendrimers to form quaternary ammonium ions (4°-amines). However, the hidden peroxidase-like activity is also found in hydroxyl-terminated dendrimer-encapsulated AuNCs (AuNCs-OH, inside backbone with 3°-amines), indicating that 3°-amines are dominant in mediating the peroxidase-like activity. The possible mechanism is further confirmed that the enrichment of polymeric 3°-amines on the surface of dendrimer-encapsulated AuNCs provides sufficient suppression of the critical mediator •OH for the peroxidase-like activity. Finally, it is demonstrated that AuNCs-NH2 with diminished cytotoxicity have great potential for use in primary neuronal protection against oxidative damage. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Investigation of Dendrimer-Membrane Interactions

    Science.gov (United States)

    Mecke, Almut; Hessler, Jessica; Lee, Inhan; Banaszak Holl, Mark; Orr, Bradford; Patri, Anil K.; Baker, J. R.

    2003-03-01

    Modified Polyamidoamine (PAMAM) dendrimers show great promise as targeted drug transport agents. Current research efforts point to the possibility of dramatic improvements to conventional chemotherapy by selectively delivering a therapeutic to antigen bearing tumor cells. In order to better understand the uptake mechanism of such devices into cells we are investigating dendrimer-surface adsorption and dendrimer-membrane interactions using atomic force microscopy, light scattering and computer simulations. Model systems consisting of supported DMPC lipid bilayers have shown interesting results suggesting the shape and architecture of nano-devices play an important role for their biologic activity. We are also investigating the effect of targeted drug vehicles on cells in vitro.

  8. Comparison of generation 3 polyamidoamine dendrimer and generation 4 polypropylenimine dendrimer on drug loading, complex structure, release behavior, and cytotoxicity

    Science.gov (United States)

    Shao, Naimin; Su, Yunzhang; Hu, Jingjing; Zhang, Jiahai; Zhang, Hongfeng; Cheng, Yiyun

    2011-01-01

    Background Polyamidoamine (PAMAM) and polypropylenimine (PPI) dendrimers are the commercially available and most widely used dendrimers in pharmaceutical sciences and biomedical engineering. In the present study, the loading and release behaviors of generation 3 PAMAM and generation 4 PPI dendrimers with the same amount of surface amine groups (32 per dendrimer) were compared using phenylbutazone as a model drug. Methods The dendrimer-phenylbutazone complexes were characterized by 1H nuclear magnetic resonance and nuclear Overhauser effect techniques, and the cytotoxicity of each dendrimer was evaluated. Results Aqueous solubility results suggest that the generation 3 PAMAM dendrimer has a much higher loading ability towards phenylbutazone in comparison with the generation 4 PPI dendrimer at high phenylbutazone-dendrimer feeding ratios. Drug release was much slower from the generation 3 PAMAM matrix than from the generation 4 PPI dendrimer. In addition, the generation 3 PAMAM dendrimer is at least 50-fold less toxic than generation 4 PPI dendrimer on MCF-7 and A549 cell lines. Conclusion Although the nuclear Overhauser effect nuclear magnetic resonance results reveal that the generation 4 PPI dendrimer with a more hydrophobic interior encapsulates more phenylbutazone, the PPI dendrimer-phenylbutazone inclusion is not stable in aqueous solution, which poses a great challenge during drug development. PMID:22267921

  9. A review on comparative study of PPI and PAMAM dendrimers

    International Nuclear Information System (INIS)

    Kaur, Daljeet; Jain, Keerti; Mehra, Neelesh Kumar; Kesharwani, Prashant; Jain, Narendra K.

    2016-01-01

    Dendrimers are hyperbranched, monodispersed macromolecules with multivalent functional end groups. Dendrimers have been explored as carrier for many drugs like anticancer, antiviral, antimalarial, antiprotozoal, anti tubercular drugs. Although a number of different types of dendrimers containing different core molecules, branching monomers and surface functional groups have been designed till date for drug delivery applications, yet the poly(propyleneimine) (PPI) and poly(amidoamine) (PAMAM) dendrimers have been the most explored dendrimers in this regard. In this review, we have summarized a comparative data on PPI and PAMAM dendrimers particularly relevant to their properties, synthesis, toxicity, biomedical applications and drug delivery attributes.

  10. Light-emitting dendrimer film morphology: A neutron reflectivity study

    Science.gov (United States)

    Vickers, S. V.; Barcena, H.; Knights, K. A.; Thomas, R. K.; Ribierre, J.-C.; Gambino, S.; Samuel, I. D. W.; Burn, P. L.; Fragneto, Giovanna

    2010-06-01

    We have used neutron reflectivity (NR) measurements to probe the physical structure of phosphorescent dendrimer films. The dendrimers consisted of fac-tris(2-phenylpyridyl)iridium(III) cores, biphenyl-based dendrons (first or second generation), and perdeuterated 2-ethylhexyloxy surface groups. We found that the shape and hydrodynamic radius of the dendrimer were both important factors in determining the packing density of the dendrimers. "Cone" shaped dendrimers were found to pack more effectively than "spherical" dendrimers even when the latter had a smaller radius. The morphology of the films determined by NR was consistent with the measured photoluminescence and charge transporting properties of the materials.

  11. A review on comparative study of PPI and PAMAM dendrimers

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Daljeet; Jain, Keerti, E-mail: keertijain02@gmail.com; Mehra, Neelesh Kumar [ISF College of Pharmacy, Pharmaceutical Nanotechnology Research Laboratory (India); Kesharwani, Prashant [Wayne State University, Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences (United States); Jain, Narendra K., E-mail: jnarendr@yahoo.co.in, E-mail: dr.jnarendr@gmail.com [ISF College of Pharmacy, Pharmaceutical Nanotechnology Research Laboratory (India)

    2016-06-15

    Dendrimers are hyperbranched, monodispersed macromolecules with multivalent functional end groups. Dendrimers have been explored as carrier for many drugs like anticancer, antiviral, antimalarial, antiprotozoal, anti tubercular drugs. Although a number of different types of dendrimers containing different core molecules, branching monomers and surface functional groups have been designed till date for drug delivery applications, yet the poly(propyleneimine) (PPI) and poly(amidoamine) (PAMAM) dendrimers have been the most explored dendrimers in this regard. In this review, we have summarized a comparative data on PPI and PAMAM dendrimers particularly relevant to their properties, synthesis, toxicity, biomedical applications and drug delivery attributes.

  12. Atomically Precise Metal Nanoclusters for Catalytic Application

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Rongchao [Carnegie Mellon Univ., Pittsburgh, PA (United States)

    2016-11-18

    The central goal of this project is to explore the catalytic application of atomically precise gold nanoclusters. By solving the total structures of ligand-protected nanoclusters, we aim to correlate the catalytic properties of metal nanoclusters with their atomic/electronic structures. Such correlation unravel some fundamental aspects of nanocatalysis, such as the nature of particle size effect, origin of catalytic selectivity, particle-support interactions, the identification of catalytically active centers, etc. The well-defined nanocluster catalysts mediate the knowledge gap between single crystal model catalysts and real-world conventional nanocatalysts. These nanoclusters also hold great promise in catalyzing certain types of reactions with extraordinarily high selectivity. These aims are in line with the overall goals of the catalytic science and technology of DOE and advance the BES mission “to support fundamental research to understand, predict, and ultimately control matter and energy at the level of electrons, atoms, and molecules”. Our group has successfully prepared different sized, robust gold nanoclusters protected by thiolates, such as Au25(SR)18, Au28(SR)20, Au38(SR)24, Au99(SR)42, Au144(SR)60, etc. Some of these nanoclusters have been crystallographically characterized through X-ray crystallography. These ultrasmall nanoclusters (< 2 nm diameter) exhibit discrete electronic structures due to quantum size effect, as opposed to quasicontinuous band structure of conventional metal nanoparticles or bulk metals. The available atomic structures (metal core plus surface ligands) of nanoclusters serve as the basis for structure-property correlations. We have investigated the unique catalytic properties of nanoclusters (i.e. not observed in conventional nanogold catalysts) and revealed the structure-selectivity relationships. Highlights of our

  13. Formation of Silver and Gold Dendrimer Nanocomposites

    International Nuclear Information System (INIS)

    Balogh, Lajos; Valluzzi, Regina; Laverdure, Kenneth S.; Gido, Samuel P.; Hagnauer, Gary L.; Tomalia, Donald A.

    1999-01-01

    Structural types of dendrimer nanocomposites have been studied and the respective formation mechanisms have been described, with illustration of nanocomposites formed from poly(amidoamine) PAMAM dendrimers and zerovalent metals, such as gold and silver. Structure of {(Au(0)) n- PAMAM} and {(Ag(0)) n- PAMAM} gold and silver dendrimer nanocomposites was found to be the function of the dendrimer structure and surface groups as well as the formation mechanism and the chemistry involved. Three different types of single nanocomposite architectures have been identified, such as internal ('I'), external ('E') and mixed ('M') type nanocomposites. Both the organic and inorganic phase could form nanosized pseudo-continuous phases while the other components are dispersed at the molecular or atomic level either in the interior or on the surface of the template/container. Single units of these nanocomposites may be used as building blocks in the synthesis of nanostructured materials

  14. On Topological Indices of Certain Dendrimer Structures

    Science.gov (United States)

    Aslam, Adnan; Bashir, Yasir; Ahmad, Safyan; Gao, Wei

    2017-05-01

    A topological index can be considered as transformation of chemical structure in to real number. In QSAR/QSPR study, physicochemical properties and topological indices such as Randić, Zagreb, atom-bond connectivity ABC, and geometric-arithmetic GA index are used to predict the bioactivity of chemical compounds. Dendrimers are highly branched, star-shaped macromolecules with nanometer-scale dimensions. Dendrimers are defined by three components: a central core, an interior dendritic structure (the branches), and an exterior surface with functional surface groups. In this paper we determine generalised Randić, general Zagreb, general sum-connectivity indices of poly(propyl) ether imine, porphyrin, and zinc-Porphyrin dendrimers. We also compute ABC and GA indices of these families of dendrimers.

  15. Electronic transport study in PAMAM dendrimers

    International Nuclear Information System (INIS)

    Vieira, Nirton C.S.; Soares, Demetrio A.W.; Fernandes, Edson G.R.; Queiroz, Alvaro A.A. de

    2005-01-01

    Dendrimers are nanomaterials that have many potential applications in medicine, including diagnosis and therapeutic procedures. Dendrimers are isomolecular polymers, with a very well controlled architecture and a thousand times smaller than cells. Dendrimers containing biocatalysts are of great interest for clinical applications in biosensors because of the way in which their chemical and electric conduction mechanism can be tailored. In this work, the polyamidoamine dendrimer (PAMAM) of generation 4 was synthesized by divergent route and characterized by NMR spectroscopy. The electronic transport properties of PAMAM in a metal-polymer type heterojunction were studied. The electrical conduction mechanism of PAMAM studied in the temperature range of 291-323 K indicates a conduction mechanism thermally activated. (author)

  16. Study of Dendrimers by Topological Indices

    Directory of Open Access Journals (Sweden)

    Soleimani Najmeh

    2017-12-01

    Full Text Available In this paper, five degree based topological indices, the first Zagreb (M1, second Zagreb (M2, first multiple Zagreb (PM1, second multiple Zagreb (PM2, and the hyper Zagreb (HM indices of two types of dendrimers are studied. In addition, two distance based topological indices, the total eccentricity (θ and eccentric connectivity (ξc indices of these dendrimers are computed.

  17. DNA condensation by partially acetylated poly(amido amine) dendrimers: effects of dendrimer charge density on complex formation.

    Science.gov (United States)

    Yu, Shi; Li, Ming-Hsin; Choi, Seok Ki; Baker, James R; Larson, Ronald G

    2013-09-03

    The ability of poly(amido amine) (or PAMAM) dendrimers to condense semiflexible dsDNA and penetrate cell membranes gives them great potential in gene therapy and drug delivery but their high positive surface charge makes them cytotoxic. Here, we describe the effects of partial neutralization by acetylation on DNA condensation using light scattering, circular dichroism, and single molecule imaging of dendrimer-DNA complexes combed onto surfaces and tethered to those surfaces under flow. We find that DNA can be condensed by generation-five (G5) dendrimers even when the surface charges are more than 65% neutralized, but that such dendrimers bind negligibly when an end-tethered DNA is stretched in flow. We also find that when fully charged dendrimers are introduced by flow to end-tethered DNA, all DNA molecules become equally highly coated with dendrimers at a rate that becomes very fast at high dendrimer concentration, and that dendrimers remain bound during subsequent flow of dendrimer-free buffer. These results suggest that the presence of dendrimer-free DNA coexisting with dendrimer-bound DNA after bulk mixing of the two in solution may result from diffusion-limited irreversible dendrimer-DNA binding, rather than, or in addition to, the previously proposed cooperative binding mechanism of dendrimers to DNA.

  18. DNA Condensation by Partially Acetylated Poly(amido amine Dendrimers: Effects of Dendrimer Charge Density on Complex Formation

    Directory of Open Access Journals (Sweden)

    Ronald G. Larson

    2013-09-01

    Full Text Available The ability of poly(amido amine (or PAMAM dendrimers to condense semiflexible dsDNA and penetrate cell membranes gives them great potential in gene therapy and drug delivery but their high positive surface charge makes them cytotoxic. Here, we describe the effects of partial neutralization by acetylation on DNA condensation using light scattering, circular dichroism, and single molecule imaging of dendrimer-DNA complexes combed onto surfaces and tethered to those surfaces under flow. We find that DNA can be condensed by generation-five (G5 dendrimers even when the surface charges are more than 65% neutralized, but that such dendrimers bind negligibly when an end-tethered DNA is stretched in flow. We also find that when fully charged dendrimers are introduced by flow to end-tethered DNA, all DNA molecules become equally highly coated with dendrimers at a rate that becomes very fast at high dendrimer concentration, and that dendrimers remain bound during subsequent flow of dendrimer-free buffer. These results suggest that the presence of dendrimer-free DNA coexisting with dendrimer-bound DNA after bulk mixing of the two in solution may result from diffusion-limited irreversible dendrimer-DNA binding, rather than, or in addition to, the previously proposed cooperative binding mechanism of dendrimers to DNA.

  19. New dendrimer - peptide host - guest complexes : towards dendrimers as peptide carriers

    NARCIS (Netherlands)

    Boas, U.; Sontjens, S.H.M.; Jensen, K.J.; Christensen, J.B.; Meijer, E.W.

    2002-01-01

    Adamantyl urea and adamantyl thiourea modified poly(propylene imine) dendrimers act as hosts for N-terminal tert-butoxycarbonyl (Boc)-protected peptides and form chloroform-soluble complexes. investigations with NMR spectroscopy show that the peptide is bound to the dendrimer by ionic interactions

  20. Brief Timelapse on Dendrimer Chemistry: Advances, Limitations, and Expectations

    KAUST Repository

    Ornelas, Catia

    2015-01-01

    , with a critical analysis on the expectations, limitations, advances, current challenges and future directions. Dendrimer timelapse demonstrates constant evolution in dendrimer chemistry enabling their application in nanomedicine, protein mimic, catalysis

  1. New dendrimer - Peptide host - Guest complexes: Towards dendrimers as peptide carriers

    DEFF Research Database (Denmark)

    Boas, Ulrik; Sontjens, S.H.M.; Jensen, Knud Jørgen

    2002-01-01

    Adamantyl urea and adamantyl thiourea modified poly(propylene imine) dendrimers act as hosts for N-terminal tert-butoxycarbonyl (Boc)-protected peptides and form chloroform-soluble complexes. investigations with NMR spectroscopy show that the peptide is bound to the dendrimer by ionic interactions...... between the dendrimer outer shell tertiary amines and the C-terminal carboxylic acid of the peptide, and also through host-urea to peptide-amide hydrogen bonding. The hydrogen-bonding nature of the peptide dendrimer interactions was further confirmed by using Fourier transform IR spectroscopy, for which...... the NH- and CO-stretch signals of the peptide amide moieties shift towards lower wave-numbers upon complexation with the dendrimer. Spatial analysis of the complexes with NOESY spectroscopy generally shows close proximity of the N-terminal Boc group of the peptide to the peripheral adamantyl groups...

  2. PREPARATION OF CHEMICALLY WELL-DEFINED CARBOHYDRATE DENDRIMER CONJUGATES

    DEFF Research Database (Denmark)

    2004-01-01

    A method for the synthesis of dendrimer conjugates having a well-defined chemical structure, comprising one or more carbohydrate moieties and one or more immunomodulating substances coupled to a dendrimer, is presented. First, the carbohydrate is bound to the dendrimer in a chemoselective manner...... conjugates and their use in vaccination, production of antibodies, high throughput screening, diagnostic assays and libraries....

  3. Oligothia dendrimers for the formation of gold nanoparticles

    NARCIS (Netherlands)

    d'Aleo, A.; Williams, R.M.; Osswald, F.; Edamana, P.; Hahn, U.; van Heyst, J.; Tichelaar, F.D.; Voegtle, F.; De Cola, L.

    2004-01-01

    The synthesis and characterization of oligothia dendrimers and their use for the formation of gold nanoparticles is described. The role played by these dendrimers in controlling the stability and size of the particles is discussed. It is shown that the generation of the dendrimers, as well as the

  4. Preliminary biological evaluation of a urea-functionalized dendrimer

    International Nuclear Information System (INIS)

    Stephan, H.; Syhre, R.; Spies, H.; Johannsen, B.; Zessin, J.; Steinbach, J.; Klein, L.; Werner, N.; Voegtle, F.

    2002-01-01

    A new third generation ethylurea-functionalized polypropyleneamine dendrimer was prepared. After labelling this dendrimer with 11-carbon the biodistribution in rats was studied. The highest level of radioactivity was found in the liver (30-35% ID). The 11 C-labelled dendrimer was well tolerated by the rats. (orig.)

  5. On the ability of PAMAM dendrimers and dendrimer/DNA aggregates to penetrate POPC model biomembranes.

    Science.gov (United States)

    Ainalem, Marie-Louise; Campbell, Richard A; Khalid, Syma; Gillams, Richard J; Rennie, Adrian R; Nylander, Tommy

    2010-06-03

    Poly(amido amine) (PAMAM) dendrimers have previously been shown, as cationic condensing agents of DNA, to have high potential for nonviral gene delivery. This study addresses two key issues for gene delivery: the interaction of the biomembrane with (i) the condensing agent (the cationic PAMAM dendrimer) and (ii) the corresponding dendrimer/DNA aggregate. Using in situ null ellipsometry and neutron reflection, parallel experiments were carried out involving dendrimers of generations 2 (G2), 4 (G4), and 6 (G6). The study demonstrates that free dendrimers of all three generations were able to traverse supported palmitoyloleoylphosphatidylcholine (POPC) bilayers deposited on silica surfaces. The model biomembranes were elevated from the solid surfaces upon dendrimer penetration, which offers a promising new way to generate more realistic model biomembranes where the contact with the supporting surface is reduced and where aqueous cavities are present beneath the bilayer. The largest dendrimer (G6) induced partial bilayer destruction directly upon penetration, whereas the smaller dendrimers (G2 and G4) leave the bilayer intact, so we propose that lower generation dendrimers have greater potential as transfection mediators. In addition to the experimental observations, coarse-grained simulations on the interaction between generation 3 (G3) dendrimers and POPC bilayers were performed in the absence and presence of a bilayer-supporting negatively charged surface that emulates the support. The simulations demonstrate that G3 is transported across free-standing POPC bilayers by direct penetration and not by endocytosis. The penetrability was, however, reduced in the presence of a surface, indicating that the membrane transport observed experimentally was not driven solely by the surface. The experimental reflection techniques were also applied to dendrimer/DNA aggregates of charge ratio = 0.5, and while G2/DNA and G4/DNA aggregates interact with POPC bilayers, G6/DNA

  6. Toxicity of PAMAM dendrimers to Chlamydomonas reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Petit, Anne-Noelle, E-mail: anne-noelle.petit@ec.gc.ca [Environment Canada, 105 McGill Street, Montreal, Quebec H2Y 2E7 (Canada); Eullaffroy, Philippe [Laboratoire Plantes, Pesticides et Developpement Durable, EA 2069, URVVC, BP 1039, Universite de Reims Champagne-Ardenne, 51687 Reims Cedex 2 (France); Debenest, Timothee; Gagne, Francois [Environment Canada, 105 McGill Street, Montreal, Quebec H2Y 2E7 (Canada)

    2010-10-15

    In recent decades, a new class of polymeric materials, PAMAM dendrimers, has attracted marked interest owing to their unique nanoscopic architecture and their hopeful perspectives in nanomedicine and therapeutics. However, the potential release of dendrimers into the aquatic environment raises the issue about their toxicity on aquatic organisms. Our investigation sought to estimate the toxicity of cationic PAMAM dendrimers on the green alga, Chlamydomonas reinhardtii. Algal cultures were exposed to different concentrations (0.3-10 mg L{sup -1}) of low dendrimer generations (G2, G4 and G5) for 72 h. Potential adverse effects on Chlamydomonas were assessed using esterase activity (cell viability), photosynthetic O{sub 2} evolution, pigments content and chlorophyll a fluorescence transient. According to the median inhibitory concentration (IC{sub 50}) appraised from esterase activity, toxicity on cell viability decreased with dendrimer generation number (2, 3 and 5 mg L{sup -1} for G2, G4 and G5 dendrimers, respectively). Moreover, the three generations of dendrimers did not induce the same changes in the photosynthetic metabolism of the green alga. O{sub 2} evolution was stimulated in cultures exposed to the lowest generations tested (i.e. G2 and G4) whereas no significant effects were observed with G5. In addition, total chlorophyll content was increased after G2 treatment at 2.5 mg L{sup -1}. Finally, G2 and G4 had positive effects on photosystem II (PSII): the amount of active PSII reaction centers, the primary charge separation and the electron transport between Q{sub A} and Q{sub B} were all increased inducing activation of the photosynthetic electron transport chain. These changes resulted in stimulation of full photosynthetic performance.

  7. Toxicity of PAMAM dendrimers to Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    Petit, Anne-Noelle; Eullaffroy, Philippe; Debenest, Timothee; Gagne, Francois

    2010-01-01

    In recent decades, a new class of polymeric materials, PAMAM dendrimers, has attracted marked interest owing to their unique nanoscopic architecture and their hopeful perspectives in nanomedicine and therapeutics. However, the potential release of dendrimers into the aquatic environment raises the issue about their toxicity on aquatic organisms. Our investigation sought to estimate the toxicity of cationic PAMAM dendrimers on the green alga, Chlamydomonas reinhardtii. Algal cultures were exposed to different concentrations (0.3-10 mg L -1 ) of low dendrimer generations (G2, G4 and G5) for 72 h. Potential adverse effects on Chlamydomonas were assessed using esterase activity (cell viability), photosynthetic O 2 evolution, pigments content and chlorophyll a fluorescence transient. According to the median inhibitory concentration (IC 50 ) appraised from esterase activity, toxicity on cell viability decreased with dendrimer generation number (2, 3 and 5 mg L -1 for G2, G4 and G5 dendrimers, respectively). Moreover, the three generations of dendrimers did not induce the same changes in the photosynthetic metabolism of the green alga. O 2 evolution was stimulated in cultures exposed to the lowest generations tested (i.e. G2 and G4) whereas no significant effects were observed with G5. In addition, total chlorophyll content was increased after G2 treatment at 2.5 mg L -1 . Finally, G2 and G4 had positive effects on photosystem II (PSII): the amount of active PSII reaction centers, the primary charge separation and the electron transport between Q A and Q B were all increased inducing activation of the photosynthetic electron transport chain. These changes resulted in stimulation of full photosynthetic performance.

  8. Dendrimers bind antioxidant polyphenols and cisplatin drug.

    Directory of Open Access Journals (Sweden)

    Amine Abderrezak

    Full Text Available Synthetic polymers of a specific shape and size play major role in drug delivery systems. Dendrimers are unique synthetic macromolecules of nanometer dimensions with a highly branched structure and globular shape with potential applications in gene and drug delivery. We examine the interaction of several dendrimers of different compositions mPEG-PAMAM (G3, mPEG-PAMAM (G4 and PAMAM (G4 with hydrophilic and hydrophobic drugs cisplatin, resveratrol, genistein and curcumin at physiological conditions. FTIR and UV-visible spectroscopic methods as well as molecular modeling were used to analyse drug binding mode, the binding constant and the effects of drug complexation on dendrimer stability and conformation. Structural analysis showed that cisplatin binds dendrimers in hydrophilic mode via Pt cation and polymer terminal NH(2 groups, while curcumin, genistein and resveratrol are located mainly in the cavities binding through both hydrophobic and hydrophilic contacts. The overall binding constants of durg-dendrimers are ranging from 10(2 M(-1 to 10(3 M(-1. The affinity of dendrimer binding was PAMAM-G4>mPEG-PAMAM-G4>mPEG-PAMAM-G3, while the order of drug-polymer stability was curcumin>cisplatin>genistein>resveratrol. Molecular modeling showed larger stability for genisten-PAMAM-G4 (ΔG = -4.75 kcal/mol than curcumin-PAMAM-G4 ((ΔG = -4.53 kcal/mol and resveratrol-PAMAM-G4 ((ΔG = -4.39 kcal/mol. Dendrimers might act as carriers to transport hydrophobic and hydrophilic drugs.

  9. Temperature-sensitive elastin-mimetic dendrimers: Effect of peptide length and dendrimer generation to temperature sensitivity.

    Science.gov (United States)

    Kojima, Chie; Irie, Kotaro; Tada, Tomoko; Tanaka, Naoki

    2014-06-01

    Dendrimers are synthetic macromolecules with unique structure, which are a potential scaffold for peptides. Elastin is one of the main components of extracellular matrix and a temperature-sensitive biomacromolecule. Previously, Val-Pro-Gly-Val-Gly peptides have been conjugated to a dendrimer for designing an elastin-mimetic dendrimer. In this study, various elastin-mimetic dendrimers using different length peptides and different dendrimer generations were synthesized to control the temperature dependency. The elastin-mimetic dendrimers formed β-turn structure by heating, which was similar to the elastin-like peptides. The elastin-mimetic dendrimers exhibited an inverse phase transition, largely depending on the peptide length and slightly depending on the dendrimer generation. The elastin-mimetic dendrimers formed aggregates after the phase transition. The endothermal peak was observed in elastin-mimetic dendrimers with long peptides, but not with short ones. The peptide length and the dendrimer generation are important factors to tune the temperature dependency on the elastin-mimetic dendrimer. Copyright © 2013 Wiley Periodicals, Inc.

  10. Plasmon tsunamis on metallic nanoclusters.

    Science.gov (United States)

    Lucas, A A; Sunjic, M

    2012-03-14

    A model is constructed to describe inelastic scattering events accompanying electron capture by a highly charged ion flying by a metallic nanosphere. The electronic energy liberated by an electron leaving the Fermi level of the metal and dropping into a deep Rydberg state of the ion is used to increase the ion kinetic energy and, simultaneously, to excite multiple surface plasmons around the positively charged hole left behind on the metal sphere. This tsunami-like phenomenon manifests itself as periodic oscillations in the kinetic energy gain spectrum of the ion. The theory developed here extends our previous treatment (Lucas et al 2011 New J. Phys. 13 013034) of the Ar(q+)/C(60) charge exchange system. We provide an analysis of how the individual multipolar surface plasmons of the metallic sphere contribute to the formation of the oscillatory gain spectrum. Gain spectra showing characteristic, tsunami-like oscillations are simulated for Ar(15+) ions capturing one electron in distant collisions with Al and Na nanoclusters.

  11. Tailoring silver nanoparticle construction using dendrimer templated silica networks

    International Nuclear Information System (INIS)

    Liu Xiaojun; Kakkar, Ashok

    2008-01-01

    We have examined the role of the internal environment of dendrimer templated silica networks in tailoring the construction of silver nanoparticle assemblies. Silica networks from which 3,5-dihydroxybenzyl alcohol based dendrimer templates have been completely removed, slowly wet with an aqueous solution of silver acetate. The latter then reacts with internal silica silanol groups, leading to chemisorption of silver ions, followed by the growth of silver oxide nanoparticles. Silica network constructed using generation 4 dendrimer contains residual dendrimer template, and mixes with aqueous silver acetate solution easily. Upon chemisorption, silver ions get photolytically reduced to silver metal under a stabilizing dendrimer environment, leading to the formation of silver metal nanoparticles

  12. PAMAM dendrimer with 4-carbomethoxypyrrolidone - In vitro assessment of neurotoxicity

    DEFF Research Database (Denmark)

    Janaszewska, Anna; Studzian, Maciej; Petersen, Johannes Fabritius

    2015-01-01

    Cytotoxicity of cationic amino-terminated PAMAM dendrimer and modified PAMAM-pyrrolidone dendrimer was compared. LDH assay and cell visualization technique were employed. Mouse embryonic hippocampal cells (mHippoE-18) were used. The experiments were performed in FBS-deprived medium. Pyrrolidone......-modification significantly diminished toxicity of PAMAM dendrimer. The absence of FBS did not reveal significant impact on the toxic effect. Results from LDH assay and MTT test were in good consistency. Low cytotoxicity of PAMAM-pyrrolidone dendrimer increases reliability of the results showing a small impact...... of this dendrimer on cell viability....

  13. Poly(amido amine) dendrimers in oral delivery.

    Science.gov (United States)

    Yellepeddi, Venkata K; Ghandehari, Hamidreza

    2016-01-01

    Poly(amidoamine) (PAMAM) dendrimers have been extensively investigated for oral delivery applications due to their ability to translocate across the gastrointestinal epithelium. In this Review, we highlight recent advances in the evaluation of PAMAM dendrimers as oral drug delivery carriers. Specifically, toxicity, mechanisms of transepithelial transport, models of the intestinal epithelial barrier including isolated human intestinal tissue model, detection of dendrimers, and surface modification are discussed. We also highlight evaluation of various PAMAM dendrimer-drug conjugates for their ability to transport across gastrointestinal epithelium for improved oral bioavailability. In addition, current challenges and future trends for clinical translation of PAMAM dendrimers as carriers for oral delivery are discussed.

  14. Bifunctional Phosphorus Dendrimers and Their Properties.

    Science.gov (United States)

    Caminade, Anne-Marie; Majoral, Jean-Pierre

    2016-04-23

    Dendrimers are hyperbranched and monodisperse macromolecules, generally considered as a special class of polymers, but synthesized step-by-step. Most dendrimers have a uniform structure, with a single type of terminal function. However, it is often desirable to have at least two different functional groups. This review will discuss the case of bifunctional phosphorus-containing dendrimers, and the consequences for their properties. Besides the terminal functions, dendritic structures may have also a function at the core, or linked off-center to the core, or at the core of dendrons (dendritic wedges). Association of two dendrons having different terminal functions leads to Janus dendrimers (two faces). The internal structure can also possess functional groups on one layer, or linked to one layer, or on several layers. Finally, there are several ways to have two types of terminal functions, besides the case of Janus dendrimers: either each terminal function bears two functions sequentially, or two different functions are linked to each terminal branching point. Examples of each type of structure will be given in this review, as well as practical uses of such sophisticated structures in the fields of fluorescence, catalysis, nanomaterials and biology.

  15. Some new aspects of dendrimer applications

    International Nuclear Information System (INIS)

    Flomenbom, Ophir; Amir, Roey J.; Shabat, Doron; Klafter, Joseph

    2005-01-01

    Dendrimers are characterized by special features that make them promising candidates for many applications. Here we focus on two such applications: dendrimers as light harvesting antennae, and dendrimers as molecular amplifiers, which may serve as novel platforms for drug delivery. Both applications stem from the unique structure of dendrimers. We present a theoretical framework based on the master equation within which we describe these applications. The quantities of interest are the first passage time (FPT), probability density function (PDF) and its moments. We examine how the FPT PDF and its characteristics depend on the geometric and energetic structures of the dendrimeric system. In particular, we investigate the dependence of the FPT properties on the number of generations (dendrimer size) and the system bias. We present analytical expressions for the FPT PDF for very efficient dendrimeric antennae and for dendrimeric amplifiers. For these cases the mean FPT scales linearly with the system length, and fluctuations around the mean FPT are negligible for large systems. Relationships of the FPT to light harvesting process for other types of system-bias are discussed

  16. Surface mediated assembly of small, metastable gold nanoclusters

    Science.gov (United States)

    Pettibone, John M.; Osborn, William A.; Rykaczewski, Konrad; Talin, A. Alec; Bonevich, John E.; Hudgens, Jeffrey W.; Allendorf, Mark D.

    2013-06-01

    The unique properties of metallic nanoclusters are attractive for numerous commercial and industrial applications but are generally less stable than nanocrystals. Thus, developing methodologies for stabilizing nanoclusters and retaining their enhanced functionality is of great interest. We report the assembly of PPh3-protected Au9 clusters from a heterogeneous mixture into films consisting of sub 3 nm nanocluster assemblies. The depositing nanoclusters are metastable in solution, but the resulting nanocluster assemblies are stabilized indefinitely in air or fresh solvent. The films exhibit distinct structure from Au nanoparticles observed by X-ray diffraction, and film dissolution data support the preservation of small nanoclusters. UV-Vis spectroscopy, electrospray ionization mass spectrometry, X-ray photoelectron spectroscopy and electron microscopy are used to elucidate information regarding the nanocluster formation and assembly mechanism. Preferential deposition of nanocluster assemblies can be achieved on multiple substrates, including polymer, Cr, Si, SiO2, SiNx, and metal-organic frameworks (MOFs). Unlike other vapor phase coating processes, nanocluster assembly on the MIL-68(In) MOF crystal is capable of preferentially coating the external surface and stabilizing the crystal structure in hydrothermal conditions, which should enhance their storage, separation and delivery capabilities.The unique properties of metallic nanoclusters are attractive for numerous commercial and industrial applications but are generally less stable than nanocrystals. Thus, developing methodologies for stabilizing nanoclusters and retaining their enhanced functionality is of great interest. We report the assembly of PPh3-protected Au9 clusters from a heterogeneous mixture into films consisting of sub 3 nm nanocluster assemblies. The depositing nanoclusters are metastable in solution, but the resulting nanocluster assemblies are stabilized indefinitely in air or fresh solvent. The

  17. Fluorescent properties of novel dendrimer dyes based on thiazole orange

    International Nuclear Information System (INIS)

    Fei Xuening; Gu Yingchun; Lan Yunquan; Shi Bin

    2011-01-01

    In this paper, polyamidoamine (PAMAM) dendrimers with active amino group of some generations (G=0.5-2) were prepared from commercial aminoacetaldehyde diethyl acetal by the divergent method. After that, thiazole orange (TO) with -COOH was incorporated with dendrimers of G=1 and 2 to afford novel dendrimer-TO dyes. The fluorescent properties studies showed that the fluorescent intensity of the same concentration of dendrimer-TO (G=2) was higher than that of the dendrimer-TO (G=1), and both of them were much stronger than free TO with -COOH. There was a fluorescent enhancement of the dendrimer dyes compared with free dye. The dendrimer dyes were of well-defined chemical structure,with little aggregation and self-quenching as well as good fluorescence properties of good stability, high intensity and sensitivity, which could be used in labeling cancer cells and further in diagnosis and detection of early-stage tumors. - Highlights: → A kind of dendrimer probe based on TO was designed and synthesized. → Dendrimers showed an obvious fluorescence enhancement compared to free dye. → Dendrimers labeled with BSA also showed fluorescence enhancement. → Dendrimers may be used in diagnosis and detection of early-stage tumors.

  18. Interaction between viologen-phosphorus dendrimers and α-synuclein

    International Nuclear Information System (INIS)

    Milowska, Katarzyna; Grochowina, Justyna; Katir, Nadia; El Kadib, Abdelkrim; Majoral, Jean-Pierre; Bryszewska, Maria; Gabryelak, Teresa

    2013-01-01

    In this study the interaction between viologen-phosphorus dendrimers and α-synuclein (ASN) was examined. Polycationic viologen-phosphorus dendrimers (two positive charges per viologen unit) are novel compounds with relatively unknown properties. The influence of these viologen dendrimers on ASN was tested using fluorimetric and circular dichroism methods. ASN contains four tyrosine residues; therefore, the influence of dendrimers on protein molecular conformation by measuring the changes in the ASN fluorescence in the presence of dendrimers was evaluated. The interaction of dendrimers with free L-tyrosine was also monitored. Results show that viologen-phosphorus dendrimers interact with ASN; they quenched the fluorescence of ASN as well as free tyrosine by dynamic and static ways. However, the quenching was not accompanied by modifications in the ASN secondary structure. - Highlights: ► Interaction between viologen-phosphorus dendrimers and α-synuclein (ASN) was investigated. ► Viologen-phosphorus dendrimers can quench the fluorescence of tyrosine in ASN. ► Dendrimers caused red-shift in maximum of fluorescence. ► Viologen-phosphorus dendrimers did not change the secondary structure of ASN.

  19. Brief Timelapse on Dendrimer Chemistry: Advances, Limitations, and Expectations

    KAUST Repository

    Ornelas, Catia

    2015-12-09

    © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Dendrimers are well-defined branched macromolecules that have been studied for a wide variety of applications. Possibility to add multiple functionalities in precise locations of the dendritic structure generated great expectations for the application of dendrimers in nanomedicine, however, the number of dendrimer-based formulations that advance to clinical studies has been somewhat deceiving. This is partially due to the nonreproducible pharmokinetic behavior observed for multifunctional dendrimers synthesized through the random-statistical approach that leads to mixtures of products. Therefore, it is crucial to develop multifunctional dendrimers with well-defined structures in order to increase the chances of meeting the clinical expectations placed on dendrimers. This talent article will give an overview of the dendrimer field, discussing the application of dendrimers in nanomedicine, light-harvesting systems, sensing and catalysis, with a critical analysis on the expectations, limitations, advances, current challenges and future directions. Dendrimer timelapse demonstrates constant evolution in dendrimer chemistry enabling their application in nanomedicine, protein mimic, catalysis, light harvesting systems, and sensing. Increasing the variety of functionalities in dendrimers located at precise sites of the dendritic backbone result in versatile multifunctional nanomaterials that in the future might approach the conceptual nanobots.

  20. Interaction between viologen-phosphorus dendrimers and {alpha}-synuclein

    Energy Technology Data Exchange (ETDEWEB)

    Milowska, Katarzyna, E-mail: milowska@biol.uni.lodz.pl [Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz (Poland); Grochowina, Justyna [Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz (Poland); Katir, Nadia [Laboratoire de Chimie de Coordination CNRS, 205 route de Narbonne, 31077 Toulouse (France); El Kadib, Abdelkrim [Institute of Nanomaterials and Nanotechnology (INANOTECH)-MAScIR (Moroccan Foundation for Advanced Science, Innovation and Research), ENSET, Avenue de I' Armee Royale, Madinat El Irfane, 10100 Rabat (Morocco); Majoral, Jean-Pierre [Laboratoire de Chimie de Coordination CNRS, 205 route de Narbonne, 31077 Toulouse (France); Bryszewska, Maria; Gabryelak, Teresa [Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz (Poland)

    2013-02-15

    In this study the interaction between viologen-phosphorus dendrimers and {alpha}-synuclein (ASN) was examined. Polycationic viologen-phosphorus dendrimers (two positive charges per viologen unit) are novel compounds with relatively unknown properties. The influence of these viologen dendrimers on ASN was tested using fluorimetric and circular dichroism methods. ASN contains four tyrosine residues; therefore, the influence of dendrimers on protein molecular conformation by measuring the changes in the ASN fluorescence in the presence of dendrimers was evaluated. The interaction of dendrimers with free L-tyrosine was also monitored. Results show that viologen-phosphorus dendrimers interact with ASN; they quenched the fluorescence of ASN as well as free tyrosine by dynamic and static ways. However, the quenching was not accompanied by modifications in the ASN secondary structure. - Highlights: Black-Right-Pointing-Pointer Interaction between viologen-phosphorus dendrimers and {alpha}-synuclein (ASN) was investigated. Black-Right-Pointing-Pointer Viologen-phosphorus dendrimers can quench the fluorescence of tyrosine in ASN. Black-Right-Pointing-Pointer Dendrimers caused red-shift in maximum of fluorescence. Black-Right-Pointing-Pointer Viologen-phosphorus dendrimers did not change the secondary structure of ASN.

  1. Pharmaceutical and biomedical potential of surface engineered dendrimers.

    Science.gov (United States)

    Satija, Jitendra; Gupta, Umesh; Jain, Narendra Kumar

    2007-01-01

    Dendrimers are hyperbranched, globular, monodisperse, nanometric polymeric architecture, having definite molecular weight, shape, and size (which make these an inimitable and optimum carrier molecule in pharmaceutical field). Dendritic architecture is having immense potential over the other carrier systems, particularly in the field of drug delivery because of their unique properties, such as structural uniformity, high purity, efficient membrane transport, high drug pay load, targeting potential, and good colloidal, biological, and shelf stability. Despite their enormous applicability in different areas, the inherent cytotoxicity, reticuloendothelial system (RES) uptake, drug leakage, immunogenicity, and hemolytic toxicity restricted their use in clinical applications, which is primarily associated with cationic charge present on the periphery due to amine groups. To overcome this toxic nature of dendrimers, some new types of nontoxic, biocompatible, and biodegradable dendrimers have been developed (e.g., polyester dendrimer, citric acid dendrimer, arginine dendrimer, carbohydrate dendrimers, etc.). The surface engineering of parent dendrimers is graceful and convenient strategy, which not only shields the positive charge to make this carrier more biomimetic but also improves the physicochemical and biological behavior of parent dendrimers. Thus, surface modification chemistry of parent dendrimers holds promise in pharmaceutical applications (such as solubilization, improved drug encapsulation, enhanced gene transfection, sustained and controlled drug release, intracellular targeting) and in the diagnostic field. Development of multifunctional dendrimer holds greater promise toward the biomedical applications because a number of targeting ligands determine specificity in the same manner as another type of group would secure stability in biological milieu and prolonged circulation, whereas others facilitate their transport through cell membranes. Therefore, as a

  2. Uses of Dendrimers for DNA Microarrays

    Directory of Open Access Journals (Sweden)

    Jean-Pierre Majoral

    2006-08-01

    Full Text Available Biosensors such as DNA microarrays and microchips are gaining an increasingimportance in medicinal, forensic, and environmental analyses. Such devices are based onthe detection of supramolecular interactions called hybridizations that occur betweencomplementary oligonucleotides, one linked to a solid surface (the probe, and the other oneto be analyzed (the target. This paper focuses on the improvements that hyperbranched andperfectly defined nanomolecules called dendrimers can provide to this methodology. Twomain uses of dendrimers for such purpose have been described up to now; either thedendrimer is used as linker between the solid surface and the probe oligonucleotide, or thedendrimer is used as a multilabeled entity linked to the target oligonucleotide. In the firstcase the dendrimer generally induces a higher loading of probes and an easier hybridization,due to moving away the solid phase. In the second case the high number of localized labels(generally fluorescent induces an increased sensitivity, allowing the detection of smallquantities of biological entities.

  3. Structural properties of dendrimer-colloid mixtures

    International Nuclear Information System (INIS)

    Lenz, Dominic A; Blaak, Ronald; Likos, Christos N

    2012-01-01

    We consider binary mixtures of colloidal particles and amphiphilic dendrimers of the second generation by means of Monte Carlo simulations. By using the effective interactions between monomer-resolved dendrimers and colloids, we compare the results of simulations of mixtures stemming from a full monomer-resolved description with the effective two-component description at different densities, composition ratios, colloid diameters and interaction strengths. Additionally, we map the two-component system onto an effective one-component model for the colloids in the presence of the dendrimers. Simulations based on the resulting depletion potentials allow us to extend the comparison to yet another level of coarse graining and to examine under which conditions this two-step approach is valid. In addition, a preliminary outlook into the phase behavior of this system is given. (paper)

  4. Theoretical Studies of Nanoclusters (Briefing Charts)

    Science.gov (United States)

    2015-07-23

    nanoclusters. However, scanning transmission electron microscopy ( STEM ) measures show cluster inversion occurred to produce MgyCux(!) a) copper atoms b...methane (née CLL -1) as a potential explosive ingredient: a theoretical study”, Propellants, Explosives, Pyrotechnics 38, 9-13 (2013). Jesus Paulo L

  5. Peptide-stabilized, fluorescent silver nanoclusters

    DEFF Research Database (Denmark)

    Gregersen, Simon; Vosch, Tom André Jos; Jensen, Knud Jørgen

    2016-01-01

    Few-atom silver nanoclusters (AgNCs) can exhibit strong fluorescence; however, they require ligands to prevent aggregation into larger nanoparticles. Fluorescent AgNCs in biopolymer scaffolds have so far mainly been synthesized in solution, and peptides have only found limited use compared to DNA...

  6. Nonlinear Optical and Time-Resolved Properties of Novel Organic Dendrimers and Dendrimer Metal

    National Research Council Canada - National Science Library

    Goodson, T., III

    2004-01-01

    .... We found in particular that gold-metal dendrimer nanocomposites have very strong optical limiting properties that may be useful for eye and sensor protection devices in the visible and near Infrared spectral regions...

  7. Dendrimers for Vaccine and Immunostimulatory Uses

    DEFF Research Database (Denmark)

    Heegaard, Peter M. H.; Boas, Ulrik; Sørensen, Nanna Skall

    2010-01-01

    for efficient immunostimulating compounds (adjuvants) that can increase the efficiency of vaccines, as dendrimers can provide molecularly defined multivalent scaffolds to produce highly defined conjugates with small molecule immunostimulators and/or antigens. The review gives an overview on the use...... of dendrimers as molecularly defined carriers/presenters of small antigens, including constructs that have built-in immunostimulatory (adjuvant) properties, and as stand-alone adjuvants that can be mixed with antigens to provide efficient vaccine formulations. These approaches allow the preparation...... of molecularly defined vaccines with highly predictable and specific properties and enable knowledge-based vaccine design substituting the traditional empirically based approaches for vaccine development and production....

  8. Structure of DNA-Functionalized Dendrimer Nanoparticles

    OpenAIRE

    Kumar, Mattaparthi Venkata Satish; Maiti, Prabal K

    2012-01-01

    Atomistic molecular dynamics simulations have been carried out to reveal the characteristic features of ethylenediamine (EDA) cored protonated poly amido amine (PAMAM) dendrimers of generation 3 (G3) and 4 (G4) that are functionalized with single stranded DNAs (ssDNAs). The four ssDNA strands that are attached via alkythiolate [-S (CH2)6-] linker molecule to the free amine groups on the surface of the PAMAM dendrimers observed to undergo a rapid conformational change during the 25 ns long sim...

  9. Radiation-sustained nanocluster metastability in oxide dispersion strengthened materials

    Science.gov (United States)

    Ribis, J.; Bordas, E.; Trocellier, P.; Serruys, Y.; de Carlan, Y.; Legris, A.

    2015-12-01

    ODS materials constitute a new promising class of structural materials for advanced fission and fusion energy application. These Fe-Cr based ferritic steels contain ultra-high density of dispersion-strengthening nanoclusters conferring excellent mechanical properties to the alloy. Hence, guarantee the nanocluster stability under irradiation remain a critical issue. Nanoclusters are non-equilibrium multicomponent compounds (YTiCrO) forming through a complex nucleation pathway during the elaboration process. In this paper, it is proposed to observe the response of these nanoclusters when the system is placed far from equilibrium by means of ion beam. The results indicate that the Y, Ti, O and Cr atoms self-organized so that nanoclusters coarsened but maintain their non-equilibrium chemical composition. It is discussed that the radiation-sustained nanocluster metastability emerges from cooperative effects: radiation-induced Ostwald ripening, permanent creation of vacancies in the clusters, and fast Cr diffusion mediated by interstitials.

  10. Radiation-sustained nanocluster metastability in oxide dispersion strengthened materials

    International Nuclear Information System (INIS)

    Ribis, J.; Bordas, E.; Trocellier, P.; Serruys, Y.; Carlan, Y. de; Legris, A.

    2015-01-01

    ODS materials constitute a new promising class of structural materials for advanced fission and fusion energy application. These Fe–Cr based ferritic steels contain ultra-high density of dispersion-strengthening nanoclusters conferring excellent mechanical properties to the alloy. Hence, guarantee the nanocluster stability under irradiation remain a critical issue. Nanoclusters are non-equilibrium multicomponent compounds (YTiCrO) forming through a complex nucleation pathway during the elaboration process. In this paper, it is proposed to observe the response of these nanoclusters when the system is placed far from equilibrium by means of ion beam. The results indicate that the Y, Ti, O and Cr atoms self-organized so that nanoclusters coarsened but maintain their non-equilibrium chemical composition. It is discussed that the radiation-sustained nanocluster metastability emerges from cooperative effects: radiation-induced Ostwald ripening, permanent creation of vacancies in the clusters, and fast Cr diffusion mediated by interstitials.

  11. Antibody-dendrimer conjugates: the number, not the size of the dendrimers, determines the immunoreactivity.

    Science.gov (United States)

    Wängler, C; Moldenhauer, G; Eisenhut, M; Haberkorn, U; Mier, W

    2008-04-01

    Radioimmunotherapy using antibodies with favorable tumor targeting properties and high binding affinity is increasingly applied in cancer therapy. The potential of this valuable cancer treatment modality could be further improved by increasing the specific activity of the labeled proteins. This can be done either by coupling a large number of chelators which leads to a decreased immunoreactivity or by conjugating a small number of multimeric chelators. In order to systematically investigate the influence of conjugations on immunoreactivity with respect to size and number of the conjugates, the anti-EGFR antibody hMAb425 was reacted with PAMAM dendrimers of different size containing up to 128 chelating agents per conjugation site. An improved dendrimer synthesis protocol was established to obtain compounds of high homogeneity suitable for the formation of defined protein conjugates. The quantitative derivatization of the PAMAM dendrimers with DOTA moieties and the characterization of the products by isotopic dilution titration using (111)In/(nat)In are shown. The DOTA-containing dendrimers were conjugated with high efficiency to hMAb425 by applying Sulfo-SMCC as cross-linking agent and a 10- to 25-fold excess of the thiol-containing dendrimers. The determination of the immunoreactivities of the antibody-dendrimer conjugates by FACS analysis revealed a median retained immunoreactivity of 62.3% for 1.7 derivatization sites per antibody molecule, 55.4% for 2.8, 27.9% for 5.3, and 17.1% for 10.0 derivatization sites per antibody but no significant differences in immunoreactivity for different dendrimer sizes. These results show that the dendrimer size does not influence the immunoreactivity of the derivatized antibody significantly over a wide molecular weight range, whereas the number of derivatization sites has a crucial effect.

  12. Fluorescent Pressure Response of Protein-Nanocluster Polymer Composites

    Science.gov (United States)

    2016-05-01

    composites as pressure sensitive indicators of brain damage. The PNC composites are made up of protein coated gold nanoclusters and a styrene-ethylene...enhancement of the BSA- protected gold nanoclusters and the corresponding conformational changes of protein, J Phys Chem C. 2013;117:639–647...public release; distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT This research focuses on the uses of polymer gold nanocluster (PNC

  13. Increase in Dye:Dendrimer Ratio Decreases Cellular Uptake of Neutral Dendrimers in RAW Cells.

    Science.gov (United States)

    Vaidyanathan, Sriram; Kaushik, Milan; Dougherty, Casey; Rattan, Rahul; Goonewardena, Sascha N; Banaszak Holl, Mark M; Monano, Janet; DiMaggio, Stassi

    2016-09-12

    Neutral generation 3 poly(amidoamine) dendrimers were labeled with Oregon Green 488 (G3-OG n ) to obtain materials with controlled fluorophore:dendrimer ratios (n = 1-2), a mixture containing mostly 3 dyes per dendrimer, a mixture containing primarily 4 or more dyes per dendrimer ( n = 4+), and a stochastic mixture ( n = 4 avg ). The UV absorbance of the dye conjugates increased linearly as n increased and the fluorescence emission decreased linearly as n increased. Cellular uptake was studied in RAW cells and HEK 293A cells as a function of the fluorophore:dendrimer ratio (n). The cellular uptake of G3-OG n ( n = 3, 4+, 4 avg ) into RAW cells was significantly lower than G3-OG n ( n = 1, 2). The uptake of G3-OG n ( n = 3, 4+, 4 avg ) into HEK 293A cells was not significantly different from G3-OG 1 . Thus, the fluorophore:dendrimer ratio was observed to change the extent of uptake in the macrophage uptake mechanism but not in the HEK 293A cell. This difference in endocytosis indicates the presence of a pathway in the macrophage that is sensitive to hydrophobicity of the particle.

  14. Practical computational toolkits for dendrimers and dendrons structure design

    Science.gov (United States)

    Martinho, Nuno; Silva, Liana C.; Florindo, Helena F.; Brocchini, Steve; Barata, Teresa; Zloh, Mire

    2017-09-01

    Dendrimers and dendrons offer an excellent platform for developing novel drug delivery systems and medicines. The rational design and further development of these repetitively branched systems are restricted by difficulties in scalable synthesis and structural determination, which can be overcome by judicious use of molecular modelling and molecular simulations. A major difficulty to utilise in silico studies to design dendrimers lies in the laborious generation of their structures. Current modelling tools utilise automated assembly of simpler dendrimers or the inefficient manual assembly of monomer precursors to generate more complicated dendrimer structures. Herein we describe two novel graphical user interface toolkits written in Python that provide an improved degree of automation for rapid assembly of dendrimers and generation of their 2D and 3D structures. Our first toolkit uses the RDkit library, SMILES nomenclature of monomers and SMARTS reaction nomenclature to generate SMILES and mol files of dendrimers without 3D coordinates. These files are used for simple graphical representations and storing their structures in databases. The second toolkit assembles complex topology dendrimers from monomers to construct 3D dendrimer structures to be used as starting points for simulation using existing and widely available software and force fields. Both tools were validated for ease-of-use to prototype dendrimer structure and the second toolkit was especially relevant for dendrimers of high complexity and size.

  15. Generation dependent cancer targeting potential of poly(propyleneimine) dendrimer.

    Science.gov (United States)

    Kesharwani, Prashant; Tekade, Rakesh K; Jain, Narendra K

    2014-07-01

    Dendrimer-mediated delivery of bioactive is a successful and widely explored concept. This paper desribes comparative data pertaining to generation dependent cancer targeting propensity of Poly(propyleneimine) (PPI) dendrimers. This debut report reportsthe drug targeting and antciancer potential of different dendrimer generations. PPI dendrimers of different generations (3.0G, 4.0G and 5.0G) were synthesized and loaded with Melphalan. Results from loading, hemolysis, hematologic, cytotoxicty and flow cytometry assay depicted that as the generation of dendrimer increased from fourth to fifth, the only parameter i.e. toxicty is increased exponentionally. However, others parameters, i.e. loading, sustained release behavior, and targeting efficacy increased negligibly. Kaplan-Meier survival curves clearly depicted comparable therapeutic potential of PPI4M with PPI5M. In vivo investigations in Balb/c mice again favored 4.0G PPI dendrimer to be preferable nanocarrier for anticancer drug delivery owing to analogous anticancer potential. The outcomes of the investigation evidently projects 4.0G PPI dendrimer over 3.0G and 5.0G dendrimer in respect of its drug delivery benefit as well as superior biocompatibility. Thus, much against the common belief, 4.0G PPI dendrimers may be considered to be optimum in respect of drug delivery precluding the use of much more toxic 5.0G PPI dendrimer, which offers no benefit over 4.0G. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Experimental measurements of U60 nanocluster stability in aqueous solution

    Science.gov (United States)

    Flynn, Shannon L.; Szymanowski, Jennifer E. S.; Gao, Yunyi; Liu, Tianbo; Burns, Peter C.; Fein, Jeremy B.

    2015-05-01

    In this study, the aqueous behavior of isolated U60 nanoclusters (K16Li25[UO2(O2)OH]60)-19 was studied under several pH conditions and nanocluster concentrations to determine if the nanoclusters exhibit solid phase buffering behavior or if they exhibit behavior more like aqueous complexes. U60 is a cage cluster consisting of 60 (UO2)(O2)2(OH)2 uranyl polyhedral which share OH and O2 groups with their neighboring uranyl polyhedral, resulting in negatively charged cage clusters whose charge is at least partially offset by K+ and Li+ in the aqueous phase. Batch experiments to monitor nanocluster stability were conducted for 16 days at pH 7.5, 8.0 and 8.5 at nanocluster suspension concentrations of 1.4, 2.8 and 6.0 g/L. The aqueous concentrations of U, Li, and K, determined after 10 kDa molecular weight filtration, achieved steady-state with the nanoclusters within 24 h. The steady-state aqueous U, Li, and K concentrations were independent of solution pH, however they increased with increasing nanocluster concentration, indicating that the nanoclusters do not buffer the aqueous activities as a bulk solid phase would, but exhibit behavior that is more characteristic of dissolved aqueous complexes. The ion activity product (I.A.P.) value was calculated using two approaches: (1) treating the nanoclusters as a solid phase with an activity of one, and (2) treating the nanoclusters as aqueous complexes with a non-unit activity equal to their concentration in solution. The I.A.P. values that were calculated with non-unit activity for the nanoclusters exhibited significantly less variation as a function of nanocluster concentration compared to the I.A.P. values calculated with a nanocluster activity of one. The results yield a calculated log dissociation constant for the U60 nanoclusters of 9.2 + 0.2/-0.3 (1σ). Our findings provide a better understanding of the thermodynamic stability and behavior of U60 nanoclusters in aqueous systems, and can be used to estimate the

  17. Nature of the effective interaction between dendrimers

    International Nuclear Information System (INIS)

    Mandal, Taraknath; Dasgupta, Chandan; Maiti, Prabal K.

    2014-01-01

    We have performed fully atomistic classical molecular dynamics simulations to calculate the effective interaction between two polyamidoamine dendrimers. Using the umbrella sampling technique, we have obtained the potential of mean force (PMF) between the dendrimers and investigated the effects of protonation level and dendrimer size on the PMF. Our results show that the interaction between the dendrimers can be tuned from purely repulsive to partly attractive by changing the protonation level. The PMF profiles are well-fitted by the sum of an exponential and a Gaussian function with the weight of the exponential function dominating over that of the Gaussian function. This observation is in disagreement with the results obtained in previous analytic [C. Likos, M. Schmidt, H. Löwen, M. Ballauff, D. Pötschke, and P. Lindner, Macromolecules 34, 2914 (2001)] and coarse-grained simulation [I. Götze, H. Harreis, and C. Likos, J. Chem. Phys. 120, 7761 (2004)] studies which predicted the effective interaction to be Gaussian

  18. Nature of the effective interaction between dendrimers

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, Taraknath, E-mail: taraknath@physics.iisc.ernet.in; Dasgupta, Chandan, E-mail: cdgupta@physics.iisc.ernet.in; Maiti, Prabal K., E-mail: maiti@physics.iisc.ernet.in [Centre for Condensed Matter Theory, Physics Department, Indian Institute of Science, Bangalore-560012 (India)

    2014-10-14

    We have performed fully atomistic classical molecular dynamics simulations to calculate the effective interaction between two polyamidoamine dendrimers. Using the umbrella sampling technique, we have obtained the potential of mean force (PMF) between the dendrimers and investigated the effects of protonation level and dendrimer size on the PMF. Our results show that the interaction between the dendrimers can be tuned from purely repulsive to partly attractive by changing the protonation level. The PMF profiles are well-fitted by the sum of an exponential and a Gaussian function with the weight of the exponential function dominating over that of the Gaussian function. This observation is in disagreement with the results obtained in previous analytic [C. Likos, M. Schmidt, H. Löwen, M. Ballauff, D. Pötschke, and P. Lindner, Macromolecules 34, 2914 (2001)] and coarse-grained simulation [I. Götze, H. Harreis, and C. Likos, J. Chem. Phys. 120, 7761 (2004)] studies which predicted the effective interaction to be Gaussian.

  19. Fluorescent Self-Assembled Polyphenylene Dendrimer Nanofibers

    NARCIS (Netherlands)

    Liu, Daojun; Feyter, Steven De; Cotlet, Mircea; Wiesler, Uwe-Martin; Weil, Tanja; Herrmann, Andreas; Müllen, Klaus; Schryver, Frans C. De

    2003-01-01

    A second-generation polyphenylene dendrimer 1 self-assembles into nanofibers on various substrates such as HOPG, silicon, glass, and mica from different solvents. The investigation with noncontact atomic force microscopy (NCAFM) and scanning electron microscopy (SEM) shows that the morphology of the

  20. Transport and Biodistribution of Dendrimers Across Human Fetal Membranes: Implications for Intravaginal Administration of Dendrimers

    Science.gov (United States)

    Menjoge, Anupa R.; Navath, Raghavendra S.; Asad, Abbas; Kannan, Sujatha; Kim, Chong Jai; Romero, Roberto; Kannan, Rangaramanujam M.

    2010-01-01

    Dendrimers are emerging as promising topical antimicrobial agents, and as targeted nanoscale drug delivery vehicles. Topical intravaginal antimicrobial agents are prescribed to treat the ascending genital infections in pregnant women. The fetal membranes separate the extra-amniotic space and fetus. The purpose of the study is to determine if the dendrimers can be selectively used for local intravaginal application to pregnant women without crossing the membranes into the fetus. In the present study, the transport and permeability of PAMAM (poly(amidoamine)) dendrimers, across human fetal membrane (using a side-by-side diffusion chamber), and its biodistribution (using immunofluorescence) are evaluated ex-vivo. Transport across human fetal membranes (from the maternal side) was evaluated using Fluorescein (FITC), an established transplacental marker (positive control, size~ 400 Da) and fluorophore-tagged G4-PAMAM dendrimers (~ 16 kDa). The fluorophore-tagged G4-PAMAM dendrimers were synthesized and characterized using 1H NMR, MALDI TOF-MS and HPLC analysis. Transfer was measured across the intact fetal membrane (chorioamnion), and the separated chorion and amnion layers. Over a five hour period, the dendrimer transport across all the three membranes was less than transport of FITC was relatively fast with as much as 49% transport across the amnion. The permeability of FITC (7.9 × 10-7 cm2/s) through the chorioamnion was 7-fold higher than that of the dendrimer (5.8 × 10-8 cm2/s). The biodistribution showed that the dendrimers were largely present in interstitial spaces in the decidual stromal cells and the chorionic trophoblast cells (in 2.5 to 4 h) and surprisingly, to a smaller extent internalized in nuclei of trophoblast cells and nuclei and cytoplasm of stromal cells. Passive diffusion and paracellular transport appear to be the major route for dendrimer transport. The overall findings further suggest that entry of drugs conjugated to dendrimers would be

  1. A polyamidoamine dendrimer-streptavidin supramolecular architecture for biosensor development.

    Science.gov (United States)

    Soda, N; Arotiba, O A

    2017-12-01

    A novel polyamidoamine dendrimer-streptavidin supramolecular architecture suitable as a versatile platform for biosensor development is reported. The dendrimer was electrodeposited on a glassy carbon electrode via cyclic voltammetry. The dendrimer electrode was further modified with streptavidin by electrostatic attraction upon drop coating. The platform i.e. the dendrimer-streptavidin modified electrode was electrochemically interrogated in phosphate buffer, ferrocyanide and H 2 O 2 . The dendrimer-streptavidin platform was used in the preparation of a simple DNA biosensor as a proof of concept. The supramolecular architecture of dendrimer-streptavidin was stable, electroactive and thus lends itself as a versatile immobilisation layer for any biotinylated bioreceptors in biosensor development. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. The structure of carbosilane dendrimers of higher generations

    International Nuclear Information System (INIS)

    Rogachev, A.V.; Kuklin, A.I.; Chernyj, A.Yu.; Ozerin, A.N.; Muzafarov, A.M.; Tatarinova, E.A.; Gordelij, V.I.

    2008-01-01

    Using small-angle neutron scattering method, we investigate the structure of carbosilane dendrimers of the ninth generation with a four-function core and butyl terminal groups. It is shown that the dendrimers in question are monodispersive objects having anisometric form. The values of the partial volume and the mean scattering length density are determined with the contrast variation method. The studied dendrimers exhibit the same size and distribution of the scattering length density. It is found that about 20% of the interior dendrimer volume is permeable to a solvent. Performing a Monte Carlo simulation, we reconstruct the spatial distribution of scattering length density over the dendrimers and reveal changing of the excluded volume for different contrasts. The spatial structure features of carbosilane dendrimers of higher generations are discussed

  3. Charge transport in highly efficient iridium cored electrophosphorescent dendrimers

    Science.gov (United States)

    Markham, Jonathan P. J.; Samuel, Ifor D. W.; Lo, Shih-Chun; Burn, Paul L.; Weiter, Martin; Bässler, Heinz

    2004-01-01

    Electrophosphorescent dendrimers are promising materials for highly efficient light-emitting diodes. They consist of a phosphorescent core onto which dendritic groups are attached. Here, we present an investigation into the optical and electronic properties of highly efficient phosphorescent dendrimers. The effect of dendrimer structure on charge transport and optical properties is studied using temperature-dependent charge-generation-layer time-of-flight measurements and current voltage (I-V) analysis. A model is used to explain trends seen in the I-V characteristics. We demonstrate that fine tuning the mobility by chemical structure is possible in these dendrimers and show that this can lead to highly efficient bilayer dendrimer light-emitting diodes with neat emissive layers. Power efficiencies of 20 lm/W were measured for devices containing a second-generation (G2) Ir(ppy)3 dendrimer with a 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene electron transport layer.

  4. A blue-emitting CdS/dendrimer nanocomposite

    International Nuclear Information System (INIS)

    Sooklal, K.; Murphy, C.J.; Hanus, L.H.; Ploehn, H.J.

    1998-01-01

    CdS/dendrimer nanocomposites that emit blue light are formed by the arrested precipitation of nanometer-scale CdS quantum dots in the presence of starburst (poly(aminoamine)) dendrimers as the stabilizing host. The authors report a strong photoluminescence with emission maxima at about 450 nm. The optoelectronic properties of the CdS clusters are shown to be sensitive to synthesis conditions, including dendrimer type, solvent type, and the concentration of dendrimer and other solutes. Thin films of these materials prepared by solution casting retain the optoelectronic properties of the parent solutions. (orig.)

  5. Optical absorption and energy transfer processes in dendrimers

    International Nuclear Information System (INIS)

    Reineker, P.; Engelmann, A.; Yudson, V.I.

    2004-01-01

    For dendrimers of various sizes the energy transfer and the optical absorption is investigated theoretically. The molecular subunits of a dendrimer are modeled as two-level systems. The electronic interaction between them is described via transfer integrals and the influence of vibrational degrees of freedom is taken into account in a first approach using a stochastic model. We discuss the time dependence of the energy transport and show that rim states of the dendrimer dominate the absorption spectra, that in general the electronic excitation energy is concentrated on peripheric molecules, and that the energetically lowest absorption peak is redshifted with increasing dendrimer size due to delocalization of the electronic excitation

  6. Interfacial electron transfer dynamics of photosensitized zinc oxide nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Murakoshi, Kei; Yanagida, Shozo [Osaka Univ. (Japan). Graduate School of Engineering; Capel, M. [Brookhaven National Lab., Upton, NY (United States)] [and others

    1997-06-01

    The authors have prepared and characterized photosensitized zinc oxide (ZnO) nanoclusters, dispersed in methanol, using carboxylated coumarin dyes for surface adsorption. Femtosecond time-resolved emission spectroscopy allows the authors to measure the photo-induced charge carrier injection rate constant from the adsorbed photosensitizer to the n-type semiconductor nanocluster. These results are compared with other photosensitized semiconductors.

  7. Synthesis and characterization of mixed ligand chiral nanoclusters

    KAUST Repository

    Guven, Zekiye P.

    2016-06-22

    Chiral mixed ligand silver nanoclusters were synthesized in the presence of a chiral and an achiral ligand. While the chiral ligand led mostly to the formation of nanoparticles, the presence of the achiral ligand drastically increased the yield of nanoclusters with enhanced chiral properties. © 2016 The Royal Society of Chemistry.

  8. Synthesis and characterization of mixed ligand chiral nanoclusters

    KAUST Repository

    Guven, Zekiye P.; Ustbas, Burcin; Harkness, Kellen M.; Coskun, Hikmet; Joshi, Chakra Prasad; Besong, Tabot M.D.; Stellacci, Francesco; Bakr, Osman; Akbulut, Ozge

    2016-01-01

    Chiral mixed ligand silver nanoclusters were synthesized in the presence of a chiral and an achiral ligand. While the chiral ligand led mostly to the formation of nanoparticles, the presence of the achiral ligand drastically increased the yield of nanoclusters with enhanced chiral properties. © 2016 The Royal Society of Chemistry.

  9. Molecular interactions in particular Van der Waals nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Jungclas, Hartmut; Schmidt, Lothar [Marburg Univ. (Germany). Chemistry Dept.; Komarov, Viacheslav V.; Popova, Anna M. [Marburg Univ. (Germany). Chemistry Dept.; Lomonosov Moscow State Univ. (Russian Federation). Skobeltzin Inst. of Nuclear Physics

    2017-04-01

    A method is presented to analyse the interaction energies in a nanocluster, which is consisting of three neutral molecules bound by non-covalent long range Van der Waals forces. One of the molecules (M{sub 0}) in the nanocluster has a permanent dipole moment, whereas the two other molecules (M{sub 1} and M{sub 2}) are non-polar. Analytical expressions are obtained for the numerical calculation of the dispersion and induction energies of the molecules in the considered nanocluster. The repulsive forces at short intermolecular distances are taken into account by introduction of damping functions. Dispersion and induction energies are calculated for a nanocluster with a definite geometry, in which the polar molecule M{sub 0} is a linear hydrocarbon molecule C{sub 5}H{sub 10} and M{sub 1} and M{sub 2} are pyrene molecules. The calculations are done for fixed distances between the two pyrene molecules. The results show that the induction energies in the considered three-molecular nanocluster are comparable with the dispersion energies. Furthermore, the sum of induction energies in the substructure (M{sub 0}, M{sub 1}) of the considered nanocluster is much higher than the sum of induction energies in a two-molecular nanocluster with similar molecules (M{sub 0}, M{sub 1}) because of the absence of an electrostatic field in the latter case. This effect can be explained by the essential intermolecular induction in the three-molecular nanocluster.

  10. Comparison of the internalization of targeted dendrimers and dendrimer-entrapped gold nanoparticles into cancer cells.

    Science.gov (United States)

    Shi, Xiangyang; Wang, Su He; Lee, Inhan; Shen, Mingwu; Baker, James R

    2009-11-01

    Dendrimer-based nanotechnology significantly advances the area of targeted cancer imaging and therapy. Herein, we compared the difference of surface acetylated fluorescein isocyanate (FI) and folic acid (FA) modified generation 5 (G5) poly(amidoamine) dendrimers (G5.NHAc-FI-FA), and dendrimer-entrapped gold nanoparticles with similar modifications ([(Au(0))(51.2)-G5.NHAc-FI-FA]) in terms of their specific internalization to FA receptor (FAR)-overexpressing cancer cells. Confocal microscopic studies show that both G5.NHAc-FI-FA and [(Au(0))(51.2-)G5.NHAc-FI-FA] exhibit similar internalization kinetics regardless of the existence of Au nanoparticles (NPs). Molecular dynamics simulation of the two different nanostructures reveals that the surface area and the FA moiety distribution from the center of the geometry are slightly different. This slight difference may not be recognized by the FARs on the cell membrane, consequently leading to similar internalization kinetics. This study underlines the fact that metal or inorganic NPs entrapped within dendrimers interact with cells in a similar way to that of dendrimers lacking host NPs. 2009 Wiley Periodicals, Inc.

  11. Liquid Crystalline Dendrimers. 1. Synthesis of Five Generations of Carbosilane Liquid Crystalline Dendrimers with Terminal Cyanobiphenyl Groups

    National Research Council Canada - National Science Library

    Shibaev, V

    1998-01-01

    Using the controlled layer by layer experimental technique via reiterative sequence of chemical reactions carbosilane LC dendrimers with terminal cyanobiphenyl mesogenic groups of generations 1 - 5 were synthesized...

  12. Monoclonal antibody-dendrimer conjugates enable radiolabeling of antibody with markedly high specific activity with minimal loss of immunoreactivity

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, H.; Togashi, K. [Kyoto Univ. (Japan). School of Medicine; Sato, N.; Saga, T.; Nakamoto, Y.; Ishimori, T.; Konishi, J. [Dept. of Nuclear Medicine and Medical Imaging, Kyoto Univ. Graduate School of Medicine, Kyoto (Japan); Toyama, S. [Inst. for Virus Research, Kyoto Univ., Kyoto (Japan); Brechbiel, M.W. [Chemistry Section, Radiation Oncology Branch, National Cancer Inst., National Inst. of Health, Bethesda, Md. (United States)

    2000-09-01

    indium and gadolinium, and did so with minimal loss of immunoreactivity. When we achieved radiolabeling with maximum specific activity, Gd conjugate showed better biodistribution than In conjugate. (orig.)

  13. Host-guest chemistry of dendrimer-drug complexes. 6. Fully acetylated dendrimers as biocompatible drug vehicles using dexamethasone 21-phosphate as a model drug.

    Science.gov (United States)

    Yang, Kun; Weng, Liang; Cheng, Yiyun; Zhang, Hongfeng; Zhang, Jiahai; Wu, Qinglin; Xu, Tongwen

    2011-03-17

    Fully acetylated poly(amidoamine) (PAMAM) dendrimer was proposed as a biocompatible drug vehicle using dexamethasone 21-phosphate (Dp21) as a model drug. NMR techniques including (1)H NMR and 2D NOE NMR were used to characterize the host-guest chemistry of acetylated dendrimer/Dp21 and cationic dendrimer/Dp21 complexes. The pH-dependent micellization, complexation, and inclusion behaviors of Dp21 were observed in the presence of acetylated and cationic PAMAM dendrimers. Acetylated dendrimer only encapsulates Dp21 at acidic conditions, while cationic dendrimer can host Dp21 at both acidic and neutral conditions. The orientation of Dp21 molecules in the dendrimer cavities depends on the quaternization degree of tertiary amine groups of dendrimer and the protonation ratio of phosphate group of Dp21. A distinctive pH-dependent release behavior of Dp21 from the acetylated and nonacetylated dendritic matrix was observed: Dp21 exhibits a much slower release rate from acetylated dendrimer at lower pH conditions and a much faster release rate from nonacetylated dendrimer with decreasing pH values. Cytotoxicity studies further confirmed the biocompatibility of acetylated dendrimers, which are much safer in the delivery of therapeutics for the treatment of various diseases than nonacetylated dendrimers. The dendrimer-drug binding and release mechanisms provide a new insight for the design and optimization of biocompatible dendrimer-based drug delivery systems. © 2011 American Chemical Society

  14. Tailoring the dendrimer core for efficient gene delivery.

    Science.gov (United States)

    Hu, Jingjing; Hu, Ke; Cheng, Yiyun

    2016-04-15

    Dendrimers have been widely used as non-viral gene vectors due to well-defined chemical structures, high density of cationic charges and ease of surface modification. Although a large number of studies have reported the important roles of dendrimer architecture, component, generation and surface functionality in gene delivery, the effect of dendrimer core on this issue still remains unclear. Recent literatures suggest that a slight alternation in dendrimer core has a profound effect in the transfection efficacy and biocompatibility. In this review, we will discuss the transfection mechanism of dendrimers with different types of cores in respect of flexibility, hydrophobicity and functionality. We hope to open a possibility of designing efficient dendrimers for gene delivery by choosing a proper dendrimer core. As a branch of researches on dendrimers and dendritic polymers, the design of biocompatible and high efficient polymeric gene carriers has attracted increasing attentions during these years. Although the effect of dendrimer generation, species, architecture and surface functionality on gene delivery have been widely reported, the effect of dendrimer core on this issue still remains unclear. Recent literatures suggest that a minor variation on the dendrimer core has a profound effect in the transfection efficacy and biocompatibility. This critical review summarized the dendrimers with different types of cores and discussed the transfection mechanism with particular focus on the flexibility, hydrophobicity, and functionality. It is hoped to provide a new insight to design efficient and safe dendrimer-based gene vectors by choosing a proper core. To the best of our knowledge, this is the first review on the effect of dendrimer core on gene delivery. The findings obtained in this filed are of central importance in the design of efficient polymeric gene vectors. This article will appeal a wide readership such as physical chemist, dendrimer chemist, biological

  15. Thin film properties of triphenylamine-cored dendrimers: A molecular approach to control aggregation

    Energy Technology Data Exchange (ETDEWEB)

    Vamvounis, George, E-mail: g.vamvounis@uq.edu.au; Pivrikas, Almantas; Shaw, Paul E.; Burn, Paul L.

    2013-12-02

    The solid-state photophysical and charge transport properties of two first-generation dendrimers are presented. The dendrimers are comprised of a triphenylamine core, dendrons containing a phenyl branching unit with thiophene (Dendrimer 1) or bithiophene (Dendrimer 2) moieties, and dodecyl surface groups. For Dendrimer 1, the excited state is located within the center of the dendrimer giving rise to a moderate solid-state photoluminescence quantum yield (Φ{sub pl}) (0.13) and significant charge trapping, with both observations due to the degree of overlap of the main electroactive chromophores on adjacent dendrimers. For Dendrimer 2, the excited state is located within the dendron and in the solid-state this leads to a strongly red-shifted and weakened emission (Φ{sub pl} ∼ 0.02) due to strong intermolecular chromophore interactions. For films of Dendrimer 2 the charge mobility was higher than Dendrimer 1 but was still limited by a low density of strongly interacting electroactive chromophores. The pronounced difference between the solid-state properties of the two dendrimers is simply engineered by the addition of an extra thiophene in each of the dendrons. - Highlights: • Photophysical and charge-transport properties of two dendrimers are investigated. • Excited-state is on the center for Dendrimer 1 and on the dendron for Dendrimer 2. • Film quantum yield of luminescence is higher for Dendrimer 1. • Dendrimer 1 displays greater charge trapping at high fields.

  16. Quaternized Polyamidoamine Dendrimers as Novel Gene Delivery System: Relationship between Degree of Quaternization and Their Influences

    International Nuclear Information System (INIS)

    Lee, Jung Hoon; Lim, Yong beom; Choi, Joon Sig; Choi, Myung Un; Yang, Chul Hak; Park, Jong Sang

    2003-01-01

    Quaternary ammonium groups were introduced to Starburst polyamidoamine (PAMAM) dendrimers for a gene carrier. These quaternary dendritic carriers exhibited reduced cytotoxicity on 293T cells compared to parent dendrimers examined and their transfection efficiency were similar with parent dendrimers. Quaternization could be a promising tool to improve properties of dendrimers as a gene delivery carrier

  17. Thin film properties of triphenylamine-cored dendrimers: A molecular approach to control aggregation

    International Nuclear Information System (INIS)

    Vamvounis, George; Pivrikas, Almantas; Shaw, Paul E.; Burn, Paul L.

    2013-01-01

    The solid-state photophysical and charge transport properties of two first-generation dendrimers are presented. The dendrimers are comprised of a triphenylamine core, dendrons containing a phenyl branching unit with thiophene (Dendrimer 1) or bithiophene (Dendrimer 2) moieties, and dodecyl surface groups. For Dendrimer 1, the excited state is located within the center of the dendrimer giving rise to a moderate solid-state photoluminescence quantum yield (Φ pl ) (0.13) and significant charge trapping, with both observations due to the degree of overlap of the main electroactive chromophores on adjacent dendrimers. For Dendrimer 2, the excited state is located within the dendron and in the solid-state this leads to a strongly red-shifted and weakened emission (Φ pl ∼ 0.02) due to strong intermolecular chromophore interactions. For films of Dendrimer 2 the charge mobility was higher than Dendrimer 1 but was still limited by a low density of strongly interacting electroactive chromophores. The pronounced difference between the solid-state properties of the two dendrimers is simply engineered by the addition of an extra thiophene in each of the dendrons. - Highlights: • Photophysical and charge-transport properties of two dendrimers are investigated. • Excited-state is on the center for Dendrimer 1 and on the dendron for Dendrimer 2. • Film quantum yield of luminescence is higher for Dendrimer 1. • Dendrimer 1 displays greater charge trapping at high fields

  18. Dendrimer effects on peptide and protein fibrillation

    DEFF Research Database (Denmark)

    Heegaard, Peter M. H.; Boas, Ulrik; Otzen, Daniel E.

    2007-01-01

    involved in a range of serious and irreversibly progressive pathological conditions (protein-misfolding diseases). Interesting as this may be, the interaction of dendrimers with such generic peptidic aggregates also offers a new perspective on the molecular mechanisms governing assembly and disassembly......, they offer numerous possibilities for interactions with and responses to biological macromolecules and biostructures including cell membranes and proteins. By way of their multiple functional surface groups, they allow the design of surfaces carrying a multitude of biological motifs and/or charges giving...... rise to quite significant biological and physico-chemical effects. Here we describe the surprising ability of dendrimers to interact with and perturb polypeptide conformations, particularly efficiently towards amyloid structures; that is, the structures of highly insoluble polypeptide aggregates...

  19. Fluorescent quantum dot hydrophilization with PAMAM dendrimer

    Science.gov (United States)

    Potapkin, Dmitry V.; Geißler, Daniel; Resch-Genger, Ute; Goryacheva, Irina Yu.

    2016-05-01

    Polyamidoamine (PAMAM) dendrimers were used to produce CdSe core/multi-shell fluorescent quantum dots (QDs) which are colloidally stable in aqueous solutions. The size, charge, and optical properties of QDs functionalized with the 4th (G4) and 5th (G5) generation of PAMAM were compared with amphiphilic polymer-covered QDs and used as criteria for the evaluation of the suitability of both water solubilization methods. As revealed by dynamic and electrophoretic light scattering (DLS and ELS), the hydrodynamic sizes of the QDs varied from 30 to 65 nm depending on QD type and dendrimer generation, with all QDs displaying highly positive surface charges, i.e., zeta potentials of around +50 mV in water. PAMAM functionalization yielded stable core/multi-shell QDs with photoluminescence quantum yields ( Φ) of up to 45 %. These dendrimer-covered QDs showed a smaller decrease in their Φ upon phase transfer compared with QDs made water soluble via encapsulation with amphiphilic brush polymer bearing polyoxyethylene/polyoxypropylene chains.

  20. Dendrimer sensors probed with neutron reflectometry

    International Nuclear Information System (INIS)

    Cavaye, Hamish; Smith, Arthur R.G.; Burn, Paul L.; Lo, Shih-Chun; Meredith, Paul; Gentle, Ian R.; James, Michael; Nelson, Andrew

    2009-01-01

    Full text: Oxidative photoluminescence (PL) quenching utilizing conjugated polymers as the sensing has proved to be one of the best of many methods for sensing explosive analytes.[1] However are a number of issues that can make polymers difficult to work with, including complex morphologies reproducibility of syntheses, and the need to include elaborate structures to reduce the packing of the polymer chains. Dendrimers, consisting of a core, dendrons, and surface groups, address these issues by being monodisperse and modular in their design. Determining how analytes are sequestered into thin films is important for solid-state sensors. We show that thin (230 ± 30 A ) and thick (750 ± 50 A) films of a first-generation dendrimer comrised of 2-ethylhexyloxy surface groups, biphenyl-based dendrons, and a 9,9,9',9'-tetra-n-propyl-2,2'-bifluorene core, can rapidly and reversibly detect p-nitrotoll oxidative luminescence quenching. For both the thin and thick films the PL is quenched by just 4 s . Combined PL and neutron reflectometry measurements on pristine and analyte-satura showed that during the adsorption process the films swelled, being on average 4% thicker for thin and thick dendrimer films. At the same time the PL was completely quenched. On removal of the analyte the films returned to their original thickness and scattering length density, and the restored, showing that the sensing process was fully reversible.

  1. Fluorescent quantum dot hydrophilization with PAMAM dendrimer

    Energy Technology Data Exchange (ETDEWEB)

    Potapkin, Dmitry V., E-mail: potapkindv@gmail.com [Saratov State University, Department of General and Inorganic Chemistry, Chemistry Institute (Russian Federation); Geißler, Daniel, E-mail: daniel.geissler@bam.de; Resch-Genger, Ute, E-mail: ute.resch@bam.de [BAM - Federal Institute for Materials Research and Testing (Germany); Goryacheva, Irina Yu., E-mail: goryachevaiy@mail.ru [Saratov State University, Department of General and Inorganic Chemistry, Chemistry Institute (Russian Federation)

    2016-05-15

    Polyamidoamine (PAMAM) dendrimers were used to produce CdSe core/multi-shell fluorescent quantum dots (QDs) which are colloidally stable in aqueous solutions. The size, charge, and optical properties of QDs functionalized with the 4th (G4) and 5th (G5) generation of PAMAM were compared with amphiphilic polymer-covered QDs and used as criteria for the evaluation of the suitability of both water solubilization methods. As revealed by dynamic and electrophoretic light scattering (DLS and ELS), the hydrodynamic sizes of the QDs varied from 30 to 65 nm depending on QD type and dendrimer generation, with all QDs displaying highly positive surface charges, i.e., zeta potentials of around +50 mV in water. PAMAM functionalization yielded stable core/multi-shell QDs with photoluminescence quantum yields (Φ) of up to 45 %. These dendrimer-covered QDs showed a smaller decrease in their Φ upon phase transfer compared with QDs made water soluble via encapsulation with amphiphilic brush polymer bearing polyoxyethylene/polyoxypropylene chains.

  2. Combining metadynamics simulation and experiments to characterize dendrimers in solution

    NARCIS (Netherlands)

    Pavan, G.M.; Barducci, A.; Albertazzi, L.; Parrinello, M.

    2013-01-01

    We report a combined theoretical-experimental approach to characterize dendrimers and Polyethylene Glycol (PEG)-dendrimer hybrids in solution. Well-tempered metadynamics simulation allows for an exhaustive sampling of the conformational fluctuations in solution. In contrast to classical molecular

  3. Composition consisting of a dendrimer and an active substance

    NARCIS (Netherlands)

    1995-01-01

    The invention relates to a composition consisting of a dendrimer provided with blocking agents and an active substance occluded in the dendrimer. According to the invention a blocking agent is a compound which is sterically of sufficient size, which readily enters into a chemical bond with the

  4. Molecular dynamic analysis of the structure of dendrimers

    Energy Technology Data Exchange (ETDEWEB)

    Canetta, E.; Maino, G. E-mail: maino@bologna.enea.it

    2004-01-01

    We present main results of molecular dynamics simulations that we have carried out in order to investigate structural properties of polyamidoamine (PAMAM) dendrimers. Obtained data confirm the PAMAM dendrimer structure proposed by experiments, performed by means of X-ray scattering (SAXS) and quasi-elastic light scattering (QELS) techniques.

  5. Molecular dynamic analysis of the structure of dendrimers

    International Nuclear Information System (INIS)

    Canetta, E.; Maino, G.

    2004-01-01

    We present main results of molecular dynamics simulations that we have carried out in order to investigate structural properties of polyamidoamine (PAMAM) dendrimers. Obtained data confirm the PAMAM dendrimer structure proposed by experiments, performed by means of X-ray scattering (SAXS) and quasi-elastic light scattering (QELS) techniques

  6. Synthesis of PAMAM dendrimers and investigations of their interaction with POPC/POPG lipids

    OpenAIRE

    Gneid, Hassan

    2014-01-01

    PAMAM dendrimers are three dimensional organic polymers synthesised by repetitive steps to achieve a controlled size and shape with a choice of surface functional groups. One of the potential applications of dendrimers is for drug/gene delivery which requires the dendrimer to interact with the cellular membranes. This study is designed to probe the interactions between PAMAM dendrimers and lipid bilayers. To investigate these interactions PAMAM dendrimers up to the third generation were synth...

  7. Dendrimer D5 is a vector for peptide transport to brain cells.

    Science.gov (United States)

    Sarantseva, S V; Bolshakova, O I; Timoshenko, S I; Kolobov, A A; Schwarzman, A L

    2011-02-01

    Dendrimers are a new class of nonviral vectors for gene or drug transport. Dendrimer capacity to penetrate through the blood-brain barrier remaines little studied. Biotinylated polylysine dendrimer D5, similarly to human growth hormone biotinylated fragment covalently bound to D5 dendrimer, penetrates through the blood-brain barrier and accumulates in Drosophila brain after injection into the abdomen. Hence, D5 dendrimer can serve as a vector for peptide transport to brain cells.

  8. Dendrimers as Potential Therapeutic Tools in HIV Inhibition

    Directory of Open Access Journals (Sweden)

    Xiangbo Li

    2013-07-01

    Full Text Available The present treatments for HIV transfection include chemical agents and gene therapies. Although many chemical drugs, peptides and genes have been developed for HIV inhibition, a variety of non-ignorable drawbacks limited the efficiency of these materials. In this review, we discuss the application of dendrimers as both therapeutic agents and non-viral vectors of chemical agents and genes for HIV treatment. On the one hand, dendrimers with functional end groups combine with the gp120 of HIV and CD4 molecule of host cell to suppress the attachment of HIV to the host cell. Some of the dendrimers are capable of intruding into the cell and interfere with the later stages of HIV replication as well. On the other hand, dendrimers are also able to transfer chemical drugs and genes into the host cells, which conspicuously increase the anti-HIV activity of these materials. Dendrimers as therapeutic tools provide a potential treatment for HIV infection.

  9. Facile Preparation of Hybrid Zinc Porphyrin Dendrimer Using Coordination Complex

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Go-Eun; Shin, Eun Ju [Sunchon National University, Suncheon (Korea, Republic of)

    2016-03-15

    Porphyrins and metalloporphyrins have been investigated extensively due to their important role in natural photosynthesis, strong absorption in visible region, good light-harvesting properties, unique photophysical and electrochemical properties, and the development of simple synthetic routes for various derivatives. Dendrimers have globular structure with branches of repeating units and wide diversity of the architecture because their size, shape, and functionalities can be tailored. Numerous dendrimers have been designed and synthesized for various applications ranging from catalyst to drug delivery. Both pyridine dendrons Py-PD and Py-AD were successfully coordinated at axial position on central zinc metal cation in zinc porphyrin dendrimers ZnP-AD, ZnP-AD2, or ZnP-AD4. Therefore, it was proven that the formation of axial coordination complex between metal-centered dendrimer and ligand-containing dendron provides another facile method for the preparation of new hybrid dendrimer.

  10. Relaxation path of metastable nanoclusters in oxide dispersion strengthened materials

    Energy Technology Data Exchange (ETDEWEB)

    Ribis, J., E-mail: joel.ribis@cea.fr [DEN-Service de Recherches Métallurgiques Appliquées, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette (France); Thual, M.A. [LLB, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191, Gif-sur-Yvette (France); Guilbert, T.; Carlan, Y. de [DEN-Service de Recherches Métallurgiques Appliquées, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette (France); Legris, A. [UMET, CNRS/UMR 8207, Bât. C6, Univ. Lille 1, 59655 Villeneuve d’Ascq (France)

    2017-02-15

    ODS steels are a promising class of structural materials for sodium cooled fast reactor application. The ultra-high density of the strengthening nanoclusters dispersed within the ferritic matrix is responsible of the excellent creep properties of the alloy. Fine characterization of the nanoclusters has been conducted on a Fe-14Cr-0.3Ti-0.3Y{sub 2}O{sub 3} ODS material using High Resolution and Energy Filtered Transmission Electron Microscopy. The nanoclusters exhibit a cubic symmetry possibly identified as f.c.c and display a non-equilibrium YTiCrO chemical composition thought to be stabilized by a vacancy supersaturation. These nanoclusters undergo relaxation towards the Y{sub 2}Ti{sub 2}O{sub 7}-like state as they grow. A Cr shell is observed around the relaxed nano-oxides, this size-dependent shell may form after the release of Cr by the particles. The relaxation energy barrier appears to be higher for the smaller particles probably owing to a volume/surface ratio effect in reason to the full coherency of the nanoclusters. - Highlights: • The nanoclusters display a f.c.c. cubic symmetry and a non-equilibrium YTiCrO chemical composition. • During thermal annealing the coherent nanocluster transform into semi-coherent pyrochlore particles. • A Cr ring is observed around the relaxed pyrochlore type particles.

  11. Developmental toxicity of low generation PAMAM dendrimers in zebrafish

    International Nuclear Information System (INIS)

    King Heiden, Tisha C.; Dengler, Emelyne; Kao, Weiyuan John; Heideman, Warren; Peterson, Richard E.

    2007-01-01

    Biological molecules and intracellular structures operate at the nanoscale; therefore, development of nanomedicines shows great promise for the treatment of disease by using targeted drug delivery and gene therapies. PAMAM dendrimers, which are highly branched polymers with low polydispersity and high functionality, provide an ideal architecture for construction of effective drug carriers, gene transfer devices and imaging of biological systems. For example, dendrimers bioconjugated with selective ligands such as Arg-Gly-Asp (RGD) would theoretically target cells that contain integrin receptors and show potential for use as drug delivery devices. While RGD-conjugated dendrimers are generally considered not to be cytotoxic, there currently exists little information on the risks that such materials pose to human health. In an effort to compliment and extend the knowledge gleaned from cell culture assays, we have used the zebrafish embryo as a rapid, medium throughput, cost-effective whole-animal model to provide a more comprehensive and predictive developmental toxicity screen for nanomaterials such as PAMAM dendrimers. Using the zebrafish embryo, we have assessed the developmental toxicity of low generation (G3.5 and G4) PAMAM dendrimers, as well as RGD-conjugated forms for comparison. Our results demonstrate that G4 dendrimers, which have amino functional groups, are toxic and attenuate growth and development of zebrafish embryos at sublethal concentrations; however, G3.5 dendrimers, with carboxylic acid terminal functional groups, are not toxic to zebrafish embryos. Furthermore, RGD-conjugated G4 dendrimers are less potent in causing embryo toxicity than G4 dendrimers. RGD-conjugated G3.5 dendrimers do not elicit toxicity at the highest concentrations tested and warrant further study for use as a drug delivery device

  12. Nanoclusters and Microparticles in Gases and Vapors

    CERN Document Server

    Smirnov, Boris M

    2012-01-01

    Research of processes involving Nanoclusters and Microparticleshas been developing fastin many fields of rescent research, in particular in materials science. To stay at the cutting edge of this development, a sound understanding of the processes is needed. In this work, several processes involving small particles are described, such as transport processes in gases, charging of small particles in gases, chemical processes, atom attachment and quenching of excited atomic particles on surfaces, nucleation, coagulation, coalescence and growth processes for particles and aggregates. This work pres

  13. Transport and biodistribution of dendrimers across human fetal membranes: implications for intravaginal administration of dendrimer-drug conjugates.

    Science.gov (United States)

    Menjoge, Anupa R; Navath, Raghavendra S; Asad, Abbas; Kannan, Sujatha; Kim, Chong J; Romero, Roberto; Kannan, Rangaramanujam M

    2010-06-01

    Dendrimers are emerging as promising topical antimicrobial agents, and as targeted nanoscale drug delivery vehicles. Topical intravaginal antimicrobial agents are prescribed to treat the ascending genital infections in pregnant women. The fetal membranes separate the extra-amniotic space and fetus. The purpose of the study is to determine if the dendrimers can be selectively used for local intravaginal application to pregnant women without crossing the membranes into the fetus. In the present study, the transport and permeability of PAMAM (poly (amidoamine)) dendrimers, across human fetal membrane (using a side by side diffusion chamber), and its biodistribution (using immunofluorescence) are evaluated ex-vivo. Transport across human fetal membranes (from the maternal side) was evaluated using Fluorescein (FITC), an established transplacental marker (positive control, size approximately 400 Da) and fluorophore-tagged G(4)-PAMAM dendrimers (approximately 16 kDa). The fluorophore-tagged G(4)-PAMAM dendrimers were synthesized and characterized using (1)H NMR, MALDI TOF MS and HPLC analysis. Transfer was measured across the intact fetal membrane (chorioamnion), and the separated chorion and amnion layers. Over a 5 h period, the dendrimer transport across all the three membranes was less than dendrimer (5.8 x 10(-8) cm(2)/s). The biodistribution showed that the dendrimers were largely present in interstitial spaces in the decidual stromal cells and the chorionic trophoblast cells (in 2.5-4 h) and surprisingly, to a smaller extent internalized in nuclei of trophoblast cells and nuclei and cytoplasm of stromal cells. Passive diffusion and paracellular transport appear to be the major route for dendrimer transport. The overall findings further suggest that entry of drugs conjugated to dendrimers would be restricted across the human fetal membranes when administered topically by intravaginal route, suggesting new ways of selectively delivering therapeutics to the mother

  14. Controllable growth and magnetic properties of nickel nanoclusters electrodeposited on the ZnO nanorod template

    International Nuclear Information System (INIS)

    Tang Yang; Zhao Dongxu; Shen Dezhen; Zhang Jiying; Wang Xiaohua

    2009-01-01

    The ZnO nanorods were used as a template to fabricate nickel nanoclusters by electrodeposition. The ZnO nanorod arrays act as a nano-semiconductor electrode for depositing metallic and magnetic nickel nanoclusters. The growth sites of Ni nanoclusters could be controlled by adjusting the applied potential. Under -1.15 V the Ni nanoclusters could be grown on the tips of ZnO nanorods. On increasing the potential to be more negative the ZnO nanorods were covered by Ni nanoclusters. The magnetic properties of the electrodeposited Ni nanoclusters also evolved with the applied potentials.

  15. Controllable growth and magnetic properties of nickel nanoclusters electrodeposited on the ZnO nanorod template

    Energy Technology Data Exchange (ETDEWEB)

    Tang Yang; Zhao Dongxu; Shen Dezhen; Zhang Jiying [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic Zone, Changchun 130033 (China); Wang Xiaohua, E-mail: dxzhao2000@yahoo.com.c [National Key Laboratory of High Power Semiconductor Laser, Changchun University of Science and Technology, 7089 WeiXing Road, ChangChun 130022 (China)

    2009-12-09

    The ZnO nanorods were used as a template to fabricate nickel nanoclusters by electrodeposition. The ZnO nanorod arrays act as a nano-semiconductor electrode for depositing metallic and magnetic nickel nanoclusters. The growth sites of Ni nanoclusters could be controlled by adjusting the applied potential. Under -1.15 V the Ni nanoclusters could be grown on the tips of ZnO nanorods. On increasing the potential to be more negative the ZnO nanorods were covered by Ni nanoclusters. The magnetic properties of the electrodeposited Ni nanoclusters also evolved with the applied potentials.

  16. SNAP dendrimers: multivalent protein display on dendrimer-like DNA for directed evolution.

    Science.gov (United States)

    Kaltenbach, Miriam; Stein, Viktor; Hollfelder, Florian

    2011-09-19

    Display systems connect a protein with the DNA encoding it. Such systems (e.g., phage or ribosome display) have found widespread application in the directed evolution of protein binders and constitute a key element of the biotechnological toolkit. In this proof-of-concept study we describe the construction of a system that allows the display of multiple copies of a protein of interest in order to take advantage of avidity effects during affinity panning. To this end, dendrimer-like DNA is used as a scaffold with docking points that can join the coding DNA with multiple protein copies. Each DNA construct is compartmentalised in water-in-oil emulsion droplets. The corresponding protein is expressed, in vitro, inside the droplets as a SNAP-tag fusion. The covalent bond between DNA and the SNAP-tag is created by reaction with dendrimer-bound benzylguanine (BG). The ability to form dendrimer-like DNA straightforwardly from oligonucleotides bearing BG allowed the comparison of a series of templates differing in size, valency and position of BG. In model selections the most efficient constructs show recoveries of up to 0.86 % and up to 400-fold enrichments. The comparison of mono- and multivalent constructs suggests that the avidity effect enhances enrichment by up to fivefold and recovery by up to 25-fold. Our data establish a multivalent format for SNAP-display based on dendrimer-like DNA as the first in vitro display system with defined tailor-made valencies and explore a new application for DNA nanostructures. These data suggest that multivalent SNAP dendrimers have the potential to facilitate the selection of protein binders especially during early rounds of directed evolution, allowing a larger diversity of candidate binders to be recovered. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Building machine learning force fields for nanoclusters

    Science.gov (United States)

    Zeni, Claudio; Rossi, Kevin; Glielmo, Aldo; Fekete, Ádám; Gaston, Nicola; Baletto, Francesca; De Vita, Alessandro

    2018-06-01

    We assess Gaussian process (GP) regression as a technique to model interatomic forces in metal nanoclusters by analyzing the performance of 2-body, 3-body, and many-body kernel functions on a set of 19-atom Ni cluster structures. We find that 2-body GP kernels fail to provide faithful force estimates, despite succeeding in bulk Ni systems. However, both 3- and many-body kernels predict forces within an ˜0.1 eV/Å average error even for small training datasets and achieve high accuracy even on out-of-sample, high temperature structures. While training and testing on the same structure always provide satisfactory accuracy, cross-testing on dissimilar structures leads to higher prediction errors, posing an extrapolation problem. This can be cured using heterogeneous training on databases that contain more than one structure, which results in a good trade-off between versatility and overall accuracy. Starting from a 3-body kernel trained this way, we build an efficient non-parametric 3-body force field that allows accurate prediction of structural properties at finite temperatures, following a newly developed scheme [A. Glielmo et al., Phys. Rev. B 95, 214302 (2017)]. We use this to assess the thermal stability of Ni19 nanoclusters at a fractional cost of full ab initio calculations.

  18. Molecularly precise dendrimer-drug conjugates with tunable drug release for cancer therapy.

    Science.gov (United States)

    Zhou, Zhuxian; Ma, Xinpeng; Murphy, Caitlin J; Jin, Erlei; Sun, Qihang; Shen, Youqing; Van Kirk, Edward A; Murdoch, William J

    2014-10-06

    The structural preciseness of dendrimers makes them perfect drug delivery carriers, particularly in the form of dendrimer-drug conjugates. Current dendrimer-drug conjugates are synthesized by anchoring drug and functional moieties onto the dendrimer peripheral surface. However, functional groups exhibiting the same reactivity make it impossible to precisely control the number and the position of the functional groups and drug molecules anchored to the dendrimer surface. This structural heterogeneity causes variable pharmacokinetics, preventing such conjugates to be translational. Furthermore, the highly hydrophobic drug molecules anchored on the dendrimer periphery can interact with blood components and alter the pharmacokinetic behavior. To address these problems, we herein report molecularly precise dendrimer-drug conjugates with drug moieties buried inside the dendrimers. Surprisingly, the drug release rates of these conjugates were tailorable by the dendrimer generation, surface chemistry, and acidity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Viologen-Phosphorus Dendrimers Inhibit α-Synuclein Fibrillation.

    Science.gov (United States)

    Milowska, Katarzyna; Grochowina, Justyna; Katir, Nadia; El Kadib, Abdelkrim; Majoral, Jean-Pierre; Bryszewska, Maria; Gabryelak, Teresa

    2013-03-04

    Inhibition of α-synuclein (ASN) fibril formation is a potential therapeutic strategy in Parkinson's disease and other synucleinopathies. The aim of this study was to examine the role of viologen-phosphorus dendrimers in the α-synuclein fibrillation process and to assess the structural changes in α-synuclein under the influence of dendrimers. ASN interactions with phosphonate and pegylated surface-reactive viologen-phosphorus dendrimers were examined by measuring the zeta potential, which allowed determining the number of dendrimer molecules that bind to the ASN molecule. The fibrillation kinetics and the structural changes were examined using ThT fluorescence and CD spectroscopy. Depending on the concentration of the used dendrimer and the nature of the reactive groups located on the surface, ASN fibrillation kinetics can be significantly reduced, and even, in the specific case of phosphonate dendrimers, the fibrillation can be totally inhibited at low concentrations. The presented results indicate that viologen-phosphorus dendrimers are able to inhibit ASN fibril formation and may be used as fibrillar regulating agents in neurodegenerative disorders.

  20. Nanoscale effects in dendrimer-mediated targeting of neuroinflammation.

    Science.gov (United States)

    Nance, Elizabeth; Zhang, Fan; Mishra, Manoj K; Zhang, Zhi; Kambhampati, Siva P; Kannan, Rangaramanujam M; Kannan, Sujatha

    2016-09-01

    Neuroinflammation, mediated by activated microglia and astrocytes, plays a key role in the pathogenesis of many neurological disorders. Systemically-administered dendrimers target neuroinflammation and deliver drugs with significant efficacy, without the need for ligands. Elucidating the nanoscale aspects of targeting neuroinflammation will enable superior nanodevices for eventual translation. Using a rabbit model of cerebral palsy, we studied the in vivo contributions of dendrimer physicochemical properties and disease pathophysiology on dendrimer brain uptake, diffusion, and cell specific localization. Neutral dendrimers move efficiently within the brain parenchyma and rapidly localize in glial cells in regions of injury. Dendrimer uptake is also dependent on the extent of blood-brain-barrier breakdown, glial activation, and disease severity (mild, moderate, or severe), which can lend the dendrimer to be used as an imaging biomarker for disease phenotype. This new understanding of the in vivo mechanism of dendrimer-mediated delivery in a clinically-relevant rabbit model provides greater opportunity for clinical translation of targeted brain injury therapies. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Transepithelial and endothelial transport of poly (amidoamine) dendrimers.

    Science.gov (United States)

    Kitchens, Kelly M; El-Sayed, Mohamed E H; Ghandehari, Hamidreza

    2005-12-14

    This article summarizes our efforts to evaluate the potential of poly (amidoamine) (PAMAM) dendrimers as carriers for oral drug delivery. Specifically, the permeability of a series of cationic PAMAM-NH2 (G0-G4) dendrimers across Caco-2 cell monolayers was evaluated as a function of dendrimer generation, concentration, and incubation time. The influence of dendrimer surface charge on the integrity, paracellular permeability, and viability of Caco-2 cell monolayers was monitored by measuring the transepithelial electrical resistance (TEER), 14C-mannitol permeability, and leakage of lactate dehydrogenase (LDH) enzyme, respectively. Microvascular extravasation of PAMAM-NH2 dendrimers in relation to their size, molecular weight, and molecular geometry is also discussed. Results of these studies show that transepithelial transport and microvascular extravasation of PAMAM dendrimers are dependent on their structural features including molecular size, molecular geometry, and surface chemistry. These results suggest that by optimizing the size and surface charge of PAMAM dendrimers, it is possible to develop oral delivery systems based on these carriers for targeted drug delivery.

  2. Passivation of cobalt nanocluster assembled thin films with hydrogen

    DEFF Research Database (Denmark)

    Romero, C.P.; Volodin, A.; Di Vece, M.

    2012-01-01

    The effect of hydrogen passivation on bare and Pd capped cobalt nanocluster assembled thin films was studied with Rutherford backscattering spectrometry (RBS) and magnetic force microscopy (MFM) after exposure to ambient conditions. The nanoclusters are produced in a laser vaporization cluster...... source in which the helium carrier gas was mixed with hydrogen. RBS revealed that oxidation of the Co nanoclusters is considerably reduced by the presence of hydrogen during cluster formation. The capping did not modify the influence of the passivation. The hydrogen passivation method is especially...... effective in cases when capping of the films is not desirable, for example for magnetic studies. Clear differences in the magnetic domain structures between hydrogen passivated and non-passivated Co nanocluster films were demonstrated by MFM and are attributed to a difference in inter-cluster magnetic...

  3. Adsorption of small gas molecules on B36 nanocluster

    Indian Academy of Sciences (India)

    Supplementary Information. Journal of Chemical Sciences. Adsorption of small gas molecules on B36 nanocluster. YOUNES VALADBEIGI. *. , HOSSEIN FARROKHPOUR and MAHMOUD TABRIZCHI. Department of chemistry, Isfahan University of Technology, Isfahan, 84156-83111, Iran. *. Corresponding Author: Younes ...

  4. Tunneling-Electron-Induced Light Emission from Single Gold Nanoclusters.

    Science.gov (United States)

    Yu, Arthur; Li, Shaowei; Czap, Gregory; Ho, W

    2016-09-14

    The coupling of tunneling electrons with the tip-nanocluster-substrate junction plasmon was investigated by monitoring light emission in a scanning tunneling microscope (STM). Gold atoms were evaporated onto the ∼5 Å thick Al2O3 thin film grown on the NiAl (110) surface where they formed nanoclusters 3-7 nm wide. Scanning tunneling spectroscopy (STS) of these nanoclusters revealed quantum-confined electronic states. Spatially resolved photon imaging showed localized emission hot spots. Size dependent study and light emission from nanocluster dimers further support the viewpoint that coupling of tunneling electrons to the junction plasmon is the main radiative mechanism. These results showed the potential of the STM to reveal the electronic and optical properties of nanoscale metallic systems in the confined geometry of the tunnel junction.

  5. Switching a Nanocluster Core from Hollow to Non-hollow

    KAUST Repository

    Bootharaju, Megalamane Siddaramappa; Joshi, Chakra Prasad; Alhilaly, Mohammad J.; Bakr, Osman

    2016-01-01

    Modulating the structure-property relationship in atomically precise nanoclusters (NCs) is vital for developing novel NC materials and advancing their applications. While promising biphasic ligand-exchange (LE) strategies have been developed

  6. Synergistic activity profile of carbosilane dendrimer G2-STE16 in combination with other dendrimers and antiretrovirals as topical anti-HIV-1 microbicide.

    Science.gov (United States)

    Sepúlveda-Crespo, Daniel; Lorente, Raquel; Leal, Manuel; Gómez, Rafael; De la Mata, Francisco J; Jiménez, José Luis; Muñoz-Fernández, M Ángeles

    2014-04-01

    Polyanionic carbosilane dendrimers represent opportunities to develop new anti-HIV microbicides. Dendrimers and antiretrovirals (ARVs) acting at different stages of HIV replication have been proposed as compounds to decrease new HIV infections. Thus, we determined the potential use of our G2-STE16 carbosilane dendrimer in combination with other carbosilane dendrimers and ARVs for the use as topical microbicide against HIV-1. We showed that these combinations obtained 100% inhibition and displayed a synergistic profile against different HIV-1 isolates in our model of TZM.bl cells. Our results also showed their potent activity in the presence of an acidic vaginal or seminal fluid environment and did not activate an inflammatory response. This study is the first step toward exploring the use of different anionic carbosilane dendrimers in combination and toward making a safe microbicide. Therefore, our results support further studies on dendrimer/dendrimer or dendrimer/ARV combinations as topical anti-HIV-1 microbicide. This paper describes the first steps toward the use of anionic carbosilane dendrimers in combination with antivirals to address HIV-1, paving the way to further studies on dendrimer/dendrimer or dendrimer/ARV combinations as topical anti-HIV-1 microbicides. © 2014.

  7. An intrinsically fluorescent dendrimer as a nanoprobe of cell transport.

    Science.gov (United States)

    Al-Jamal, Khuloud T; Ruenraroengsak, Pakatip; Hartell, Nicholas; Florence, Alexander T

    2006-07-01

    Dendrimers, spherical or quasi-spherical synthetic polymers in the nano-size range, have found useful applications as prospective carriers in drug and gene delivery. The investigation of dendrimer uptake by cells has been previously achieved by the incorporation of a fluorescent dye to the dendrimer either by chemical conjugation or by physical interaction. Here we describe the synthesis of two intrinsically fluorescent lysine based cationic dendrimers which lack a fluorophore, but which has sufficient fluorescence intensity to be detected at low concentrations. The nomenclature used to describe our compounds results in, for example the 6th generation dendrimer being notated as Gly-Lys(63) (NH2)(64); Gly denotes that the compound has a glycine in the core coupled to 63 lysine branching units (Lys(63)) and that the surface has 64 free amino groups (NH2)(64). The use of these dendrimers in probing transport avoids the need for fluorescent tagging with its attendant problems. The uptake of Gly-Lys(63) (NH2)(64) into Caco-2 cells was followed using confocal microscopy. Being cationic, it first adsorbs to the cell surface, enters the cytoplasm and reaches the nucleus within 35-45 min. Estimates of the diffusion coefficient of the dendrimer within the cell cytoplasm leads to a value of 6.27 ( +/- 0.49) x 10(-11) cm(2) s(-1), which is up to 1000 times lower than the diffusion coefficient of the dendrimer in water. Intrinsically fluorescent dendrimers of different size and charge are useful probes of transport in cells.

  8. Energy transfer to xanthene dyes in dansylated POPAM dendrimers

    Science.gov (United States)

    Aumanen, Jukka; Korppi-Tommola, Jouko

    2011-12-01

    Excitation energy transfer (EET) in host-guest complexes of dansylated POPAM dendrimers and xanthene dyes have been studied by transient absorption spectroscopy. EET from dansyl periphery to guests: rose bengal, eosin, or fluorescein, showed non-exponential behaviour as a result of distribution of donor-acceptor distances. Time constants range from 100 fs to 8 ps, independent of the dye and the dendrimer generation. Experiments suggested that in dendrimers binding more than one guest, EET among the guests becomes effective. Guest-host and guest-guest interactions induce non-radiative relaxation channels making excitation decays of the guests clearly faster in complexes than in solution.

  9. The effect of dendrimer on cotton dyeability with direct dyes

    Directory of Open Access Journals (Sweden)

    Khakzar Bafrooei F.

    2014-01-01

    Full Text Available Pretreatment of cotton fabric with poly(propylene imine dendrimer enhanced its colour strength using C.I. Direct Red 81 and C.I. Direct Blue 78. Application of this dendrimer and the direct dye simultaneously on cotton fabric by the exhaust and the continuous dyeing method were studied; slight improvements in the dyeing results were obtained. Pretreatment of the cotton fabric with dendrimer in an emulsion form using the pad-dry method followed by continuous dyeing markedly increased the colour strength. In addition, level dyeing was obtained, and no negative effects on the fastness properties of the dyes used were observed.

  10. Continuous-time quantum walks on multilayer dendrimer networks

    Science.gov (United States)

    Galiceanu, Mircea; Strunz, Walter T.

    2016-08-01

    We consider continuous-time quantum walks (CTQWs) on multilayer dendrimer networks (MDs) and their application to quantum transport. A detailed study of properties of CTQWs is presented and transport efficiency is determined in terms of the exact and average return probabilities. The latter depends only on the eigenvalues of the connectivity matrix, which even for very large structures allows a complete analytical solution for this particular choice of network. In the case of MDs we observe an interplay between strong localization effects, due to the dendrimer topology, and good efficiency from the linear segments. We show that quantum transport is enhanced by interconnecting more layers of dendrimers.

  11. Ab initio Investigation of Helium in Vanadium Oxide Nanoclusters

    Science.gov (United States)

    Danielson, Thomas; Tea, Eric; Hin, Celine

    Nanostructured ferritic alloys (NFAs) are strong candidate materials for the next generation of fission reactors and future fusion reactors. They are characterized by a large number density of oxide nanoclusters dispersed throughout a BCC iron matrix, where current oxide nanoclusters are primarily comprised of Y-Ti-O compounds. The oxide nanoclusters provide the alloy with high resistance to neutron irradiation, high yield strength and high creep strength at the elevated temperatures of a reactor environment. In addition, the oxide nanoclusters serve as trapping sites for transmutation product helium providing substantially increased resistance to catastrophic cracking and embrittlement. Although the mechanical properties and radiation resistance of the existing NFAs is promising, the problem of forming large scale reactor components continues to present a formidable challenge due to the high hardness and unpredictable fracture behavior of the alloys. An alternative alloy has been previously proposed and fabricated where vanadium is added in order to form vanadium oxide nanoclusters that serve as deflection sites for crack propagation. Although experiments have shown evidence that the fracture behavior of the alloys is improved, it is unknown whether or not the vanadium oxide nanoclusters are effective trapping sites for helium. We present results obtained using density functional theory investigating the thermodynamic stability of helium with the vanadium oxide matrix to make a comparison of trapping effectiveness to traditional Y-Ti-O compounds.

  12. Tailoring the magnetic properties of cobalt-ferrite nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Vega, A. Estrada de la; Garza-Navarro, M. A., E-mail: marco.garzanr@uanl.edu.mx; Durán-Guerrero, J. G.; Moreno Cortez, I. E.; Lucio-Porto, R.; González-González, V. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica (Mexico)

    2016-01-15

    In this contribution, we report on the tuning of magnetic properties of cobalt-ferrite nanoclusters. The cobalt-ferrite nanoclusters were synthesized from a two-step approach that consists of the synthesis of cobalt-ferrite nanoparticles in organic media, followed by their dispersion into aqueous dissolution to form an oil-in-water emulsion. These emulsions were prepared at three different concentrations of the cationic surfactant cetyltrimethylammonium bromide (CTAB), in order to control the size and clustering density of the nanoparticles in the nanoclusters. The synthesized samples were characterized by transmission electron microscopy and their related techniques, such as bright-field and Z-contrast imaging, electron diffraction and energy-dispersive X-ray spectrometry; as well as static magnetic measures. The experimental evidence indicates that the size, morphology, and nanoparticles clustering density in the nanoclusters is highly dependent of the cobalt-ferrite:CTAB molar ratio that is used in their synthesis. In addition, due to the clustering of the nanoparticles into the nanoclusters, their magnetic moments are blocked to relax cooperatively. Hence, the magnetic response of the nanoclusters can be tailored by controlling the size and nanoparticles clustering density.

  13. Design of interior-functionalized fully acetylated dendrimers for anticancer drug delivery.

    Science.gov (United States)

    Hu, Jingjing; Su, Yunzhang; Zhang, Hongfeng; Xu, Tongwen; Cheng, Yiyun

    2011-12-01

    In this study, dendrimers was synthesized by introducing functional groups into the interior pockets of fully acetylated dendrimers. NMR techniques including COSY and 2D-NOESY revealed the molecular structures of the synthesized dendrimers and the encapsulation of guest molecule such as methotrexate within their interior pockets. The synthesized polymeric nanocarriers showed much lower cytotoxicity on two cell lines than cationic dendrimers, and exhibited better performance than fully acetylated dendrimers in the sustained release of methotrexate. The results provided a new strategy in the design of non-toxic dendrimers with high performance in the delivery of anti-cancer drugs for clinical applications. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. Atomistic computer simulations on multi-loaded PAMAM dendrimers: a comparison of amine- and hydroxyl-terminated dendrimers

    Science.gov (United States)

    Badalkhani-Khamseh, Farideh; Ebrahim-Habibi, Azadeh; Hadipour, Nasser L.

    2017-12-01

    Poly(amidoamine) (PAMAM) dendrimers have been extensively studied as delivery vectors in biomedical applications. A limited number of molecular dynamics (MD) simulation studies have investigated the effect of surface chemistry on therapeutic molecules loading, with the aim of providing insights for biocompatibility improvement and increase in drug loading capacity of PAMAM dendrimers. In this work, fully atomistic MD simulations were employed to study the association of 5-Fluorouracil (5-FU) with amine (NH2)- and hydroxyl (OH)-terminated PAMAM dendrimers of generations 3 and 4 (G3 and G4). MD results show a 1:12, 1:1, 1:27, and 1:4 stoichiometry, respectively, for G3NH2-FU, G3OH-FU, G4NH2-FU, and G4OH-FU complexes, which is in good agreement with the isothermal titration calorimetry results. The results obtained showed that NH2-terminated dendrimers assume segmented open structures with large cavities and more drug molecules can encapsulate inside the dendritic cavities of amine terminated dendrimers. However, OH-terminated have a densely packed structure and therefore, 5-FU drug molecules are more stable to locate close to the surface of the dendrimers. Intermolecular hydrogen bonding analysis showed that 5-FU drug molecules have more tendency to form hydrogen bonds with terminal monomers of OH-terminated dendrimers, while in NH2-terminated these occur both in the inner region and the surface. Furthermore, MM-PBSA analysis revealed that van der Waals and electrostatic energies are both important to stabilize the complexes. We found that drug molecules are distributed uniformly inside the amine and hydroxyl terminated dendrimers and therefore, both dendrimers are promising candidates as drug delivery systems for 5-FU drug molecules.

  15. Dual stimuli-sensitive dendrimers: Photothermogenic gold nanoparticle-loaded thermo-responsive elastin-mimetic dendrimers.

    Science.gov (United States)

    Fukushima, Daichi; Sk, Ugir Hossain; Sakamoto, Yasuhiro; Nakase, Ikuhiko; Kojima, Chie

    2015-08-01

    Dendrimers are synthetic macromolecules with unique structures that can work as nanoplatforms for both photothermogenic gold nanoparticles (AuNPs) and thermosensitive elastin-like peptides (ELPs) with valine-proline-glycine-valine-glycine (VPGVG) repeats. In this study, photothermogenic AuNPs were loaded into thermo-responsive elastin-mimetic dendrimers (dendrimers conjugating ELPs at their periphery) to produce dual stimuli-sensitive nanoparticles. Polyamidoamine G4 dendrimers were modified with acetylated VPGVG and (VPGVG)2, and the resulting materials were named ELP1-den and ELP2-den, respectively. The AuNPs were prepared by the reduction of Au ions using a dendrimer-nanotemplated method. The AuNP-loaded elastin-mimetic dendrimers exhibited photothermal properties. ELP1-den and ELP2-den showed similar temperature-dependent changes in their conformations. Phase transitions were observed at around 55°C and 35°C for the AuNP-loaded ELP1-den and AuNP-loaded ELP2-den, respectively, but not for the corresponding PEGylated dendrimer. In contrast to the AuNP-loaded PEGylated dendrimer, AuNP-loaded ELP2-den readily associated with cells and induced efficient photocytotoxicity at 37°C. The cell association and the photocytotoxicity properties of AuNP-loaded ELP2-den could be controlled by temperature. These results therefore suggest that dual stimuli-sensitive dendrimer nanoparticles of this type could be used for photothermal therapy. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. From dendrimers to fractal polymers and beyond

    Directory of Open Access Journals (Sweden)

    Charles N. Moorefield

    2013-01-01

    Full Text Available The advent of dendritic chemistry has facilitated materials research by allowing precise control of functional component placement in macromolecular architecture. The iterative synthetic protocols used for dendrimer construction were developed based on the desire to craft highly branched, high molecular weight, molecules with exact mass and tailored functionality. Arborols, inspired by trees and precursors of the utilitarian macromolecules known as dendrimers today, were the first examples to employ predesigned, 1 → 3 C-branched, building blocks; physical characteristics of the arborols, including their globular shapes, excellent solubilities, and demonstrated aggregation, combined to reveal the inherent supramolecular potential (e.g., the unimolecular micelle of these unique species. The architecture that is a characteristic of dendritic materials also exhibits fractal qualities based on self-similar, repetitive, branched frameworks. Thus, the fractal design and supramolecular aspects of these constructs are suggestive of a larger field of fractal materials that incorporates repeating geometries and are derived by complementary building block recognition and assembly. Use of terpyridine-M2+-terpyridine (where, M = Ru, Zn, Fe, etc connectivity in concert with mathematical algorithms, such as forms the basis for the Seirpinski gasket, has allowed the beginning exploration of fractal materials construction. The propensity of the fractal molecules to self-assemble into higher order architectures adds another dimension to this new arena of materials and composite construction.

  17. Engineering of dendrimer surfaces to enhance transepithelial transport and reduce cytotoxicity.

    Science.gov (United States)

    Jevprasesphant, Rachaneekorn; Penny, Jeffrey; Attwood, David; McKeown, Neil B; D'Emanuele, Antony

    2003-10-01

    To evaluate the cytotoxicity, permeation, and transport mechanisms of PAMAM dendrimers and surface-modified cationic PAMAM dendrimers using monolayers of the human colon adenocarcinoma cell line, Caco-2. Cytotoxicity was determined using the MTT assay. The effect of dendrimers on monolayer integrity was determined from measurements of transepithelial electrical resistance (TEER) and [14C]mannitol apparent permeability coefficient (Papp). The Papp of dendrimers through monolayers was measured in both the apical (A)-to-basolateral (B) and B --> A directions at 4 degrees C and 37 degrees C and also in the presence and absence of ethylenediamine tetraacetic acid (EDTA) and colchicine. The cytotoxicity and permeation of dendrimers increased with both concentration and generation. The cytotoxicity of cationic dendrimers (G2, G3, G4) was greater than that of anionic dendrimers (G2.5, G3.5) but was reduced by conjugation with lauroyl chloride: the least cytotoxic conjugates were those with six attached lauroyl chains. At 37 degrees C the Papp of cationic dendrimers was higher than that of anionic dendrimers and, in general, increased with the number of attached lipid chains. Cationic dendrimers decreased TEER and significantly increased the Papp of mannitol. Modified dendrimers also reduced TEER and caused a more marked increase in the Papp of mannitol. The Papp values of dendrimers and modified dendrimers were higher in the presence of EDTA, lower in the presence of colchicine, and lower at 4 degrees C than at 37 degrees C. The properties of dendrimers may be significantly modified by surface engineering. Conjugation of cationic PAMAM dendrimers with lauroyl chloride decreased their cytotoxicity and increased their permeation through Caco-2 cell monolayers. Both PAMAM dendrimers and lauroyl-PAMAM dendrimer conjugates can cross epithelial monolayers by paracellular and transcellular pathways.

  18. Optimization of carboxylate-terminated poly(amidoamine) dendrimer-mediated cisplatin formulation.

    Science.gov (United States)

    Kulhari, Hitesh; Pooja, Deep; Singh, Mayank K; Chauhan, Abhay S

    2015-02-01

    Abstract Cisplatin is mainly used in the treatment of ovarian, head and neck and testicular cancer. Poor solubility and non-specific interactions causes hurdles in the development of successful cisplatin formulation. There were few reports on poly(amidoamine) (PAMAM) dendrimer-cisplatin complexes for anticancer treatment. But the earlier research was mainly focused on therapeutic effect of PAMAM dendrimer-cisplatin complex, with less attention paid on the formulation development of these complexes. Objective of the present study is to optimize and validate the carboxylate-terminated, EDA core PAMAM dendrimer-based cisplatin formulation with respect to various variables such as dendrimer core, generation, drug entrapment, purification, yield, reproducibility, stability, storage and in-vitro release. Dendrimer-cisplatin complex was prepared by an efficient method which significantly increases the % platinum (Pt) content along with the product yield. Dendrimers showed reproducible (∼27%) platinum loading by weight. Variation in core and generations does not produce significant change in the % Pt content. Percentage Pt content of dendrimeric formulation increases with increase in drug/dendrimer mole ratio. Formulation with low drug/dendrimer mole ratio showed delayed release compared to the higher drug/dendrimer mole ratio; these dendrimer formulations are stable in room temperature. In vitro release profiles of the stored dendrimer-cisplatin samples showed comparatively slow release of cisplatin, which may be due to formation of strong bond between cisplatin and dendrimer. This study will contribute to create a fine print for the formulation development of PAMAM dendrimer-cisplatin complexes.

  19. Smart dendrimer-based nanogel for enhancing 5-fluorouracil ...

    Indian Academy of Sciences (India)

    Author for correspondence (nckhoavnn@yahoo.com) chemical properties of the ..... accounting for 90% of loaded 5-FU from dialysis membrane, whereas ... of the NIPAM layer-coated dendrimer contributed to control the drug sustainably from ...

  20. Preparation and evaluation of peptide-dendrimer-paclitaxel ...

    African Journals Online (AJOL)

    Tropical Journal of Pharmaceutical Research April 2017; 16 (4): 737-742 ... conjugates for treatment of heterogeneous stage 1 non- small cell lung ... Keywords: Paclitaxel, Lung cancer, Non-small cell lung cancer, Dendrimer, Peptide, PAMAM.

  1. Formulation and Development of Dendrimer-Based Transdermal ...

    African Journals Online (AJOL)

    Shandong Traditional Chinese Medicine University, Jinan 250012, China ... system for the management of some diseased conditions. Keywords: Dendrimers ... anti-inflammatory and analgesic activity [3]. ..... Cost-effective management of.

  2. Dendrimer Advances for the Central Nervous System Delivery of Therapeutics

    Science.gov (United States)

    2013-01-01

    The effectiveness of noninvasive treatment for central nervous system (CNS) diseases is generally limited by the poor access of therapeutic agents into the CNS. Most CNS drugs cannot permeate into the brain parenchyma because of the blood-brain barrier (BBB), and overcoming this has become one of the most significant challenges in the development of CNS therapeutics. Rapid advances in nanotechnology have provided promising solutions to this challenge. This review discusses the latest applications of dendrimers in the treatment of CNS diseases with an emphasis on brain tumors. Dendrimer-mediated drug delivery, imaging, and diagnosis are also reviewed. The toxicity, biodistribution, and transport mechanisms in dendrimer-mediated delivery of CNS therapeutic agents bypassing or crossing the BBB are also discussed. Future directions and major challenges of dendrimer-mediated delivery of CNS therapeutic agents are included. PMID:24274162

  3. Thermodynamic properties of a liquid crystal carbosilane dendrimer

    Science.gov (United States)

    Samosudova, Ya. S.; Markin, A. V.; Smirnova, N. N.; Ogurtsov, T. G.; Boiko, N. I.; Shibaev, V. P.

    2016-11-01

    The temperature dependence of the heat capacity of a first-generation liquid crystal carbosilane dendrimer with methoxyphenyl benzoate end groups is studied for the first time in the region of 6-370 K by means of precision adiabatic vacuum calorimetry. Physical transformations are observed in this interval of temperatures, and their standard thermodynamic characteristics are determined and discussed. Standard thermodynamic functions C p ° ( T), H°( T) - H°(0), S°( T) - S°(0), and G°( T) - H°(0) are calculated from the obtained experimental data for the region of T → 0 to 370 K. The standard entropy of formation of the dendrimer in the partially crystalline state at T = 298.15 K is calculated, and the standard entropy of the hypothetic reaction of its synthesis at this temperature is estimated. The thermodynamic properties of the studied dendrimer are compared to those of second- and fourth-generation liquid crystal carbosilane dendrimers with the same end groups studied earlier.

  4. Dendrimer advances for the central nervous system delivery of therapeutics.

    Science.gov (United States)

    Xu, Leyuan; Zhang, Hao; Wu, Yue

    2014-01-15

    The effectiveness of noninvasive treatment for central nervous system (CNS) diseases is generally limited by the poor access of therapeutic agents into the CNS. Most CNS drugs cannot permeate into the brain parenchyma because of the blood-brain barrier (BBB), and overcoming this has become one of the most significant challenges in the development of CNS therapeutics. Rapid advances in nanotechnology have provided promising solutions to this challenge. This review discusses the latest applications of dendrimers in the treatment of CNS diseases with an emphasis on brain tumors. Dendrimer-mediated drug delivery, imaging, and diagnosis are also reviewed. The toxicity, biodistribution, and transport mechanisms in dendrimer-mediated delivery of CNS therapeutic agents bypassing or crossing the BBB are also discussed. Future directions and major challenges of dendrimer-mediated delivery of CNS therapeutic agents are included.

  5. Tecto-dendrimers: a study of covalently bound nanospheres

    Energy Technology Data Exchange (ETDEWEB)

    Welch, Paul M [Los Alamos National Laboratory; Welch, Cynthia F [Los Alamos National Laboratory

    2008-01-01

    We present a computational and theoretical study of the size, shape, and solution properties of tecto-dendrimers. This class of polymer, composed of a central dendrimer with multiple dendrimers attached at its periphery, holds promise for multi-drug delivery and environmental remediation applications. We find (i) that the maximum number of tecto-units that may be attached to the central core varies logarightmically with the ratio of the sizes of the dendrimers, (ii) that their density profiles display a minimum near the junction of the tecto-units with the core, (iii) that a simple expression captures their radius of gyration, (iv) that their intrinsic viscosity will display a maximum as a function of the number of tecto-units attached, and (v) that their sphericity increases with increasing number of attached tecto-units. These results should bear upon both the synthesis and application of these materials.

  6. Synthesis of crystalline Ge nanoclusters in PE-CVD-deposited SiO2 films

    DEFF Research Database (Denmark)

    Leervad Pedersen, T.P.; Skov Jensen, J.; Chevallier, J.

    2005-01-01

    The synthesis of evenly distributed Ge nanoclusters in plasma-enhanced chemical-vapour-deposited (PE-CVD) SiO2 thin films containing 8 at. % Ge is reported. This is of importance for the application of nanoclusters in semiconductor technology. The average diameter of the Ge nanoclusters can...

  7. Synthesis of Dendrimer Containing Carbazole Unit as a Core Chromophore

    International Nuclear Information System (INIS)

    Han, Seung Choul; Lee, Jae Wook; Jin, Sungho

    2012-01-01

    Dendrimers, which are prepared by repetition of a given set of reactions using either divergent or convergent strategies, are highly branched and regular macromolecules with well-defined structures and have served as functional objects in nanotechnology and nano-materials science. Following conventional organic small molecules and polymers, dendrimers are now regarded as the third class of materials for use in organic light-emitting diodes (OLEDs) and have attracted much attention due to their distinguished properties. Dendrimers contain three distinct structural parts that are the core, end-groups, and branched units connecting core and periphery. For light-emitting dendrimers, the core is usually selected as the luminescent chromophore, and the dendrons and their periphery are charge transporting units and can also tune the solubility. In contrast to linear polymers, dendrimers are sphere-like with dimensions of the order of nanometers depending on the generation number. By careful structural design, dendrimers combine the potential advantages of both small molecules and polymers. Therefore, the innovative strategy different from conventional convergent and divergent routes has been required to simplify dendrimer synthesis. Recent solid chemistry is the click chemistry which is the copper-catalyzed 1,3-dipolar cycloaddition reaction between alkyne and azide developed by Sharpless and Tornφe. This reaction has many advantages: very high yields, mild and simple reaction conditions, oxygen and water tolerance, and easy isolation of product. This reaction is clearly a breakthrough in the synthesis of dendrimers and dendritic and polymer materials. We have developed the fusion and stitching methods for the synthesis of various dendrimers using click chemistry between an alkyne and an azide. Overall, this method was found to be a straightforward strategy for the synthesis of triazole-based dendrimers. Taking advantage of this fact, herein we report a feasible route

  8. Silver Nanocluster Reparative Effect in Hernioplasty

    Directory of Open Access Journals (Sweden)

    Nikolay M. Anichkov

    2014-06-01

    Full Text Available Background: The acceleration of re-epithelialization and fibroblast differentiation were noted during the experiments with silver nanoclusters (SNs by interrupting the negative development of inflammation at the level of cytokines and promoting a positive course of reparative processes. The aim of this work was to elaborate the experimental model of prosthesis hernioplasty in subcutaneous and intraperitoneal locations of hernioprostheses with SNs, which allowed us to study the course of reparative reactions in all layers of the anterior abdominal wall. Material and Methods: We used a modified hernioprosthesis made from polyester fibers coated with a metal-polymer composition, including the stabilized SN in a concentration of 6.8 and 11.3 mg per 1 g of the hernioprosthesis mesh. During this research we used guinea pigs to study the in vivo tissue reactions. The clinical part of the study included the group of 212 patients who underwent removal of an inguinal hernia. We have identified various factors associated with infectious and toxic effects on the body by determining the level of the serum glutamate-pyruvate-transaminase (SGPT. Results: In implantation of the hernioprostheses, including the high concentration of SN in the laparotomy wound, the exudative component of the inflammation was weakly expressed. It was mostly the proliferative changes that took place. We did not find either CD8-positive type T lymphocytes or PAX5-positive type B activated cells in the exudate. Conclusion: Our research has shown that the use of hernioprostheses that include silver nanoclusters leads to the reduction of inflammation in the exudative phase and to a more favorable course of reparative processes.

  9. Host-guest chemistry of dendrimer-drug complexes. 4. An in-depth look into the binding/encapsulation of guanosine monophosphate by dendrimers.

    Science.gov (United States)

    Hu, Jingjing; Fang, Min; Cheng, Yiyun; Zhang, Jiahai; Wu, Qinglin; Xu, Tongwen

    2010-06-03

    In the present study, we investigated the host-guest chemistry of dendrimer/guanosine monophosphate (GMP) and present an in-depth look into the binding/encapsulation of GMP by dendrimers using NMR studies. (1)H NMR spectra showed a significant downfield shift of methylene protons in the outmost layer of the G5 dendrimer, indicating the formation of ion pairs between cationic amine groups of dendrimer and anionic phosphate groups of GMP. Chemical shift titration results showed that the binding constant between G5 dendrimer and GMP is 17,400 M(-1) and each G5 dendrimer has 107 binding sites. The binding of GMP to dendrimers prevents its aggregation in aqueous solutions and thereby enhances its stability. Nuclear Overhauser effect measurements indicated that a GMP binding and encapsulation balance occurs on the surface and in the interior of dendrimer. The binding/encapsulation transitions can be easily tailored by altering the surface and interior charge densities of the dendrimer. All these findings provide a new insight into the host-guest chemistry of dendrimer/guest complexes and may play important roles in the study of dendrimer/DNA aggregates by a "bottom-up" strategy.

  10. Dendrimers in drug delivery and targeting: Drug-dendrimer interactions and toxicity issues

    Directory of Open Access Journals (Sweden)

    Kanika Madaan

    2014-01-01

    Full Text Available Dendrimers are the emerging polymeric architectures that are known for their defined structures, versatility in drug delivery and high functionality whose properties resemble with biomolecules. These nanostructured macromolecules have shown their potential abilities in entrapping and/or conjugating the high molecular weight hydrophilic/hydrophobic entities by host-guest interactions and covalent bonding (prodrug approach respectively. Moreover, high ratio of surface groups to molecular volume has made them a promising synthetic vector for gene delivery. Owing to these properties dendrimers have fascinated the researchers in the development of new drug carriers and they have been implicated in many therapeutic and biomedical applications. Despite of their extensive applications, their use in biological systems is limited due to toxicity issues associated with them. Considering this, the present review has focused on the different strategies of their synthesis, drug delivery and targeting, gene delivery and other biomedical applications, interactions involved in formation of drug-dendrimer complex along with characterization techniques employed for their evaluation, toxicity problems and associated approaches to alleviate their inherent toxicity.

  11. Dendrimers in drug delivery and targeting: Drug-dendrimer interactions and toxicity issues

    Science.gov (United States)

    Madaan, Kanika; Kumar, Sandeep; Poonia, Neelam; Lather, Viney; Pandita, Deepti

    2014-01-01

    Dendrimers are the emerging polymeric architectures that are known for their defined structures, versatility in drug delivery and high functionality whose properties resemble with biomolecules. These nanostructured macromolecules have shown their potential abilities in entrapping and/or conjugating the high molecular weight hydrophilic/hydrophobic entities by host-guest interactions and covalent bonding (prodrug approach) respectively. Moreover, high ratio of surface groups to molecular volume has made them a promising synthetic vector for gene delivery. Owing to these properties dendrimers have fascinated the researchers in the development of new drug carriers and they have been implicated in many therapeutic and biomedical applications. Despite of their extensive applications, their use in biological systems is limited due to toxicity issues associated with them. Considering this, the present review has focused on the different strategies of their synthesis, drug delivery and targeting, gene delivery and other biomedical applications, interactions involved in formation of drug-dendrimer complex along with characterization techniques employed for their evaluation, toxicity problems and associated approaches to alleviate their inherent toxicity. PMID:25035633

  12. Biological properties of water-soluble phosphorhydrazone dendrimers

    Directory of Open Access Journals (Sweden)

    Anne-Marie Caminade

    2013-01-01

    Full Text Available Dendrimers are hyperbranched and perfectly defined macromolecules, constituted of branches emanating from a central core in an iterative fashion. Phosphorhydrazone dendrimers constitute a special family of dendrimers, possessing one phosphorus atom at each branching point. The internal structure of these dendrimers is hydrophobic, but hydrophilic terminal groups can induce the solubility of the whole structure in water. Indeed, the properties of these compounds are mainly driven by the type of terminal groups their bear; this is especially true for the biological properties. For instance, positively charged terminal groups are efficient for transfection experiments, as drug carriers, as anti-prion agents, and as inhibitor of the aggregation of Alzheimer's peptides, whereas negatively charged dendrimers have anti-HIV properties and can influence the human immune system, leading to anti-inflammatory properties usable against rheumatoid arthritis. This review will give the most representative examples of the biological properties of water-soluble phosphorhydrazone dendrimers, organized depending on the type of terminal groups they bear.

  13. Biphasic interactions between a cationic dendrimer and actin.

    Science.gov (United States)

    Ruenraroengsak, Pakatip; Florence, Alexander T

    2010-12-01

    Gene delivery systems face the problem not only of the route toward the cell and tissues in question, but also of the molecularly crowded environment of both the cytoplasm and the nucleus itself. One of the physical barriers in the cytoplasm for diffusing nanoparticles is an actin network. Here, we describe the finding that a self-fluorescent sixth generation cationic dendrimer (6 nm in diameter) interacts reversibly and possibly electrostatically with actin filaments in vitro. Not only does this interaction slow the diffusion of the dendrimer but it also affects actin polymerization in a biphasic manner. At low concentrations the dendrimer behaves like a G-binding actin protein, retarding actin polymerization, whereas at high concentrations the dendrimer acts as a nucleating protein accelerating the polymerization. Thus in vivo the diffusion of a dendrimer carrier such as this has both physical and chemical elements: by decreasing polymerization it might accelerate its own transport, and by enhancing actin polymerization retard it. This finding suggests that such a dendrimer may have a role as an anticancer agent through its inhibitory effect on actin polymerization.

  14. In vitro evaluation of dendrimer prodrugs for oral drug delivery.

    Science.gov (United States)

    Najlah, Mohammad; Freeman, Sally; Attwood, David; D'Emanuele, Antony

    2007-05-04

    Dendrimer-based prodrugs were used to enhance the transepithelial permeability of naproxen, a low solubility model drug. The stability of the dendrimer-naproxen link was assessed. Naproxen was conjugated to G0 polyamidoamine (PAMAM) dendrimers either by an amide bond or an ester bond. The stability of G0 prodrugs was evaluated in 80% human plasma and 50% rat liver homogenate. The cytotoxicity of conjugates towards Caco-2 cells was determined and the transport of the conjugates across Caco-2 monolayers (37 degrees C) was reported. In addition, one lauroyl chain (L) was attached to the surface group of G0 PAMAM dendrimer of the diethylene glycol ester conjugate (G0-deg-NAP) to enhance permeability. The lactic ester conjugate, G0-lact-NAP, hydrolyzed slowly in 80% human plasma and in 50% rat liver homogenate (t(1/2)=180 min). G0-deg-NAP was hydrolyzed more rapidly in 80% human plasma (t(1/2)=51 min) and was rapidly cleaved in 50% liver homogenate (t(1/2)=4.7 min). The conjugates were non-toxic when exposed to Caco-2 cells for 3h. Permeability studies showed a significant enhancement in the transport of naproxen when conjugated to dendrimers; L-G0-deg-NAP yielding the highest permeability. Dendrimer-based prodrugs with appropriate linkers have potential as carriers for the oral delivery of low solubility drugs such as naproxen.

  15. Exciton Transport Simulations in Phenyl Cored Thiophene Dendrimers

    Science.gov (United States)

    Kim, Kwiseon; Erkan Kose, Muhammet; Graf, Peter; Kopidakis, Nikos; Rumbles, Garry; Shaheen, Sean E.

    2009-03-01

    Phenyl cored 3-arm and 4-arm thiophene dendrimers are promising materials for use in photovoltaic devices. It is important to understand the energy transfer mechanisms in these molecules to guide the synthesis of novel dendrimers with improved efficiency. A method is developed to estimate the exciton diffusion lengths for the dendrimers and similar chromophores in amorphous films. The approach exploits Fermi's Golden Rule to estimate the energy transfer rates for an ensemble of bimolecular complexes in random orientations. Using Poisson's equation to evaluate Coulomb integrals led to efficient calculation of excitonic couplings between the transition densities. Monte-Carlo simulations revealed the dynamics of energy transport in the dendrimers. Experimental exciton diffusion lengths of the dendrimers range 10 ˜ 20 nm, increasing with the size of the dendrimer. Simulated diffusion lengths correlate well with experiments. The chemical structure of the chromophore, the shape of the transition densities and the exciton lifetime are found to be the most important factors that determine the exciton diffusion length in amorphous films.

  16. Gene Transfer in Eukaryotic Cells Using Activated Dendrimers

    Science.gov (United States)

    Dennig, Jörg

    Gene transfer into eukaryotic cells plays an important role in cell biology. Over the last 30 years a number of transfection methods have been developed to mediate gene transfer into eukaryotic cells. Classical methods include co-precipitation of DNA with calcium phosphate, charge-dependent precipitation of DNA with DEAE-dextran, electroporation of nucleic acids, and formation of transfection complexes between DNA and cationic liposomes. Gene transfer technologies based on activated PAMAM-dendrimers provide another class of transfection reagents. PAMAM-dendrimers are highly branched, spherical molecules. Activation of newly synthesized dendrimers involves hydrolytic removal of some of the branches, and results in a molecule with a higher degree of flexibility. Activated dendrimers assemble DNA into compact structures via charge interactions. Activated dendrimer - DNA complexes bind to the cell membrane of eukaryotic cells, and are transported into the cell by non-specific endocytosis. A structural model of the activated dendrimer - DNA complex and a potential mechanism for its uptake into cells will be discussed.

  17. Ultrafast Dynamics of Dansylated POPAM Dendrimers and Energy Transfer in their Dye Complexes

    Science.gov (United States)

    Aumanen, J.; Kesti, T.; Sundström, V.; Vögtle, F.; Korppi-Tommola, J.

    We have studied internal dynamics of dansylated poly(propyleneamine) dendrimers of different generations in solution and excitation energy transfer from dansyl chromophores to xanthene dyes that form van der Waals complexes with the dendrimers

  18. DNA compaction by poly (amido amine) dendrimers of ammonia cored and ethylene diamine cored

    Science.gov (United States)

    Qamhieh, K.; Al-Shawwa, J.

    2017-06-01

    The complexes build-up of DNA and soft particles poly amidoamine (PAMAM) dendrimers of ammonia cored of generations (G1-G6) and ethylenediamine cored of generations (G1-G10) have been studied, using a new theoretical model developed by Qamhieh and coworkers. The model describes the interaction between linear polyelectrolyte (LPE) chain and ion-penetrable spheres. Many factors affecting LPE/dendrimer complex have been investigated such as dendrimer generation, the Bjerrum length, salt concentration, and rigidity of the LPE chain represented by the persistence length. It is found that the wrapping chain length around dendrimer increases by increasing dendrimer`s generation, Bjerrum length, and salt concentration, while decreases by increasing the persistence length of the LPE chain. Also we can conclude that the wrapping length of LPE chain around ethylenediamine cored dendrimers is larger than its length around ammonia cored dendrimers.

  19. Molecular boxes on a molecular printboard: encapsulation of anionic dyes in immobilized dendrimers

    NARCIS (Netherlands)

    Onclin, S.; Huskens, Jurriaan; Ravoo, B.J.; Reinhoudt, David

    2005-01-01

    Fifth-generation poly(propylene imine) dendrimers, modified with 64 apolar adamantyl groups, have been immobilized on cyclodextrin host monolayers (molecular printboards) on glass by supramolecular microcontact printing. The immobilized dendrimers retain their guest-binding properties and function

  20. Electrical switching and memory phenomena observed in redox-gradient dendrimer sandwich devices

    OpenAIRE

    Li, JianChang; Blackstock, Silas C.; Szulczewski, Greg J.

    2005-01-01

    We report on the fabrication of dendrimer sandwich devices with electrical switching and memory properties. The storage media is consisted of a redox-gradient dendrimer layer sandwiched in organic barrier thin films. The dendrimer layer acts as potential well where redox-state changes and consequent electrical transitions of the embedded dendrimer molecules are expected to be effectively triggered and retained, respectively. Experimental results indicated that electrical switching could be re...

  1. Understanding specific and nonspecific toxicities: a requirement for the development of dendrimer-based pharmaceuticals

    OpenAIRE

    McNerny, Daniel Q.; Leroueil, Pascale R.; Baker, James R.

    2010-01-01

    Dendrimer conjugates for pharmaceutical development are capable of enhancing the local delivery of cytotoxic drugs. The ability to conjugate different targeting ligands to the dendrimer allows for the cytotoxic drug to be focused at the intended target cell while minimizing collateral damage in normal cells. Dendrimers offer several advantages over other polymer conjugates by creating a better defined, more monodisperse therapeutic scaffold. Toxicity from the dendrimer, targeted and nonspecif...

  2. Permeability of surface modified polyamidoamine (PAMAM) dendrimers across Caco-2 cell monolayers

    OpenAIRE

    Yellepeddi, Venkata K.; Pisal, Dipak S.; Kumar, Ajay; Kaushik, Radhey S.; Hildreth, Michael B.; Guan, Xiangming; Palakurthi, Srinath

    2007-01-01

    Aim of this study was to prepare polyamine-conjugated PAMAM dendrimers and study their permeability across Caco-2 cell monolayers. Polyamines, namely, arginine and ornithine were conjugated to the amine terminals of the G4 PAMAM dendrimers by Fmoc synthesis. The apical-to-basolateral (AB) and basolateral-to-apical (BA) apparent permeability coefficients (Papp) for the PAMAM dendrimers increased by conjugating the dendrimers with both of the polyamines. The enhancement in permeability was depe...

  3. NanoClusters Enhance Drug Delivery in Mechanical Ventilation

    Science.gov (United States)

    Pornputtapitak, Warangkana

    The overall goal of this thesis was to develop a dry powder delivery system for patients on mechanical ventilation. The studies were divided into two parts: the formulation development and the device design. The pulmonary system is an attractive route for drug delivery since the lungs have a large accessible surface area for treatment or drug absorption. For ventilated patients, inhaled drugs have to successfully navigate ventilator tubing and an endotracheal tube. Agglomerates of drug nanoparticles (also known as 'NanoClusters') are fine dry powder aerosols that were hypothesized to enable drug delivery through ventilator circuits. This Thesis systematically investigated formulations of NanoClusters and their aerosol performance in a conventional inhaler and a device designed for use during mechanical ventilation. These engineered powders of budesonide (NC-Bud) were delivered via a MonodoseRTM inhaler or a novel device through commercial endotracheal tubes, and analyzed by cascade impaction. NC-Bud had a higher efficiency of aerosol delivery compared to micronized stock budesonide. The delivery efficiency was independent of ventilator parameters such as inspiration patterns, inspiration volumes, and inspiration flow rates. A novel device designed to fit directly to the ventilator and endotracheal tubing connections and the MonodoseRTM inhaler showed the same efficiency of drug delivery. The new device combined with NanoCluster formulation technology, therefore, allowed convenient and efficient drug delivery through endotracheal tubes. Furthermore, itraconazole (ITZ), a triazole antifungal agent, was formulated as a NanoCluster powder via milling (top-down process) or precipitation (bottom-up process) without using any excipients. ITZ NanoClusters prepared by wet milling showed better aerosol performance compared to micronized stock ITZ and ITZ NanoClusters prepared by precipitation. ITZ NanoClusters prepared by precipitation methods also showed an amorphous state

  4. Study of nanocluster-assembled ZnO thin films by nanocluster-beam deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Zhiwei; Lei, Wei; Zhang, Xiaobing [School of Electronic Science and Engieering, Southeast University, Nanjing (China); Tay, Beng Kang [School of Electronical and Electronic Engineering, Nanyang Technological University, Nanyang (Singapore)

    2012-01-15

    Nanocluster-assembled ZnO thin films were obtained by nanocluster-beam deposition, in which nanoclusters were produced by a magnetron sputtering gas aggregation source. Two kinds of ZnO thin films were obtained using this method with the one grown under the on-line heating temperature of 700 C, and the other grown without on-line heating. Film microstructure and optical properties are investigated by various diagnostic techniques. It was found that both of film microstructure of ZnO thin films keep wurtzite structure as that of ZnO bulk materials. The averaged particle size for the film grown without on-line heating is around 6 nm, which is a little lower than that grown with the on-line heating. It was also found that as increasing the wavelength, both of the absorbance spectra for the films decrease sharply near ultra-visible to extend slowly to the visible and infrared wavelength range. For the film grown without on-line heating, the bandgap energy was estimated to 3.77 eV, while for the film grown with on-line heating, the bandgap energy was redshift to 3.71 eV. Similar behavior was also found for PL spectra analysis, where PL spectrum exhibited a peak centered at 3.31 eV without on-line heating, while it redshift to 3.20 eV with on-line heating. The mechanisms behind these behaviors were presented in this article. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Cluster perturbation theory for calculation of electronic properties of ensembles of metal nanoclusters

    Science.gov (United States)

    Zhumagulov, Yaroslav V.; Krasavin, Andrey V.; Kashurnikov, Vladimir A.

    2018-05-01

    The method is developed for calculation of electronic properties of an ensemble of metal nanoclusters with the use of cluster perturbation theory. This method is applied to the system of gold nanoclusters. The Greens function of single nanocluster is obtained by ab initio calculations within the framework of the density functional theory, and then is used in Dyson equation to group nanoclusters together and to compute the Greens function as well as the electron density of states of the whole ensemble. The transition from insulator state of a single nanocluster to metallic state of bulk gold is observed.

  6. Ultrafast, 2 min synthesis of monolayer-protected gold nanoclusters (d < 2 nm)

    Science.gov (United States)

    Martin, Matthew N.; Li, Dawei; Dass, Amala; Eah, Sang-Kee

    2012-06-01

    An ultrafast synthesis method is presented for hexanethiolate-coated gold nanoclusters (d gold nanoclusters are separated from the reaction byproducts fast and easily without any need for post-synthesis cleaning.An ultrafast synthesis method is presented for hexanethiolate-coated gold nanoclusters (d gold nanoclusters are separated from the reaction byproducts fast and easily without any need for post-synthesis cleaning. Electronic supplementary information (ESI) available: Experimental details of gold nanocluster synthesis and mass-spectrometry. See DOI: 10.1039/c2nr30890h

  7. Atomically Precise Nanocluster Assemblies Encapsulating Plasmonic Gold Nanorods.

    Science.gov (United States)

    Chakraborty, Amrita; Fernandez, Ann Candice; Som, Anirban; Mondal, Biswajit; Natarajan, Ganapati; Paramasivam, Ganesan; Lahtinen, Tanja; Häkkinen, Hannu; Nonappa, Nonappa; Pradeep, Thalappil

    2018-04-01

    We present the self-assembled structures of atomically precise, ligand-protected noble metal nanoclusters leading to encapsulation of plasmonic gold nanorods (GNRs). Unlike highly sophisticated DNA nanotechnology, our approach demonstrates a strategically simple hydrogen bonding-directed self-assembly of nanoclusters leading to octahedral nanocrystals encapsulating GNRs. Specifically, we use the p-mercaptobenzoic acid (pMBA) protected atomically precise nanocluster, Na4[Ag44(pMBA)30] and pMBA functionalized GNRs. High resolution transmission and scanning transmission electron tomographic reconstructions suggest that the geometry of the GNR surface is responsible for directing the assembly of silver nanoclusters via H-bonding leading to octahedral symmetry. Further, use of water dispersible gold nanoclusters, Au~250(pMBA)n and Au102(pMBA)44 also formed layered shells encapsulating GNRs. Such cluster assemblies on colloidal particles present a new category of precision hybrids with diverse possibilities. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Synthesis and optical properties of water-soluble biperylene-based dendrimers.

    Science.gov (United States)

    Shao, Pin; Jia, Ningyang; Zhang, Shaojuan; Bai, Mingfeng

    2014-05-30

    We report the synthesis and photophysical properties of three biperylene-based dendrimers, which show red fluorescence in water. A fluorescence microscopy study demonstrated uptake of biperylene-based dendrimers in living cells. Our results indicate that these biperylene-based dendrimers are promising candidates in fluorescence imaging applications with the potential as therapeutic carriers.

  9. A selective glucose sensor: the cooperative effect of monoboronic acid-modified poly(amidoamine) dendrimers.

    Science.gov (United States)

    Tsai, Ching-Hua; Tang, Yi-Hsuan; Chen, Hui-Ting; Yao, Yi-Wen; Chien, Tun-Cheng; Kao, Chai-Lin

    2018-05-01

    Selective glucose binding was identified through five generations of monoboronic acid-functionalized PAMAM dendrimers. The best selectivity obtained when using G3 dendrimers (1b) generated 71.1, 94.9, and 1309 times stronger binding than when using galactose, fructose, and lactose, respectively. Further experiments using dendrimer analogues and glucose derivatives suggested that two nearby monoboronic acids cooperatively bound one glucose.

  10. The effect of dendrimer charge inversion in complexes with linear polyelectrolytes

    NARCIS (Netherlands)

    Lyulin, S.V.; Lyulin, A.V.; Darinskii, A.A.; Emri, I.

    2005-01-01

    The structure of complexes formed by charged dendrimers and oppositely charged linear chains with a charge of at least the same as that of dendrimers was studied by computer simulation using the Brownian dynamics method. The freely jointed, free-draining model of the dendrimer and the linear chain

  11. Investigation of interactions between dendrimer-coated magnetite nanoparticles and bovine serum albumin

    International Nuclear Information System (INIS)

    Pan Bifeng; Gao Feng; Ao Limei

    2005-01-01

    We investigated the interactions between dendrimer-coated magnetite nanoparticles (MNPs) and the protein serum albumin. The investigation was based on the fluorescence quenching of tryptophan residue of serum albumin after binding with the dendrimer-coated magnetite nanoparticles. The extent of the interactions between bovine serum albumin and dendrimer-coated MNPs strongly depends on their surface groups and pH value

  12. Build-up enhancement of photoluminescence from phenylazomethine bismuth dendrimer using Bi(OTf)3

    Science.gov (United States)

    Kambe, Tetsuya; Imaoka, Shotaro; Imaoka, Takane; Yamamoto, Kimihisa

    2018-05-01

    Metal assembly to a dendrimer can provide various functionalities based on the branched structure. Here, we researched assembly phenomena of bismuth salts in the phenylazomethine dendrimer and achieved enhancement of emission intensity per metal unit by using Bi(OTf)3. This enhancement suggested increasing of Bi-N coordination bonds derived from the bismuth units in the dendrimer.

  13. Transport of surface engineered polyamidoamine (PAMAM) dendrimers across IPEC-J2 cell monolayers.

    Science.gov (United States)

    Pisal, Dipak S; Yellepeddi, Venkata K; Kumar, Ajay; Palakurthi, Srinath

    2008-11-01

    The aim of our study was to prepare arginine-and ornithine-conjugated Polyamidoamine (PAMAM) dendrimers and study their permeability across IPEC-J2 cell monolayers, a new intestinal cell line model for drug absorption studies. Arginine and ornithine were conjugated to the amine terminals of the PAMAM(G4) dendrimers by Fmoc synthesis. The apical-to-basolateral (AB) and basolateral-to-apical (BA) apparent permeability coefficients (P(app)) for the PAMAM dendrimers increased by conjugating the dendrimers with both of these polyamines. The enhancement in permeability was dependent on the dendrimer concentration and duration of incubation. Correlation between monolayer permeability and the decrease in transepithelial electrical resistance (TEER) with the PAMAM dendrimers and the polyamine-conjugated dendrimers suggests that paracellular transport is one of the mechanisms of transport across the epithelial cells. Cytotoxicity of these surface-modified dendrimers was evaluated in IPEC-J2 cells by MTT (methylthiazoletetrazolium) assay. Arginine-conjugated dendrimers were insignificantly more toxic than PAMAM dendrimer as well as ornithine-conjugated dendrimers. Though investigations on the possible involvement of other transport mechanisms are in progress, results of the present study suggest the potential of dendrimer-polyamine conjugates as the carriers for antigen/drug delivery through the oral mucosa.

  14. Interactions of poly(amidoamine) dendrimers with human serum albumin: binding constants and mechanisms.

    Science.gov (United States)

    Giri, Jyotsnendu; Diallo, Mamadou S; Simpson, André J; Liu, Yi; Goddard, William A; Kumar, Rajeev; Woods, Gwen C

    2011-05-24

    The interactions of nanomaterials with plasma proteins have a significant impact on their in vivo transport and fate in biological fluids. This article discusses the binding of human serum albumin (HSA) to poly(amidoamine) [PAMAM] dendrimers. We use protein-coated silica particles to measure the HSA binding constants (K(b)) of a homologous series of 19 PAMAM dendrimers in aqueous solutions at physiological pH (7.4) as a function of dendrimer generation, terminal group, and core chemistry. To gain insight into the mechanisms of HSA binding to PAMAM dendrimers, we combined (1)H NMR, saturation transfer difference (STD) NMR, and NMR diffusion ordered spectroscopy (DOSY) of dendrimer-HSA complexes with atomistic molecular dynamics (MD) simulations of dendrimer conformation in aqueous solutions. The binding measurements show that the HSA binding constants (K(b)) of PAMAM dendrimers depend on dendrimer size and terminal group chemistry. The NMR (1)H and DOSY experiments indicate that the interactions between HSA and PAMAM dendrimers are relatively weak. The (1)H NMR STD experiments and MD simulations suggest that the inner shell protons of the dendrimers groups interact more strongly with HSA proteins. These interactions, which are consistently observed for different dendrimer generations (G0-NH(2)vs G4-NH(2)) and terminal groups (G4-NH(2)vs G4-OH with amidoethanol groups), suggest that PAMAM dendrimers adopt backfolded configurations as they form weak complexes with HSA proteins in aqueous solutions at physiological pH (7.4).

  15. Synthesis and Catalytic Evaluation of Dendrimer-Encapsulated Cu Nanoparticles: An Undergraduate Experiment Exploring Catalytic Nanomaterials

    Science.gov (United States)

    Feng, Z. Vivian; Lyon, Jennifer L.; Croley, J. Sawyer; Crooks, Richard M.; Vanden Bout, David A.; Stevenson, Keith J.

    2009-01-01

    Copper nanoparticles were synthesized using generation 4 hydroxyl-terminated (G4-OH) poly(amidoamine) (PAMAM) dendrimers as templates. The synthesis is conducted by coordinating copper ions with the interior amines of the dendrimer, followed by chemical reduction to form dendrimer-encapsulated copper nanoparticles (Cu-DEN). The catalytic…

  16. Stopped-flow kinetic studies of poly(amidoamine) dendrimer-calf thymus DNA to form dendriplexes.

    Science.gov (United States)

    Dey, Debabrata; Kumar, Santosh; Maiti, Souvik; Dhara, Dibakar

    2013-11-07

    Poly(amidoamine) (PAMAM) dendrimers are known to be highly efficient nonviral carriers in gene delivery. Dendrimer-mediated transfection is known to be a function of the dendrimer to DNA charge ratio as well as the size of the dendrimer. In the present study, the binding kinetics of four PAMAM dendrimers (G1, G2, G3, and G4) with calf thymus DNA (CT-DNA) has been studied using stopped-flow fluorescence spectroscopy. The effect of dendrimer-to-DNA charge ratio and dendrimer generation on the binding kinetics was investigated. In most cases, the results of dendrimer-CT-DNA binding can be explained by a two-step reaction mechanism: a rapid electrostatic binding between the dendrimer and DNA, followed by a conformational change of the dendrimer-DNA complex that ultimately leads to DNA condensation. It was observed that the charge ratio on the dendrimer and the DNA phosphate groups, as well as the dendrimer generation (size), has a marked effect on the kinetics of binding between the DNA and the dendrimers. The rate constant (k'1) of the first step was much higher compared to that of the second step (k'2), and both were found to increase with an increase in dendrimer concentration. Among the four generations of dendrimers, G4 exhibited significantly faster binding kinetics compared to the three smaller generation dendrimers.

  17. Nanocluster irradiation evolution in Fe-9%Cr ODS and ferritic-martensitic alloys

    Science.gov (United States)

    Swenson, M. J.; Wharry, J. P.

    2017-12-01

    The objective of this study is to evaluate the influence of dose rate and cascade morphology on nanocluster evolution in a model Fe-9%Cr oxide dispersion strengthened steel and the commercial ferritic/martensitic (F/M) alloys HCM12A and HT9. We present a large, systematic data set spanning the three alloys, three irradiating particle types, four orders of magnitude in dose rate, and doses ranging 1-100 displacements per atom over 400-500 °C. Nanoclusters are characterized using atom probe tomography. ODS oxide nanoclusters experience partial dissolution after irradiation due to inverse Ostwald ripening, while F/M nanoclusters undergo Ostwald ripening. Damage cascade morphology is indicative of nanocluster number density evolution. Finally, the effects of dose rate on nanocluster morphology provide evidence for a temperature dilation theory, which purports that a negative temperature shift is necessary for higher dose rate irradiations to emulate nanocluster evolution in lower dose rate irradiations.

  18. Straightforward and robust synthesis of monodisperse surface-functionalized gold nanoclusters

    Directory of Open Access Journals (Sweden)

    Silvia Varela-Aramburu

    2016-09-01

    Full Text Available Gold nanoclusters are small (1–3 nm nanoparticles with a high surface area that are useful for biomedical studies and drug delivery. The synthesis of small, surface-functionalized gold nanoclusters is greatly dependent on the reaction conditions. Here, we describe a straightforward, efficient and robust room temperature one-pot synthesis of 2 nm gold nanoclusters using thioglucose as a reducing and stabilizing agent, which was discovered by serendipity. The resultant monodisperse gold nanoclusters are more stable than those generated using some other common methods. The carboxylic acid contained in the stabilizing agent on the cluster surface serves as anchor for nanocluster functionalization. Alternatively, the addition of thiols serves to functionalize the nanoclusters. The resulting non-cytotoxic nanoclusters are taken up by cells and constitute a tuneable platform for biomedical applications including drug delivery.

  19. Inhibition of the norepinephrine transporter by χ-conotoxin dendrimers.

    Science.gov (United States)

    Wan, Jingjing; Brust, Andreas; Bhola, Rebecca F; Jha, Prerna; Mobli, Mehdi; Lewis, Richard J; Christie, Macdonald J; Alewood, Paul F

    2016-05-01

    Peptide dendrimers are a novel class of macromolecules of emerging interest with the potential of delayed renal clearance due to their molecular size and enhanced activity due to the multivalency effect. In this work, an active analogue of the disulfide-rich χ-conotoxin χ-MrIA (χ-MrIA), a norepinephrine reuptake (norepinephrine transporter) inhibitor, was grafted onto a polylysine dendron. Dendron decoration was achieved by employing copper-catalyzed alkyne-azide cycloaddition with azido-PEG chain-modified χ-MrIA analogues, leading to homogenous 4-mer and 8-mer χ-MrIA dendrimers with molecular weights ranging from 8 to 22 kDa. These dendrimers were investigated for their impact on peptide secondary structure, in vitro functional activity, and potential anti-allodynia in vivo. NMR studies showed that the χ-MrIA tertiary structure was maintained in the χ-MrIA dendrimers. In a functional norepinephrine transporter reuptake assay, χ-MrIA dendrimers showed slightly increased potency relative to the azido-PEGylated χ-MrIA analogues with similar potency to the parent peptide. In contrast to χ-MrIA, no anti-allodynic action was observed when the χ-MrIA dendrimers were administered intrathecally in a rat model of neuropathic pain, suggesting that the larger dendrimer structures are unable to diffuse through the spinal column tissue and reach the norepinephrine transporter. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

  20. Enhanced pulsed magneto-motive ultrasound imaging using superparamagnetic nanoclusters

    International Nuclear Information System (INIS)

    Mehrmohammadi, M; Qu, M; Emelianov, S Y; Yoon, K Y; Johnston, K P

    2011-01-01

    Recently, pulsed magneto-motive ultrasound (pMMUS) imaging augmented with ultra-small magnetic nanoparticles has been introduced as a tool capable of imaging events at molecular and cellular levels. The sensitivity of a pMMUS system depends on several parameters, including the size, geometry and magnetic properties of the nanoparticles. Under the same magnetic field, larger magnetic nanostructures experience a stronger magnetic force and produce larger displacement, thus improving the sensitivity and signal-to-noise ratio (SNR) of pMMUS imaging. Unfortunately, large magnetic iron-oxide nanoparticles are typically ferromagnetic and thus are very difficult to stabilize against colloidal aggregation. In the current study we demonstrate improvement of pMMUS image quality by using large size superparamagnetic nanoclusters characterized by strong magnetization per particle. Water-soluble magnetic nanoclusters of two sizes (15 and 55 nm average size) were synthesized from 3 nm iron precursors in the presence of citrate capping ligand. The size distribution of synthesized nanoclusters and individual nanoparticles was characterized using dynamic light scattering (DLS) analysis and transmission electron microscopy (TEM). Tissue mimicking phantoms containing single nanoparticles and two sizes of nanoclusters were imaged using a custom-built pMMUS imaging system. While the magnetic properties of citrate-coated nanoclusters are identical to those of superparamagnetic nanoparticles, the magneto-motive signal detected from nanoclusters is larger, i.e. the same magnetic field produced larger magnetically induced displacement. Therefore, our study demonstrates that clusters of superparamagnetic nanoparticles result in pMMUS images with higher contrast and SNR.

  1. Dendrimers: relationship between structure and biocompatibility in vitro, and preliminary studies on the biodistribution of 125I-labelled polyamidoamine dendrimers in vivo.

    Science.gov (United States)

    Malik, N; Wiwattanapatapee, R; Klopsch, R; Lorenz, K; Frey, H; Weener, J W; Meijer, E W; Paulus, W; Duncan, R

    2000-03-01

    Dendrimers are highly branched macromolecules of low polydispersity that provide many exciting opportunities for design of novel drug-carriers, gene delivery systems and imaging agents. They hold promise in tissue targeting applications, controlled drug release and moreover, their interesting nanoscopic architecture might allow easier passage across biological barriers by transcytosis. However, from the vast array of structures currently emerging from synthetic chemistry it is essential to design molecules that have real potential for in vivo biological use. Here, polyamidoamine (PAMAM, Starburst), poly(propyleneimine) with either diaminobutane or diaminoethane as core, and poly(ethylene oxide) (PEO) grafted carbosilane (CSi-PEO) dendrimers were used to study systematically the effect of dendrimer generation and surface functionality on biological properties in vitro. Generally, dendrimers bearing -NH(2) termini displayed concentration- and in the case of PAMAM dendrimers generation-dependent haemolysis, and changes in red cell morphology were observed after 1 h even at low concentrations (10 microg/ml). At concentrations below 1 mg/ml CSi-PEO dendrimers and those dendrimers with carboxylate (COONa) terminal groups were neither haemolytic nor cytotoxic towards a panel of cell lines in vitro. In general, cationic dendrimers were cytotoxic (72 h incubation), displaying IC(50) values=50-300 microg/ml dependent on dendrimer-type, cell-type and generation. Preliminary studies with polyether dendrimers prepared by the convergent route showed that dendrimers with carboxylate and malonate surfaces were not haemolytic at 1 h, but after 24 h, unlike anionic PAMAM dendrimers they were lytic. Cationic 125I-labelled PAMAM dendrimers (gen 3 and 4) administered intravenously (i.v.) to Wistar rats ( approximately 10 microg/ml) were cleared rapidly from the circulation (<2% recovered dose in blood at 1 h). Anionic PAMAM dendrimers (gen 2.5, 3.5 and 5.5) showed longer circulation

  2. The application of poly(amidoamine dendrimers for modification of jute yarns: Preparation and dyeing properties

    Directory of Open Access Journals (Sweden)

    Ali Akbar Zolriasatein

    2015-03-01

    Full Text Available In this study, poly(amidoamine (PAMAM G-2 dendrimer was used for jute yarn. Fourier transform infrared spectroscopy (FT-IR revealed that all carbonyl groups of jute fibers reacted with amino groups of polyamidoamine dendrimers. SEM observation indicated the good dispersion PAMAM dendrimers. Jute yarns pretreated with PAMAM dendrimer displayed markedly enhanced color strength with reactive dyes, even when dyeing had been carried out in the absence of electrolyte or alkali. Dendrimer-treated jute yarn showed much better light-fastness than untreated jute yarn.

  3. Transepithelial Transport of PEGylated Anionic Poly(amidoamine) Dendrimers: Implications for Oral Drug Delivery

    OpenAIRE

    Sweet, Deborah M.; Kolhatkar, Rohit B.; Ray, Abhijit; Swaan, Peter; Ghandehari, Hamidreza

    2009-01-01

    The purpose of this work was to assess the impact of PEGylation on transepithelial transport of anionic poly(amidoamine) dendrimers. Cytotoxicity, uptake and transport across Caco-2 cells of PEGylated G3.5 and G4.5 PAMAM dendrimers were studied. Methoxy polyethylene glycol (750 Da) was conjugated to carboxylic acid-terminated PAMAM dendrimers at feed ratios of 1, 2 and 4 PEG per dendrimer. Compared to the control, PEGylation of anionic dendrimers did not significantly alter cytotoxicity up to...

  4. Luminescent Metal Nanoclusters for Potential Chemosensor Applications

    Directory of Open Access Journals (Sweden)

    Muthaiah Shellaiah

    2017-12-01

    Full Text Available Studies of metal nanocluster (M-NCs-based sensors for specific analyte detection have achieved significant progress in recent decades. Ultra-small-size (<2 nm M-NCs consist of several to a few hundred metal atoms and exhibit extraordinary physical and chemical properties. Similar to organic molecules, M-NCs display absorption and emission properties via electronic transitions between energy levels upon interaction with light. As such, researchers tend to apply M-NCs in diverse fields, such as in chemosensors, biological imaging, catalysis, and environmental and electronic devices. Chemo- and bio-sensory uses have been extensively explored with luminescent NCs of Au, Ag, Cu, and Pt as potential sensory materials. Luminescent bi-metallic NCs, such as Au-Ag, Au-Cu, Au-Pd, and Au-Pt have also been used as probes in chemosensory investigations. Both metallic and bi-metallic NCs have been utilized to detect various analytes, such as metal ions, anions, biomolecules, proteins, acidity or alkalinity of a solution (pH, and nucleic acids, at diverse detection ranges and limits. In this review, we have summarized the chemosensory applications of luminescent M-NCs and bi-metallic NCs.

  5. Catalytic photooxidation of pentachlorophenol using semiconductor nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    WILCOXON,JESS P.

    2000-04-17

    Pentachlorophenol (PCP) is a toxic chlorinated aromatic molecule widely used as fungicide, a bactericide and a wood preservation, and thus ubiquitous in the environment. The authors report photo-oxidation of PCP using a variety of nanosize semiconductor metal oxides and sulfides in both aqueous and polar organic solvents and compare the photo-oxidation kinetics of these nanoclusters to widely studied bulk powders like Degussa P-25 TiO{sub 2} and CdS. They study both the light intensity dependence of PCP photooxidation for nanosize SnO{sub 2} and the size dependence of PCP photooxidation for both nanosize SnO{sub 2} and MoS{sub 2}. They find an extremely strong size dependence for the latter which they attribute to its size-dependent band gap and the associated change in redox potentials due to quantum confinement of the hole-electron pair. The authors show that nanosize MoS{sub 2} with a diameter of d=3.0 nm and an absorbance edge of {approximately}450 nm is a very effective photooxidation catalyst for complete PCP mineralization, even when using only visible light irradiation.

  6. Energy transfer dynamics in Light-Harvesting Dendrimers

    Science.gov (United States)

    Melinger, Joseph S.; McMorrow, Dale; Kleiman, Valeria D.

    2002-03-01

    We explore energy transfer dynamics in light-harvesting phenylacetylene symmetric and asymmetric dendrimers. Femtosecond pump-probe spectroscopy is used to probe the ultrafast dynamics of electronic excitations in these dendrimers. The backbone of the macromolecule consists of branches of increasing conjugation length, creating an energy gradient, which funnels energy to an accepting perylene trap. In the case of the symmetric dendrimer (nanostar), the energy transfer efficiency is known to approach nearly unity, although the nature and timescale of the energy transfer process is still unknown. For the asymmetric dendrimers, energy transfer efficiencies are very high, with the possibility of more complex transfer processes. We experimentally monitor the transport of excitons through the light-harvesting dendrimer. The transients show a number of components, with timescales ranging from <300fs to several tens of picoseconds, revealing the complex photophysics taking place in these macromolecules. We interpret our results in terms of the Förster mechanism in which energy transfer occurs through dipole-dipole interactions.

  7. Cationic PAMAM dendrimers as pore-blocking binary toxin inhibitors.

    Science.gov (United States)

    Förstner, Philip; Bayer, Fabienne; Kalu, Nnanya; Felsen, Susanne; Förtsch, Christina; Aloufi, Abrar; Ng, David Y W; Weil, Tanja; Nestorovich, Ekaterina M; Barth, Holger

    2014-07-14

    Dendrimers are unique highly branched macromolecules with numerous groundbreaking biomedical applications under development. Here we identified poly(amido amine) (PAMAM) dendrimers as novel blockers for the pore-forming B components of the binary anthrax toxin (PA63) and Clostridium botulinum C2 toxin (C2IIa). These pores are essential for delivery of the enzymatic A components of the internalized toxins from endosomes into the cytosol of target cells. We demonstrate that at low μM concentrations cationic PAMAM dendrimers block PA63 and C2IIa to inhibit channel-mediated transport of the A components, thereby protecting HeLa and Vero cells from intoxication. By channel reconstitution and high-resolution current recording, we show that the PAMAM dendrimers obstruct transmembrane PA63 and C2IIa pores in planar lipid bilayers at nM concentrations. These findings suggest a new potential role for the PAMAM dendrimers as effective polyvalent channel-blocking inhibitors, which can protect human target cells from intoxication with binary toxins from pathogenic bacteria.

  8. Transepithelial Transport of PAMAM Dendrimers Across Isolated Human Intestinal Tissue.

    Science.gov (United States)

    Hubbard, Dallin; Enda, Michael; Bond, Tanner; Moghaddam, Seyyed Pouya Hadipour; Conarton, Josh; Scaife, Courtney; Volckmann, Eric; Ghandehari, Hamidreza

    2015-11-02

    Poly(amido amine) (PAMAM) dendrimers have shown transepithelial transport across intestinal epithelial barrier in rats and across Caco-2 cell monolayers. Caco-2 models innately lack mucous barriers, and rat isolated intestinal tissue has been shown to overestimate human permeability. This study is the first report of transport of PAMAM dendrimers across isolated human intestinal epithelium. It was observed that FITC labeled G4-NH2 and G3.5-COOH PAMAM dendrimers at 1 mM concentration do not have a statistically higher permeability compared to free FITC controls in isolated human jejunum and colonic tissues. Mannitol permeability was increased at 10 mM concentrations of G3.5-COOH and G4-NH2 dendrimers. Significant histological changes in human colonic and jejunal tissues were observed at G3.5-COOH and G4-NH2 concentrations of 10 mM implying that dose limiting toxicity may occur at similar concentrations in vivo. The permeability through human isolated intestinal tissue in this study was compared to previous rat and Caco-2 permeability data. This study implicates that PAMAM dendrimer oral drug delivery may be feasible, but it may be limited to highly potent drugs.

  9. Mechanism of PAMAM Dendrimers Internalization in Hippocampal Neurons.

    Science.gov (United States)

    Vidal, Felipe; Vásquez, Pilar; Díaz, Carola; Nova, Daniela; Alderete, Joel; Guzmán, Leonardo

    2016-10-03

    Polyamidoamine (PAMAM) dendrimers are hyperbranched macromolecules which have been described as one of the most promising drug nanocarrier systems. A key process to understand is their cellular internalization mechanism because of its direct influence on their intracellular distribution, association with organelles, entry kinetics, and cargo release. Despite that internalization mechanisms of dendrimers have been studied in different cell types, in the case of neurons they are not completely described. Considering the relevance of central nervous system (CNS) diseases and neuropharmacology, the aim of this report is to describe the molecular internalization mechanism of different PAMAM-based dendrimer systems in hippocampal neurons. Four dendrimers based on fourth generation PAMAM with different surface properties were studied: unmodified G4, with a positively charged surface; PP50, with a substitution of the 50% of amino surface groups with polyethylene glycol neutral groups; PAc, with a substitution of the 30% of amino surface groups with acrylate anionic groups; and PFO, decorated with folic acid groups in a 25% of total terminal groups. Confocal images show that both G4 and PFO are able to enter the neurons, but not PP50 and PAc. Colocalization study with specific endocytosis markers and specific endocytosis inhibitor assay demonstrate that clathrin-mediated endocytosis would be the main internalization mechanism for G4, whereas clathrin- and caveolae-mediated endocytosis would be implicated in PFO internalization. These results show the existence of different internalization mechanisms for PAMAM dendrimers in neurons and the possibility to control their internalization properties with specific chemical modifications.

  10. Skin Delivery of EGCG and Silibinin: Potential of Peptide Dendrimers for Enhanced Skin Permeation and Deposition.

    Science.gov (United States)

    Shetty, Pallavi Krishna; Manikkath, Jyothsna; Tupally, Karnaker; Kokil, Ganesh; Hegde, Aswathi R; Raut, Sushil Y; Parekh, Harendra S; Mutalik, Srinivas

    2017-08-01

    The aim of the present study was to evaluate the ability of the peptide dendrimers to facilitate transdermal delivery of antioxidants, silibinin, and epigallocatechin-3-gallate (EGCG). Drug-peptide dendrimer complexes were prepared and evaluated for their ability to permeate across the skin. The data revealed the ready formation of complexes between drug and peptide dendrimer in a molar ratio of 1:1. In vitro permeation studies using excised rat skin and drug-peptide dendrimer complexes showed highest values for cumulative drug permeation at the end of 12 h (Q 12 ), with corresponding permeability coefficient (Kp) and enhancement ratio values also determined at this time point. With silibinin, 3.96-, 1.81-, and 1.06-fold increase in skin permeation was observed from silibinin-peptide dendrimer complex, simultaneous application of silibinin + peptide dendrimer, and pretreatment of skin with peptide dendrimer, respectively, in comparison with passive diffusion. With EGCG, 9.82-, 2.04-, and 1.72-fold increase in skin permeation was observed from EGCG-peptide dendrimer complex, simultaneous application of EGCG + peptide dendrimer, and pretreatment of skin with peptide dendrimer, respectively, in comparison with passive diffusion. The present study demonstrates the application of peptide dendrimers in effectively delivering antioxidants such as EGCG and silibinin into the skin, thus offering the potential to provide antioxidant effects when delivered via appropriately formulated topical preparations.

  11. Interaction studies reveal specific recognition of an anti-inflammatory polyphosphorhydrazone dendrimer by human monocytes.

    Science.gov (United States)

    Ledall, Jérémy; Fruchon, Séverine; Garzoni, Matteo; Pavan, Giovanni M; Caminade, Anne-Marie; Turrin, Cédric-Olivier; Blanzat, Muriel; Poupot, Rémy

    2015-11-14

    Dendrimers are nano-materials with perfectly defined structure and size, and multivalency properties that confer substantial advantages for biomedical applications. Previous work has shown that phosphorus-based polyphosphorhydrazone (PPH) dendrimers capped with azabisphosphonate (ABP) end groups have immuno-modulatory and anti-inflammatory properties leading to efficient therapeutic control of inflammatory diseases in animal models. These properties are mainly prompted through activation of monocytes. Here, we disclose new insights into the molecular mechanisms underlying the anti-inflammatory activation of human monocytes by ABP-capped PPH dendrimers. Following an interdisciplinary approach, we have characterized the physicochemical and biological behavior of the lead ABP dendrimer with model and cell membranes, and compared this experimental set of data to predictive computational modelling studies. The behavior of the ABP dendrimer was compared to the one of an isosteric analog dendrimer capped with twelve azabiscarboxylate (ABC) end groups instead of twelve ABP end groups. The ABC dendrimer displayed no biological activity on human monocytes, therefore it was considered as a negative control. In detail, we show that the ABP dendrimer can bind both non-specifically and specifically to the membrane of human monocytes. The specific binding leads to the internalization of the ABP dendrimer by human monocytes. On the contrary, the ABC dendrimer only interacts non-specifically with human monocytes and is not internalized. These data indicate that the bioactive ABP dendrimer is recognized by specific receptor(s) at the surface of human monocytes.

  12. Transepithelial transport of PEGylated anionic poly(amidoamine) dendrimers: implications for oral drug delivery.

    Science.gov (United States)

    Sweet, Deborah M; Kolhatkar, Rohit B; Ray, Abhijit; Swaan, Peter; Ghandehari, Hamidreza

    2009-08-19

    The purpose of this work was to assess the impact of PEGylation on transepithelial transport of anionic poly(amidoamine) dendrimers. Cytotoxicity, uptake and transport across Caco-2 cells of PEGylated G3.5 and G4.5 PAMAM dendrimers were studied. Methoxy polyethylene glycol (750 Da) was conjugated to carboxylic acid-terminated PAMAM dendrimers at feed ratios of 1, 2 and 4 PEG per dendrimer. Compared to the control, PEGylation of anionic dendrimers did not significantly alter cytotoxicity up to a concentration of 0.1 mM. PEGylation of G3.5 dendrimers significantly decreased cellular uptake and transepithelial transport while PEGylation of G4.5 dendrimers led to a significant increase in uptake, but also a significant decrease in transport. Dendrimer PEGylation reduced the opening of tight junctions as evidenced by confocal microscopy techniques. Modulation of the tight junctional complex correlated well with changes in PEGylated dendrimer transport and suggests that anionic dendrimers are transported primarily through the paracellular route. PEGylated dendrimers show promise in oral delivery applications where increased functionality for drug conjugation and release is desired.

  13. Molecular analysis of interactions between dendrimers and asymmetric membranes at different transport stages.

    Science.gov (United States)

    He, XiaoCong; Qu, ZhiGuo; Xu, Feng; Lin, Min; Wang, JiuLing; Shi, XingHua; Lu, TianJian

    2014-01-07

    Studying dendrimer-biomembrane interactions is important for understanding drug and gene delivery. In this study, coarse-grained molecular dynamics simulations were performed to investigate the behaviors of polyamidoamine (PAMAM) dendrimers (G4 and G5) as they interacted with asymmetric membranes from different sides of the bilayer, thus mimicking different dendrimer transport stages. The G4 dendrimer could insert into the membrane during an equilibrated state, and the G5 dendrimer could induce pore formation in the membrane when the dendrimers interacted with the outer side (outer interactions) of an asymmetric membrane [with 10% dipalmitoyl phosphatidylserine (DPPS) in the inner leaflet of the membrane]. During the interaction with the inner side of the asymmetric membrane (inner interactions), the G4 and G5 dendrimers only adsorbed onto the membrane. As the membrane asymmetry increased (e.g., increased DPPS percentage in the inner leaflet of the membrane), the G4 and G5 dendrimers penetrated deeper into the membrane during the outer interactions and the G4 and G5 dendrimers were adsorbed more tightly onto the membrane for the inner interactions. When the DPPS content reached 50%, the G4 dendrimer could completely penetrate through the membrane from the outer side to the inner side. Our study provides molecular understanding and reference information about different dendrimer transport stages during drug and gene delivery.

  14. Immobilization of dendrimers on Si-C linked carboxylic acid-terminated monolayers on silicon(111)

    International Nuclear Information System (INIS)

    Boecking, Till; Wong, Elicia L.S.; James, Michael; Watson, Jolanta A.; Brown, Christopher L.; Chilcott, Terry C.; Barrow, Kevin D.; Coster, Hans G.L.

    2006-01-01

    Poly(amidoamine) dendrimers were attached to activated undecanoic acid monolayers, covalently linked to smooth silicon surfaces via Si-C bonds. The resulting ultra-thin dendrimer films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray reflectometry (XR) and atomic force microscopy (AFM). XPS results suggested amide bond formation between the dendrimer and the surface carboxylic acid groups. XR yielded thicknesses of 10 A for the alkyl region of the undecanoic acid monolayer and 12 A for the dendrimer layer, considerably smaller than the diameter of these spherical macromolecules in solution. This was consistent with AFM images showing collapsed dendrimers on the surface. It was concluded that the deformation arose from a large number of amine groups on the surface of each dendrimer reacting efficiently with the activated surface, whereby the dendrimers can deform to fill voids while spreading over the activated surface to form a homogeneous macromolecular layer

  15. Deposition and characterization of Pt nanocluster films by means of gas aggregation cluster source

    Energy Technology Data Exchange (ETDEWEB)

    Kylián, Ondřej, E-mail: ondrej.kylian@gmail.com; Prokeš, Jan; Polonskyi, Oleksandr; Čechvala, Juraj; Kousal, Jaroslav; Pešička, Josef; Hanuš, Jan; Biederman, Hynek

    2014-11-28

    In this study we report on the deposition of Pt nanocluster films prepared by gas aggregation source that was operated with argon as working gas. The aim of this study was optimization of deposition process as well as determination of properties of deposited nanocluster films and their temporal stability. It was found that the production of Pt nanoclusters reached maximum value for pressure of 100 Pa and increases monotonously with magnetron current. The deposition rate at optimized deposition conditions was 0.7 nm of the Pt nanocluster film per second. Deposited films were porous and composed of 4 nm Pt nanoclusters. The nanoclusters were metallic and no sights of their oxidation were observed after 1 year on open air as witnessed by X-ray photoelectron spectroscopy. Regarding the electrical properties, a dramatic decrease of the resistivity was observed with increasing amount of deposited nanoclusters. This decrease saturated for the films approximately 50 nm thick. Such behavior indicates transition between different mechanisms of electrical conductivity: charge hopping for thin discontinuous films and current conduction through conducting path formed when higher amount of nanoclusters is deposited. Different mechanisms of electrical conduction for thin and thick layers of Pt were confirmed by subsequent investigation of temperature dependence of resistivity. In addition, no changes in resistivity were observed after one year on open air that confirms stability of produced Pt nanocluster films. - Highlights: • Pt nanocluster films were deposited by gas aggregation nanocluster source. • Conditions leading to effective deposition of Pt nanocluster films were found. • Deposited nanocluster films have good temporal stability. • Electrical properties of Pt films were found to depend on their thickness.

  16. Host-guest chemistry of dendrimer-drug complexes: 7. Formation of stable inclusions between acetylated dendrimers and drugs bearing multiple charges.

    Science.gov (United States)

    Fang, Min; Zhang, Jiahai; Wu, Qinglin; Xu, Tongwen; Cheng, Yiyun

    2012-03-15

    Drug molecules bearing multiple charges usually form precipitates with cationic dendrimers, which presents a challenge during the preparation of dendrimer inclusions for these drugs. In the present study, fully acetylated polyamidoamine (PAMAM) dendrimers were proposed as stable vehicles for drug molecules bearing two negative charges such as Congo red and indocyanine green. NMR techniques including (1)H NMR and (1)H-(1)H NOESY were used to characterize the host-guest chemistry of acetylated dendrimer and these guest molecules. The cationic PAMAM dendrimer was found to form a precipitate with Congo red and indocyanine green, but the acetylated one avoided the formation of cross-linking structures in aqueous solutions. NOESY studies revealed the encapsulation of Congo red and indocyanine green within the interior cavities of PAMAM dendrimers at mild acidic conditions and acetylated dendrimers show much stronger ability to encapsulate the guest molecules than cationic ones. Also, UV-vis-NIR studies suggest that acetylated dendrimers significantly improve the photostability of indocyanine green and prevent the formation of indocyanine green J-aggregates in aqueous solutions. The present study provides a new insight into dendrimer-based host-guest systems, especially for those guest molecules bearing multiple charges. © 2012 American Chemical Society

  17. Dendrimer-based biosensor for chemiluminescent detection of DNA hybridization

    International Nuclear Information System (INIS)

    Liu, P.; Hun, X.; Qing, H.

    2011-01-01

    We report on a highly sensitive chemiluminescent (CL) biosensor for the sequence-specific detection of DNA using a novel bio barcode DNA probe modified with gold nanoparticles that were covered with a dendrimer. The modified probe is composed of gold nanoparticles, a dendrimer, the CL reagent, and the DNA. The capture probe DNA was immobilized on magnetic beads covered with gold. It first hybridizes with the target DNA and then with one terminal end of the signal DNA on the barcoded DNA probe. CL was generated by adding H 2 O 2 and Co(II) ions as the catalyst. The immobilization of dendrimer onto the gold nanoparticles can significantly enhance sensitivity and gives a detection limit of 6 fmol L -1 of target DNA. (author)

  18. Recent Advances in Click Chemistry Applied to Dendrimer Synthesis

    Directory of Open Access Journals (Sweden)

    Mathieu Arseneault

    2015-05-01

    Full Text Available Dendrimers are monodisperse polymers grown in a fractal manner from a central point. They are poised to become the cornerstone of nanoscale devices in several fields, ranging from biomedicine to light-harvesting. Technical difficulties in obtaining these molecules has slowed their transfer from academia to industry. In 2001, the arrival of the “click chemistry” concept gave the field a major boost. The flagship reaction, a modified Hüisgen cycloaddition, allowed researchers greater freedom in designing and building dendrimers. In the last five years, advances in click chemistry saw a wider use of other click reactions and a notable increase in the complexity of the reported structures. This review covers key developments in the click chemistry field applied to dendrimer synthesis from 2010 to 2015. Even though this is an expert review, basic notions and references have been included to help newcomers to the field.

  19. On Topological Indices of Certain Families of Nanostar Dendrimers.

    Science.gov (United States)

    Husin, Mohamad Nazri; Hasni, Roslan; Arif, Nabeel Ezzulddin; Imran, Muhammad

    2016-06-24

    A topological index of graph G is a numerical parameter related to G which characterizes its molecular topology and is usually graph invariant. In the field of quantitative structure-activity (QSAR)/quantitative structure-activity structure-property (QSPR) research, theoretical properties of the chemical compounds and their molecular topological indices such as the Randić connectivity index, atom-bond connectivity (ABC) index and geometric-arithmetic (GA) index are used to predict the bioactivity of different chemical compounds. A dendrimer is an artificially manufactured or synthesized molecule built up from the branched units called monomers. In this paper, the fourth version of ABC index and the fifth version of GA index of certain families of nanostar dendrimers are investigated. We derive the analytical closed formulas for these families of nanostar dendrimers. The obtained results can be of use in molecular data mining, particularly in researching the uniqueness of tested (hyper-branched) molecular graphs.

  20. On Topological Indices of Certain Families of Nanostar Dendrimers

    Directory of Open Access Journals (Sweden)

    Mohamad Nazri Husin

    2016-06-01

    Full Text Available A topological index of graph G is a numerical parameter related to G which characterizes its molecular topology and is usually graph invariant. In the field of quantitative structure-activity (QSAR/quantitative structure-activity structure-property (QSPR research, theoretical properties of the chemical compounds and their molecular topological indices such as the Randić connectivity index, atom-bond connectivity (ABC index and geometric-arithmetic (GA index are used to predict the bioactivity of different chemical compounds. A dendrimer is an artificially manufactured or synthesized molecule built up from the branched units called monomers. In this paper, the fourth version of ABC index and the fifth version of GA index of certain families of nanostar dendrimers are investigated. We derive the analytical closed formulas for these families of nanostar dendrimers. The obtained results can be of use in molecular data mining, particularly in researching the uniqueness of tested (hyper-branched molecular graphs.

  1. Dendrimer-magnetic nanostructure: a Monte Carlo simulation

    Science.gov (United States)

    Jabar, A.; Masrour, R.

    2017-11-01

    In this paper, the magnetic properties of ternary mixed spins (σ,S,q) Ising model on a dendrimer nanostructure are studied using Monte Carlo simulations. The ground state phase diagrams of dendrimer nanostructure with ternary mixed spins σ = 1/2, S = 1 and q = 3/2 Ising model are found. The variation of the thermal total and partial magnetizations with the different exchange interactions, the external magnetic fields and the crystal fields have been also studied. The reduced critical temperatures have been deduced. The magnetic hysteresis cycles have been discussed. In particular, the corresponding magnetic coercive filed values have been deduced. The multiples hysteresis cycles are found. The dendrimer nanostructure has several applications in the medicine.

  2. Structural properties of star-like dendrimers in solution

    International Nuclear Information System (INIS)

    Rathgeber, S.; Gast, A.P.; Hedrick, J.L.

    2002-01-01

    We measured the form factor of star-like poly-ε-caprolactone dendrimers under good solvent conditions with small-angle neutron scattering (SANS). The parameters varied in the experiment were the dendrimer generation g=1,2,3 and the number of segments between the branching units n=5,10,15,20. The results are discussed in the frame work of the Beaucage model from which we cannot only derive the radius of gyration R g of the dendrimers but also their fractal dimensions. Decreasing the number of spacer units between the branching points results in a strong stretching of the dendrons. The fractal dimension increases monotonically with increasing generation and spacer number between the limit expected for a low-functionality star P∼5/3 (loose, polymeric structure) and that expected for a high-functionality star P∼3 (compact shape). (orig.)

  3. Hydrogel of Ketoconazole and PAMAM Dendrimers: Formulation and Antifungal Activity

    Directory of Open Access Journals (Sweden)

    Elzbieta Tryniszewska

    2012-04-01

    Full Text Available Ketoconazole (KET, an imidazole derivative with well-known antifungal properties, is lipophilic and practically insoluble in water, therefore its clinical use has some practical disadvantages. The aim of the present study was to investigate the influence of PAMAM-NH2 and PAMAM-OH dendrimers generation 2 and generation 3 on the solubility and antifungal activity of KET and to design and evaluate KET hydrogel with PAMAM dendrimers. It was shown that the surface charge of PAMAM dendrimers strongly affects their influence on the improvement of solubility and antifungal activity of KET. The MIC and MFC values obtained by broth dilution method indicate that PAMAM-NH2 dendrimers significantly (up to 16-fold increased the antifungal activity of KET against Candida strains (e.g., in culture Candida albicans 1103059/11 MIC value was 0.008 μg/mL and 0.064 μg/mL, and MFC was 2 μg/mL and 32 μg/mL for KET in 10 mg/mL solution of PAMAM-NH2 G2 and pure KET, respectively. Antifungal activity of designed KET hydrogel with PAMAM-NH2 dendrimers measured by the plate diffusion method was definitely higher than pure KET hydrogel and than commercial available product. It was shown that the improvement of solubility and in the consequence the higher KET release from hydrogels seems to be a very significant factor affecting antifungal activity of KET in hydrogels containing PAMAM dendrimers.

  4. Impact of Dendrimers on Solubility of Hydrophobic Drug Molecules

    Directory of Open Access Journals (Sweden)

    Sonam Choudhary

    2017-05-01

    Full Text Available Adequate aqueous solubility has been one of the desired properties while selecting drug molecules and other bio-actives for product development. Often solubility of a drug determines its pharmaceutical and therapeutic performance. Majority of newly synthesized drug molecules fail or are rejected during the early phases of drug discovery and development due to their limited solubility. Sufficient permeability, aqueous solubility and physicochemical stability of the drug are important for achieving adequate bioavailability and therapeutic outcome. A number of different approaches including co-solvency, micellar solubilization, micronization, pH adjustment, chemical modification, and solid dispersion have been explored toward improving the solubility of various poorly aqueous-soluble drugs. Dendrimers, a new class of polymers, possess great potential for drug solubility improvement, by virtue of their unique properties. These hyper-branched, mono-dispersed molecules have the distinct ability to bind the drug molecules on periphery as well as to encapsulate these molecules within the dendritic structure. There are numerous reported studies which have successfully used dendrimers to enhance the solubilization of poorly soluble drugs. These promising outcomes have encouraged the researchers to design, synthesize, and evaluate various dendritic polymers for their use in drug delivery and product development. This review will discuss the aspects and role of dendrimers in the solubility enhancement of poorly soluble drugs. The review will also highlight the important and relevant properties of dendrimers which contribute toward drug solubilization. Finally, hydrophobic drugs which have been explored for dendrimer assisted solubilization, and the current marketing status of dendrimers will be discussed.

  5. "light-on" sensing of antioxidants using gold nanoclusters

    KAUST Repository

    Hu, Lianzhe; Deng, Lin; Alsaiari, Shahad K.; Zhang, Dingyuan; Khashab, Niveen M.

    2014-01-01

    preservatives, and cosmetics has proved to be very vital. Gold nanoclusters (Au-NCs) have a core size below 2 nm and contain several metal atoms. They have interesting photophysical properties, are readily functionalized, and are safe to use in various

  6. Distinct metal-exchange pathways of doped Ag25 nanoclusters

    KAUST Repository

    Bootharaju, Megalamane Siddaramappa; Sinatra, Lutfan; Bakr, Osman

    2016-01-01

    Atomically precise metal nanoclusters (NCs) containing more than one type of metal atom (i.e., doped or alloyed), due to synergistic effects, open new avenues for engineering the catalytic and optical properties of NCs in a manner that homometal NCs

  7. In-vitro Synthesis of Gold Nanoclusters in Neurons

    Science.gov (United States)

    2016-04-01

    ARL-TN-0753 ● APR 2016 US Army Research Laboratory In-vitro Synthesis of Gold Nanoclusters in Neurons by Maggie Gillan and...longer needed. Do not return it to the originator. ARL-TN-0753 ● APR 2016 US Army Research Laboratory In-vitro Synthesis of...

  8. Organization of copper nanoclusters in Langmuir–Blodgett films

    Indian Academy of Sciences (India)

    Stable nanoclusters of Cu were synthesized using Langmuir–Blodgett films of octadecylsuccinic acid (ODSA) as template. The Langmuir–Blodgett films of ODSA formed from subphase containing copper ions were first subjected to sulphidation (S) using sodium sulphide and then hydrogenated (H) using hydrogen gas.

  9. Enhanced electrochemical water oxidation: the impact of nanoclusters and nanocavities

    NARCIS (Netherlands)

    Zhang, X.; Cao, C.; Bieberle, A.

    2017-01-01

    The structures of transition metal surfaces and metal oxides are commonly believed to have a significant effect on the catalytic reactions. Density functional theory calculations are therefore used in this study to investigate the oxygen evolution reaction (OER) over nanostructured, i.e. nanocluster

  10. Nanoclustering as a dominant feature of plasma membrane organization

    NARCIS (Netherlands)

    Garcia-Parajo, M.F.; Cambi, A.; Torreno-Pina, J.A.; Thompson, N.; Jacobson, K.

    2014-01-01

    Early studies have revealed that some mammalian plasma membrane proteins exist in small nanoclusters. The advent of super-resolution microscopy has corroborated and extended this picture, and led to the suggestion that many, if not most, membrane proteins are clustered at the plasma membrane at

  11. Understanding Peptide Dendrimer Interactions with Model Cell Membrane Mimics

    DEFF Research Database (Denmark)

    Lind, Tania Kjellerup

    few new drugs have been marketed over the last decades, making it impossible to keep pace with the disturbing levels of multi-drug resistant bacteria. Research in the area of novel drugs, which are less prone to induce resistance, and in-depth knowledge on their uptake mechanisms is thus of paramount...... fusion method, which presents improved means for studying drug-membrane interactions in the future. The interaction mechanism of a family of dendrimers was examined and in particular one dendrimer (BALY) was extensively studied by the combined use of quartz crystal microbalance, atomic force microscopy...

  12. The neighbourhood polynomial of some families of dendrimers

    Science.gov (United States)

    Nazri Husin, Mohamad; Hasni, Roslan

    2018-04-01

    The neighbourhood polynomial N(G,x) is generating function for the number of faces of each cardinality in the neighbourhood complex of a graph and it is defined as (G,x)={\\sum }U\\in N(G){x}|U|, where N(G) is neighbourhood complex of a graph, whose vertices of the graph and faces are subsets of vertices that have a common neighbour. A dendrimers is an artificially manufactured or synthesized molecule built up from branched units called monomers. In this paper, we compute this polynomial for some families of dendrimer.

  13. Exciton localization-delocalization transition in an extended dendrimer

    Energy Technology Data Exchange (ETDEWEB)

    Pouthier, Vincent, E-mail: vincent.pouthier@univ-fcomte.fr [Institut UTINAM, Université de Franche-Comté, CNRS UMR 6213, 25030 Besançon Cedex (France)

    2013-12-21

    Exciton-mediated quantum state transfer between the periphery and the core of an extended dendrimer is investigated numerically. By mapping the dynamics onto that of a linear chain, it is shown that a localization-delocalization transition arises for a critical value of the generation number G{sub c} ≈ 5. This transition originates in the quantum interferences experienced by the excitonic wave due to the multiple scatterings that arise each time the wave tunnels from one generation to another. These results suggest that only small-size dendrimers could be used for designing an efficient quantum communication protocol.

  14. Exciton localization-delocalization transition in an extended dendrimer

    International Nuclear Information System (INIS)

    Pouthier, Vincent

    2013-01-01

    Exciton-mediated quantum state transfer between the periphery and the core of an extended dendrimer is investigated numerically. By mapping the dynamics onto that of a linear chain, it is shown that a localization-delocalization transition arises for a critical value of the generation number G c ≈ 5. This transition originates in the quantum interferences experienced by the excitonic wave due to the multiple scatterings that arise each time the wave tunnels from one generation to another. These results suggest that only small-size dendrimers could be used for designing an efficient quantum communication protocol

  15. M-Polynomial and Related Topological Indices of Nanostar Dendrimers

    Directory of Open Access Journals (Sweden)

    Mobeen Munir

    2016-09-01

    Full Text Available Dendrimers are highly branched organic macromolecules with successive layers of branch units surrounding a central core. The M-polynomial of nanotubes has been vastly investigated as it produces many degree-based topological indices. These indices are invariants of the topology of graphs associated with molecular structure of nanomaterials to correlate certain physicochemical properties like boiling point, stability, strain energy, etc. of chemical compounds. In this paper, we first determine M-polynomials of some nanostar dendrimers and then recover many degree-based topological indices.

  16. Evolution of embedded lithium nanoclusters in lithium implanted alumina

    International Nuclear Information System (INIS)

    Gaikwad, P.V.; Sharma, S.K.; Mukherjee, S.; Sudarshan, K.; Kshirsagar, A.; Pujari, P.K.

    2016-01-01

    High dose of ion implantation followed by annealing is considered a feasible way to generate thermally stable nanoclusters inside a transparent host matrix. Low energy (50 keV) Li ions have been implanted into single crystals of alumina with different fluence (1 × 10"1"5–1 × 10"1"7 ions/cm"2). The samples have been annealed at temperatures ranging from 500 to 1100 °C in air in step of 100 °C. Depth dependent Doppler broadening measurements have been carried out using high purity germanium detector coupled to a variable energy slow positron beam. Fractional area in the central and wing regions of Doppler broadened annihilation radiation spectrum, namely, S- and W- parameters, were evaluated from each spectrum. Any variation in positron annihilation probability with valence and core electrons which occurs on trapping of positrons at a defect site is reflected in these parameters. The effect of ion fluence and annealing temperature on evolution of defects and formation of embedded Li nanoclusters have been studied by indexing the variation in line shape S- (W-) parameter as a function of positron implantation depth. These studies supplemented by theoretical calculations confirm that with annealing up to 700 °C, vacancy clusters are created due to the aggregation of vacancies wherein Li nanoclusters are formed. On annealing at higher temperature, there is evidence for the breakdown of these Li clusters leaving behind vacancy clusters in the samples. - Highlights: • Embedded Li nanoclusters are efficiently created by annealing Li implanted Al_2O_3 crystal. • Depth dependent DBAR is a suitable method to characterize embedded nanoclusters. • The formation of Li nanoclusters is assisted by vacancy migration to form clusters. • At very high annealing temperature (>1000 °C), Li nanoclusters undergo breakdown. • e"+ annihilation at V_A_l site shows a unique observation i.e. a reduction in S-parameter.

  17. Dynamics simulation of a π-conjugated light-harvesting dendrimer II: phenylene-based dendrimer (phDG2)

    International Nuclear Information System (INIS)

    Kodama, Yasunobu; Ishii, Soh; Ohno, Kaoru

    2009-01-01

    We investigate the light-harvesting property of a π-conjugated dendrimer, phenylene-based dendrimer (phDG2), by carrying out a semi-classical Ehrenfest dynamics simulation based on the time-dependent density functional theory. Similar to our previous study of star-shaped stilbenoid phthalocyanine (SSS1Pc), phDG2 shows electron and hole transfer from the periphery to the core through a π-conjugated network when an electron is selectively excited in the periphery. The one-way electron and hole transfer occurs more easily in dendrimers with planar structure than in those with steric hindrance because π-conjugation is well maintained in the planar structure. The present results explain recent experiments by Akai et al (2005 J. Lumin. 112 449).

  18. Synthesis of Poly(3,4,5-trihydroxybenzoate) dendrimers from Polyphenols and Their Chemiluminescence

    International Nuclear Information System (INIS)

    Jung, Dai Il; Song, Ju Hyun; Shin, Eun Hye; Kim, Yun Young; Lee, Do Hun; Choi, Soon Kyu; Hahn, Jung Tai

    2010-01-01

    Polyphenol dendrimers were synthesized to obtain a strong CL compound, and their CL intensities were found to be considerably stronger than the CL intensity of GA. The esterification of the hydroxyl groups of GA in the dendrimer was very effective in developing a strong CL. Further, the relationship between the CL intensity and structure of polyphenol dendrimers must be clarified to understand the reason behind the strong light emission of high-per-branch compounds such as poly(3,4,5-trihydroxybenzoate ester) dendrimers. Polyphenol CL dendrimers can be used for a wide variety of CL assays by utilizing the hydroxyl groups of the polyphenol for forming a hydrogen bond with oxygen in the analyte structure. Dendrimer chemistry is rapidly expanding both for fundamental reasons as well as due to requirements in technological applications. A recent interesting development in dendrimer chemistry concerns the coordination of metal ions by interior branches or exterior units. Dendrimers containing photoactive units are particularly interesting for two reasons: (1) cooperation among the photoactive components can allow the dendrimer to perform specific functions, and (2) changes in the properties of photoactive components can be exploited to monitor the participation of dendrimers in chemical processes

  19. Fabrication of dendrimer-releasing lipidic nanoassembly for cancer drug delivery.

    Science.gov (United States)

    Sun, Qihang; Ma, Xinpeng; Zhang, Bo; Zhou, Zhuxian; Jin, Erlei; Shen, Youqing; Van Kirk, Edward A; Murdoch, William J; Radosz, Maciej; Sun, Weilin

    2016-06-24

    An inherent dilemma in the use of nanomedicines for cancer drug delivery is their limited penetration into tumors due to their large size. We have demonstrated that dendrimer/lipid nanoassemblies can solve this problem by means of tumor-triggered disassembly and the release of small (several nanometers) dendrimers to facilitate tumor penetration. Herein, we report a general strategy for the fabrication of nanoassemblies from hydrophobic and hydrophilic dendrimers with phospholipids. Hydrophobic dendrimers could assemble with lipids via hydrophobic interactions, whereas hydrophilic dendrimers could only assemble with lipids in the presence of anionic surfactants via both electrostatic and hydrophobic interactions. The nanoassemblies of hydrophobic dendrimers/lipids were found to be capable of stripping off their lipid layers via fusion with the cell membrane and then intracellular or extracellular release of dendrimers, whereas the nanoassemblies of hydrophilic dendrimers/lipids were internalized via endocytosis and then released their dendrimers inside the cells. Therefore, these dendrimer/lipid nanoassemblies could be used for the delivery of different cancer drugs.

  20. Fluorophore:dendrimer ratio impacts cellular uptake and intracellular fluorescence lifetime.

    Science.gov (United States)

    Dougherty, Casey A; Vaidyanathan, Sriram; Orr, Bradford G; Banaszak Holl, Mark M

    2015-02-18

    G5-NH2-TAMRAn (n = 1-4, 5+, and 1.5(avg)) were prepared with n = 1-4 as a precise dye:dendrimer ratio, 5+ as a mixture of dendrimers with 5 or more dye per dendrimer, and 1.5(avg) as a Poisson distribution of dye:dendrimer ratios with a mean of 1.5 dye per dendrimer. The absorption intensity increased sublinearly with n whereas the fluorescence emission and lifetime decreased with an increasing number of dyes per dendrimer. Flow cytometry was employed to quantify uptake into HEK293A cells. Dendrimers with 2-4 dyes were found to have greater uptake than dendrimer with a single dye. Fluorescence lifetime imaging microscopy (FLIM) showed that the different dye:dendrimer ratio alone was sufficient to change the fluorescence lifetime of the material observed inside cells. We also observed that the lifetime of G5-NH2-TAMRA5+ increased when present in the cell as compared to solution. However, cells treated with G5-NH2-TAMRA1.5(avg) did not exhibit the high lifetime components present in G5-NH2-TAMRA1 and G5-NH2-TAMRA5+. In general, the effects of the dye:dendrimer ratio on fluorescence lifetime were of similar magnitude to environmentally induced lifetime shifts.

  1. Interaction of PAMAM dendrimers with bovine insulin depends on nanoparticle end-groups

    International Nuclear Information System (INIS)

    Nowacka, Olga; Milowska, Katarzyna; Bryszewska, Maria

    2015-01-01

    We have looked at the interactions between polyamidoamine (PAMAM) dendrimers with different terminal groups (−COOH, −NH 2 , −OH) and bovine insulin. The influence of PAMAM dendrimers on insulin was tested by measuring zeta potential and fluorescence quenching. The secondary structure of insulin in the presence of dendrimers was examined by circular dichroism. The effect of dendrimers on dithiotreitol-induced aggregation of insulin was investigated by spectrophotometry. Dendrimers quenched the fluorescence of insulin, but did not change its secondary structure. Thus dendrimers neither induce hormone aggregation nor inhibit the aggregation process induced by dithiotreitol (DTT), except at 0.01 µmol/l. Dendrimers–insulin interactions are mainly electrostatic. - Highlight: • The interactions between PAMAM dendrimers and insulin were investigated. • The PAMAM dendrimers can quench the fluorescence of insulin. • The PAMAM dendrimers did not change the secondary structure of insulin. • Dendrimers did not induce aggregation of hormone. • Dendrimers–insulin interaction is mainly electrostatic

  2. Dendrimers: a class of polymers in the nanotechnology for the delivery of active pharmaceuticals.

    Science.gov (United States)

    Samad, Abdus; Alam, Md Intakhab; Saxena, Kinshuk

    2009-01-01

    Dendrimers represent a class of novel polymers having unique molecular architectures characterized by their well-defined structure, with a high degree of molecular uniformity, low polydispersity and properties that make them attractive materials for the development of nanomedicines. The dendrimer drug delivery can be achieved by coupling a drug through one of two approaches. Hydrophobic drugs can be complexed within the hydrophobic dendrimer interior to make them water-soluble or drugs can be covalently coupled onto the surface of the dendrimer. In addition, dendrimers have been shown to be capable of bypassing efflux transporters. A new generation of dendrimer-based delivery systems will enable the efficient transport of drugs across cellular barriers. This review deals principally with the synthesis, characterization and recent applications of dendrimers. In future it will only ever be possible to designate a dendrimer as safe means of drug delivery related to a specific application. However, so far limited clinical experience using dendrimers makes it impossible to designate any particular system which is safe and non toxic. Although there is widespread concern as to the safety of nanosized particles, preclinical and clinical experience gained during the development of polymeric excipients, biomedical polymers and polymer therapeutics showed that judicious development of dendrimer chemistry for each specific application will ensure development of safe and important materials for biomedical and pharmaceutical use.

  3. Poly (amidoamine) dendrimer-mediated hybrid formulation for combination therapy of ramipril and hydrochlorothiazide.

    Science.gov (United States)

    Singh, Mayank Kumar; Pooja, Deep; Kulhari, Hitesh; Jain, Sanjay Kumar; Sistla, Ramakrishna; Chauhan, Abhay Singh

    2017-01-01

    We present a dendrimer-based hybrid formulation strategy to explore the potential of poly (amidoamine) PAMAM dendrimers to be used as drug carriers for combination therapy of an anti-hypertensive drug ramipril (RAPL) and a diuretic hydrochlorothiazide (HCTZ). The drug-dendrimer complexes were prepared by phase-equilibration method. The results showed that the solubility of RAPL and HCTZ was dependent on dendrimer concentration and pH of dendrimer solution. The solubility profile of both RAPL and HCTZ dendrimer complexes illustrated a non-linear relationship with dendrimer concentration. At 0.8% (w/v) dendrimer concentration, solubility of RAPL was increased 4.91 folds with amine-terminated while for HCTZ, solubility enhancement was highest (3.72 folds) with carboxy-terminated. The complexes were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance analysis and high performance liquid chromatography. In-vitro drug dissolution performance of pure drugs, individual drug loaded dendrimer formulations and hybrid formulations was studied in USP dissolution medium (pH7.0) and in simulated gastric fluid (pH1.2). Dendrimer mediated formulations showed faster and complete dissolution compared to pure RAPL or HCTZ. Surprisingly, similar pattern of dissolution profile was established with hybrid formulations as compared to individual drug loaded dendrimers. The dendrimer-based hybrid formulations were found to be stable at dark and refrigerated conditions up to 5weeks. Conclusively, the proposed formulation strategy establishes a novel multitasking platform using dendrimer for simultaneous loading and delivery of multiple drugs for pharmaceutical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Hydrophilic magnetic nanoclusters with thermo-responsive properties and their drug controlled release

    International Nuclear Information System (INIS)

    Meerod, Siraprapa; Rutnakornpituk, Boonjira; Wichai, Uthai; Rutnakornpituk, Metha

    2015-01-01

    Synthesis and drug controlled release properties of thermo-responsive magnetic nanoclusters grafted with poly(N-isopropylacrylamide) (poly(NIPAAm)) and poly(NIPAAm-co-poly(ethylene glycol) methyl ether methacrylate) (PEGMA) copolymers were described. These magnetic nanoclusters were synthesized via an in situ radical polymerization in the presence of acrylamide-grafted magnetic nanoparticles (MNPs). Poly(NIPAAm) provided thermo-responsive properties, while PEGMA played a role in good water dispersibility to the nanoclusters. The ratios of PEGMA to NIPAAm in the (co)polymerization in the presence of the MNPs were fine-tuned such that the nanoclusters with good water dispersibility, good magnetic sensitivity and thermo responsiveness were obtained. The size of the nanoclusters was in the range of 50–100 nm in diameter with about 100–200 particles/cluster. The nanoclusters were well dispersible in water at room temperature and can be suddenly agglomerated when temperature was increased beyond the lower critical solution temperature (LCST) (32 °C). The release behavior of an indomethacin model drug from the nanoclusters was also investigated. These novel magnetic nanoclusters with good dispersibility in water and reversible thermo-responsive properties might be good candidates for the targeting drug controlled release applications. - Highlights: • Nanoclusters with good water dispersibility and magnetic response were prepared. • They were grafted with thermo-responsive poly(NIPAAm) and/or poly(PEGMA). • Poly(NIPAAm) provided thermo-responsive properties to the nanoclusters. • Poly(PEGMA) provided good water dispersibilityto the nanoclusters. • Accelerated and controllable releases of a drug from the nanoclusters were shown

  5. Photoluminescent Gold Nanoclusters in Cancer Cells: Cellular Uptake, Toxicity, and Generation of Reactive Oxygen Species

    OpenAIRE

    Marija Matulionyte; Dominyka Dapkute; Laima Budenaite; Greta Jarockyte; Ricardas Rotomskis

    2017-01-01

    In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. The...

  6. Mass spectrometric identification of Au68(SR)34 molecular gold nanoclusters with 34-electron shell closing.

    Science.gov (United States)

    Dass, Amala

    2009-08-26

    The molecular formula Au(68)(SCH(2)CH(2)Ph)(34) has been assigned to the 14 kDa nanocluster using MALDI-TOF mass spectrometry. The 34-electron shell closing in a macroscopically obtained thiolated gold nanocluster is demonstrated. The Au(68) nanocluster is predicted to have a 49 atom Marks decahedral core with 19 inner core atoms and 30 outer atoms chelating with the staple motifs. The nanoclusters' predicted formulation is [Au](19+30) [Au(SR)(2)](11) [Au(2)(SR)(3)](4).

  7. Electrostatic Interactions Positively Regulate K-Ras Nanocluster Formation and Function▿

    Science.gov (United States)

    Plowman, Sarah J.; Ariotti, Nicholas; Goodall, Andrew; Parton, Robert G.; Hancock, John F.

    2008-01-01

    The organization of Ras proteins into plasma membrane nanoclusters is essential for high-fidelity signal transmission, but whether the nanoscale enviroments of different Ras nanoclusters regulate effector interactions is unknown. We show using high-resolution spatial mapping that Raf-1 is recruited to and retained in K-Ras-GTP nanoclusters. In contrast, Raf-1 recruited to the plasma membrane by H-Ras is not retained in H-Ras-GTP nanoclusters. Similarly, upon epidermal growth factor receptor activation, Raf-1 is preferentially recruited to K-Ras-GTP and not H-Ras-GTP nanoclusters. The formation of K-Ras-GTP nanoclusters is inhibited by phosphorylation of S181 in the C-terminal polybasic domain or enhanced by blocking S181 phosphorylation, with a concomitant reduction or increase in Raf-1 plasma membrane recruitment, respectively. Phosphorylation of S181 does not, however, regulate in vivo interactions with the nanocluster scaffold galectin-3 (Gal3), indicating separate roles for the polybasic domain and Gal3 in driving K-Ras nanocluster formation. Together, these data illustrate that Ras nanocluster composition regulates effector recruitment and highlight the importance of lipid/protein nanoscale environments to the activation of signaling cascades. PMID:18458061

  8. Collagen targeting using multivalent protein-functionalized dendrimers

    NARCIS (Netherlands)

    Breurken, M.; Lempens, E.H.M.; Temming, R.P.; Helms, B.A.; Meijer, E.W.; Merkx, M.

    2011-01-01

    Collagen is an attractive marker for tissue remodeling in a variety of common disease processes. Here we report the preparation of protein dendrimers as multivalent collagen targeting ligands by native chemical ligation of the collagen binding protein CNA35 to cysteine-functionalized dendritic

  9. SANS contrast variation on a dendrimer host-guest complex

    NARCIS (Netherlands)

    Kleppinger, R.; Mortensen, K.; Meijer, E.W.

    2002-01-01

    Small-angle neutron scattering (SANS) technique was used to study the configurational changes in an oligoethyleneoxy-functionalized poly(propyleneimine) dendrimer (host) when forming complexes with rose bengal (guest). Guinier fits to the scattering data recorded at max. contrast indicated a

  10. Interaction of porphyrins with PAMAM dendrimers in aqueous solution

    Czech Academy of Sciences Publication Activity Database

    Kubát, Pavel; Lang, Kamil; Zelinger, Zdeněk

    2007-01-01

    Roč. 131, - (2007), s. 200-205 ISSN 0167-7322 R&D Projects: GA ČR GA203/04/0426 Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z40320502 Keywords : porphyrin * PAMAM dendrimer * aggragation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.982, year: 2007

  11. Charge and energy transports via poly-phenylacetylene based dendrimers

    Science.gov (United States)

    Shin, Yongwoo; Li, Minghai; Lin, Xi

    2010-03-01

    Poly-Phenylacetylene (PPA) is widely used in photoconductivity, photoluminescence, and light harvesting applications. In this work, we investigate the charge and exciton transport energetics and mechanisms in the PPA-based dendrimers using our recently developed adapted Su-Schrieffer-Heeger (SSH) model Hamiltonians and ab initio Hartree-Fock (HF) calculations. We found both doping and photo-excitation lead to the formation of optical phonon dressed pi electron states, namely the self-localized polarons, in the energy gap. Independent from their origins, these polarons can be self-trapped at multiple lattice locations along the PPA chain, and migrate from one to the next with an activation barrier of ˜0.006 eV, slightly higher than the corresponding barrier found in trans-polyacetylene. The PPA-based dendrimers can be constructed via the meta-positions of phenyl rings. In this case, we found the dendrimer junctions form attractive potential wells for both polarons and excitons, and the width and height of these junction potential wells can be controlled by the geometry of the dendrimers.

  12. Control of mobility in molecular organic semiconductors by dendrimer generation

    Science.gov (United States)

    Lupton, J. M.; Samuel, I. D.; Beavington, R.; Frampton, M. J.; Burn, P. L.; Bässler, H.

    2001-04-01

    Conjugated dendrimers are of interest as novel materials for light-emitting diodes. They consist of a luminescent chromophore at the core with highly branched conjugated dendron sidegroups. In these materials, light emission occurs from the core and is independent of generation. The dendron branching controls the separation between the chromophores. We present here a family of conjugated dendrimers and investigate the effect of dendron branching on light emission and charge transport. We apply a number of transport measurement techniques to thin films of a conjugated dendrimer in a light-emitting diode configuration to determine the effect of chromophore spacing on charge transport. We find that the mobility is reduced by two orders of magnitude as the size of the molecule doubles with increased branching or dendrimer generation. The degree of branching allows a unique control of mobility by molecular structure. An increase in chromophore separation also results in a reduction of intermolecular interactions, which reduces the red emission tail in film photoluminescence. We find that the steady-state charge transport is well described by a simple device model incorporating the effect of generation, and use the materials to shed light on the interpretation of transient electroluminescence data. We demonstrate the significance of the ability to tune the mobility in bilayer devices, where a more balanced charge transport can be achieved.

  13. Complexing Methylene Blue with Phosphorus Dendrimers to Increase Photodynamic Activity

    Directory of Open Access Journals (Sweden)

    Monika Dabrzalska

    2017-02-01

    Full Text Available The efficiency of photodynamic therapy is limited mainly due to low selectivity, unfavorable biodistribution of photosensitizers, and long-lasting skin sensitivity to light. However, drug delivery systems based on nanoparticles may overcome the limitations mentioned above. Among others, dendrimers are particularly attractive as carriers, because of their globular architecture and high loading capacity. The goal of the study was to check whether an anionic phosphorus dendrimer is suitable as a carrier of a photosensitizer—methylene blue (MB. As a biological model, basal cell carcinoma cell lines were used. We checked the influence of the MB complexation on its singlet oxygen production ability using a commercial fluorescence probe. Next, cellular uptake, phototoxicity, reactive oxygen species (ROS generation, and cell death were investigated. The MB-anionic dendrimer complex (MB-1an was found to generate less singlet oxygen; however, the complex showed higher cellular uptake and phototoxicity against basal cell carcinoma cell lines, which was accompanied with enhanced ROS production. Owing to the obtained results, we conclude that the photodynamic activity of MB complexed with an anionic dendrimer is higher than free MB against basal cell carcinoma cell lines.

  14. Dendrimer-coated magnetic particles for radionuclide separation

    NARCIS (Netherlands)

    Grüttner, Cordula; Böhmer, Volker; Casnati, Alessandro; Dozol, Jean-Francois; Reinhoudt, David; Reinoso garcia, M.M.; Rudershausen, Sandra; Teller, Joachim; Ungaro, Rocco; Verboom, Willem; Wang, Pingshan

    2005-01-01

    Magnetic particles were synthesised for radionuclide removal from nuclear wastes by magnetic separation. Dendrimers with terminal amino groups attached to the particle surface were used to bind chelating groups for lanthanides and actinides. This led to a 50–400-fold increase of the distribution

  15. Dendrimer and an active substance occluded in the dendrimer : a process for the preparation thereof and a process for releasing the active substance

    NARCIS (Netherlands)

    1998-01-01

    The invention relates to a dendrimer composition in which an effective number of the terminal functionalities are provided with blocking agents, and at least one active substance species is occluded in the dendrimer. A blocking agent is a sufficiently sterically sized compound which readily enters

  16. Host-guest chemistry of dendrimer-drug complexes. 2. Effects of molecular properties of guests and surface functionalities of dendrimers.

    Science.gov (United States)

    Hu, Jingjing; Cheng, Yiyun; Wu, Qinglin; Zhao, Libo; Xu, Tongwen

    2009-08-06

    The host-guest chemistry of dendrimer-drug complexes is investigated by NMR techniques, including (1)H NMR and 2D-NOESY studies. The effects of molecular properties of drug molecules (protonation ability and spatial steric hindrance of charged groups) and surface functionalities of dendrimers (positively charged amine groups and negatively charged carboxylate groups) on the host-guest interactions are discussed. Different interaction mechanisms between dendrimers and drug molecules are proposed on the basis of NMR results. Primary amine- and secondary amine-containing drugs preferentially bind to negatively charged dendrimers by strong electrostatic interactions, whereas tertiary amine and quaternary ammonium-containing drugs have weak binding ability with dendrimers due to relatively low protonation ability of the tertiary amine group and serious steric hindrance of the quaternary ammonium group. Positively charged drugs locate only on the surface of negatively charged dendrimers, whereas negatively charged drugs locate both on the surface and in the interior cavities of positively charged dendrimers. The host-guest chemistry of dendrimer-drug complexes is promising for the development of new drug delivery systems.

  17. Understanding the Structure-Function Relationships of Dendrimers in Environmental and Biomedical Applications

    Science.gov (United States)

    Wang, Bo

    We are living an era wherein nanoparticles (NPs) have been widely applied in our lives. Dendrimers are special polymeric NPs with unique physiochemical properties, which have been intensely explored for a variety of applications. Current studies on dendrimers are bottlenecked by insufficient understandings of their structure and dynamic behaviors from a molecular level. With primarily computational approaches supplemented by many other experimental technics, this dissertation aims to establish structure-function relationships of dendrimers in environmental and biomedical applications. More specifically, it thoroughly investigates the interactions between dendrimers and different biomolecules including carbon-based NPs, metal-based NPs, and proteins/peptides. Those results not only provide profound knowledge for evaluating the impacts of dendrimers on environmental and biological systems but also facilitate designing next-generation functional polymeric nanomaterials. The dissertation is organized as following. Chapter 1 provides an overview of current progresses on dendrimer studies, where methodology of Discrete Molecular Dynamics (DMD), my major research tool, is also introduced. Two directions of utilizing dendrimers will be discussed in following chapters. Chapter 2 will focus on environmental applications of dendrimers, where two back-to-back studies are presented. I will start from describing some interesting observations from experiments i.e. dendrimers dispersed model oil molecules. Then, I will reveal why surface chemistries of dendrimers lead to different remediation efficiencies by computational modelings. Finally, I will demonstrate different scenarios of dendrimer-small molecules association. Chapter 3 is centered on dendrimers in the biomedical applications including two subtopics. In the first topic, we will discuss dendrimers as surfactants that modulating the interactions between proteins and NPs. Some fundamental concepts regarding to NPs

  18. Extremely efficient catalysis of carbon-carbon bond formation using "click" dendrimer-stabilized palladium nanoparticles.

    Science.gov (United States)

    Astruc, Didier; Ornelas, Cátia; Diallo, Abdou K; Ruiz, Jaime

    2010-07-20

    This article is an account of the work carried out in the authors' laboratory illustrating the usefulness of dendrimer design for nanoparticle palladium catalysis. The "click" synthesis of dendrimers constructed generation by generation by 1-->3 C connectivity, introduces 1,2,3-triazolyl ligands insides the dendrimers at each generation. Complexation of the ligands by Pd(II) followed by reduction to Pd(0) forms dendrimer-stabilized Pd nanoparticles (PdNPs) that are extremely reactive in the catalysis of olefin hydrogenation and C-C bond coupling reactions. The stabilization can be outer-dendritic for the small zeroth-generation dendrimer or intra-dendritic for the larger first- and second-generation dendrimers. The example of the Miyaura-Suzuki reaction that can be catalyzed by down to 1 ppm of PdNPs with a "homeopathic" mechanism (the less, the better) is illustrated here, including catalysis in aqueous solvents.

  19. Interaction of phosphorus dendrimers with HIV peptides—Fluorescence studies of nano-complexes formation

    Energy Technology Data Exchange (ETDEWEB)

    Ciepluch, Karol, E-mail: ciepluch@biol.uni.lodz.pl [Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska Street 141/143, 90-236 Lodz (Poland); Ionov, Maksim [Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska Street 141/143, 90-236 Lodz (Poland); Majoral, Jean-Pierre [Laboratoire de Chimie de Coordination du CNRS (LCC), 205 Route de Narbonne, F-31077 Toulouse cedex 4 (France); Muñoz-Fernández, Maria Angeles [Laboratorio InmunoBiología Molecular, Hospital General Universitario Gregorio Marañón, Madrid (Spain); Bryszewska, Maria [Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska Street 141/143, 90-236 Lodz (Poland)

    2014-04-15

    In this study, dendrimers emerge as an alternative approach for delivery of HIV peptides to dendritic cells. Gp160, NH-EIDNYTNTIYTLLEE-COOH; P24, NH-DTINEEAAEW-COOH and Nef, NHGMDDPEREVLEWRFDSRLAF-COOH peptides were complexed with two types of positively charged phosphorus-containing dendrimers (CPD). Fluorescence polarization, dynamic light scattering, transmission and electron microscopy (TEM) techniques were chosen to evaluate the dendriplexes stability. We were able to show that complexes were stable in time and temperature. This is crucial for using these peptide/dendrimer nano-complexes in a new vaccine against HIV-1 infection. -- Highlights: • The phosphorus dendrimers as nanocarriers of HIV-peptides are proposed. • The complexes of dendrimers and HIV-peptides were stable in time, temperature. • The results convince that phosphorus dendrimers could be consider as anti-HIV vaccine candidates.

  20. Interaction of phosphorus dendrimers with HIV peptides—Fluorescence studies of nano-complexes formation

    International Nuclear Information System (INIS)

    Ciepluch, Karol; Ionov, Maksim; Majoral, Jean-Pierre; Muñoz-Fernández, Maria Angeles; Bryszewska, Maria

    2014-01-01

    In this study, dendrimers emerge as an alternative approach for delivery of HIV peptides to dendritic cells. Gp160, NH-EIDNYTNTIYTLLEE-COOH; P24, NH-DTINEEAAEW-COOH and Nef, NHGMDDPEREVLEWRFDSRLAF-COOH peptides were complexed with two types of positively charged phosphorus-containing dendrimers (CPD). Fluorescence polarization, dynamic light scattering, transmission and electron microscopy (TEM) techniques were chosen to evaluate the dendriplexes stability. We were able to show that complexes were stable in time and temperature. This is crucial for using these peptide/dendrimer nano-complexes in a new vaccine against HIV-1 infection. -- Highlights: • The phosphorus dendrimers as nanocarriers of HIV-peptides are proposed. • The complexes of dendrimers and HIV-peptides were stable in time, temperature. • The results convince that phosphorus dendrimers could be consider as anti-HIV vaccine candidates

  1. Influence of dendrimer's structure on its activity against amyloid fibril formation

    International Nuclear Information System (INIS)

    Klajnert, B.; Cortijo-Arellano, M.; Cladera, J.; Bryszewska, M.

    2006-01-01

    Inhibition of fibril assembly is a potential therapeutic strategy in neurodegenerative disorders such as prion and Alzheimer's diseases. Highly branched, globular polymers-dendrimers-are novel promising inhibitors of fibril formation. In this study, the effect of polyamidoamine (PAMAM) dendrimers (generations 3rd, 4th, and 5th) on amyloid aggregation of the prion peptide PrP 185-208 and the Alzheimer's peptide Aβ 1-28 was examined. Amyloid fibrils were produced in vitro and their formation was monitored using the dye thioflavin T (ThT). Fluorescence studies were complemented with electron microscopy. The results show that the higher the dendrimer generation, the larger the degree of inhibition of the amyloid aggregation process and the more effective are dendrimers in disrupting the already existing fibrils. A hypothesis on dendrimer-peptide interaction mechanism is presented based on the dendrimers' molecular structure

  2. Electrostatic Swelling and Conformational Variation Observed in High-Generation Polyelectrolyte Dendrimers

    International Nuclear Information System (INIS)

    Butler, Paul D.; Chen, Wei-Ren; Herwig, Kenneth W.; Hong, Kunlun; Liu, Yun; Porcar, L.; Shew, Chwen-Yang; Smith, Gregory Scott; Chen, Hsin-Lung; Chen, Chun-Yu; Li, Xin; Liu, Emily

    2010-01-01

    A coordinated study combining small angle neutron scattering (SANS) and small angle x-ray scattering (SAXS) measurements was conducted to investigate the structural characteristics of aqueous (D2O) generation 7 and 8 (G7 and G8) PAMAM dendrimer solutions as a function of molecular protonation at room temperature. The change in intra-molecular conformation was clearly exhibited in the data analysis by separating the variation in the inter-molecular correlation. Our results unambiguously demonstrate an increased molecular size and evolved intra-molecular density profile upon increasing the molecular protonation. This is contrary to the existing understanding that in higher generation polyelectrolyte dendrimers, steric crowding stiffens the local motion of dendrimer segments exploring additional available intra-dendrimer volume and therefore inhibits the electrostatic swelling. Our observation is relevant to elucidation of the general microscopic picture of polyelectrolyte dendrimer structure, as well as the development of dendrimer-based packages with based on the stimuli-responsive principle.

  3. pH controlled gating of toxic protein pores by dendrimers

    Science.gov (United States)

    Mandal, Taraknath; Kanchi, Subbarao; Ayappa, K. G.; Maiti, Prabal K.

    2016-06-01

    Designing effective nanoscale blockers for membrane inserted pores formed by pore forming toxins, which are expressed by several virulent bacterial strains, on a target cell membrane is a challenging and active area of research. Here we demonstrate that PAMAM dendrimers can act as effective pH controlled gating devices once the pore has been formed. We have used fully atomistic molecular dynamics (MD) simulations to characterize the cytolysin A (ClyA) protein pores modified with fifth generation (G5) PAMAM dendrimers. Our results show that the PAMAM dendrimer, in either its protonated (P) or non-protonated (NP) states can spontaneously enter the protein lumen. Protonated dendrimers interact strongly with the negatively charged protein pore lumen. As a consequence, P dendrimers assume a more expanded configuration efficiently blocking the pore when compared with the more compact configuration adopted by the neutral NP dendrimers creating a greater void space for the passage of water and ions. To quantify the effective blockage of the protein pore, we have calculated the pore conductance as well as the residence times by applying a weak force on the ions/water. Ionic currents are reduced by 91% for the P dendrimers and 31% for the NP dendrimers. The preferential binding of Cl- counter ions to the P dendrimer creates a zone of high Cl- concentration in the vicinity of the internalized dendrimer and a high concentration of K+ ions in the transmembrane region of the pore lumen. In addition to steric effects, this induced charge segregation for the P dendrimer effectively blocks ionic transport through the pore. Our investigation shows that the bio-compatible PAMAM dendrimers can potentially be used to develop therapeutic protocols based on the pH sensitive gating of pores formed by pore forming toxins to mitigate bacterial infections.Designing effective nanoscale blockers for membrane inserted pores formed by pore forming toxins, which are expressed by several virulent

  4. Solubility improvement of an anthelmintic benzimidazole carbamate by association with dendrimers

    Directory of Open Access Journals (Sweden)

    L. Fernández

    2011-12-01

    Full Text Available The improvement of aqueous solubility of methyl (5-[propylthio]-1H-benzimidazol-2-yl carbamate, albendazole (ABZ using polyamidoamine (PAMAM dendrimers as solubility enhancers was investigated. Full generation PAMAM dendrimers with amine terminal groups, (G3, with hydroxyl terminal groups (G3OH and half generation PAMAM dendrimers with carboxylate terminal groups (G2.5 and G3.5, were chosen for this study. The nature of dendrimer-ABZ association was investigated by UV absorption, fluorescence emission measurements and by ¹H-NMR spectroscopy. The results obtained show that these polymeric structures have the capacity to enhance the solubility of ABZ, both lipophilic and specific hydrogen bond interactions contributing to the guest-host association. Although all studied dendrimers have hydrophobic internal nanoenvironments with similar dimensions, their surfaces differ significantly and the nature and the localization of the interactions involved in ABZ-dendrimer association depend on the type of terminal groups.

  5. Solubility improvement of an anthelmintic benzimidazole carbamate by association with dendrimers

    International Nuclear Information System (INIS)

    Fernandez, L.; Sigal, E.; Santo, M.; Otero, L.; Silber, J. J.

    2011-01-01

    The improvement of aqueous solubility of methyl (5-[propylthio]-1H-benzimidazole-2-yl) carbamate, albendazole (ABZ) using polyamidoamine (PAMAM) dendrimers as solubility enhancers was investigated. Full generation PAMAM dendrimers with amine terminal groups, (G3), with hydroxyl terminal groups (G3OH) and half generation PAMAM dendrimers with carboxylate terminal groups (G2.5 and G3.5), were chosen for this study. The nature of dendrimer-ABZ association was investigated by UV absorption, fluorescence emission measurements and by 1 H-NMR spectroscopy. The results obtained show that these polymeric structures have the capacity to enhance the solubility of ABZ, both lipophilic and specific hydrogen bond interactions contributing to the guest-host association. Although all studied dendrimers have hydrophobic internal nanoenvironments with similar dimensions, their surfaces differ significantly and the nature and the localization of the interactions involved in ABZ-dendrimer association depend on the type of terminal groups. (author)

  6. Solubility improvement of an anthelmintic benzimidazole carbamate by association with dendrimers

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, L.; Sigal, E.; Santo, M., E-mail: msanto@exa.unrc.edu.ar [Departamento de Fisica, Facultad de Ciencias Exactas Fisicoquimicas y Naturales, Universidad Nacional de Rio Cuarto (Argentina); Otero, L.; Silber, J. J. [Departamento de Quimica. Facultad de Ciencias Exactas Fisicoquimicas y Naturales, Universidad Nacional de Rio Cuarto, Rio Cuarto (Argentina)

    2011-10-15

    The improvement of aqueous solubility of methyl (5-[propylthio]-1H-benzimidazole-2-yl) carbamate, albendazole (ABZ) using polyamidoamine (PAMAM) dendrimers as solubility enhancers was investigated. Full generation PAMAM dendrimers with amine terminal groups, (G3), with hydroxyl terminal groups (G3OH) and half generation PAMAM dendrimers with carboxylate terminal groups (G2.5 and G3.5), were chosen for this study. The nature of dendrimer-ABZ association was investigated by UV absorption, fluorescence emission measurements and by {sup 1}H-NMR spectroscopy. The results obtained show that these polymeric structures have the capacity to enhance the solubility of ABZ, both lipophilic and specific hydrogen bond interactions contributing to the guest-host association. Although all studied dendrimers have hydrophobic internal nanoenvironments with similar dimensions, their surfaces differ significantly and the nature and the localization of the interactions involved in ABZ-dendrimer association depend on the type of terminal groups. (author)

  7. In Vitro Evaluation of Third Generation PAMAM Dendrimer Conjugates

    Directory of Open Access Journals (Sweden)

    Mohammad Najlah

    2017-10-01

    Full Text Available The present study compares the use of high generation G3 and low generation G0 Polyamidoamine (PAMAM dendrimers as drug carriers of naproxen (NAP, a poorly water soluble drug. Naproxen was conjugated to G3 in different ratios and to G0 in a 1:1 ratio via a diethylene glycol linker. A lauroyl chain (L, a lipophilic permeability enhancer, was attached to G3 and G0 prodrugs. The G3 and G0 conjugates were more hydrophilic than naproxen as evaluated by the measurement of partitioning between 1-octanol and a phosphate buffer at pH 7.4 and pH 1.2. The unmodified surface PAMAM-NAP conjugates showed significant solubility enhancements of NAP at pH 1.2; however, with the number of NAP conjugated to G3, this was limited to 10 molecules. The lactate dehydrogenase (LDH assay indicated that the G3 dendrimer conjugates had a concentration dependent toxicity towards Caco-2 cells. Attaching naproxen to the surface of the dendrimer increased the IC50 of the resulting prodrugs towards Caco-2 cells. The lauroyl G3 conjugates showed the highest toxicity amongst the PAMAM dendrimer conjugates investigated and were significantly more toxic than the lauroyl-G0-naproxen conjugates. The permeability of naproxen across monolayers of Caco-2 cells was significantly increased by its conjugation to either G3 or G0 PAMAM dendrimers. Lauroyl-G0 conjugates displayed considerably lower cytotoxicity than G3 conjugates and may be preferable for use as a drug carrier for low soluble drugs such as naproxen.

  8. Quantitative assessment of surface functionality effects on microglial uptake and retention of PAMAM dendrimers

    Science.gov (United States)

    Liaw, Kevin; Gök, Ozgul; DeRidder, Louis B.; Kannan, Sujatha; Kannan, Rangaramanujam M.

    2018-04-01

    Dendrimers are a promising class of polymeric nanoparticles for delivery of therapeutics and diagnostics. Polyamidoamine (PAMAM) dendrimers have shown significant efficacy in many animal models, with performance dependent on surface functionalities. Understanding the effects of end groups on biological interactions is critical for rational design of dendrimer-mediated therapies. In this study, we quantify the cellular trafficking kinetics (endocytosis and exocytosis) of generation 4 neutral (D4-OH), cationic (D4-NH2), anionic (D3.5-COOH), and generation 6 neutral (D6-OH) PAMAM dendrimers to investigate the nanoscale effects of surface functionality and size on cellular interactions. Resting and LPS-activated microglia were studied due to their central roles in dendrimer therapies for central nervous system disorders. D4-OH exhibits greater cellular uptake and lower retention than the larger D6-OH. D4-OH and D3.5-COOH exhibit similar trafficking kinetics, while D4-NH2 exhibits significant membrane interactions, resulting in faster cell association but lower internalization. Cationic charge may also enhance vesicular escape for greater cellular retention and preferential partitioning to nuclei. LPS activation further improves uptake of dendrimers, with smaller and cationic dendrimers experiencing the greatest increases in uptake compared to resting microglia. These studies have implications for the dependence of trafficking pathway on dendrimer properties and inform the design of dendrimer constructs tailored to specific therapeutic needs. Cationic dendrimers are ideal for delivering genetic materials to nuclei, but toxicity may be a limiting factor. Smaller, neutral dendrimers are best suited for delivering high levels of therapeutics in acute neuroinflammation, while larger or cationic dendrimers provide robust retention for sustained release of therapeutics in longer-term diseases.

  9. Surface, core, and structure modifications of phosphorus-containing dendrimers. Influence on the thermal stability

    OpenAIRE

    Turrin , Cédric-Olivier; Maraval , Valérie; Leclaire , Julien; Dantras , Eric; Lacabanne , Colette; Caminade , Anne-Marie; Majoral , Jean-Pierre

    2003-01-01

    International audience; Three new series of phosphorus-containing dendrimers are described. Their solubility depends on the type of end groups they bear. Perfluoroalkyl chains give dendrimers soluble in chlorofluorocarbons, whereas guanidinium and pyridinium derivatives give watersoluble compounds. The thermal stability of these compounds, as well as of 19 other dendrimers of various generations, having various cores, or various end groups, or branching points is studied. The main feature of ...

  10. Switching the selectivity of a polyglycerol dendrimer monomolecularly imprinted with D-(−)-fructose

    OpenAIRE

    Hashidzume, Akihito; Zimmerman, Steven C.

    2009-01-01

    A polyglycerol dendrimer unimolecularly imprinted with D-(−)-fructose (Fru) was synthesized. The dendrimer formed adducts with several monosaccharides, Fru, D-(+)-galactose, D-(+)-glucose, D-(+)-mannose, and methyl-α-D-mannopyranoside (MMan), by removal of four water molecules. The dendrimer preferred Fru in the absence of N,N,N′,N′-tetramethylmethylenediamine (TMDAM), whereas it preferred MMan in the presence of TMDAM.

  11. Characterization of an engineered cellulose based membrane by thiol dendrimer for heavy metals removal

    OpenAIRE

    Algarra, Manuel; Vázquez, María Isabel; Alonso, Beatriz S.; Casado, Carmen Mª.; Casado, Juan; Benavente, Juana

    2014-01-01

    Diaminobutane based poly(propyleneimine) dendrimer functionalized with sixteen thiol groups, DAB-3-(SH)16, was successfully embeded in a swollen cellulosic support in order to achieve an easily handle engineered membrane. The membrane was characterised by physicochemical, electrical and transport measurements, and the effect of the dendrimer was established by comparing these results with those obtained for the original cellulosic support. Results show that dendrimer inclusion improves the me...

  12. Trapping time statistics and efficiency of transport of optical excitations in dendrimers

    OpenAIRE

    Heijs, D.J.; Malyshev, V.A.; Knoester, J.

    2004-01-01

    We theoretically study the trapping time distribution and the efficiency of the excitation energy transport in dendritic systems. Trapping of excitations, created at the periphery of the dendrimer, on a trap located at its core, is used as a probe of the efficiency of the energy transport across the dendrimer. The transport process is treated as incoherent hopping of excitations between nearest-neighbor dendrimer units and is described using a rate equation. We account for radiative and non-r...

  13. Size-dependent structure of CdSe nanoclusters formed after ion implantation in MgO

    NARCIS (Netherlands)

    van Huis, MA; van Veen, A; Schut, H; Eijt, SWH; Kooi, BJ; De Hosson, JTM

    The band gap as well as the optical and structural properties of semiconductor CdSe nanoclusters change as a function of the nanocluster size. Embedded CdSe nanoclusters in MgO were created by means of sequential Cd and Se ion implantation followed by thermal annealing. Changes during annealing were

  14. Size effect on the adsorption and dissociation of CO{sub 2} on Co nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Haiyan; Cao, Dapeng; Fisher, Adrian [International Research Center for Soft Matter, State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029 (China); Johnston, Roy L. [School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom); Cheng, Daojian, E-mail: chengdj@mail.buct.edu.cn [International Research Center for Soft Matter, State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029 (China)

    2017-02-28

    Highlights: • Co{sub 13}, Co{sub 38} and Co{sub 55} nanoclusters were predicted as the high-symmetry structures. • CO{sub 2} dissociation on the size-selected Co{sub 13}, Co{sub 38} and Co{sub 55} nanoclusters was studied. • Co{sub 55} nanocluster possesses the highest activity relevant to CO{sub 2} dissociation. • A non-monotonous behavior of the dissociation barrier of CO{sub 2} with the size was found. - Abstract: Spin-polarized density functional theory calculations were carried out to study the adsorption and dissociation properties of CO{sub 2} on size-selected Co{sub 13}, Co{sub 38} and Co{sub 55} nanoclusters. Based on genetic algorithm method, Co{sub 13}, Co{sub 38} and Co{sub 55} nanoclusters were predicted as the most stable high-symmetry structures among these Co{sub n} (n = 2–58) nanoclusters from the Gupta potential. For the adsorption of CO{sub 2}, CO and O on size-selected Co{sub 13}, Co{sub 38} and Co{sub 55} nanoclusters, the lowest adsorption strength is found for all the different adsorbates on Co{sub 55} nanocluster. For the dissociation of CO{sub 2} on these size-selected Co nanoclusters, the largest Co{sub 55} nanocluster possesses the greatest catalytic activity for the dissociation of CO{sub 2}, with the smallest reaction barrier of 0.38 eV. Our results reveal a non-monotonous behavior of the catalytic activities of Co nanoclusters on size, which is of fundamental interest for the design of new Co catalysts for the conversion of CO{sub 2}.

  15. Poly(amidoamine) (PAMAM) dendrimers: from biomimicry to drug delivery and biomedical applications.

    Science.gov (United States)

    Esfand, R; Tomalia, D A.

    2001-04-01

    Poly(amidoamine) (PAMAM) dendrimers are the first complete dendrimer family to be synthesized, characterized and commercialized. Based on this extensive activity, they are recognized as a unique new class of synthetic nanostructures. Dendrimers allow the precise control of size, shape and placement of functional groups that is desirable for many life science applications. From this perspective, this review focuses on crucial properties of biomimetic dendrimers that will broaden the potential for their use as macromolecular vectors in novel drug delivery and biomedical applications.

  16. Magnetic properties of dendrimer structures with different coordination numbers: A Monte Carlo study

    International Nuclear Information System (INIS)

    Masrour, R.; Jabar, A.

    2016-01-01

    We investigate the magnetic properties of Cayley trees of large molecules with dendrimer structure using Monte Carlo simulations. The thermal magnetization and magnetic susceptibility of a dendrimer structure are given with different coordination numbers, Z=3, 4, 5 and different generations g=3 and 2. The variation of magnetizations with the exchange interactions and crystal fields have been given of this system. The magnetic hysteresis cycles have been established. - Highlights: • The dendrimer structure is investigated using Monte Carlo simulations. • The transition temperatures are obtained for different coordination numbers and generations. • The magnetic hysteresis cycle has been established. • The dendrimer structure exhibit the superparamagnetic behavior.

  17. Effect of solvent-controlled aggregation on the intrinsic emission properties of PAMAM dendrimers

    International Nuclear Information System (INIS)

    Jasmine, Maria J.; Kavitha, Manniledam; Prasad, Edamana

    2009-01-01

    Solvent-induced aggregation and its effect on the intrinsic emission properties of amine, hydroxy and carboxylate terminated, poly(amidoamine) (PAMAM) dendrimers have been investigated in glycerol, ethylene glycol, methanol, ethylene diamine and water. Altering the solvent medium induces remarkable changes in the intrinsic emission properties of the PAMAM dendrimers at identical concentration. Upon excitation at 370 nm, amine terminated PAMAM dendrimer exhibits an intense emission at 470 nm in glycerol, ethylene glycol as well as glycerol-water mixtures. Conversely, weak luminescence is observed for hydroxy and carboxylate terminated PAMAM dendrimers in the same solvent systems. When the solvent is changed to ethylene diamine, hydroxy terminated PAMAM exhibits intense blue emission at 425 nm. While the emission intensity is varied when the solvent milieu is changed, excited state lifetime values of PAMAM dendrimers remain independent of the solvent used. UV-visible absorption and dynamic light scattering (DLS) experiments confirm the formation of solvent-controlled dendrimer aggregates in the systems. Comparison of the fluorescence and DLS data reveals that the size distribution of the dendrimer aggregates in each solvent system is distinct, which control the intrinsic emission intensity from PAMAM dendrimers. The experimental results suggest that intrinsic emission intensity from PAMAM dendrimers can be regulated by proper selection of solvents at neutral conditions and room temperature

  18. Oligodeoxynucleotide nanostructure formation in the presence of polypropyleneimine dendrimers and their uptake in breast cancer cells

    International Nuclear Information System (INIS)

    Chen, Alex M; Santhakumaran, Latha M; Nair, Sandhya K; Amenta, Peter S; Thomas, Thresia; He, Huixin; Thomas, T J

    2006-01-01

    We studied the efficacy of five generations of polypropyleneimine (PPI) dendrimer to provoke nanostructure formation from a 21-nucleotide antisense oligodeoxynucleotide (ODN). Nanostructure formation was observed with all generations of dendrimer by light scattering and microscopic techniques. The efficacy of the dendrimers increased with generation number. Atomic force microscopy (AFM) was used to study the morphology of the structures at different condensation stages. Based on the observed nanostructures, we propose a zipping condensation mechanism, which is very different from the condensation pathways of high molecular weight DNA polymers. Electron microscopy showed the presence of toroidal nanoparticles. Confocal microscopic analysis showed that the nanostructures formed with G-4 and G-5 dendrimers could undergo facile cellular uptake in a breast cancer cell line, MDA-MB-231, whereas nanostructures formed with G-1 to G-3 dendrimers lacked this ability. Nanoparticles formed with G-1 to G-3 dendrimers showed significantly lower zeta potential (5.2-6.5 mV) than those (12-18 mV) of particles formed with G-4 and G-5 dendrimers. These results show that the structure and charge density of the dendrimers are important in ODN nanoparticle formation and cellular transport and that G-4 and G-5 dendrimers are useful in cellular delivery of antisense ODN

  19. Synthesis of Polyamidoamine Dendrimer for Encapsulating Tetramethylscutellarein for Potential Bioactivity Enhancement.

    Science.gov (United States)

    Shadrack, Daniel M; Mubofu, Egid B; Nyandoro, Stephen S

    2015-11-04

    The biomedical potential of flavonoids is normally restricted by their low water solubility. However, little has been reported on their encapsulation into polyamidoamine (PAMAM) dendrimers to improve their biomedical applications. Generation four (G4) PAMAM dendrimer containing ethylenediaminetetraacetic acid core with acrylic acid and ethylenediamine as repeating units was synthesized by divergent approach and used to encapsulate a flavonoid tetramethylscutellarein (TMScu, 1) to study its solubility and in vitro release for potential bioactivity enhancement. The as-synthesized dendrimer and the dendrimer-TMScu complex were characterized by spectroscopic and spectrometric techniques. The encapsulation of 1 into dendrimer was achieved by a co-precipitation method with the encapsulation efficiency of 77.8% ± 0.69% and a loading capacity of 6.2% ± 0.06%. A phase solubility diagram indicated an increased water solubility of 1 as a function of dendrimer concentration at pH 4.0 and 7.2. In vitro release of 1 from its dendrimer complex indicated high percentage release at pH 4.0. The stability study of the TMScu-dendrimer at 0, 27 and 40 °C showed the formulations to be stable when stored in cool and dark conditions compared to those stored in light and warmer temperatures. Overall, PAMAM dendrimer-G4 is capable of encapsulating 1, increasing its solubility and thus could enhance its bioactivity.

  20. Optimization of dendrimer structure for sentinel lymph node imaging: Effects of generation and terminal group.

    Science.gov (United States)

    Niki, Yuichiro; Ogawa, Mikako; Makiura, Rie; Magata, Yasuhiro; Kojima, Chie

    2015-11-01

    The detection of the sentinel lymph node (SLN), the first lymph node draining tumor cells, is important in cancer diagnosis and therapy. Dendrimers are synthetic macromolecules with highly controllable structures, and are potent multifunctional imaging agents. In this study, 12 types of dendrimer of different generations (G2, G4, G6, and G8) and different terminal groups (amino, carboxyl, and acetyl) were prepared to determine the optimal dendrimer structure for SLN imaging. Radiolabeled dendrimers were intradermally administrated to the right footpads of rats. All G2 dendrimers were predominantly accumulated in the kidney. Amino-terminal, acetyl-terminal, and carboxyl-terminal dendrimers of greater than G4 were mostly located at the injection site, in the blood, and in the SLN, respectively. The carboxyl-terminal dendrimers were largely unrecognized by macrophages and T-cells in the SLN. Finally, SLN detection was successfully performed by single photon emission computed tomography imaging using carboxyl-terminal dendrimers of greater than G4. The early detection of tumor cells in the sentinel draining lymph nodes (SLN) is of utmost importance in terms of determining cancer prognosis and devising treatment. In this article, the authors investigated various formulations of dendrimers to determine the optimal one for tumor detection. The data generated from this study would help clinicians to fight the cancer battle in the near future. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Magnetic properties of dendrimer structures with different coordination numbers: A Monte Carlo study

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com; Jabar, A.

    2016-11-01

    We investigate the magnetic properties of Cayley trees of large molecules with dendrimer structure using Monte Carlo simulations. The thermal magnetization and magnetic susceptibility of a dendrimer structure are given with different coordination numbers, Z=3, 4, 5 and different generations g=3 and 2. The variation of magnetizations with the exchange interactions and crystal fields have been given of this system. The magnetic hysteresis cycles have been established. - Highlights: • The dendrimer structure is investigated using Monte Carlo simulations. • The transition temperatures are obtained for different coordination numbers and generations. • The magnetic hysteresis cycle has been established. • The dendrimer structure exhibit the superparamagnetic behavior.

  2. Oligodeoxynucleotide nanostructure formation in the presence of polypropyleneimine dendrimers and their uptake in breast cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Alex M [Department of Chemistry, Rutgers University, 73 Warren Street, Newark, NJ 07102 (United States); Santhakumaran, Latha M [Department of Medicine, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ 08903 (United States); Nair, Sandhya K [Department of Medicine, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ 08903 (United States); Amenta, Peter S [Department of Pathology and Laboratory Medicine, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ 08903 (United States); Thomas, Thresia [Department of Environmental and Health Sciences Institute, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ 08903 (United States); He, Huixin [Department of Chemistry, Rutgers University, 73 Warren Street, Newark, NJ 07102 (United States); Thomas, T J [Department of Medicine, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ 08903 (United States)

    2006-11-14

    We studied the efficacy of five generations of polypropyleneimine (PPI) dendrimer to provoke nanostructure formation from a 21-nucleotide antisense oligodeoxynucleotide (ODN). Nanostructure formation was observed with all generations of dendrimer by light scattering and microscopic techniques. The efficacy of the dendrimers increased with generation number. Atomic force microscopy (AFM) was used to study the morphology of the structures at different condensation stages. Based on the observed nanostructures, we propose a zipping condensation mechanism, which is very different from the condensation pathways of high molecular weight DNA polymers. Electron microscopy showed the presence of toroidal nanoparticles. Confocal microscopic analysis showed that the nanostructures formed with G-4 and G-5 dendrimers could undergo facile cellular uptake in a breast cancer cell line, MDA-MB-231, whereas nanostructures formed with G-1 to G-3 dendrimers lacked this ability. Nanoparticles formed with G-1 to G-3 dendrimers showed significantly lower zeta potential (5.2-6.5 mV) than those (12-18 mV) of particles formed with G-4 and G-5 dendrimers. These results show that the structure and charge density of the dendrimers are important in ODN nanoparticle formation and cellular transport and that G-4 and G-5 dendrimers are useful in cellular delivery of antisense ODN.

  3. Peptide- and saccharide-conjugated dendrimers for targeted drug delivery: a concise review

    Science.gov (United States)

    Liu, Jie; Gray, Warren D.; Davis, Michael E.; Luo, Ying

    2012-01-01

    Dendrimers comprise a category of branched materials with diverse functions that can be constructed with defined architectural and chemical structures. When decorated with bioactive ligands made of peptides and saccharides through peripheral chemical groups, dendrimer conjugates are turned into nanomaterials possessing attractive binding properties with the cognate receptors. At the cellular level, bioactive dendrimer conjugates can interact with cells with avidity and selectivity, and this function has particularly stimulated interests in investigating the targeting potential of dendrimer materials for the design of drug delivery systems. In addition, bioactive dendrimer conjugates have so far been studied for their versatile capabilities to enhance stability, solubility and absorption of various types of therapeutics. This review presents a brief discussion on three aspects of the recent studies to use peptide- and saccharide-conjugated dendrimers for drug delivery: (i) synthesis methods, (ii) cell- and tissue-targeting properties and (iii) applications of conjugated dendrimers in drug delivery nanodevices. With more studies to elucidate the structure–function relationship of ligand–dendrimer conjugates in transporting drugs, the conjugated dendrimers hold promise to facilitate targeted delivery and improve drug efficacy for discovery and development of modern pharmaceutics. PMID:23741608

  4. Exciton confinement in organic dendrimer quantum wells for opto-electronic applications

    Science.gov (United States)

    Lupton, J. M.; Samuel, I. D. W.; Burn, P. L.; Mukamel, S.

    2002-01-01

    Organic dendrimers are a fascinating new class of materials for opto-electronic applications. We present coupled electronic oscillator calculations on novel nanoscale conjugated dendrimers for use in organic light-emitting diodes. Strong confinement of excitations at the center of the dendrimers is observed, which accounts for the dependence of intermolecular interactions and charge transport on the degree of branching of the dendrimer. The calculated absorption spectra are in excellent agreement with the measured data and show that benzene rings are shared between excitations on the linear segments of the hyperbranched molecules. The coupled electronic oscillator approach is ideally suited to treat large dendritic molecules.

  5. Transepithelial transport and toxicity of PAMAM dendrimers: implications for oral drug delivery.

    Science.gov (United States)

    Sadekar, S; Ghandehari, H

    2012-05-01

    This article summarizes efforts to evaluate poly(amido amine) (PAMAM) dendrimers as carriers for oral drug delivery. Specifically, the effect of PAMAM generation, surface charge and surface modification on toxicity, cellular uptake and transepithelial transport is discussed. Studies on Caco-2 monolayers, as models of intestinal epithelial barrier, show that by engineering surface chemistry of PAMAM dendrimers, it is possible to minimize toxicity while maximizing transepithelial transport. It has been demonstrated that PAMAM dendrimers are transported by a combination of paracellular and transcellular routes. Depending on surface chemistry, PAMAM dendrimers can open the tight junctions of epithelial barriers. This tight junction opening is in part mediated by internalization of the dendrimers. Transcellular transport of PAMAM dendrimers is mediated by a variety of endocytic mechanisms. Attachment or complexation of cytotoxic agents to PAMAM dendrimers enhances the transport of such drugs across epithelial barriers. A remaining challenge is the design and development of linker chemistries that are stable in the gastrointestinal tract (GIT) and the blood stream, but amenable to cleavage at the target site of action. Recent efforts have focused on the use of PAMAM dendrimers as penetration enhancers. Detailed in vivo oral bioavailability of PAMAM dendrimer-drug conjugates, as a function of physicochemical properties will further need to be assessed. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Oligodeoxynucleotide nanostructure formation in the presence of polypropyleneimine dendrimers and their uptake in breast cancer cells

    Science.gov (United States)

    Chen, Alex M.; Santhakumaran, Latha M.; Nair, Sandhya K.; Amenta, Peter S.; Thomas, Thresia; He, Huixin; Thomas, T. J.

    2006-11-01

    We studied the efficacy of five generations of polypropyleneimine (PPI) dendrimer to provoke nanostructure formation from a 21-nucleotide antisense oligodeoxynucleotide (ODN). Nanostructure formation was observed with all generations of dendrimer by light scattering and microscopic techniques. The efficacy of the dendrimers increased with generation number. Atomic force microscopy (AFM) was used to study the morphology of the structures at different condensation stages. Based on the observed nanostructures, we propose a zipping condensation mechanism, which is very different from the condensation pathways of high molecular weight DNA polymers. Electron microscopy showed the presence of toroidal nanoparticles. Confocal microscopic analysis showed that the nanostructures formed with G-4 and G-5 dendrimers could undergo facile cellular uptake in a breast cancer cell line, MDA-MB-231, whereas nanostructures formed with G-1 to G-3 dendrimers lacked this ability. Nanoparticles formed with G-1 to G-3 dendrimers showed significantly lower zeta potential (5.2-6.5 mV) than those (12-18 mV) of particles formed with G-4 and G-5 dendrimers. These results show that the structure and charge density of the dendrimers are important in ODN nanoparticle formation and cellular transport and that G-4 and G-5 dendrimers are useful in cellular delivery of antisense ODN.

  7. A nanocluster-based fluorescent sensor for sensitive hemoglobin detection.

    Science.gov (United States)

    Yang, Dongqin; Meng, Huijie; Tu, Yifeng; Yan, Jilin

    2017-08-01

    In this report, a fluorescence sensor for sensitive detection of hemoglobin was developed. Gold nanoclusters were first synthesized with bovine serum albumin. It was found that both hydrogen peroxide and hemoglobin could weakly quench the fluorescence from the gold nanoclusters, but when these two were applied onto the nanolcusters simultaneously, a much improved quenching was resulted. This enhancing effect was proved to come from the catalytic generation of hydroxyl radical by hemoglobin. Under an optimized condition, the quenching linearly related to the concentration of hemoglobin in the range of 1-250nM, and a limit of detection as low as 0.36nM could be obtained. This provided a sensitive means for the quantification of Hb. The sensor was then successfully applied for blood analyses with simple sample pretreatment. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. The expanding universe of thiolated gold nanoclusters and beyond.

    Science.gov (United States)

    Jiang, De-en

    2013-08-21

    Thiolated gold nanoclusters form a universe of their own. Researchers in this field are constantly pushing the boundary of this universe by identifying new compositions and in a few "lucky" cases, solving their structures. Such solved structures, even if there are only few, provide important hints for predicting the many identified compositions that are yet to be crystallized or structure determined. Structure prediction is the most pressing issue for a computational chemist in this field. The success of the density functional theory method in gauging the energetic ordering of isomers for thiolated gold clusters has been truly remarkable, but to predict the most stable structure for a given composition remains a great challenge. In this feature article from a computational chemist's point of view, the author shows how one understands and predicts structures for thiolated gold nanoclusters based on his old and new results. To further entertain the reader, the author also offers several "imaginative" structures, claims, and challenges for this field.

  9. Poly(amido)amine (PAMAM) dendrimer-cisplatin complexes for chemotherapy of cisplatin-resistant ovarian cancer cells

    Science.gov (United States)

    Yellepeddi, Venkata Kashyap; Vangara, Kiran Kumar; Palakurthi, Srinath

    2013-09-01

    Dendrimer-cisplatin complexes were prepared using PAMAM dendrimers with terminal -NH2 and -COOH groups as well as biotin-conjugated dendrimers. Preformulation parameters of dendrimer-cisplatin complexes were studied using differential scanning calorimetry (DSC) and inductively coupled plasma-mass spectrometry (ICP-MS). Cytotoxicity and mechanism of cytotoxicity of dendrimer-cisplatin complexes was investigated in OVCAR-3, SKOV, A2780 and cisplatin-resistant CP70 human ovarian cancer cell lines. The loading of cisplatin in dendrimers was 11 % (w/w). PAMAM G4 dendrimers with amine surface groups (biotinylated and native) have shown 2.5- to 3.0-fold reduction in IC50 values in ovarian cancer cells when compared with carboxylate surface dendrimers ( p cisplatin complexes resulted in a 7.0-fold increase ( p cisplatin chemotherapy of ovarian cancer.

  10. Theory of Nanocluster Size Distributions from Ion Beam Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, C.W.; Yi, D.O.; Sharp, I.D.; Shin, S.J.; Liao, C.Y.; Guzman, J.; Ager III, J.W.; Haller, E.E.; Chrzan, D.C.

    2008-06-13

    Ion beam synthesis of nanoclusters is studied via both kinetic Monte Carlo simulations and the self-consistent mean-field solution to a set of coupled rate equations. Both approaches predict the existence of a steady state shape for the cluster size distribution that depends only on a characteristic length determined by the ratio of the effective diffusion coefficient to the ion flux. The average cluster size in the steady state regime is determined by the implanted species/matrix interface energy.

  11. Chemical- or radiation-assisted selective dealloying in bimetallic nanoclusters

    International Nuclear Information System (INIS)

    Mattei, G.; De Marchi, G.; Maurizio, C.; Mazzoldi, P.; Sada, C.; Bello, V.; Battaglin, G.

    2003-01-01

    A selective dealloying in bimetallic nanoclusters prepared by ion implantation has been found upon thermal annealing in oxidizing atmosphere or irradiation with light ions. In the first process, the incoming oxygen interacts preferentially with copper promoting Cu 2 O formation, therefore extracting copper from the alloy. In the second process the irradiation with Ne ions promotes a preferential extraction of Au from the alloy, resulting in the formation of Au-enriched 'satellite' nanoparticles around the original Au x Cu 1-x cluster

  12. Chiral Gold Nanoclusters: Atomic Level Origins of Chirality.

    Science.gov (United States)

    Zeng, Chenjie; Jin, Rongchao

    2017-08-04

    Chiral nanomaterials have received wide interest in many areas, but the exact origin of chirality at the atomic level remains elusive in many cases. With recent significant progress in atomically precise gold nanoclusters (e.g., thiolate-protected Au n (SR) m ), several origins of chirality have been unveiled based upon atomic structures determined by using single-crystal X-ray crystallography. The reported chiral Au n (SR) m structures explicitly reveal a predominant origin of chirality that arises from the Au-S chiral patterns at the metal-ligand interface, as opposed to the chiral arrangement of metal atoms in the inner core (i.e. kernel). In addition, chirality can also be introduced by a chiral ligand, manifested in the circular dichroism response from metal-based electronic transitions other than the ligand's own transition(s). Lastly, the chiral arrangement of carbon tails of the ligands has also been discovered in a very recent work on chiral Au 133 (SR) 52 and Au 246 (SR) 80 nanoclusters. Overall, the origins of chirality discovered in Au n (SR) m nanoclusters may provide models for the understanding of chirality origins in other types of nanomaterials and also constitute the basis for the development of various applications of chiral nanoparticles. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Methotrexate loaded polyether-copolyester dendrimers for the treatment of gliomas: enhanced efficacy and intratumoral transport capability.

    Science.gov (United States)

    Dhanikula, Renu Singh; Argaw, Anteneh; Bouchard, Jean-Francois; Hildgen, Patrice

    2008-01-01

    Therapeutic benefit in glial tumors is often limited due to low permeability of delivery systems across the blood-brain barrier (BBB), drug resistance, and poor penetration into the tumor tissue. In an attempt to overcome these hurdles, polyether-copolyester (PEPE) dendrimers were evaluated as drug carriers for the treatment of gliomas. Dendrimers were conjugated to d-glucosamine as the ligand for enhancing BBB permeability and tumor targeting. The efficacy of methotrexate (MTX)-loaded dendrimers was established against U87 MG and U 343 MGa cells. Permeability of rhodamine-labeled dendrimers and MTX-loaded dendrimers across the in vitro BBB model and their distribution into avascular human glioma tumor spheroids was also studied. Glucosylated dendrimers were found to be endocytosed in significantly higher amounts than nonglucosylated dendrimers by both the cell lines. IC 50 of MTX after loading in dendrimers was lower than that of the free MTX, suggesting that loading MTX in PEPE dendrimers increased its potency. Similar higher activity of MTX-loaded glucosylated and nonglucosylated dendrimers was found in the reduction of tumor spheroid size. These MTX-loaded dendrimers were able to kill even MTX-resistant cells highlighting their ability to overcome MTX resistance. In addition, the amount of MTX-transported across BBB was three to five times more after loading in the dendrimers. Glucosylation further increased the cumulative permeation of dendrimers across BBB and hence increased the amount of MTX available across it. Glucosylated dendrimers distributed through out the avascular tumor spheroids within 6 h, while nonglucosylated dendrimers could do so in 12 h. The results show that glucosamine can be used as an effective ligand not only for targeting glial tumors but also for enhanced permeability across BBB. Thus, glucosylated PEPE dendrimers can serve as potential delivery system for the treatment of gliomas.

  14. Transcorneal iontophoresis of dendrimers: PAMAM corneal penetration and dexamethasone delivery.

    Science.gov (United States)

    Souza, Joel G; Dias, Karina; Silva, Silas A M; de Rezende, Lucas C D; Rocha, Eduardo M; Emery, Flavio S; Lopez, Renata F V

    2015-02-28

    Iontophoresis of nanocarriers in the eye has been proposed to sustain drug delivery and maintain therapeutic concentrations. Fourth generation polyamidoamine (PAMAM) dendrimers are semi-rigid nanoparticles with surface groups that are easily modified. These dendrimers are known to modulate tight junctions, increase paracellular transport of small molecules and be translocated across epithelial barriers, exhibiting high uptake by different cell lines. The first aim of this study was to investigate the effect of iontophoresis on PAMAM penetration and distribution into the cornea. The second aim was to evaluate, ex vivo and in vivo, the effect of these dendrimers in dexamethasone (Dex) transcorneal iontophoresis. Anionic (PAMAM G3.5) and cationic (PAMAM G4) dendrimers were labeled with fluorescein isothiocyanate (FITC), and their distribution in the cornea was investigated using confocal microscopy after ex vivo anodal and cathodal iontophoresis for various application times. The particle size distribution and zeta potential of the dendrimers in an isosmotic solution were determined using dynamic light scattering and Nanoparticle Tracking Analysis (NTA), where the movement of small particles and the formation of large aggregates, from 5 to 100 nm, could be observed. Transcorneal iontophoresis increased the intensity and depth of PAMAM-FITC fluorescence in the cornea, suggesting improved transport of the dendrimers across the epithelium toward the stroma. PAMAM complexes with Dex were characterized by (13)C-NMR, (1)H-NMR and DOSY. PAMAM G3.5 and PAMAM G4 increased the aqueous solubility of Dex by 10.3 and 3.9-fold, respectively; however, the particle size distribution and zeta potential remained unchanged. PAMAM G3.5 decreased the Dex diffusion coefficient 48-fold compared with PAMAM G4. The ex vivo studies showed that iontophoresis increased the amount of Dex that penetrated into the cornea by 2.9, 5.6 and 3.0-fold for Dex, Dex-PAMAM G4 and Dex-PAMAM G3

  15. Pt, Co–Pt and Fe–Pt alloy nanoclusters encapsulated in virus capsids

    International Nuclear Information System (INIS)

    Okuda, M; Eloi, J-C; Jones, S E Ward; Schwarzacher, W; Verwegen, M; Cornelissen, J J L M

    2016-01-01

    Nanostructured Pt-based alloys show great promise, not only for catalysis but also in medical and magnetic applications. To extend the properties of this class of materials, we have developed a means of synthesizing Pt and Pt-based alloy nanoclusters in the capsid of a virus. Pure Pt and Pt-alloy nanoclusters are formed through the chemical reduction of [PtCl 4 ] − by NaBH 4 with/without additional metal ions (Co or Fe). The opening and closing of the ion channels in the virus capsid were controlled by changing the pH and ionic strength of the solution. The size of the nanoclusters is limited to 18 nm by the internal diameter of the capsid. Their magnetic properties suggest potential applications in hyperthermia for the Co–Pt and Fe–Pt magnetic alloy nanoclusters. This study introduces a new way to fabricate size-restricted nanoclusters using virus capsid. (paper)

  16. A Comparative XAFS Study of Gold-thiolate Nanoparticles and Nanoclusters

    International Nuclear Information System (INIS)

    Chevrier, D M; Chatt, A; Zhang, P; Sham, T K

    2013-01-01

    Tiopronin-capped gold nanoparticles and gold nanoclusters of sizes 3.0 and 1.5 nm, respectively, were investigated with XAFS at the gold L 3 -edge. The specific EXAFS fitting procedure is discussed for obtaining reliable fit parameters for each system. The difficulties and challenges faced when analysing EXAFS data for gold nanoparticles and nanoclusters are also mentioned. Fitting results for gold nanoparticles reveal a small amount of surface Au-thiolate interactions with a large Au-Au metal core. For gold nanoclusters, only a one-shell fit was obtainable. Instead of Au-Au metal core, long-range interactions are expected for gold nanoclusters. Tiopronin-capped gold nanoclusters are proposed to be polymeric in nature, which helps explain the observed red luminescence.

  17. pH-Induced transformation of ligated Au25 to brighter Au23 nanoclusters.

    Science.gov (United States)

    Waszkielewicz, Magdalena; Olesiak-Banska, Joanna; Comby-Zerbino, Clothilde; Bertorelle, Franck; Dagany, Xavier; Bansal, Ashu K; Sajjad, Muhammad T; Samuel, Ifor D W; Sanader, Zeljka; Rozycka, Miroslawa; Wojtas, Magdalena; Matczyszyn, Katarzyna; Bonacic-Koutecky, Vlasta; Antoine, Rodolphe; Ozyhar, Andrzej; Samoc, Marek

    2018-05-01

    Thiolate-protected gold nanoclusters have recently attracted considerable attention due to their size-dependent luminescence characterized by a long lifetime and large Stokes shift. However, the optimization of nanocluster properties such as the luminescence quantum yield is still a challenge. We report here the transformation of Au25Capt18 (Capt labels captopril) nanoclusters occurring at low pH and yielding a product with a much increased luminescence quantum yield which we have identified as Au23Capt17. We applied a simple method of treatment with HCl to accomplish this transformation and we characterized the absorption and emission of the newly created ligated nanoclusters as well as their morphology. Based on DFT calculations we show which Au nanocluster size transformations can lead to highly luminescent species such as Au23Capt17.

  18. The formation of Cr2O3 nanoclusters over graphene sheet and carbon nanotubes

    Science.gov (United States)

    Dabaghmanesh, Samira; Neek-Amal, Mehdi; Partoens, Bart; Neyts, Erik C.

    2017-11-01

    Carbon supported metal oxide nanoparticles hold promise for various future applications in diverse areas including spintronics, catalysis and biomedicine. These applications, however, typically depend on the structure and morphology of the nanoparticles. In this contribution, we employ classical molecular dynamic simulations based on a recently developed force field to study the structural properties of Cr2O3 nanoclusters over graphene and carbon nanotubes. We observe that Cr2O3 nanoclusters tend to aggregate over both freestanding graphene and carbon nanotubes and form larger nanoclusters. These large nanoclusters are characterized by their worm-like shape with a lattice constant similar to that of bulk Cr2O3. We also investigate the structural deformation induced in graphene due to the presence of Cr2O3 nanoclusters.

  19. Synthesis and Doping of Ligand-Protected Atomically-Precise Metal Nanoclusters

    KAUST Repository

    Aljuhani, Maha A.

    2016-05-01

    Rapidly expanding research in nanotechnology has led to exciting progress in a versatile array of applications from medical diagnostics to catalysis. This success resulted from the manipulation of the desired properties of nanomaterials by controlling their size, shape, and composition. Among the most thriving areas of research about nanoparticle is the synthesis and doping of the ligand-protected atomically-precise metal nanoclusters. In this thesis, we developed three different novel metal nanoclusters, such as doped Ag29 with five gold (Au) atoms leading to enhance its quantum yield with remarkable stability. We also developed half-doped (alloyed) cluster of Ni6 nanocluster with molybdenum (Mo). This enabled enhanced stability and better catalytic activity. The third metal nanocluster that we synthesized was Au28 nanocluster by using di-thiolate as the ligand stabilizer instead of mono-thiolate. The new metal clusters obtained have been characterized by spectroscopic, electrochemical and crystallographic methods.

  20. Generalized rate-equation analysis of excitation exchange between silicon nanoclusters and erbium ions

    International Nuclear Information System (INIS)

    Kenyon, A. J.; Wojdak, M.; Ahmad, I.; Loh, W. H.; Oton, C. J.

    2008-01-01

    We discuss the use of rate equations to analyze the sensitization of erbium luminescence by silicon nanoclusters. In applying the general form of second-order coupled rate-equations to the Si nanocluster-erbium system, we find that the photoluminescence dynamics cannot be described using a simple rate equation model. Both rise and fall times exhibit a stretched exponential behavior, which we propose arises from a combination of a strongly distance-dependent nanocluster-erbium interaction, along with the finite size distribution and indirect band gap of the silicon nanoclusters. Furthermore, the low fraction of erbium ions that can be excited nonresonantly is a result of the small number of ions coupled to nanoclusters

  1. In Silico Characterization of the Binding Affinity of Dendrimers to Penicillin-Binding Proteins (PBPs): Can PBPs be Potential Targets for Antibacterial Dendrimers?

    Science.gov (United States)

    Ahmed, Shaimaa; Vepuri, Suresh B; Ramesh, Muthusamy; Kalhapure, Rahul; Suleman, Nadia; Govender, Thirumala

    2016-04-01

    We have shown that novel silver salts of poly (propyl ether) imine (PETIM) dendron and dendrimers developed in our group exhibit preferential antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus aureus. This led us to examine whether molecular modeling methods could be used to identify the key structural design principles for a bioactive lead molecule, explore the mechanism of binding with biological targets, and explain their preferential antibacterial activity. The current article reports the conformational landscape as well as mechanism of binding of generation 1 PETIM dendron and dendrimers to penicillin-binding proteins (PBPs) in order to understand the antibacterial activity profiles of their silver salts. Molecular dynamics at different simulation protocols and conformational analysis were performed to elaborate on the conformational features of the studied dendrimers, as well as to create the initial structure for further binding studies. The results showed that for all compounds, there were no significant conformational changes due to variation in simulation conditions. Molecular docking calculations were performed to investigate the binding theme between the studied dendrimers and PBPs. Interestingly, in significant accordance with the experimental data, dendron and dendrimer with aliphatic cores were found to show higher activity against S. aureus than the dendrimer with an aromatic core. The latter showed higher activity against MRSA. The findings from this computational and molecular modeling report together with the experimental results serve as a road map toward designing more potent antibacterial dendrimers against resistant bacterial strains.

  2. Comparative toxicological assessment of PAMAM and thiophosphoryl dendrimers using embryonic zebrafish

    Directory of Open Access Journals (Sweden)

    Pryor JB

    2014-04-01

    Full Text Available Joseph B Pryor,1 Bryan J Harper,1 Stacey L Harper1,21Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR, USA; 2School of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, OR, USAAbstract: Dendrimers are well-defined, polymeric nanomaterials currently being investigated for biomedical applications such as medical imaging, gene therapy, and tissue targeted therapy. Initially, higher generation (size dendrimers were of interest because of their drug carrying capacity. However, increased generation was associated with increased toxicity. The majority of studies exploring dendrimer toxicity have focused on a small range of materials using cell culture methods, with few studies investigating the toxicity across a wide range of materials in vivo. The objective of the present study was to investigate the role of surface charge and generation in dendrimer toxicity using embryonic zebrafish (Danio rerio as a model vertebrate. Due to the generational and charge effects observed at the cellular level, higher generation cationic dendrimers were hypothesized to be more toxic than lower generation anionic or neutral dendrimers with the same core composition. Polyamidoamine (PAMAM dendrimers elicited significant morbidity and mortality as generation was decreased. No significant adverse effects were observed from the suite of thiophosphoryl dendrimers studied. Exposure to ≥50 ppm cationic PAMAM dendrimers G3-amine, G4-amine, G5-amine, and G6-amine caused 100% mortality by 24 hours post-fertilization. Cationic PAMAM G6-amine at 250 ppm was found to be statistically more toxic than both neutral PAMAM G6-amidoethanol and anionic PAMAM G6-succinamic acid at the same concentration. The toxicity observed within the suite of varying dendrimers provides evidence that surface charge may be the best indicator of dendrimer toxicity. Dendrimer class and generation are other potential

  3. RGD peptide-modified multifunctional dendrimer platform for drug encapsulation and targeted inhibition of cancer cells.

    Science.gov (United States)

    He, Xuedan; Alves, Carla S; Oliveira, Nilsa; Rodrigues, João; Zhu, Jingyi; Bányai, István; Tomás, Helena; Shi, Xiangyang

    2015-01-01

    Development of multifunctional nanoscale drug-delivery systems for targeted cancer therapy still remains a great challenge. Here, we report the synthesis of cyclic arginine-glycine-aspartic acid (RGD) peptide-conjugated generation 5 (G5) poly(amidoamine) dendrimers for anticancer drug encapsulation and targeted therapy of cancer cells overexpressing αvβ3 integrins. In this study, amine-terminated G5 dendrimers were used as a platform to be sequentially modified with fluorescein isothiocyanate (FI) via a thiourea linkage and RGD peptide via a polyethylene glycol (PEG) spacer, followed by acetylation of the remaining dendrimer terminal amines. The developed multifunctional dendrimer platform (G5.NHAc-FI-PEG-RGD) was then used to encapsulate an anticancer drug doxorubicin (DOX). We show that approximately six DOX molecules are able to be encapsulated within each dendrimer platform. The formed complexes are water-soluble, stable, and able to release DOX in a sustained manner. One- and two-dimensional NMR techniques were applied to investigate the interaction between dendrimers and DOX, and the impact of the environmental pH on the release rate of DOX from the dendrimer/DOX complexes was also explored. Furthermore, cell biological studies demonstrate that the encapsulation of DOX within the G5.NHAc-FI-PEG-RGD dendrimers does not compromise the anticancer activity of DOX and that the therapeutic efficacy of the dendrimer/DOX complexes is solely related to the encapsulated DOX drug. Importantly, thanks to the role played by RGD-mediated targeting, the developed dendrimer/drug complexes are able to specifically target αvβ3 integrin-overexpressing cancer cells and display specific therapeutic efficacy to the target cells. The developed RGD peptide-targeted multifunctional dendrimers may thus be used as a versatile platform for targeted therapy of different types of αvβ3 integrin-overexpressing cancer cells. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. On-Demand Bioadhesive Dendrimers with Reduced Cytotoxicity

    Directory of Open Access Journals (Sweden)

    Feng Gao

    2018-03-01

    Full Text Available Tissue adhesives based on polyamidoamine (PAMAM dendrimer, grafted with UV-sensitive aryldiazirine (PAMAM-g-diazirine are promising new candidates for light active adhesion on soft tissues. Diazirine carbene precursors form interfacial and intermolecular covalent crosslinks with tissues after UV light activation that requires no premixing or inclusion of free radical initiators. However, primary amines on the PAMAM dendrimer surface present a potential risk due to their cytotoxic and immunological effects. PAMAM-g-diazirine formulations with cationic pendant amines converted into neutral amide groups were evaluated. In vitro toxicity is reduced by an order of magnitude upon amine capping while retaining bioadhesive properties. The in vivo immunological response to PAMAM-g-diazirine formulations was found to be optimal in comparison to standard poly(lactic-co-glycolic acid (PLGA thin films.

  5. Photoinduced electron transfer between benzyloxy dendrimer phthalocyanine and benzoquinone

    Science.gov (United States)

    Zhang, Tiantian; Ma, Dongdong; Pan, Sujuan; Wu, Shijun; Jiang, Yufeng; Zeng, Di; Yang, Hongqin; Peng, Yiru

    2016-10-01

    Photo-induced electron transfer (PET) is an important and fundamental process in natural photosynthesis. To mimic such interesting PET process, a suitable donor and acceptor couple were properly chosen. Dendrimer phthalocyanines and their derivatives have emerged as promising materials for artificial photosynthesis systems. In this paper, the electron transfer between the light harvest dendrimer phthalocyanine (donor) and the 1,4-benzoquinone (acceptor) was studied by UV/Vis and fluorescence spectroscopic methods. It was found that fluorescence of phthalocyanine was quenched by benzoquinone (BQ) via excited state electron transfer, from the phthalocyanine to the BQ upon excitation at 610 nm. The Stern-Volmer constant (KSV) of electron transfer was calculated. Our study suggests that this dendritic phthalocyanine is an effective new electron donor and transmission complex and could be used as a potential artificial photosynthesis system.

  6. Current-voltage characteristics of dendrimer light-emitting diodes

    International Nuclear Information System (INIS)

    Stevenson, S G; Samuel, I D W; Staton, S V; Knights, K A; Burn, P L; Williams, J H T; Walker, Alison B

    2010-01-01

    We have investigated current-voltage (I-V) characteristics of unipolar and bipolar organic diodes that use phosphorescent dendrimers as the emissive organic layer. Through simulation of the measured I-V characteristics we were able to determine the device parameters for each device structure studied, leading to a better understanding of injection and transport behaviour in these devices. It was found that the common practice of assuming injection barriers are equal to the difference between bare electrode work functions and molecular orbital levels is unsuitable for the devices considered here, particularly for gold contacts. The studies confirm that different aromatic units in the dendrons can give significant differences in the charge transporting properties of the dendrimers.

  7. Current-voltage characteristics of dendrimer light-emitting diodes

    Science.gov (United States)

    Stevenson, S. G.; Samuel, I. D. W.; Staton, S. V.; Knights, K. A.; Burn, P. L.; Williams, J. H. T.; Walker, Alison B.

    2010-09-01

    We have investigated current-voltage (I-V) characteristics of unipolar and bipolar organic diodes that use phosphorescent dendrimers as the emissive organic layer. Through simulation of the measured I-V characteristics we were able to determine the device parameters for each device structure studied, leading to a better understanding of injection and transport behaviour in these devices. It was found that the common practice of assuming injection barriers are equal to the difference between bare electrode work functions and molecular orbital levels is unsuitable for the devices considered here, particularly for gold contacts. The studies confirm that different aromatic units in the dendrons can give significant differences in the charge transporting properties of the dendrimers.

  8. Current-voltage characteristics of dendrimer light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Stevenson, S G; Samuel, I D W [Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS (United Kingdom); Staton, S V; Knights, K A; Burn, P L [Department of Chemistry, Chemistry Research Laboratory, 12 Mansfield Road, Oxford, OX1 3TA (United Kingdom); Williams, J H T; Walker, Alison B, E-mail: a.b.walker@bath.ac.u [Department of Physics, University of Bath, Bath, BA2 7AY (United Kingdom)

    2010-09-29

    We have investigated current-voltage (I-V) characteristics of unipolar and bipolar organic diodes that use phosphorescent dendrimers as the emissive organic layer. Through simulation of the measured I-V characteristics we were able to determine the device parameters for each device structure studied, leading to a better understanding of injection and transport behaviour in these devices. It was found that the common practice of assuming injection barriers are equal to the difference between bare electrode work functions and molecular orbital levels is unsuitable for the devices considered here, particularly for gold contacts. The studies confirm that different aromatic units in the dendrons can give significant differences in the charge transporting properties of the dendrimers.

  9. Wiring of heme enzymes by methylene-blue labeled dendrimers

    DEFF Research Database (Denmark)

    Álvarez-Martos, Isabel; Shahdost-fard, Faezeh; Ferapontova, Elena

    2017-01-01

    Redox-modified branched 3D dendrimeric nanostructures may be considered as perspective wires for electrical connection between redox enzymes and electrodes. Here, we studied electron transfer (ET) reactions and bioelectrocatalysis of heme-containing horseradish peroxidase (HRP) and heme- and moli......Redox-modified branched 3D dendrimeric nanostructures may be considered as perspective wires for electrical connection between redox enzymes and electrodes. Here, we studied electron transfer (ET) reactions and bioelectrocatalysis of heme-containing horseradish peroxidase (HRP) and heme......- and molibdopterin-containing sulfite oxidase (SOx), wired to gold by the methylene blue (MB)-labeled polyamidoamine (PAMAM) dendrimers. The enzymes’ electrochemical transformation and bioelectrocatalytic function could be followed at both unlabeled and MB-labeled dendrimer-modified electrodes with the formal redox......, optimization of bioelectrocatalysis of complex intermembrane and, possibly, membrane enzymes....

  10. Biological properties of new viologen-phosphorus dendrimers.

    Science.gov (United States)

    Ciepluch, Karol; Katir, Nadia; El Kadib, Abdelkrim; Felczak, Aleksandra; Zawadzka, Katarzyna; Weber, Monika; Klajnert, Barbara; Lisowska, Katarzyna; Caminade, Anne-Marie; Bousmina, Mostapha; Bryszewska, Maria; Majoral, Jean Pierre

    2012-03-05

    Some biological properties of eight dendrimers incorporating both phosphorus linkages and viologen units within their cascade structure or at the periphery were investigated for the first time. In particular cytotoxicity, hemotoxicity, and antimicrobial and antifungal activity of these new macromolecules were examined. Even if for example all these species exhibited good antimicrobial properties, it was demonstrated that their behavior strongly depends on several parameters as their size and molecular weight, the number of viologen units and the nature of the terminal groups.

  11. Optically nonlinear energy transfer in light-harvesting dendrimers

    OpenAIRE

    Andrews, David; Bradshaw, DS

    2004-01-01

    Dendrimeric polymers are the subject of intense research activity geared towards their implementation in nanodevice applications such as energy harvesting systems,organic light-emitting diodes, photosensitizers, low-threshold lasers, and quantum logic elements, etc. A recent development in this area has been the construction of dendrimers specifically designed to exhibit novel forms of optical nonlinearity, exploiting the unique properties of these materials at high levels of photon flux. Sta...

  12. Blue Light Emitting Polyphenylene Dendrimers with Bipolar Charge Transport Moieties

    Directory of Open Access Journals (Sweden)

    Guang Zhang

    2016-10-01

    Full Text Available Two light-emitting polyphenylene dendrimers with both hole and electron transporting moieties were synthesized and characterized. Both molecules exhibited pure blue emission solely from the pyrene core and efficient surface-to-core energy transfers when characterized in a nonpolar environment. In particular, the carbazole- and oxadiazole-functionalized dendrimer (D1 manifested a pure blue emission from the pyrene core without showing intramolecular charge transfer (ICT in environments with increasing polarity. On the other hand, the triphenylamine- and oxadiazole-functionalized one (D2 displayed notable ICT with dual emission from both the core and an ICT state in highly polar solvents. D1, in a three-layer organic light emitting diode (OLED by solution processing gave a pure blue emission with Commission Internationale de l’Éclairage 1931 CIE xy = (0.16, 0.12, a peak current efficiency of 0.21 cd/A and a peak luminance of 2700 cd/m2. This represents the first reported pure blue dendrimer emitter with bipolar charge transport and surface-to-core energy transfer in OLEDs.

  13. Second-Order Nonlinear Optical Dendrimers and Dendronized Hyperbranched Polymers.

    Science.gov (United States)

    Tang, Runli; Li, Zhen

    2017-01-01

    Second-order nonlinear optical (NLO) dendrimers with a special topological structure were regarded as the most promising candidates for practical applications in the field of optoelectronic materials. Dendronized hyperbranched polymers (DHPs), a new type of polymers with dendritic structures, proposed and named by us recently, demonstrated interesting properties and some advantages over other polymers. Some of our work concerning these two types of polymers are presented herein, especially focusing on the design idea and structure-property relationship. To enhance their comprehensive NLO performance, dendrimers were designed and synthesized by adjusting their isolation mode, increasing the number of the dendritic generation, modifying their topological structure, introducing isolation chromophores, and utilizing the Ar-Ar F self-assembly effect. To make full use of the advantages of both the structural integrity of dendrimers and the convenient one-pot synthesis of hyperbranched polymers, DHPs were explored by utilizing low-generation dendrons as big monomers to construct hyperbranched polymers. These selected works could provide valuable information to deeply understand the relationship between the structure and properties of functional polymers with dendritic structures, but not only limited to the NLO ones, and might contribute much to the further development of functional polymers with rational design. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Blue Light Emitting Polyphenylene Dendrimers with Bipolar Charge Transport Moieties.

    Science.gov (United States)

    Zhang, Guang; Auer-Berger, Manuel; Gehrig, Dominik W; Blom, Paul W M; Baumgarten, Martin; Schollmeyer, Dieter; List-Kratochvil, E J W; Müllen, Klaus

    2016-10-20

    Two light-emitting polyphenylene dendrimers with both hole and electron transporting moieties were synthesized and characterized. Both molecules exhibited pure blue emission solely from the pyrene core and efficient surface-to-core energy transfers when characterized in a nonpolar environment. In particular, the carbazole- and oxadiazole-functionalized dendrimer ( D1 ) manifested a pure blue emission from the pyrene core without showing intramolecular charge transfer (ICT) in environments with increasing polarity. On the other hand, the triphenylamine- and oxadiazole-functionalized one ( D2 ) displayed notable ICT with dual emission from both the core and an ICT state in highly polar solvents. D1 , in a three-layer organic light emitting diode (OLED) by solution processing gave a pure blue emission with Commission Internationale de l'Éclairage 1931 CIE xy = (0.16, 0.12), a peak current efficiency of 0.21 cd/A and a peak luminance of 2700 cd/m². This represents the first reported pure blue dendrimer emitter with bipolar charge transport and surface-to-core energy transfer in OLEDs.

  15. Structural analysis of binding functionality of folic acid-PEG dendrimers against folate receptor.

    Science.gov (United States)

    Sampogna-Mireles, Diana; Araya-Durán, Ingrid D; Márquez-Miranda, Valeria; Valencia-Gallegos, Jesús A; González-Nilo, Fernando D

    2017-03-01

    Dendrimers functionalized with folic acid (FA) are drug delivery systems that can selectively target cancer cells with folate receptors (FR-α) overexpression. Incorporation of polyethylene glycol (PEG) can enhance dendrimers solubility and pharmacokinetics, but ligand-receptor binding must not be affected. In this work we characterized, at atomic level, the binding functionality of conventional site-specific dendrimers conjugated with FA with PEG 750 or PEG 3350 as a linker. After Molecular Dynamics simulation, we observed that both PEG's did not interfere over ligand-receptor binding functionality. Although binding kinetics could be notably affected, the folate fragment from both dendrimers remained exposed to the solvent before approaching selectively to FR-α. PEG 3350 provided better solubility and protection from enzymatic degradation to the dendrimer than PEG 750. Also, FA-PEG3350 dendrimer showed a slightly better interaction with FR-α than FA-PEG750 dendrimer. Therefore, theoretical evidence supports that both dendrimers are suitable as drug delivery systems for cancer therapies. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Electron Transfer in Methylene-Blue-Labeled G3 Dendrimers Tethered to Gold

    DEFF Research Database (Denmark)

    Álvarez-Martos, Isabel; Kartashov, Andrey; Ferapontova, Elena

    2016-01-01

    , and their dependence on the dendrimer surface packing, contribute to both mechanistic pathways. Electrical wiring of horse-radish peroxidase and hexose oxidase by using MB-labeled dendrimers allowed the bioelectrocatalytic reduction of H2O2 and oxidation of glucose by these enzymes. The demonstrated electrical...

  17. Structural Distortion of Dendrimers on Gold Surfaces: A Tapping-Mode AFM Investigation

    National Research Council Canada - National Science Library

    Hierlemann, A

    1998-01-01

    .... The individual dendrimer molecules forming a monolayer were clearly imaged. Upon exposure to hexadecanethiol, the shapes of individual dendrimers change and they become taller and narrower as more stable thiol-Au bonds replace some of the amine-Au bonds...

  18. Proton-conductive materials formed by coumarin photocrosslinked ionic liquid crystal dendrimers

    NARCIS (Netherlands)

    Concellon, A.; Liang, T.; Schenning, A.P.H.J.; Luis Serrano, J.; Romero, P.; Marcos, M.

    2018-01-01

    In this work, we have successfully examined for the first time the use of ionic dendrimers as building blocks for the preparation of 1D and 2D proton conductive materials. For this purpose, a new family of liquid crystalline dendrimers has been synthesized by ionic self-assembly of poly(amidoamine)

  19. Molecular dynamics study of charged dendrimers in salt-free solution : effect of counterions

    NARCIS (Netherlands)

    Gurtovenko, A.A.; Lyulin, S.V.; Karttunen, M.E.J.; Vattulainen, I.

    2006-01-01

    Polyamidoamine dendrimers, being protonated under physiological conditions, represent a promising class of nonviral, nanosized vectors for drug and gene delivery. We performed extensive molecular dynamics simulations of a generic model dendrimer in a salt-free solution with dendrimer’s terminal

  20. Expand classical drug administration ways by emerging routes using dendrimer drug delivery systems: a concise overview.

    Science.gov (United States)

    Mignani, Serge; El Kazzouli, Saïd; Bousmina, Mosto; Majoral, Jean-Pierre

    2013-10-01

    Drugs are introduced into the body by numerous routes such as enteral (oral, sublingual and rectum administration), parenteral (intravascular, intramuscular, subcutaneous and inhalation administration), or topical (skin and mucosal membranes). Each route has specific purposes, advantages and disadvantages. Today, the oral route remains the preferred one for different reasons such as ease and compliance by patients. Several nanoformulated drugs have been already approved by the FDA, such as Abelcet®, Doxil®, Abraxane® or Vivagel®(Starpharma) which is an anionic G4-poly(L-lysine)-type dendrimer showing potent topical vaginal microbicide activity. Numerous biochemical studies, as well as biological and pharmacological applications of both dendrimer based products (dendrimers as therapeutic compounds per se, like Vivagel®) and dendrimers as drug carriers (covalent conjugation or noncovalent encapsulation of drugs) were described. It is widely known that due to their outstanding physical and chemical properties, dendrimers afforded improvement of corresponding carried-drugs as dendrimer-drug complexes or conjugates (versus plain drug) such as biodistribution and pharmacokinetic behaviors. The purpose of this manuscript is to review the recent progresses of dendrimers as nanoscale drug delivery systems for the delivery of drugs using enteral, parenteral and topical routes. In particular, we focus our attention on the emerging and promising routes such as oral, transdermal, ocular and transmucosal routes using dendrimers as delivery systems. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. pH and generation dependent morphologies of PAMAM dendrimers on a graphene substrate.

    Science.gov (United States)

    Gosika, Mounika; Maiti, Prabal K

    2018-03-07

    The adsorption of PAMAM dendrimers at solid/water interfaces has been extensively studied, and is mainly driven by electrostatic and van der Waals interactions between the substrate and the dendrimers. However, the pH dependence of the adsorption driven predominantly by the van der Waals interactions is poorly explored, although it is crucial for investigating the potentiality of these dendrimers in supercapacitors and surface patterning. Motivated by this aspect, we have studied the adsorption behavior of PAMAM dendrimers of generations 2 (G2) to 5 (G5) with pH and salt concentration variation, on a charge neutral graphene substrate, using fully atomistic molecular dynamics simulations. The instantaneous snapshots from our simulations illustrate that the dendrimers deform significantly from their bulk structures. Based on various structural property calculations, we classify the adsorbed dendrimer morphologies into five categories and map them to a phase diagram. Interestingly, the morphologies we report here have striking analogies with those reported in star-polymer adsorption studies. From the fractional contacts and other structural property analyses we find that the deformations are more pronounced at neutral pH as compared to high and low pH. Higher generation dendrimers resist deformation following the deformation trend, G2 > G3 > G4 > G5 at any given pH level. As the adsorption here is mainly driven by van der Waals interactions, we observe no desorption of the dendrimers as the salt molarity is increased, unlike that reported in the electrostatically driven adsorption studies.

  2. Dendrimers destabilize proteins in a generation-dependent manner involving electrostatic interactions

    DEFF Research Database (Denmark)

    Gichm, Lise; Christensen, Casper; Boas, Ulrik

    2008-01-01

    Dendrimers are well-defined chemical polymers with a characteristic branching pattern that gives rise to attractive features such as antibacterial and antitumor activities as well as drug delivery properties. In addition, dendrimers can solubilize prion protein aggregates at very low concentratio...

  3. Paramagnetic NMR investigation of dendrimer-based host-guest interactions.

    Directory of Open Access Journals (Sweden)

    Fei Wang

    Full Text Available In this study, the host-guest behavior of poly(amidoamine (PAMAM dendrimers bearing amine, hydroxyl, or carboxylate surface functionalities were investigated by paramagnetic NMR studies. 2,2,6,6-Tetramethylpiperidinyloxy (TEMPO derivatives were used as paramagnetic guest molecules. The results showed that TEMPO-COOH significantly broaden the ¹H NMR peaks of amine- and hydroxyl-terminated PAMAM dendrimers. In comparison, no paramagnetic relaxation enhancement (PRE was observed between TEMPO-NH₂, TEMPO-OH and the three types of PAMAM dendrimers. The PRE phenomenon observed is correlated with the encapsulation of TEMPO-COOH within dendrimer pockets. Protonation of the tertiary amine groups within PAMAM dendrimers plays an important role during this process. Interestingly, the absence of TEMPO-COOH encapsulation within carboxylate-terminated PAMAM dendrimer is observed due to the repulsion of TEMPO-COO- anion and anionic dendrimer surface. The combination of paramagnetic probes and ¹H NMR linewidth analysis can be used as a powerful tool in the analysis of dendrimer-based host-guest systems.

  4. Molecular dynamics simulation of coarse-grained poly(L-lysine) dendrimers.

    Science.gov (United States)

    Rahimi, Ali; Amjad-Iranagh, Sepideh; Modarress, Hamid

    2016-03-01

    Poly(L-lysine) (PLL) dendrimer are amino acid based macromolecules and can be used as drug delivery agents. Their branched structure allows them to be functionalized by various groups to encapsulate drug agents into their structure. In this work, at first, an attempt was made on all-atom simulation of PLL dendrimer of different generations. Based on all-atom results, a course-grained model of this dendrimer was designed and its parameters were determined, to be used for simulation of three generations of PLL dendrimer, at two pHs. Similar to the all-atom, the coarse-grained results indicated that by increasing the generation, the dendrimer becomes more spherical. At pH 7, the dendrimer had larger size, whereas at pH 12, due to back folding of branching chains, they had the tendency to penetrate into the inner layers. The calculated radial probability and radial distribution functions confirm that at pH 7, the PLL dendrimer has more cavities and as a result it can encapsulate more water molecules into its inner structure. By calculating the moment of inertia and the aspect ratio, the formation of spherical structure for PLL dendrimer was confirmed.

  5. Dynamics of complexation of a charged dendrimer by linear polyelectrolyte: Computer modelling

    NARCIS (Netherlands)

    Lyulin, S.V.; Darinskii, A.A.; Lyulin, A.V.

    2007-01-01

    Brownian-dynamics simulations have been performed for complexes formed by a charged dendrimer and a long oppositely charged linear polyelectrolyte when overcharging phenomenon is always observed. After a complex formation the orientational mobility of the individual dendrimer bonds, the fluctuations

  6. Photo-physical and structural interactions between viologen phosphorus-based dendrimers and human serum albumin

    International Nuclear Information System (INIS)

    Ciepluch, Karol; Katir, Nadia; El Kadib, Abdelkrim; Weber, Monika; Caminade, Anne-Marie; Bousmina, Mostapha; Pierre Majoral, Jean; Bryszewska, Maria

    2012-01-01

    This work deals with photo-physical and structural interactions between viologen phosphorus dendrimers and human serum albumin (HSA). Viologens are derivatives of 4,4′-bipyridinium salts. Aiming to rationalize the parameters governing such interactions eight types of these polycationic dendrimers in which the generation, the number of charges, the nature of the core and of the terminal groups vary from one to another, were designed and used. The influence of viologen-based dendrimers' on human serum albumin has been investigated. The photo-physical interactions of the two systems have been monitored by fluorescence quenching of free L-tryptophan and of HSA tryptophan residue. Additionally, using circular dichroism (CD) the effect of dendrimers on the secondary structure of albumin was measured. The obtained results show that viologen dendrimers interact with human serum albumin quenching its fluorescence either by collisional (dynamic) way or by forming complexes in a ground state (static quenching). In some cases the quenching is accompanied by changes of the secondary structure of HSA. - Highlights: ► Photo-physical interactions between viologen phosphorus dendrimers and human serum albumin (HSA) were investigated. ► The viologen dendrimers can quench the fluorescence of tryptophan in HSA. ► CD spectra to explain the changes in secondary structure of albumin after exposition of dendrimers.

  7. Photosensitizer and peptide-conjugated PAMAM dendrimer for targeted in vivo photodynamic therapy.

    Science.gov (United States)

    Narsireddy, Amreddy; Vijayashree, Kurra; Adimoolam, Mahesh G; Manorama, Sunkara V; Rao, Nalam M

    2015-01-01

    Challenges in photodynamic therapy (PDT) include development of efficient near infrared-sensitive photosensitizers (5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphine [PS]) and targeted delivery of PS to the tumor tissue. In this study, a dual functional dendrimer was synthesized for targeted PDT. For targeting, a poly(amidoamine) dendrimer (G4) was conjugated with a PS and a nitrilotriacetic acid (NTA) group. A peptide specific to human epidermal growth factor 2 was expressed in Escherichia coli with a His-tag and was specifically bound to the NTA group on the dendrimer. Reaction conditions were optimized to result in dendrimers with PS and the NTA at a fractional occupancy of 50% and 15%, respectively. The dendrimers were characterized by nuclear magnetic resonance, matrix-assisted laser desorption/ionization, absorbance, and fluorescence spectroscopy. Using PS fluorescence, cell uptake of these particles was confirmed by confocal microscopy and fluorescence-activated cell sorting. PS-dendrimers are more efficient than free PS in PDT-mediated cell death assays in HER2 positive cells, SK-OV-3. Similar effects were absent in HER2 negative cell line, MCF-7. Compared to free PS, the PS-dendrimers have shown significant tumor suppression in a xenograft animal tumor model. Conjugation of a PS with dendrimers and with a targeting agent has enhanced photodynamic therapeutic effects of the PS.

  8. Transport of dendrimer nanocarriers through epithelial cells via the transcellular route.

    Science.gov (United States)

    Jevprasesphant, Rachaneekorn; Penny, Jeffrey; Attwood, David; D'Emanuele, Antony

    2004-06-18

    The mechanism of transport of G3 PAMAM and surface-modified (with lauroyl chains) G3 PAMAM dendrimer nanocarriers across Caco-2 cell monolayers has been investigated. Flow-cytometry studies following quenching of extracellular fluorescence demonstrated the cellular internalisation of dendrimers. Optical sectioning of cells incubated with fluorescein isothiocyanate (FITC)-conjugated dendrimer and lauroyl-dendrimer using confocal laser scanning microscopy revealed colocalisation of a marker for cell nuclei (4',6-diamidino-2-phenylindole, DAPI) and FITC fluorescence, also suggesting cellular internalisation of dendrimers. Transmission electron microscopic analyses of cells incubated with gold-labelled G3 PAMAM dendrimers confirmed endocytosis-mediated cellular internalisation when dendrimers were applied to the apical domain of Caco-2 cells. These findings are in agreement with our previous studies using Caco-2 cell monolayers that showed a significant decrease of dendrimer uptake in the presence of colchicine (endocytosis inhibitor) and when temperature was reduced from 37 to 4 degrees C. Copyright 2004 Elsevier B.V.

  9. Diglycolamide-functionalized dendrimers : Studies on Americium(III) pertraction from radioactive waste

    NARCIS (Netherlands)

    Ansari, Seraj A.; Mohapatra, Prasanta K.; Leoncini, Andrea; Huskens, Jurriaan; Verboom, Willem

    2017-01-01

    Diglycolamide (DGA)-functionalized poly(propylene imine) diaminobutane dendrimers were evaluated as the carrier in supported liquid membranes (SLMs) for selective recovery of trivalent actinides over uranium. The 0, 1st, and 2nd generation dendrimers with 2, 4, and 8 DGA moieties, termed as LI, LII,

  10. Endocytic Uptake, Transport and Macromolecular Interactions of Anionic PAMAM Dendrimers within Lung Tissue.

    Science.gov (United States)

    Morris, Christopher J; Aljayyoussi, Ghaith; Mansour, Omar; Griffiths, Peter; Gumbleton, Mark

    2017-12-01

    Polyamidoamine (PAMAM) dendrimers are a promising class of nanocarrier with applications in both small and large molecule drug delivery. Here we report a comprehensive evaluation of the uptake and transport pathways that contribute to the lung disposition of dendrimers. Anionic PAMAM dendrimers and control dextran probes were applied to an isolated perfused rat lung (IPRL) model and lung epithelial monolayers. Endocytosis pathways were examined in primary alveolar epithelial cultures by confocal microscopy. Molecular interactions of dendrimers with protein and lipid lung fluid components were studied using small angle neutron scattering (SANS). Dendrimers were absorbed across the intact lung via a passive, size-dependent transport pathway at rates slower than dextrans of similar molecular sizes. SANS investigations of concentration-dependent PAMAM transport in the IPRL confirmed no aggregation of PAMAMs with either albumin or dipalmitoylphosphatidylcholine lung lining fluid components. Distinct endocytic compartments were identified within primary alveolar epithelial cells and their functionality in the rapid uptake of fluorescent dendrimers and model macromolecular probes was confirmed by co-localisation studies. PAMAM dendrimers display favourable lung biocompatibility but modest lung to blood absorption kinetics. These data support the investigation of dendrimer-based carriers for controlled-release drug delivery to the deep lung.

  11. Regional Morphology and Transport of PAMAM Dendrimers Across Isolated Rat Intestinal Tissue.

    Science.gov (United States)

    Hubbard, Dallin; Bond, Tanner; Ghandehari, Hamidreza

    2015-12-01

    Intestinal permeability of PAMAM dendrimers has been observed, giving rationale for their use in oral drug delivery as potential carriers of associated molecules. This study assessed the apparent permeability coefficients (Papp) of dendrimers across isolated rat intestinal regional mucosae, along with estimation of the maximum non-toxic concentration. Caco-2 monolayers were also used to assess the comparative Papp values between isolated mucosae and cell culture models. Concentrations from 0.1 to 10 mM of anionic and cationic dendrimers were tested in mucosae to assess their Papp, membrane TEER, [(14)C]-mannitol Papp, and histology. 0.1 mM concentrations of dendrimers were assessed over 120 min in Caco-2 cell monolayers as concentrations above that were cytotoxic. Jejunal transport of dendrimers was higher than transport in colonic epithelium. Monolayer Papp values of dendrimers were comparable to those of jejunal mucosae. Mucosae exposed to dendrimer concentrations of 10 mM for 120 min caused significant reduction in TEER and changes in tissue morphology; however, G3.5 was the only analogue that caused significant TEER reduction and morphological changes at 1 mM concentrations. Transport in jejunal mucosae appears to be the greatest indicating that the small intestinal will be the most likely region to target for oral drug delivery using PAMAM dendrimers. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Photo-physical and structural interactions between viologen phosphorus-based dendrimers and human serum albumin

    Energy Technology Data Exchange (ETDEWEB)

    Ciepluch, Karol, E-mail: ciepluch@biol.uni.lodz.pl [Department of General Biophysics, University of Lodz, 141/143 Pomorska St., 90-236 Lodz (Poland); Katir, Nadia [Laboratoire de Chimie de Coordination du CNRS (LCC), 205 route de Narbonne, F-31077 Toulouse cedex 4 (France); Institute of Nanomaterials and Nanotechnology (INANOTECH)-MAScIR (Moroccan Foundation for Advanced Science, Innovation and Research), ENSET, Avenue de l' Armee Royale, Madinat El Irfane, 10100 Rabat (Morocco); El Kadib, Abdelkrim [Institute of Nanomaterials and Nanotechnology (INANOTECH)-MAScIR (Moroccan Foundation for Advanced Science, Innovation and Research), ENSET, Avenue de l' Armee Royale, Madinat El Irfane, 10100 Rabat (Morocco); Weber, Monika [Department of General Biophysics, University of Lodz, 141/143 Pomorska St., 90-236 Lodz (Poland); Caminade, Anne-Marie [Laboratoire de Chimie de Coordination du CNRS (LCC), 205 route de Narbonne, F-31077 Toulouse cedex 4 (France); Bousmina, Mostapha [Hassan II Academy of Sciences and Technology, Avenue MVI, Km4, 10220 Rabat (Morocco); Pierre Majoral, Jean [Laboratoire de Chimie de Coordination du CNRS (LCC), 205 route de Narbonne, F-31077 Toulouse cedex 4 (France); Hassan II Academy of Sciences and Technology, Avenue MVI, Km4, 10220 Rabat (Morocco); Bryszewska, Maria [Department of General Biophysics, University of Lodz, 141/143 Pomorska St., 90-236 Lodz (Poland)

    2012-06-15

    This work deals with photo-physical and structural interactions between viologen phosphorus dendrimers and human serum albumin (HSA). Viologens are derivatives of 4,4 Prime -bipyridinium salts. Aiming to rationalize the parameters governing such interactions eight types of these polycationic dendrimers in which the generation, the number of charges, the nature of the core and of the terminal groups vary from one to another, were designed and used. The influence of viologen-based dendrimers' on human serum albumin has been investigated. The photo-physical interactions of the two systems have been monitored by fluorescence quenching of free L-tryptophan and of HSA tryptophan residue. Additionally, using circular dichroism (CD) the effect of dendrimers on the secondary structure of albumin was measured. The obtained results show that viologen dendrimers interact with human serum albumin quenching its fluorescence either by collisional (dynamic) way or by forming complexes in a ground state (static quenching). In some cases the quenching is accompanied by changes of the secondary structure of HSA. - Highlights: Black-Right-Pointing-Pointer Photo-physical interactions between viologen phosphorus dendrimers and human serum albumin (HSA) were investigated. Black-Right-Pointing-Pointer The viologen dendrimers can quench the fluorescence of tryptophan in HSA. Black-Right-Pointing-Pointer CD spectra to explain the changes in secondary structure of albumin after exposition of dendrimers.

  13. Functionalized Poly(propylene imine) Dendrimers as Novel Phase Transfer Catalyst in Supercritical Cabon Dioxide

    NARCIS (Netherlands)

    Goetheer, E.L.V.; Baars, M.W.P.L.; Broeke, van den L.J.P.; Meijer, E.W.; Keurentjes, J.T.F.

    2000-01-01

    Perfluoro-functionalized poly(propylene imine) dendrimers have been used as reactive extractants for anionic species and as phase transfer catalysts for two types of reactions. Different generations of dendrimers have been used for applications in carbon dioxide. First, the reactive extraction of

  14. Synthesis and protonation behavior of carboxylate-functionalized poly(propylene imine) dendrimers

    NARCIS (Netherlands)

    Duijvenbode, van R.C.; Rajanayagam, A.; Koper, G.J.M.; Baars, M.W.P.L.; Waal, de B.F.M.; Meijer, E.W.; Borkovec, M.

    2000-01-01

    Five generations of carboxylate-functionalized poly(propyleneimine) dendrimers have been synthesized starting from a double Michael addition of amine-functionalized poly(propyleneimine) dendrimers to methyl acrylate followed by basic hydrolysis using LiOH in a water/methanol mixture. The dendritic

  15. Atomic level insights into realistic molecular models of dendrimer-drug complexes through MD simulations

    Science.gov (United States)

    Jain, Vaibhav; Maiti, Prabal K.; Bharatam, Prasad V.

    2016-09-01

    Computational studies performed on dendrimer-drug complexes usually consider 1:1 stoichiometry, which is far from reality, since in experiments more number of drug molecules get encapsulated inside a dendrimer. In the present study, molecular dynamic (MD) simulations were implemented to characterize the more realistic molecular models of dendrimer-drug complexes (1:n stoichiometry) in order to understand the effect of high drug loading on the structural properties and also to unveil the atomistic level details. For this purpose, possible inclusion complexes of model drug Nateglinide (Ntg) (antidiabetic, belongs to Biopharmaceutics Classification System class II) with amine- and acetyl-terminated G4 poly(amidoamine) (G4 PAMAM(NH2) and G4 PAMAM(Ac)) dendrimers at neutral and low pH conditions are explored in this work. MD simulation analysis on dendrimer-drug complexes revealed that the drug encapsulation efficiency of G4 PAMAM(NH2) and G4 PAMAM(Ac) dendrimers at neutral pH was 6 and 5, respectively, while at low pH it was 12 and 13, respectively. Center-of-mass distance analysis showed that most of the drug molecules are located in the interior hydrophobic pockets of G4 PAMAM(NH2) at both the pH; while in the case of G4 PAMAM(Ac), most of them are distributed near to the surface at neutral pH and in the interior hydrophobic pockets at low pH. Structural properties such as radius of gyration, shape, radial density distribution, and solvent accessible surface area of dendrimer-drug complexes were also assessed and compared with that of the drug unloaded dendrimers. Further, binding energy calculations using molecular mechanics Poisson-Boltzmann surface area approach revealed that the location of drug molecules in the dendrimer is not the decisive factor for the higher and lower binding affinity of the complex, but the charged state of dendrimer and drug, intermolecular interactions, pH-induced conformational changes, and surface groups of dendrimer do play an

  16. Poly(Propylene Imine Dendrimers and Amoxicillin as Dual-Action Antibacterial Agents

    Directory of Open Access Journals (Sweden)

    Natalia Wrońska

    2015-10-01

    Full Text Available Besides acting as antimicrobial compounds, dendrimers can be considered as agents that improve the therapeutic effectiveness of existing antibiotics. In this work we present a new approach to using amoxicillin (AMX against reference strains of common Gram-negative pathogens, alone and in combination with poly(propylene imine (PPI dendrimers, or derivatives thereof, in which 100% of the available hydrogen atoms are substituted with maltose (PPI 100%malG3. The concentrations of dendrimers used remained in the range non-toxic to eukaryotic cells. The results indicate that PPI dendrimers significantly enhance the antibacterial effect of amoxicillin alone, allowing antibiotic doses to be reduced. It is important to reduce doses of amoxicillin because its widespread use in medicine could lead to the development of bacterial resistance and environmental pollution. This is the first report on the combined antibacterial activity of PPI surface-modified maltose dendrimers and amoxicillin.

  17. Trapping time statistics and efficiency of transport of optical excitations in dendrimers

    Science.gov (United States)

    Heijs, Dirk-Jan; Malyshev, Victor A.; Knoester, Jasper

    2004-09-01

    We theoretically study the trapping time distribution and the efficiency of the excitation energy transport in dendritic systems. Trapping of excitations, created at the periphery of the dendrimer, on a trap located at its core, is used as a probe of the efficiency of the energy transport across the dendrimer. The transport process is treated as incoherent hopping of excitations between nearest-neighbor dendrimer units and is described using a rate equation. We account for radiative and nonradiative decay of the excitations while diffusing across the dendrimer. We derive exact expressions for the Laplace transform of the trapping time distribution and the efficiency of trapping, and analyze those for various realizations of the energy bias, number of dendrimer generations, and relative rates for decay and hopping. We show that the essential parameter that governs the trapping efficiency is the product of the on-site excitation decay rate and the trapping time (mean first passage time) in the absence of decay.

  18. Synthesis and biological evaluation of boronated polyglycerol dendrimers as potential agent for neutron capture therapy

    International Nuclear Information System (INIS)

    Silva, Gerald S.; Camillo, Maria A.P.; Higa, Olga Z.; Pugliesi, Reynaldo; Fermamdes, Edson G.R.; Queiroz, Alvaro A.A. de

    2005-01-01

    In this work, the polyglycerol dendrimer (PGLD) generation 5 was used to obtain a boronated macromolecule for boron neutron capture therapy. The PGLD dendrimer was synthesized by the ring opening polymerization of deprotonated glycidol using polyglycerol as core functionality in a step-growth processes denominated divergent synthesis. The PGLD dendritic structure was confirmed by gel permeation chromatography, nuclear magnetic resonance ( 1 H-NMR, 13 C-NMR) and matrix assisted laser desorption/ionization techniques. The synthesized dendrimer presented low dispersion in molecular weights (M w /M n = 1.05) and a degree of branching of 0.82, which characterize the polymer dendritic structure. Quantitative neutron capture radiography was used to investigate the boron-10 enrichment of the polyglycerol dendrimer. The in vitro cytotoxicity to Chinese hamster ovary cells of 10 B-PGLD dendrimer indicate lower cytotoxicity, suggesting that the macromolecule is a biocompatible material. (author)

  19. Probing the binding of cationic lipids with dendrimers.

    Science.gov (United States)

    Mandeville, J S; Bourassa, P; Tajmir-Riahi, H A

    2013-01-14

    Polycationic polymers are used extensively in biology to disrupt cell membranes and thus enhance the transport of materials into the cell. We report the bindings of several lipids cholesterol (Chol), 1,2-dioleoyl-3-trimethylammonium-propane(DOTAP), dioctadecyldimethylammoniumbromide (DDAB), and dioleoylphosphatidylethanolamine (DOPE) to dendrimers of different compositions such as mPEG-PAMAM (G3), mPEG-PAMAM (G4), and PAMAM (G4) under physiological conditions. FTIR, UV-visible spectroscopic, methods and molecular modeling were used to analyze the lipid binding mode, the binding constant, and the effects of lipid complexation on the dendrimer structure. The structural analysis showed that lipids bind dendrimers through both hydrophilic and hydrophobic contacts with overall binding constants of K(chol-mPEG-G3) = 1.7 × 10(3) M(-1), K(chol-mPEG-PAMAM-G4) = 2.7 × 10(3) M(-1), K(chol-PAMAM-G4) = 1.0 × 10(3) M(-1), K(DOPE-mPEG-G3) = 1.5 × 10(3) M(-1), K(DOPE-mPEG-PAMAM-G4) = 1.6 × 10(3) M(-1), K(DOPE-PAMAM-G4) = 5.3 × 10(2) M(-1), K(DDAB-mPEG-G3) = 1.5 × 10(3) M(-1), K(DDAB-mPEG-PAMAM-G4) = 1.9 × 10(2) M(-1), K(DDAB-PAMAM-G4) = 7.0 × 10(2) M(-1), K(DOTAP-mPEG-G3) = 1.9 × 10(3) M(-1), K(DOTAP-mPEG-PAMAM-G4) = 1.5 × 10(3) M(-1), and K(DOTAP-PAMAM-G4) = 5.7 × 10(2) M(-1). Weaker interaction was observed as dendrimer cationic charges increased. The free binding energies from docking were -5.15 (cholesterol), -5.79 (DDAB), and -5.36 kcal/mol (DOTAP) with the order of stability DDAB-PAMAM-G-4 > DOTAP-PAMAM-G4 > cholesterol-PAMAM-G4, consistent with the spectroscopic results. Dendrimers might act as carriers to transport lipids in vitro.

  20. The adsorption-desorption transition of double-stranded DNA interacting with an oppositely charged dendrimer induced by multivalent anions.

    Science.gov (United States)

    Jiang, Yangwei; Zhang, Dong; Zhang, Yaoyang; Deng, Zhenyu; Zhang, Linxi

    2014-05-28

    The adsorption-desorption transition of DNA in DNA-dendrimer solutions is observed when high-valence anions, such as hexavalent anions, are added to the DNA-dendrimer solutions. In the DNA-dendrimer solutions with low-valence anions, dendrimers bind tightly with the V-shaped double-stranded DNA. When high-valence anions, such as pentavalent or hexavalent anions, are added to the DNA-dendrimer solutions, the double-stranded DNA chains can be stretched straightly and the dendrimers are released from the double-stranded DNA chains. In fact, adding high-valence anions to the solutions can change the charge spatial distribution in the DNA-dendrimer solutions, and weaken the electrostatic interactions between the positively charged dendrimers and the oppositely charged DNA chains. Adsorption-desorption transition of DNA is induced by the overcharging of dendrimers. This investigation is capable of helping us understand how to control effectively the release of DNA in gene/drug delivery because an effective gene delivery for dendrimers includes non-covalent DNA-dendrimer binding and the effective release of DNA in gene therapy.

  1. Polymer stabilized Ni-Ag and Ni-Fe alloy nanoclusters: Structural and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Kabir, L.; Mandal, A.R. [Department of Physics, Visva-Bharati, Santiniketan-731 235 (India); Mandal, S.K., E-mail: sk_mandal@hotmail.co [Department of Physics, Visva-Bharati, Santiniketan-731 235 (India)

    2010-04-15

    We report here the structural and magnetic behaviors of nickel-silver (Ni-Ag) and nickel-iron (Ni-Fe) nanoclusters stabilized with polymer (polypyrrole). High resolution transmission electron microscopy (HRTEM) indicates Ni-Ag nanoclusters to stabilize in core-shell configuration while that of Ni-Fe nanoclusters in a mixed type of geometry. Structural characterizations by X-ray diffraction (XRD) reveal the possibility of alloying in such bimetallic nanoclusters to some extent even at temperatures much lower than that of bulk alloying. Electron paramagnetic resonance (EPR) spectra clearly reveal two different absorption behaviors: one is ascribed to non-isolated Ni{sup 2+} clusters surrounded by either silver or iron giving rise to a broad signal, other (very narrow signal) being due to the isolated superparamagnetic Ni{sup 2+} clusters or bimetallic alloy nanoclusters. Results obtained for Ni-Ag and Ni-Fe nanoclusters have been further compared with the behavior exhibited by pure Ni nanoclusters in polypyrrole host. Temperature dependent studies (at 300 and 77 K) of EPR parameters, e.g. linewidth, g-value, line shape and signal intensity indicating the significant influence of surrounding paramagnetic silver or ferromagnetic iron within polymer host on the EPR spectra have been presented.

  2. Polymer stabilized Ni-Ag and Ni-Fe alloy nanoclusters: Structural and magnetic properties

    Science.gov (United States)

    Kabir, L.; Mandal, A. R.; Mandal, S. K.

    2010-04-01

    We report here the structural and magnetic behaviors of nickel-silver (Ni-Ag) and nickel-iron (Ni-Fe) nanoclusters stabilized with polymer (polypyrrole). High resolution transmission electron microscopy (HRTEM) indicates Ni-Ag nanoclusters to stabilize in core-shell configuration while that of Ni-Fe nanoclusters in a mixed type of geometry. Structural characterizations by X-ray diffraction (XRD) reveal the possibility of alloying in such bimetallic nanoclusters to some extent even at temperatures much lower than that of bulk alloying. Electron paramagnetic resonance (EPR) spectra clearly reveal two different absorption behaviors: one is ascribed to non-isolated Ni 2+ clusters surrounded by either silver or iron giving rise to a broad signal, other (very narrow signal) being due to the isolated superparamagnetic Ni 2+ clusters or bimetallic alloy nanoclusters. Results obtained for Ni-Ag and Ni-Fe nanoclusters have been further compared with the behavior exhibited by pure Ni nanoclusters in polypyrrole host. Temperature dependent studies (at 300 and 77 K) of EPR parameters, e.g. linewidth, g-value, line shape and signal intensity indicating the significant influence of surrounding paramagnetic silver or ferromagnetic iron within polymer host on the EPR spectra have been presented.

  3. Polymer stabilized Ni-Ag and Ni-Fe alloy nanoclusters: Structural and magnetic properties

    International Nuclear Information System (INIS)

    Kabir, L.; Mandal, A.R.; Mandal, S.K.

    2010-01-01

    We report here the structural and magnetic behaviors of nickel-silver (Ni-Ag) and nickel-iron (Ni-Fe) nanoclusters stabilized with polymer (polypyrrole). High resolution transmission electron microscopy (HRTEM) indicates Ni-Ag nanoclusters to stabilize in core-shell configuration while that of Ni-Fe nanoclusters in a mixed type of geometry. Structural characterizations by X-ray diffraction (XRD) reveal the possibility of alloying in such bimetallic nanoclusters to some extent even at temperatures much lower than that of bulk alloying. Electron paramagnetic resonance (EPR) spectra clearly reveal two different absorption behaviors: one is ascribed to non-isolated Ni 2+ clusters surrounded by either silver or iron giving rise to a broad signal, other (very narrow signal) being due to the isolated superparamagnetic Ni 2+ clusters or bimetallic alloy nanoclusters. Results obtained for Ni-Ag and Ni-Fe nanoclusters have been further compared with the behavior exhibited by pure Ni nanoclusters in polypyrrole host. Temperature dependent studies (at 300 and 77 K) of EPR parameters, e.g. linewidth, g-value, line shape and signal intensity indicating the significant influence of surrounding paramagnetic silver or ferromagnetic iron within polymer host on the EPR spectra have been presented.

  4. Microwave-heating synthesis and sensing applications of bright gold nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    He, Ding-Fei; Xiang, Yang; Wang, Xu [Department of Physics, Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Yu, Xue-Feng, E-mail: yxf@whu.edu.cn [Department of Physics, Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072 (China)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer We establish a microwave-heating method to synthesize protein-stabilized Au nanoclusters. Black-Right-Pointing-Pointer The obtained Au nanoclusters show bright red fluorescence. Black-Right-Pointing-Pointer The Au nanoclusters can be used as efficient fluorescence probe for Cu{sup 2+} ion sensing. -- Abstract: A rapid microwave-heating method has been developed for the synthesis of bright Au nanoclusters by using bull serum albumin as the template in an aqueous environment. The reaction time needed is only 7.0 min, and the weight of the products at one batch can reach 15 g. The Au nanoclusters exhibit bright fluorescence at {approx}613 nm with quantum yield of {approx}6.0%. By adjusting the pH value, the products can be controlled to precipitate or re-disperse in aqueous solution. Furthermore, the Au nanoclusters have exhibited high sensitivity and selectivity in the determination of Cu{sup 2+} ions in water. These results suggest an efficient method for obtaining metal nanoclusters for the detection and sensing applications.

  5. A DFT study for the structural and electronic properties of Zn m Se n nanoclusters

    Science.gov (United States)

    Yadav, Phool Singh; Pandey, Dheeraj Kumar

    2012-09-01

    An ab initio study has been performed for the stability, structural and electronic properties of 19 small zinc selenide Zn m Se n ( m + n = 2-4) nanoclusters. Out of these nanoclusters, one nanocluster is found to be unstable due to its imaginary vibrational frequency. A B3LYP-DFT/6-311G(3df) method is used in the optimization of the geometries of the nanoclusters. We have calculated the zero point energy (ZPE), which is ignored by the other workers. The binding energies (BE), HOMO-LUMO gaps and bond lengths have been obtained for all the optimized nanoclusters. For the same value of ` m' and ` n', we designate the most stable structure the one, which has maximum final binding energy (FBE) per atom. The adiabatic and vertical ionization potentials (IP) and electron affinities (EA), dipole moments and charge on atoms have been investigated for the most stable nanoclusters. For the same value of ` m' and ` n', the nanocluster containing maximum number of Se atoms is found to be most stable.

  6. Organic Light-Emitting Diodes Using Multifunctional Phosphorescent Dendrimers with Iridium-Complex Core and Charge-Transporting Dendrons

    Science.gov (United States)

    Tsuzuki, Toshimitsu; Shirasawa, Nobuhiko; Suzuki, Toshiyasu; Tokito, Shizuo

    2005-06-01

    We report a novel class of light-emitting materials for use in organic light-emitting diodes (OLEDs): multifunctional phosphorescent dendrimers that have a phosphorescent core and dendrons based on charge-transporting building blocks. We synthesized first-generation and second-generation dendrimers consisting of a fac-tris(2-phenylpyridine)iridium [Ir(ppy)3] core and hole-transporting phenylcarbazole-based dendrons. Smooth amorphous films of these dendrimers were formed by spin-coating them from solutions. The OLEDs using the dendrimer exhibited bright green or yellowish-green emission from the Ir(ppy)3 core. The OLEDs using the film containing a mixture of the dendrimer and an electron-transporting material exhibited higher efficiency than those using the neat dendrimer film. The external quantum efficiency of OLEDs using the film containing a mixture of the first-generation dendrimer and an electron-transporting material was as high as 7.6%.

  7. Physicochemical and biological properties of self-assembled antisense/poly(amidoamine) dendrimer nanoparticles: the effect of dendrimer generation and charge ratio

    OpenAIRE

    Nomani, Alireza; Haririan, Ismaeil; Rahimnia, Ramin; Fouladdel, Shamileh; Gazori, Tarane; Dinarvand, Rassoul; Omidi, Yadollah; Azizi, Ebrahim

    2010-01-01

    To gain a deeper understanding of the physicochemical phenomenon of self-assembled nanoparticles of different generations and ratios of poly (amidoamine) dendrimer (PAMAM) dendrimer and a short-stranded DNA (antisense oligonucleotide), multiple methods were used to characterize these nanoparticles including photon correlation spectroscopy (PCS); zeta potential measurement; and atomic force microscopy (AFM). PCS and AFM results revealed that, in contrast to larger molecules of DNA, smaller mol...

  8. Morphological and magnetic properties of cobalt nanoclusters electrodeposited onto HOPG

    International Nuclear Information System (INIS)

    Rivera, M.; Rios-Reyes, C.H.; Mendoza-Huizar, L.H.

    2008-01-01

    In this work, the morphological and magnetic properties of cobalt nanoclusters obtained from two different sulphate electrolyte solutions were studied. The aggregates were electrodeposited onto highly oriented pyrolytic graphite electrodes in overpotential conditions, in order to investigate the cationic influence on the final properties of the aggregates. In both cases, scanning electron microscopy and atomic force microscopy showed random isolated clusters on the electrode surface, where size variations were determined by the electrolyte solution. By using magnetic force microscopy, the distribution of the electrodeposited magnetic material was more clearly observed which gave some insights on the growth mechanism of these aggregates.

  9. Ion implantation induced conducting nano-cluster formation in PPO

    International Nuclear Information System (INIS)

    Das, A.; Patnaik, A.; Ghosh, G.; Dhara, S.

    1997-01-01

    Conversion of polymers and non-polymeric organic molecules from insulating to semiconducting materials as an effect of energetic ion implantation is an established fact. Formation of nano-clusters enriched with carbonaceous materials are made responsible for the insulator-semiconductor transition. Conduction in these implanted materials is observed to follow variable range hopping (VRH) mechanism. Poly(2,6-dimethyl phenylene oxide) [PPO] compatible in various proportion with polystyrene is used as a high thermal resistant insulating polymer. PPO has been used for the first time in the ion implantation study

  10. Enantioselective silver nanoclusters: Preparation, characterization and photoluminescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Farrag, Mostafa, E-mail: mostafafarrag@aun.edu.eg

    2016-09-01

    Herein, we report a new wet-synthesis method to separate some water-soluble chiral silver nanoclusters with high yield. The cluster material was obtained by the reduction of silver nitrate with NaBH{sub 4} in the presence of three ligands L-penicillamine (L-pen), D-penicillamine (D-pen) and racemic mixture of penicillamine (rac-pen), functioning as capping ligand. For characterizing all silver cluster samples, the particle size was assessed by transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) and their average chemical formula was determined from thermogravimetric analysis (TGA) and elemental analysis (EA). The particles sizes of all three clusters are 2.1 ± 0.2 nm. The optical properties of the samples were studied by four different methods: UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL) and circular dichroism (CD) spectroscopy. The spectra are dominated by the typical and intense plasmon peak at 486 nm accompanied by a small shoulder at 540 nm. Infrared spectroscopy was measured for the free ligand and protected silver nanoclusters, where the disappearance of the S-H vibrational band (2535–2570 cm{sup −1}) in the silver nanoclusters confirmed anchoring of ligand to the cluster surface through the sulfur atom. PL studies yielded the fluorescent properties of the samples. The main focus of this work, however, lies in the chirality of the particles. For all silver clusters CD spectra were recorded. While for clusters capped with one of the two enantiomers (D- or L-form) typical CD spectra were observed, no significant signals were detected for a racemic ligand mixture. Furthermore, silver clusters show quite large asymmetry factors (up to 3 × 10{sup −4}) in comparison to most other ligand protected clusters. These large factors and bands in the visible range of the spectrum suggest a strong chiral induction from the ligand to the metal core. Textural features of the

  11. Ultrafast coherence transfer in DNA-templated silver nanoclusters

    DEFF Research Database (Denmark)

    Thyrhaug, Erling; Bogh, Sidsel Ammitzbøll; Carro, Miguel

    2017-01-01

    DNA-templated silver nanoclusters of a few tens of atoms or less have come into prominence over the last several years due to very strong absorption and efficient emission. Applications in microscopy and sensing have already been realized, however little is known about the excited-state structure...... and dynamics in these clusters. Here we report on a multidimensional spectroscopy investigation of the energy-level structure and the early-time relaxation cascade, which eventually results in the population of an emitting state. We find that the ultrafast intramolecular relaxation is strongly coupled...

  12. Effect of quencher, denaturants, temperature and pH on the fluorescent properties of BSA protected gold nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Chib, Rahul, E-mail: Rahul.chib@live.unthsc.edu [Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107 (United States); Butler, Susan [Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107 (United States); Raut, Sangram [Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107 (United States); Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129 (United States); Shah, Sunil; Borejdo, Julian [Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107 (United States); Gryczynski, Zygmunt [Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107 (United States); Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129 (United States); Gryczynski, Ignacy, E-mail: ignacy.gryczynski@unthsc.edu [Department of Cell Biology and Immunology, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107 (United States)

    2015-12-15

    In this paper, we have synthesized BSA protected gold nanoclusters (BSA Au nanocluster) and studied the effect of quencher, protein denaturant, pH and temperature on the fluorescence properties of the tryptophan molecule of the BSA Au nanocluster and native BSA. We have also studied their effect on the peak emission of BSA Au nanoclusters (650 nm). The photophysical characterization of a newly developed fluorophore in different environments is absolutely necessary to futher develop their biomedical and analytical applications. It was observed from our experiments that the tryptophan in BSA Au nanoclusters is better shielded from the polar environment. Tryptophan in native BSA showed a red shift in its peak emission wavelength position. Tryptophan is a highly polarity sensitive dye and a minimal change in its microenvironment can be easily observed in its photophysical properties. - Highlights: • Tryptophan is easily accessible in native BSA compared to BSA Au nanoclusters. • Guanidine HCL denatures native BSA more compared to BSA Au nanoclusters. • High temperature decreases the quantum yield of tryptophan and BSA Au nanocluster. • Emission wavelength of BSA Au nanoclusters remains constant with increasing pH. • BSA Au nanoclusters are robust to the changes in their environments.

  13. Effect of quencher, denaturants, temperature and pH on the fluorescent properties of BSA protected gold nanoclusters

    International Nuclear Information System (INIS)

    Chib, Rahul; Butler, Susan; Raut, Sangram; Shah, Sunil; Borejdo, Julian; Gryczynski, Zygmunt; Gryczynski, Ignacy

    2015-01-01

    In this paper, we have synthesized BSA protected gold nanoclusters (BSA Au nanocluster) and studied the effect of quencher, protein denaturant, pH and temperature on the fluorescence properties of the tryptophan molecule of the BSA Au nanocluster and native BSA. We have also studied their effect on the peak emission of BSA Au nanoclusters (650 nm). The photophysical characterization of a newly developed fluorophore in different environments is absolutely necessary to futher develop their biomedical and analytical applications. It was observed from our experiments that the tryptophan in BSA Au nanoclusters is better shielded from the polar environment. Tryptophan in native BSA showed a red shift in its peak emission wavelength position. Tryptophan is a highly polarity sensitive dye and a minimal change in its microenvironment can be easily observed in its photophysical properties. - Highlights: • Tryptophan is easily accessible in native BSA compared to BSA Au nanoclusters. • Guanidine HCL denatures native BSA more compared to BSA Au nanoclusters. • High temperature decreases the quantum yield of tryptophan and BSA Au nanocluster. • Emission wavelength of BSA Au nanoclusters remains constant with increasing pH. • BSA Au nanoclusters are robust to the changes in their environments.

  14. Protein mediated synthesis of fluorescent Au-nanoclusters for metal sensory coatings

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, Manja; Raff, Johannes [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Biogeochemistry

    2017-06-01

    Fluorescent Au-nanocluster were successfully synthesized and used for the selective detection of Cu{sup 2} {sup +}. The synthesized Au-BSA-nanoclusters remain functional also after immobilization and show high thermal stability. Additionally, the transfer of the protein mediated Au-nanocluster synthesis route to S-layer proteins was achieved. (The presented work is part of the project BIONEWS dealing with long-term stable cells for the set-up and regeneration of sensor and actor materials for strategic relevant metals, in particular rare earth elements).

  15. Size-Dependent Specific Surface Area of Nanoporous Film Assembled by Core-Shell Iron Nanoclusters

    Directory of Open Access Journals (Sweden)

    Jiji Antony

    2006-01-01

    Full Text Available Nanoporous films of core-shell iron nanoclusters have improved possibilities for remediation, chemical reactivity rate, and environmentally favorable reaction pathways. Conventional methods often have difficulties to yield stable monodispersed core-shell nanoparticles. We produced core-shell nanoclusters by a cluster source that utilizes combination of Fe target sputtering along with gas aggregations in an inert atmosphere at 7∘C. Sizes of core-shell iron-iron oxide nanoclusters are observed with transmission electron microscopy (TEM. The specific surface areas of the porous films obtained from Brunauer-Emmett-Teller (BET process are size-dependent and compared with the calculated data.

  16. Ge nanoclusters in PECVD-deposited glass caused only by heat treatment

    DEFF Research Database (Denmark)

    Ou, Haiyan; Rørdam, Troels Peter; Rottwitt, Karsten

    2008-01-01

    This paper reports the formation of Ge nanoclusters in a multi-layer structure consisting of alternating thin films of Ge-doped silica glass and SiGe, deposited by plasma-enhanced chemical vapor deposition (PECVD) and post annealed at 1100 °C in N2 atmosphere. We studied the annealed samples...... embedded with Ge nanoclusters after annealing. These nanoclusters are crystalline and varied in size. There were no clusters in the Ge-doped glass layer. Raman spectra verified the existence of crystalline Ge clusters. The positional shift of the Ge vibrational peak with the change of the focus depth...

  17. Experimental measurements of U24Py nanocluster behavior in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Flynn, Shannon L.; Szymanowski, Jennifer E.S.; Fein, Jeremy B. [Univ. of Notre Dame, IN (United States). Department of Civil and Environmental Engineering and Earth Sciences; Dembowski, Mateusz [Univ. of Notre Dame, IN (United States). Department of Chemistry and Biochemistry; Burns, Peter C. [Univ. of Notre Dame, IN (United States). Department of Civil and Environmental Engineering and Earth Sciences; Univ. of Notre Dame, IN (United States). Department of Chemistry and Biochemistry

    2016-07-01

    Uranyl peroxide nanoclusters may impact the mobility and partitioning of uranium at contaminated sites and could be used in the isolation of uranium during the reprocessing of nuclear waste. Their behavior in aqueous systems must be better understood to predict the environmental fate of uranyl peroxide nanoclusters and for their use in engineered systems. The aqueous stability of only one uranyl peroxide nanocluster, U60 (K{sub 16}Li{sub 44}[UO{sub 2}(O{sub 2})OH]{sub 60}), has been studied to date [Flynn, S. L., Szymanowski, J. E. S., Gao, Y., Liu, T., Burns, P. C., Fein, J. B.: Experimental measurements of U60 nanocluster stability in aqueous solution. Geochemica et Cosmochimica Acta 156, 94-105 (2015)]. In this study, we measured the aqueous stability of a second uranyl peroxide nanocluster, U24Py (Na{sub 30}[(UO{sub 2}){sub 24}(O{sub 2}){sub 24}(HP{sub 2}O{sub 7}){sub 6}(H{sub 2}P{sub 2}O{sub 7}){sub 6}]), in batch systems as a function of time, pH, and nanocluster concentration, and then compared the aqueous behavior of U24Py to U60 to determine whether the size and morphology differences result in differences in their aqueous behaviors. Systems containing U24Py nanoclusters took over 30 days to achieve steady-state concentrations of monomeric U, Na, and P, illustrating slower reaction kinetics than parallel U60 systems. Furthermore, U24Py exhibited lower stability in solution than U60, with an average of 72% of the total mass in each nanocluster suspension being associated with the U24Py nanocluster, whereas 97% was associated with the U60 nanocluster in parallel experiments [Flynn, S. L., Szymanowski, J. E. S., Gao, Y., Liu, T., Burns, P. C., Fein, J. B.: Experimental measurements of U60 nanocluster stability in aqueous solution. Geochemica et Cosmochimica Acta 156, 94-105 (2015)]. The measurements from the batch experiments were used to calculate ion activity product (IAP) values for the reaction between the U24Py nanocluster and its constituent monomeric

  18. Rational design of dendrimer/lipid nanoassemblies in drug delivery for cancer chemotherapy

    Science.gov (United States)

    Sun, Qihang

    Nanocarriers can minimize the side effects and improve therapeutic efficacy of anticancer drugs. Although some success has been achieved via active or passive drug delivery to tumor cells, the known nanocarriers are far from satisfying therapeutic efficacy expectations. This is because they usually fail in one of the four crucial requirements, that is, to retain drug in blood circulation but release it reliably in tumor cells and to be stealthy in transport in circulation and tumor tissue but sticky upon arrival at the tumor cell. Therefore, the goal of this work is to fabricate nanoassemblies of dendrimers and lipids to address all these challenges. Particularly, nanoassemblies designed and prepared in this work are illustrated to improve the tumor tissue penetration. Examples of dendrimers synthesized in this work are water-insoluble, pH-dependent water-insoluble and water-soluble biodegradable polyester dendrimers. These dendrimers are shown to be encapsulated by commonly used fusogenic and long-circulating lipids to form reliable nanoassemblies. The dendrimer/lipid nanocarriers are used to demonstrate a cascade drug delivery. They are expected to be stable in circulation, due to their appropriately large size, but to release the drug-loaded dendrimers in tumor tissue. The released dendrimers carrying drugs are much smaller and hence expected to have a much deeper penetration throughout the tumor tissue.

  19. Synergistic effect of amino acids modified on dendrimer surface in gene delivery.

    Science.gov (United States)

    Wang, Fei; Wang, Yitong; Wang, Hui; Shao, Naimin; Chen, Yuanyuan; Cheng, Yiyun

    2014-11-01

    Design of an efficient gene vector based on dendrimer remains a great challenge due to the presence of multiple barriers in gene delivery. Single-functionalization on dendrimer cannot overcome all the barriers. In this study, we synthesized a list of single-, dual- and triple-functionalized dendrimers with arginine, phenylalanine and histidine for gene delivery using a one-pot approach. The three amino acids play different roles in gene delivery: arginine is essential in formation of stable complexes, phenylalanine improves cellular uptake efficacy, and histidine increases pH-buffering capacity and minimizes cytotoxicity of the cationic dendrimer. A combination of these amino acids on dendrimer generates a synergistic effect in gene delivery. The dual- and triple-functionalized dendrimers show minimal cytotoxicity on the transfected NIH 3T3 cells. Using this combination strategy, we can obtain triple-functionalized dendrimers with comparable transfection efficacy to several commercial transfection reagents. Such a combination strategy should be applicable to the design of efficient and biocompatible gene vectors for gene delivery. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. Development of a Topical Resveratrol Formulation for Commercial Applications Using Dendrimer Nanotechnology.

    Science.gov (United States)

    Pentek, Tyler; Newenhouse, Eric; O'Brien, Brennin; Chauhan, Abhay Singh

    2017-01-14

    Resveratrol (RSV) is well known for its anti-oxidant and anti-aging properties. However, resveratrol is insoluble in water and has stability issues. Recently, efforts were placed to prepare a resveratrol-based advanced anti-aging topical product but it contains harsh organic solvents and oils that could be harmful to the human body and the environment. Hence, we propose the use of a multifunctional dendrimer to solve the solubility and stability issues of resveratrol. A dendrimer-resveratrol complex was prepared, optimized and tested for solubility enhancement, stability in solution and cream dosage forms. We have also developed a high performance liquid chromatography method to measure the resveratrol within the final product. PAMAM dendrimers increased the solubility and stability of resveratrol in water and semisolid dosage forms. Therefore, this product would be water based 'green' formulation devoid of harsh organic solvents and oils and can be safely applied to the skin. Additionally, we have shown that the dendrimer helped to increase overall RSV loading and skin penetration of resveratrol. The dendrimer-RSV formulation was successfully scaled up towards commercialization. Dendrimer with RSV has led to an innovation in anti-aging cream and solutions that could be commercially marketed. Dendrimer-RSV complex could also be added to other product forms for additional purposes and applications.

  1. Assess the Intra-molecular Cavity in PAMAM Dendrimers by Small Angle Neutron Scattering

    International Nuclear Information System (INIS)

    Chen, Wei-Ren

    2008-01-01

    In this report, we present a contrast variation small angle neutron scattering (SANS) study of a series of neutral PAMAM dendrimer in aqueous solutions using three different generations (G4-6) at a concentration of about 10 mg/ml. Varying the solvent hydrogen-deuterium ratio, the scattering contributions from the water molecules and the constituent components of PAMAM dendrimer can be determined. Using an analytical model of the scattering cross section I(Q) incorporating the effect of water penetration, we have quantified the intra-molecular space of PAMAM dendrimer by evaluating the number of guest water molecules and we draw a direct comparison to computational predictions. As expected, the overall available internal cavity was seen to increase as a function of increasing dendrimer generation. However, the fraction of water accessible volume in the internal cavity of a dendrimer was found to remain invariant for the three generation PAMAM dendrimers studied in this report. We have also estimated the average water density inside a dendrimer, which is found to be higher than that of bulk water

  2. Neutron Reflectometry Investigations of the Interaction of DNA-PAMAM Dendrimers with Model Biological Membranes

    International Nuclear Information System (INIS)

    Ainalem, M.L.; Rennie, A.R.; Campbell, Richard; Edler, Karen; Nylander, Tommy

    2009-01-01

    The systemic delivery of DNA for gene therapy requires control of DNA compaction by an agent, such a lipid, surfactant or a polymer (e.g. cationic dendrimers) as well as understanding of how this complex interacts with a biological membrane. Poly (amido amine) (PAMAM) dendrimers have been reported to be a promising synthetic gene-transfection agent. We have studied the structure of the complexes formed between DNA and PAMAM dendrimers with SANS, dynamic light scattering and cryo-TEM. Here we noted that the structure of the complex formed strongly depends on the generation of the dendrimer. The results of the adsorption of generation 2 (G2) and 4 (G4) PAMAM dendrimers to surface deposited bilayers, consisting of palmitoyl oleoyl phosphatidyl choline on silicon surface, have been studied using neutron reflectometry (NR). The NR data shows that the dendrimers are able to penetrate the bilayer. However, the complex is less able to penetrate the bilayer, but rather stays on the top of the bilayer. The dendrimers appear slightly flattened on the surface in comparison with their size in bulk as determined by light scattering. We will also report on the interfacial behavior of the DNA-PAMAM complexes at other types of studies of interfaces, important for biomedical applications, where NR has allowed us to determine the layer structure and composition. (author)

  3. Tautomeric forms of PPI dendrimers functionalized with 4-(4′-ethoxybenzoyloxy)salicylaldehyde chromophores

    International Nuclear Information System (INIS)

    Franckevičius, M.; Vaišnoras, R.; Marcos, M.; Serrano, J.L.; Gruodis, A.; Galikova, N.; Gulbinas, V.

    2012-01-01

    Highlights: ► SA chromophore groups are formed by bonding terminal groups to PPI dendrimers. ► SA chromophore groups reveal four most stable tautomeric forms. ► Tautomeric properties of SA groups depend on the dendrimer generation and solvent. ► Aggregation of SA chromophores facilitates formation of the trans-keto tautomers. ► Fluorescence of PPI SA dendrimers is attributed to nπ ∗ states of keto tautomers. -- Abstract: Bonding of the promesogenic unit derived from 4-(4′-ethoxybenzoyloxy)salicylaldehyde to the amino terminated PPI dendrimer chains results in formation of the salicylidenimine chromophore groups. Absorption and fluorescence investigations of the dendrimer solutions supported by the quantum chemistry calculations revealed that the chromophore groups may exist in enol and keto tautomeric forms with relative concentrations depending on the dendrimer generation and solvent. The dendrimer fluorescence is attributed to nπ ∗ states of keto tautomers which may also be formed from excited enol tautomers.

  4. Analysis of the spatial structure of rigid polyphenylene dendrimers by small-angle neutron scattering

    International Nuclear Information System (INIS)

    Rosenfeldt, S.; Dingenouts, N.; Poetschke, D.; Ballauff, M.; Berresheim, A.J.; Muellen, K.; Lindner, P.; Saalwaechter, K.

    2005-01-01

    The analysis of the spatial structure of a rigid polyphenylene dendrimer G4-M of fourth generation by small-angle neutron scattering (SANS) is presented. This dendrimer is composed of phenyl units and is therefore devoid of any flexible unit. The scattering intensity of dilute solutions of the dendrimer was measured by SANS at different contrast which was adjusted by mixtures of protonated and deuterated toluene. Hence, the method of contrast variation could be applied and the data yield the scattering function extrapolated to infinite contrast. The comparison of this data with simulations demonstrates that the scaffold of the dendrimer is rigid as expected from its chemical structure. The positions of the various units setting up consecutive shells of the dendrimer are relatively well localized and the entire structure cannot be modeled in terms of spherically symmetric models. No backfolding of the terminal groups can occur and the model calculations demonstrate that higher generations of this dendritic scaffold must exhibit a dense shell and a congestion of the terminal groups. This finding is directly corroborated by recent solid-state NMR data. All results show that the rigid dendrimer investigated here presents the first example for a dendritic structure whose segment density does not have its maximum at the center. Rigid scaffolds are therefore the only way to achieve the goal of a 'dense-shell' dendrimer whereas flexible scaffolds leads invariably to the 'dense-core' case

  5. Development of TREN dendrimers over mesoporous SBA-15 for CO2 adsorption

    International Nuclear Information System (INIS)

    Bhagiyalakshmi, Margandan; Park, Sang Do; Cha, Wang Seog; Jang, Hyun Tae

    2010-01-01

    Mesoporous SBA-15 was synthesized using rice husk ash (RHA) as the silica source and their defective Si-OH groups were grafted with tris(2-aminoethyl) amine (TREN) dendrimers generation through step-wise growth technique. The X-ray diffraction (XRD) and nitrogen adsorption/desorption results of parent SBA-15 obtained from RHA, suggests its resemblance with SBA-15 synthesized using conventional silica sources. Furthermore, the nitrogen adsorption/desorption results of SBA-15/TREN dendrimer generations (G1-G3) illustrates the growth of dendrimer inside the mesopores of SBA-15 and their CO 2 adsorption capacity was determined at 25 deg. C. The maximum CO 2 adsorption capacity of 5-6 and 7-8 wt% over second and third dendrimer generation was observed which is discernibly higher than the reported melamine and PAMAM dendrimers. The experimental CO 2 adsorption capacity was found to be less than theoretically calculated CO 2 adsorption capacity due to inter and intra molecular amidation as result of steric hindrance during the dendrimer growth. These SBA-15/TREN dendrimer generations also exhibit thermal stability up to 350 deg. C and CO 2 adsorption capacity remains unaltered upon seven consecutive runs.

  6. PEGylation of polylysine dendrimers improves absorption and lymphatic targeting following SC administration in rats.

    Science.gov (United States)

    Kaminskas, Lisa M; Kota, Jagannath; McLeod, Victoria M; Kelly, Brian D; Karellas, Peter; Porter, Christopher Jh

    2009-12-03

    Polylysine dendrimers have potential as highly flexible, biodegradable nanoparticular carriers that may also promote lymphatic transport. The current study was undertaken to determine the impact of PEGylation on the absorption and lymphatic transport of polylysine dendrimers modified by surface derivatisation with PEG (200, 570 or 2000Da) or 4-benzene sulphonate following SC or IV dosing. PEGylation led to the PEG(200) derived dendrimer being rapidly and completely absorbed into the blood after SC administration, however only 3% of the administered dose was recovered in pooled thoracic lymph over 30h. Increasing the PEG chain length led to a systematic decrease in absorption into the blood and an enhancement of the proportion recovered in the lymphatics (up to 29% over 30h). For the PEG(570) and PEG(2000) derived dendrimers, indirect access to the lymph via equilibration across the capillary beds also appeared to play a role in lymphatic targeting after both IV and SC dosing. In contrast, the anionic benzene sulphonate-capped dendrimer was not well absorbed from the SC injection site (26% bioavailability) into either the blood or the lymph. The data suggest that PEGylated poly-L-lysine dendrimers are well absorbed from SC injection sites and that the extent of lymphatic transport may be enhanced by increasing the size of the PEGylated dendrimer complex.

  7. Effect of generation on the electronic properties of light-emitting dendrimers

    Science.gov (United States)

    Burn, Paul L.; Halim, Mounir; Pillow, Jonathan N. G.; Samuel, Ifor D. W.

    1999-12-01

    We have compared the optical and electronic properties of a series of porphyrin centered dendrimers containing stilbene dendrons. The first and second generation dendrimers could be spin-coated from solution to form good quality thin films. Incorporation into single layer light-emitting diodes gave red-light emission with maximum external quantum efficiencies of 0.02% and 0.04% for the first and second generation dendrimers respectively. We have determined by photoluminescence studies that energy can be transferred efficiently from the stilbene dendrons to the porphyrin core and that PL emission is from the core. Cyclic voltammetry studies on the dendrimers show that the reductions are porphyrin centered with the dendrons only affecting the rate of heterogeneous electron transfer between the electrode and the dendrimers. This suggests that charge mobility within a dendrimer film in an LED will be affected by the porphyrin edge to porphyrin edge distance. We have studied the hydrodynamic radii of the dendrimers by gel permeation chromatography and found as expected that the average porphyrin edge to dendron edge distance increases with generation. This is consistent with the slowing of heterogeneous electron transfer observed in the cyclic voltammetry on increasing the generation number and suggests that the dendrons are interleaved in the solid state to facilitate charge transport.

  8. Transepithelial transport of PAMAM dendrimers across isolated rat jejunal mucosae in ussing chambers.

    Science.gov (United States)

    Hubbard, Dallin; Ghandehari, Hamidreza; Brayden, David J

    2014-08-11

    Oral delivery remains a challenge for poorly permeable hydrophilic macromolecules. Poly(amido amine) (PAMAM) dendrimers have shown potential for their possible oral delivery. Transepithelial transport of carboxyl-terminated G3.5 and amine-terminated G4 PAMAM dendrimers was assessed using isolated rat jejunal mucosae mounted in Ussing chambers. The 1 mM FITC-labeled dendrimers were added to the apical side of mucosae. Apparent permeability coefficients (Papp) from the apical to the basolateral side were significantly increased for FITC when conjugated to G3.5 PAMAM dendrimer compared to FITC alone. Minimal signs of toxicity were observed when mucosae were exposed to both dendrimers with respect to transepithelial electrical resistance changes, carbachol-induced short circuit current stimulation, and histological changes. [(14)C]-mannitol fluxes were not altered in the presence of 1 mM dendrimers, suggesting that the paracellular pathway was not affected at this concentration in this model. These results give insight into the mechanism of PAMAM dendrimer transepithelial rat jejunal transport, as well as toxicological considerations important for oral drug delivery.

  9. Cholesterol-conjugated supramolecular assemblies of low generations polyamidoamine dendrimers for enhanced EGFP plasmid DNA transfection

    Energy Technology Data Exchange (ETDEWEB)

    Golkar, Nasim; Samani, Soliman Mohammadi; Tamaddon, Ali Mohammad, E-mail: amtamadon@gmail.com [Shiraz University of Medical Sciences, Department of Pharmaceutics, School of Pharmacy (Iran, Islamic Republic of)

    2016-05-15

    Aimed to prepare an enhanced gene delivery system with low cytotoxicity and high transfection efficiency, various cholesterol-conjugated derivates of low generation polyamidoamine (PAMAM) dendrimers were prepared. The conjugates were characterized by TNBS assay, FTIR, and {sup 1}H-NMR spectroscopy. Self-assembly of the dendrimer conjugates (G1-Chol, G2-Chol, and G3-Chol) was investigated by pyrene assay. Following formation of the complexes between enhanced green fluorescence protein plasmid and the dendrimer conjugates at various N (primary amine)/P (phosphate) mole ratios, plasmid condensation, biologic stability, cytotoxicity, and protein expression were investigated. The conjugates self-assembled into micellar dispersions with the critical micelle concentration values (<50 µg/ml) depending on the dendrimer generation and cholesterol/amine mole ratio. Cholesterol conjugation resulted in higher resistance of the condensed plasmid DNA in a competition assay with heparin sulfate. Also, the transfection efficiency was determined higher for the cholesterol conjugates than unmodified dendrimers in HepG2 cells, showing the highest for G2-Chol at 40 % degree of cholesterol modification (G2-Chol{sub 40 %}) among various dendrimer generations. Interestingly, such conjugate showed a complete protection of plasmid against serum nucleases. Our results confirmed that the cholesterol conjugation to PAMAM dendrimers of low generations bearing little cytotoxicity improves their several physicochemical and biological characteristics required for an enhanced delivery of plasmid DNA into cells.

  10. Phosphorus Dendrimers as Carriers of siRNA—Characterisation of Dendriplexes

    Directory of Open Access Journals (Sweden)

    Jean-Pierre Majoral

    2013-04-01

    Full Text Available There are many types of dendrimers used as nanomolecules for gene delivery but there is still an ongoing search for ones that are able to effectively deliver drugs to cells. The possibility of gene silencing using siRNA gives hope for effective treatment of numerous diseases. The aim of this work was to investigate in vitro biophysical properties of dendriplexes formed by siRNA and cationic phosphorus dendrimers of 3rd and 4th generation. First, using the ethidium bromide intercalation method, it was examined whether dendrimers have an ability to form complexes with siRNA. Next, the characterisation of dendriplexes formed at different molar ratios was carried out using biophysical methods. The effects of zeta potential, size and changes of siRNA conformation on the complexation with dendrimers were examined. It was found that both phosphorus dendrimers interacted with siRNA. The zeta potential values of dendriplexes ranged from negative to positive and the hydrodynamic diameter depended on the number of dendrimer molecules in the complex. Furthermore, using circular dichroism spectroscopy it was found that cationic phosphorus dendrimers changed only slightly the shape of siRNA CD spectra, thus they did not induce significant changes in the nucleic acid secondary structure during complex formation.

  11. Coherent radiation by quantum dots and magnetic nanoclusters

    International Nuclear Information System (INIS)

    Yukalov, V. I.; Yukalova, E. P.

    2014-01-01

    The assemblies of either quantum dots or magnetic nanoclusters are studied. It is shown that such assemblies can produce coherent radiation. A method is developed for solving the systems of nonlinear equations describing the dynamics of such assemblies. The method is shown to be general and applicable to systems of different physical nature. Despite mathematical similarities of dynamical equations, the physics of the processes for quantum dots and magnetic nanoclusters is rather different. In a quantum dot assembly, coherence develops due to the Dicke effect of dot interactions through the common radiation field. For a system of magnetic clusters, coherence in the spin motion appears due to the Purcell effect caused by the feedback action of a resonator. Self-organized coherent spin radiation cannot arise without a resonator. This principal difference is connected with the different physical nature of dipole forces between the objects. Effective dipole interactions between the radiating quantum dots, appearing due to photon exchange, collectivize the dot radiation. While the dipolar spin interactions exist from the beginning, yet before radiation, and on the contrary, they dephase spin motion, thus destroying the coherence of moving spins. In addition, quantum dot radiation exhibits turbulent photon filamentation that is absent for radiating spins

  12. Formation of nanoclusters of gadolinium atoms in silicon

    International Nuclear Information System (INIS)

    Iliev, Kh.M.; Saparniyazova, Z.M.; Ismajlov, K.A.; Madzhitov, M.Kh.

    2011-01-01

    A technology of stage wise low temperature diffusion of gadolinium into silicon that makes it possible to form nanoclusters of impurity atoms with a significant magnetic moment distributed throughout the volume of the material has been developed. It is shown that, unlike the samples obtained by high temperature diffusion doping, the samples prepared by the new technology do not have surface erosion, and alloys and silicides are not formed in the near surface region. Nanoclusters of impurity atoms of gadolinium in the volume of the crystal lattice of the silicon are studied using an MIK-5 infrared microscope. It is found that, in the stage wise low temperature diffusion, the temperature and time of the diffusion have an effect not only on the depth of penetration of the impurities but also on the sizes of the resulting clusters; these factors can also prevent the formation of clusters. The study of the effect of low temperature treatments on the size and distribution of clusters shows that, upon annealing in the temperature range of 500-700 degrees Celsius, the ordering of the clusters of gadolinium impurity atoms is observed. A further increase in the annealing temperature leads to the destruction of gadolinium clusters in the silicon bulk. (authors)

  13. Fluorescence enhancement of DNA-silver nanoclusters from guanine proximity

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, Hsin-chih [Los Alamos National Laboratory; Sharma, Jaswinder [Los Alamos National Laboratory; Yoo, Hyojong [Los Alamos National Laboratory; Martinez, Jennifer S [Los Alamos National Laboratory

    2010-01-01

    Oligonucleotide-templated, silver nanoclusters (DNA/Ag NCs) are a versatile set of fluorophores and have already been used for live cell imaging, detection of specific metal ions, and single-nucleotide variation identification. Compared to commonly used organic dyes, these fluorescent nanoclusters have much better photostability and are often a few times brighter. Owing to their small size, simple preparation, and biocompatibility (i.e. made of nontoxic metals), DNA/Ag NCs should find more applications in biological imaging and chemical detection in the years to come. While clearly promising as new fluorophores, DNA/Ag NCs possess a unique and poorly understood dynamic process not shared by organic dyes or photoluminescent nanocrystals - the conversion among different NC species due to silver oxidation/reduction or NC regrouping. While this environmental sensitivity can be viewed as a drawback, in the appropriate context, it can be used as a sensor or reporter. Often reversible, conversions among different NC species have been found to depend upon a number of factors, including time, temperature, oxygen and salt content. In this communication, we report significant fluorescence enhancement of DNA/Ag NCs via interactions with guanine-rich DNA sequences. Moreover, we demonstrated this property can be used for sensitive detection of specific target DNA from a human oncogene (i.e. Braf gene).

  14. Multifunctional Dendrimer-templated Antibody Presentation on Biosensor Surfaces for Improved Biomarker Detection.

    Science.gov (United States)

    Han, Hye Jung; Kannan, Rangaramanujam M; Wang, Sunxi; Mao, Guangzhao; Kusanovic, Juan Pedro; Romero, Roberto

    2010-02-08

    Dendrimers, with their well-defined globular shape and a high density of functional groups, are ideal nanoscale materials for templating sensor surfaces. This work exploits dendrimers as a versatile platform for capturing biomarkers with improved sensitivity and specificity. Synthesis, characterization, fabrication, and functional validation of the dendrimer-based assay platform are described. Bifunctional hydroxyl/thiol functionalized G4-polyamidoamine (PAMAM) dendrimer is synthesized and immobilized on to the polyethylene-glycol (PEG)-functionalized assay plate by coupling PEG-maleimide and dendrimer thiol groups. Simultaneously, part of the dendrimer thiol groups are converted to hydrazide functionalities. The resulting dendrimer-modified surface is coupled to the capture antibody in the Fc region of the oxidized antibody. This preserves the orientation flexibility of the antigen binding region (Fv) of the antibody. To validate the approach, the fabricated plates are further used as a solid phase for developing a sandwich type ELISA to detect IL-6 and IL-1β, important biomarkers for early stages of chorioamnionitis. The dendrimer-modified plate provides assays with significantly enhanced sensitivity, lower nonspecific adsorption, and a detection limit of 0.13 pg ml -1 for IL-6 luminol detection and 1.15 pg ml -1 for IL-1β TMB detection, which are significantly better than those for the traditional ELISA. The assays were validated in human serum samples from normal (non-pregnant) woman and pregnant women with pyelonephritis. The specificity and the improved sensitivity of the dendrimer-based capture strategy could have significant implications for the detection of a wide range of cytokines and biomarkers since the capture strategy could be applied to multiplex microbead assays, conductometric immunosensors and field effect biosensors.

  15. The Debye light scattering equation’s scaling relation reveals the purity of synthetic dendrimers

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, Hui-Yu; Chen, Hsiao-Ping [National Chung Cheng University, Department of Chemistry and Biochemistry (China); Tang, Yi-Hsuan [Kaohsiung Medical University, Department of Medicinal and Applied Chemistry (China); Chen, Hui-Ting [Kaohsiung Medical University, Department of Fragrance and Cosmetic Science (China); Kao, Chai-Lin, E-mail: clkao@kmu.edu.tw [Kaohsiung Medical University, Department of Medicinal and Applied Chemistry (China); Wang, Shau-Chun, E-mail: chescw@ccu.edu.tw [National Chung Cheng University, Department of Chemistry and Biochemistry (China)

    2016-03-15

    Spherical dendrimer structures cannot be structurally modeled using conventional polymer models of random coil or rod-like configurations during the calibration of the static light scattering (LS) detectors used to determine the molecular weight (M.W.) of a dendrimer or directly assess the purity of a synthetic compound. In this paper, we used the Debye equation-based scaling relation, which predicts that the static LS intensity per unit concentration is linearly proportional to the M.W. of a synthetic dendrimer in a dilute solution, as a tool to examine the purity of high-generational compounds and to monitor the progress of dendrimer preparations. Without using expensive equipment, such as nuclear magnetic resonance or mass spectrometry, this method only required an affordable flow injection set-up with an LS detector. Solutions of the purified dendrimers, including the poly(amidoamine) (PAMAM) dendrimer and its fourth to seventh generation pyridine derivatives with size range of 5–9 nm, were used to establish the scaling relation with high linearity. The use of artificially impure mixtures of six or seven generations revealed significant deviations from linearity. The raw synthesized products of the pyridine-modified PAMAM dendrimer, which included incompletely reacted dendrimers, were also examined to gauge the reaction progress. As a reaction toward a particular generational derivative of the PAMAM dendrimers proceeded over time, deviations from the linear scaling relation decreased. The difference between the polydispersity index of the incompletely converted products and that of the pure compounds was only about 0.01. The use of the Debye equation-based scaling relation, therefore, is much more useful than the polydispersity index for monitoring conversion processes toward an indicated functionality number in a given preparation.Graphical abstract.

  16. The Debye light scattering equation’s scaling relation reveals the purity of synthetic dendrimers

    International Nuclear Information System (INIS)

    Tseng, Hui-Yu; Chen, Hsiao-Ping; Tang, Yi-Hsuan; Chen, Hui-Ting; Kao, Chai-Lin; Wang, Shau-Chun

    2016-01-01

    Spherical dendrimer structures cannot be structurally modeled using conventional polymer models of random coil or rod-like configurations during the calibration of the static light scattering (LS) detectors used to determine the molecular weight (M.W.) of a dendrimer or directly assess the purity of a synthetic compound. In this paper, we used the Debye equation-based scaling relation, which predicts that the static LS intensity per unit concentration is linearly proportional to the M.W. of a synthetic dendrimer in a dilute solution, as a tool to examine the purity of high-generational compounds and to monitor the progress of dendrimer preparations. Without using expensive equipment, such as nuclear magnetic resonance or mass spectrometry, this method only required an affordable flow injection set-up with an LS detector. Solutions of the purified dendrimers, including the poly(amidoamine) (PAMAM) dendrimer and its fourth to seventh generation pyridine derivatives with size range of 5–9 nm, were used to establish the scaling relation with high linearity. The use of artificially impure mixtures of six or seven generations revealed significant deviations from linearity. The raw synthesized products of the pyridine-modified PAMAM dendrimer, which included incompletely reacted dendrimers, were also examined to gauge the reaction progress. As a reaction toward a particular generational derivative of the PAMAM dendrimers proceeded over time, deviations from the linear scaling relation decreased. The difference between the polydispersity index of the incompletely converted products and that of the pure compounds was only about 0.01. The use of the Debye equation-based scaling relation, therefore, is much more useful than the polydispersity index for monitoring conversion processes toward an indicated functionality number in a given preparation.Graphical abstract

  17. Photosensitizer and peptide-conjugated PAMAM dendrimer for targeted in vivo photodynamic therapy

    Directory of Open Access Journals (Sweden)

    Narsireddy A

    2015-11-01

    Full Text Available Amreddy Narsireddy,1 Kurra Vijayashree,2 Mahesh G Adimoolam,1 Sunkara V Manorama,1 Nalam M Rao21CSIR – Indian Institute of Chemical Technology, 2CSIR – Centre for Cellular and Molecular Biology, Hyderabad, IndiaAbstract: Challenges in photodynamic therapy (PDT include development of efficient near infrared-sensitive photosensitizers (5,10,15,20-tetrakis(4-hydroxyphenyl-21H,23H-porphine [PS] and targeted delivery of PS to the tumor tissue. In this study, a dual functional dendrimer was synthesized for targeted PDT. For targeting, a poly(amidoamine dendrimer (G4 was conjugated with a PS and a nitrilotriacetic acid (NTA group. A peptide specific to human epidermal growth factor 2 was expressed in Escherichia coli with a His-tag and was specifically bound to the NTA group on the dendrimer. Reaction conditions were optimized to result in dendrimers with PS and the NTA at a fractional occupancy of 50% and 15%, respectively. The dendrimers were characterized by nuclear magnetic resonance, matrix-assisted laser desorption/ionization, absorbance, and fluorescence spectroscopy. Using PS fluorescence, cell uptake of these particles was confirmed by confocal microscopy and fluorescence-activated cell sorting. PS-dendrimers are more efficient than free PS in PDT-mediated cell death assays in HER2 positive cells, SK-OV-3. Similar effects were absent in HER2 negative cell line, MCF-7. Compared to free PS, the PS-dendrimers have shown significant tumor suppression in a xenograft animal tumor model. Conjugation of a PS with dendrimers and with a targeting agent has enhanced photodynamic therapeutic effects of the PS.Keywords: photodynamic therapy, dendrimers, nanoparticle, targeted delivery, Affibody, xenograft animal model

  18. Synthesis and Characterization of Poly(Amidoamine Dendrimers Encapsulatd 198Au Nanoparticles

    Directory of Open Access Journals (Sweden)

    R. Ritawidya1,2

    2012-12-01

    Full Text Available Brachytherapy or internal radiotherapy is one of many methods used for treatment of cancer. This modality requires an agent with radionuclides that emits  or β particle with a proper energy. 198Au (99% β max = 0.96 MeV and t1/2 = 2.69 days is one of radionuclides that has been considered to be effective for the above-mentioned purpose. The purpose of this research was to synthesis and characterize poly(amidoamine (PAMAM G3.0 dendrimers encapsulated 198Au nanoparticles as a new brachytherapy agent. PAMAM G3.0 dendrimers encapsulated 198Au nanoparticles was successfully synthesized by a bottom-up method using sodium borohydride as a reductor. Purification was then performed by a size exclusion chromatography in order to separate large Au nanoparticles that were formed outside the cavity of PAMAM G3.0 dendrimers. Prior to the synthesis of PAMAM G3.0 dendrimers encapsulated 198Au nanoparticles, the synthetic procedure was first established by using a non-radioactive Au. The PAMAM G3.0 dendrimers encapsulated Au nanoparticles produced was then characterized by using an UV-Vis spectroscopy, a transmission electron microscopy (TEM, particle size analyzer (PSA, and an atomic absorption spectroscopy (AAS. Characterization results revealed that PAMAM G3.0 dendrimers encapsulated Au nanoparticles that were prepared from a reaction mixture of PAMAM G3.0 dendrimers and Au HAuCl4 with mol ratio of 2.8, was found to be a proper formula. It produced PAMAM G3.0 dendrimers encapsulated Au nanoparticles with diameter of 1.743 nm, spheris, uniform and drug loading value of 26.34%. This formula was then used in synthesis using radioactive Au, 198Au. Characterization results of PAMAM G3.0 dendrimers encapsulated 198Au nanoparticles gave a radiochemical purity of 99.4% and zero charge.

  19. Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires

    Directory of Open Access Journals (Sweden)

    Magnus Willander

    2013-09-01

    Full Text Available Cetyltrimethyl ammonium bromide cationic (CTAB surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD, scanning electron microscopy (SEM and high resolution transmission electron microscopy (HRTEM techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS. This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms.

  20. Hydrothermal Synthesis of Nanoclusters of ZnS Comprised on Nanowires.

    Science.gov (United States)

    Ibupoto, Zafar Hussain; Khun, Kimleang; Liu, Xianjie; Willander, Magnus

    2013-09-09

    Cetyltrimethyl ammonium bromide cationic (CTAB) surfactant was used as template for the synthesis of nanoclusters of ZnS composed of nanowires, by hydrothermal method. The structural and morphological studies were performed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) techniques. The synthesized ZnS nanoclusters are composed of nanowires and high yield on the substrate was observed. The ZnS nanocrystalline consists of hexagonal phase and polycrystalline in nature. The chemical composition of ZnS nanoclusters composed of nanowires was studied by X-ray photo electron microscopy (XPS). This investigation has shown that the ZnS nanoclusters are composed of Zn and S atoms.

  1. Multilayered nanoclusters of platinum and gold: insights on electrodeposition pathways, electrocatalysis, surface and bulk compositional properties

    CSIR Research Space (South Africa)

    Mkwizu, TS

    2013-06-01

    Full Text Available Electrochemical, surface and bulk compositional properties of multilayered nanoclusters of Pt and Au, electrochemically deposited on glassy carbon under conditions involving sequential surface–limited redox–replacement reactions (performed at open...

  2. Mechanical stability of titanium and plasma polymer nanoclusters in nanocomposite coatings

    Energy Technology Data Exchange (ETDEWEB)

    Palesch, E. [Institute of Materials Chemistry, Brno University of Technology, Brno (Czech Republic); Marek, A. [HVM Plasma, spol. s r.o., Prague (Czech Republic); Solar, P.; Kylian, O. [Faculty of Mathematics and Physics, Charles University, Prague (Czech Republic); Vyskocil, J. [HVM Plasma, spol. s r.o., Prague (Czech Republic); Biederman, H. [Faculty of Mathematics and Physics, Charles University, Prague (Czech Republic); Cech, V., E-mail: cech@fch.vutbr.cz [Institute of Materials Chemistry, Brno University of Technology, Brno (Czech Republic)

    2013-10-01

    The mechanical stability of nanoclusters embedded in nanocomposite coatings was investigated by scratch and wear tests supported by atomic force microscopy using surface topography mode. Titanium and plasma polymer nanoclusters were deposited on planar substrates (glass, titanium) using a magnetron-based gas aggregation cluster source. The deposited clusters were overcoated with a thin titanium film of different thicknesses to stabilize the position of the clusters in the nanocomposite coating. Nanotribological measurements were carried out to optimize the thickness of the overcoating film for sufficient interfacial adhesion of the cluster/film system. - Highlights: ► Titanium and plasma polymer nanoclusters were overcoated with thin titanium film. ► The mechanical stability of nanoclusters was characterized by nanotribological tests. ► The film thickness was optimized to stabilize the position of the clusters in coating.

  3. A colloidal assembly approach to synthesize magnetic porous composite nanoclusters for efficient protein adsorption

    Science.gov (United States)

    Yang, Qi; Lan, Fang; Yi, Qiangying; Wu, Yao; Gu, Zhongwei

    2015-10-01

    A combination strategy of the inverse emulsion crosslinking approach and the colloidal assembly technique is first proposed to synthesize Fe3O4/histidine composite nanoclusters as new-type magnetic porous nanomaterials. The nanoclusters possess uniform morphology, high magnetic content and excellent protein adsorption capacity, exhibiting their great potential for bio-separation.A combination strategy of the inverse emulsion crosslinking approach and the colloidal assembly technique is first proposed to synthesize Fe3O4/histidine composite nanoclusters as new-type magnetic porous nanomaterials. The nanoclusters possess uniform morphology, high magnetic content and excellent protein adsorption capacity, exhibiting their great potential for bio-separation. Electronic supplementary information (ESI) available: Experimental details. See DOI: 10.1039/c5nr05800g

  4. Ge nanoclusters in PECVD-deposited glass after heat treating and electron irradiation

    DEFF Research Database (Denmark)

    Ou, Haiyan; Rørdam, Troels Peter; Rottwitt, Karsten

    2007-01-01

    This paper reports the formation of Ge nanoclusters in silica glass thin films deposited by plasma-enhanced chemical vapor deposition (PECVD). We studied the samples by transmission electron microscopy (TEM) and Raman spectroscopy after annealing. TEM investigation shows that the Ge nanoclusters...... at two areaswere formed by different mechanisms. The Ge nanoclusters formed in a single row along the interface of a silicon substrate and the silica glass film by annealing during high-temperature heat treatment. Ge nanoclusters did not initially form in the bulk of the film but could be subsequently...... formed by the electron-beam irradiation. The interface between the silicon substrate and the silica glass film was investigated by Raman spectroscopy. The shift of the Raman peaks around 286.8 cm−1 and 495 cm−1 suggests that the interface is a Si1−xGex alloy film and that the composition x varies along...

  5. Pure white-light emitting ultrasmall organic-inorganic hybrid perovskite nanoclusters.

    Science.gov (United States)

    Teunis, Meghan B; Lawrence, Katie N; Dutta, Poulami; Siegel, Amanda P; Sardar, Rajesh

    2016-10-14

    Organic-inorganic hybrid perovskites, direct band-gap semiconductors, have shown tremendous promise for optoelectronic device fabrication. We report the first colloidal synthetic approach to prepare ultrasmall (∼1.5 nm diameter), white-light emitting, organic-inorganic hybrid perovskite nanoclusters. The nearly pure white-light emitting ultrasmall nanoclusters were obtained by selectively manipulating the surface chemistry (passivating ligands and surface trap-states) and controlled substitution of halide ions. The nanoclusters displayed a combination of band-edge and broadband photoluminescence properties, covering a major part of the visible region of the solar spectrum with unprecedentedly large quantum yields of ∼12% and photoluminescence lifetime of ∼20 ns. The intrinsic white-light emission of perovskite nanoclusters makes them ideal and low cost hybrid nanomaterials for solid-state lighting applications.

  6. Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

    Science.gov (United States)

    Martino, Anthony; Yamanaka, Stacey A.; Kawola, Jeffrey S.; Showalter, Steven K.; Loy, Douglas A.

    1998-01-01

    A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5-10 nm in diameter with a monodisperse size distribution.

  7. Synthesis and Optical Properties of a Dithiolate/Phosphine-Protected Au28 Nanocluster

    KAUST Repository

    Aljuhani, Maha A.; Bootharaju, Megalamane Siddaramappa; Sinatra, Lutfan; Basset, Jean-Marie; Mohammed, Omar F.; Bakr, Osman

    2016-01-01

    While monothiols and simple phosphines are commonly exploited for size-controlled synthesis of atomically precise gold nanoclusters (NCs), dithiols or dithiol-phosphine combinations are seldom applied. Herein, we used a dithiol (benzene-1,3-dithiol

  8. Synthesis of Co–Al layered double hydroxide nanoclusters as reduction nanocatalyst in aqueous media

    Directory of Open Access Journals (Sweden)

    Daisuke Kino

    2017-12-01

    Full Text Available Layered double hydroxides (LDHs have attracted attention as green materials due to their catalytic ability in benign aqueous solvents. We here demonstrate the synthesis of colloidal Co–Al LDH nanoclusters with an average size of <10 nm via a facile liquid-phase reaction for the enhancement of the catalytic activity. To the best of our knowledge, the present LDH is the smallest Co–Al LDH with an extremely large surface area and stability in an aqueous solvent, forming a stable and concentrated colloidal solution as high as 40 g/L. We investigated the formation mechanism, and the catalytic activity of Co–Al LDH nanoclusters. The Co–Al LDH nanoclusters showed 47 times higher rate of the reduction of dye molecules in the aqueous media than standard Co–Al LDH particles with a micrometer size. LDH nanoclusters demonstrated here are promising green nanocatalysts for the aqueous reaction processes.

  9. Magnetic properties of MnAs nanoclusters embedded in a GaAs semiconductor matrix

    International Nuclear Information System (INIS)

    Hai, Pham Nam; Takahashi, Keisuke; Yokoyama, Masafumi; Ohya, Shinobu; Tanaka, Masaaki

    2007-01-01

    We have clarified fundamental magnetic properties of MnAs nanoclusters (10 nm in diameter) embedded in a thin GaAs matrix (referred to as GaAs:MnAs) through tunneling magnetoresistance (TMR) characteristics of magnetic tunnel junctions (MTJs) consisting of a GaAs:MnAs thin film and a MnAs metal thin film as ferromagnetic electrodes. Although MnAs nanoclusters have coercive forces as small as 150 Oe at 7 K, they show unusually high blocking temperature, which is as large as 300 K. The remanent magnetization of the MnAs nanocluster system linearly decreases with increasing temperature. Those magnetic behaviors cannot be explained by the non-interacting particle model, revealing the important existence of dipolar interactions in MnAs nanocluster system

  10. Synthesis and Doping of Ligand-Protected Atomically-Precise Metal Nanoclusters

    KAUST Repository

    Aljuhani, Maha A.

    2016-01-01

    by controlling their size, shape, and composition. Among the most thriving areas of research about nanoparticle is the synthesis and doping of the ligand-protected atomically-precise metal nanoclusters. In this thesis, we developed three different novel metal

  11. Low potential stable glucose detection at dendrimers modified polyaniline nanotubes

    Directory of Open Access Journals (Sweden)

    Alessandra Nogueira Santos

    2010-03-01

    Full Text Available The utilization of nanostructured materials for development of biosensors is a growing field in medical diagnostics. In this work a glucose biosensor based on bioactive polyglycerol (PGLD and chitosan dendrimers (CHD was developed. PGLD and CHD were bioconjugated with the enzyme glucose oxidase (GOx to obtain dendrimers with glucose sensing properties. Polyaniline nanotubes (PANINT´s were used as electron mediator due to their high ability to promote electron-transfer reactions involving GOx. The PGLD-GOx and CHD-GOx were entrapped in PANINT´s during template electrochemical polymerization of aniline. The prepared PGLD-GOx/PANINT´s and CHD-GOx/PANINT´s biosensors exhibit a strong and stable amperometric response to glucose even at a low potential of +100 mV. The based PGLD-GOx/PANINT´s and CHD-GOx/PANINT´s biosensors showed a good performance in glucose concentrations range in human blood. A comparison of the sensitivities to glucose showed that both biosensors have a linearity range between 0.02 and 10 mM, though PGLD-GOx/PANINT´s is more sensitive (10.41 vs. 7.04 nA.mM-1. The difference in the biosensor behavior and the high sensitivity of the PGLD-GOx/PANINT´s may be due to the specific organization of GOx layer at surface of the modifier macromolecule PGLD and their distribution in PANINT´s. The enzyme affinity for the substrate, K Mapp remains quite good after GOx immobilization on PGLD and CHD dendrimers and entrapment of the bioconjugates in PANINT´s.

  12. Optically nonlinear energy transfer in light-harvesting dendrimers

    Science.gov (United States)

    Andrews, David L.; Bradshaw, David S.

    2004-08-01

    Dendrimeric polymers are the subject of intense research activity geared towards their implementation in nanodevice applications such as energy harvesting systems, organic light-emitting diodes, photosensitizers, low-threshold lasers, and quantum logic elements, etc. A recent development in this area has been the construction of dendrimers specifically designed to exhibit novel forms of optical nonlinearity, exploiting the unique properties of these materials at high levels of photon flux. Starting from a thorough treatment of the underlying theory based on the principles of molecular quantum electrodynamics, it is possible to identify and characterize several optically nonlinear mechanisms for directed energy transfer and energy pooling in multichromophore dendrimers. Such mechanisms fall into two classes: first, those where two-photon absorption by individual donors is followed by transfer of the net energy to an acceptor; second, those where the excitation of two electronically distinct but neighboring donor groups is followed by a collective migration of their energy to a suitable acceptor. Each transfer process is subject to minor dissipative losses. In this paper we describe in detail the balance of factors and the constraints that determines the favored mechanism, which include the excitation statistics, structure of the energy levels, laser coherence factors, chromophore selection rules and architecture, possibilities for the formation of delocalized excitons, spectral overlap, and the overall distribution of donors and acceptors. Furthermore, it transpires that quantum interference between different mechanisms can play an important role. Thus, as the relative importance of each mechanism determines the relevant nanophotonic characteristics, the results reported here afford the means for optimizing highly efficient light-harvesting dendrimer devices.

  13. Photoinduced Electron Transfer of PAMAM Dendrimer-Zinc(II) Porphyrin Associates at Polarized Liquid|Liquid Interfaces.

    Science.gov (United States)

    Nagatani, Hirohisa; Sakae, Hiroki; Torikai, Taishi; Sagara, Takamasa; Imura, Hisanori

    2015-06-09

    The heterogeneous photoinduced electron-transfer reaction of the ion associates between NH2-terminated polyamidoamine (PAMAM) dendrimers and 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato zinc(II) (ZnTPPS(4-)) was studied at the polarized water|1,2-dichloroethane (DCE) interface. The positive photocurrent arising from the photoreduction of ZnTPPS(4-) by a lipophilic quencher, decamethylferrocene, in the interfacial region was significantly enhanced by the ion association with the PAMAM dendrimers. The photocurrent response of the dendrimer-ZnTPPS(4-) associates was dependent on the pH condition and on the generation of dendrimer. A few cationic additives such as polyallylamine and n-octyltrimethyammonium were also examined as alternatives to the PAMAM dendrimer, but the magnitude of the photocurrent enhancement was rather small. The high photoreactivity of the dendrimer-ZnTPPS(4-) associates was interpreted mainly as a result of the high interfacial concentration of photoreactive porphyrin units associated stably with the dendrimer which was preferably adsorbed at the polarized water|DCE interface. The photochemical data observed in the second and fourth generation PAMAM dendrimer systems demonstrated that the higher generation dendrimer which can incorporate a porphyrin molecule more completely in the interior is less efficient for the photocurrent enhancement at the interface. These results indicated that the photoreactivity of ionic reactant at a polarized liquid|liquid interface can readily be modified via ion association with the charged dendrimer.

  14. Poly(amido)amine (PAMAM) dendrimer-cisplatin complexes for chemotherapy of cisplatin-resistant ovarian cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Yellepeddi, Venkata Kashyap; Vangara, Kiran Kumar; Palakurthi, Srinath, E-mail: palakurthi@tamhsc.edu [Texas A and M Health Science Center, Irma Lerma Rangel College of Pharmacy (United States)

    2013-09-15

    Dendrimer-cisplatin complexes were prepared using PAMAM dendrimers with terminal -NH{sub 2} and -COOH groups as well as biotin-conjugated dendrimers. Preformulation parameters of dendrimer-cisplatin complexes were studied using differential scanning calorimetry (DSC) and inductively coupled plasma-mass spectrometry (ICP-MS). Cytotoxicity and mechanism of cytotoxicity of dendrimer-cisplatin complexes was investigated in OVCAR-3, SKOV, A2780 and cisplatin-resistant CP70 human ovarian cancer cell lines. The loading of cisplatin in dendrimers was {approx}11 % (w/w). PAMAM G4 dendrimers with amine surface groups (biotinylated and native) have shown 2.5- to 3.0-fold reduction in IC{sub 50} values in ovarian cancer cells when compared with carboxylate surface dendrimers (p < 0.05). A correlation was observed among cytotoxicity of the complexes, cellular uptake, and platinum-DNA adduct formation. Treatment with dendrimer-cisplatin complexes resulted in a 7.0-fold increase (p < 0.05) in expression of apoptotic genes (Bcl2, Bax, p53) and 13.2- to 27.1-fold increase (p < 0.05) in the activity of caspases 3, 8, and 9 in vitro. Results suggest that PAMAM dendrimers can be used as potential carrier for cisplatin chemotherapy of ovarian cancer.

  15. Synthesis and in-vitro cytotoxicity of dendrimer cytostatic conjugates

    OpenAIRE

    Scutaru, Ana Maria

    2011-01-01

    Bendamustine and melphalan are nitrogen mustard derivatives from the group of alkylating agents and are used for the treatment of various cancers such as chronic lymphocytic leukemia (CLL) or breast cancer. However their use is limited by numerous side effects. Therefore, 1,3,5-tris(3-aminopropyl)benzene (G0) and the G1 analogous 1,3,5-tris[3,5-bis(3-aminopropyl)-N-propylbenzamide]benzene were chosen to synthesize cytostatic-dendrimer conjugates and to achieve ‘tumor targeting' through the EP...

  16. Study of the complexation of oxacillin in 1-(4-Carbomethoxypyrrolidone)-terminated PAMAM dendrimers

    DEFF Research Database (Denmark)

    Hansen, Jon Stefan; Ficker, Mario; Petersen, Johannes Fabritius

    2013-01-01

    The complexation of oxacillin to three generations of 1-(4-carbomethoxypyrrolidone)-terminated PAMAM dendrimers was studied with NMR in CD3OD and CDCl3. The stochiometries, which were determined from Job plots, were found to be both solvent- and generation-dependent. The dissociation constants (Kd......) and Gibbs energies for complexation of oxacillin into the 1-(4-carbomethoxypyrrolidone)-terminated PAMAM dendrimer hosts were determined by (1)H NMR titrations and showed weaker binding of oxacillin upon increasing the size (generation) of the dendrimer....

  17. Polymerization of a divalent/tetravalent metal-storing atom-mimicking dendrimer

    OpenAIRE

    Albrecht, Ken; Hirabayashi, Yuki; Otake, Masaya; Mendori, Shin; Tobari, Yuta; Azuma, Yasuo; Majima, Yutaka; Yamamoto, Kimihisa

    2016-01-01

    The phenylazomethine dendrimer (DPA) has a layer-by-layer electron density gradient that is an analog of the Bohr atom (atom mimicry). In combination with electron pair mimicry, the polymerization of this atom-mimicking dendrimer was achieved. The valency of the mimicked atom was controlled by changing the chemical structure of the dendrimer. By mimicking a divalent atom, a one-dimensional (1D) polymer was obtained, and by using a planar tetravalent atom mimic, a 2D polymer was obtained. Thes...

  18. Enhancement of Muramyldipeptide (MDP) Immunostimulatory Activity by Controlled Multimerization on Dendrimers

    DEFF Research Database (Denmark)

    Sørensen, Nanna Skall; Boas, Ulrik; Heegaard, Peter M. H.

    2011-01-01

    Peptidoglycan is a widespread bacterial PAMP molecule and a powerful initiator of innate immune responses. It consists of repeating units of MDP, which as a monomer is only weakly immunostimulatory. Here, MDP-coupled dendrimers were prepared and investigated for stimulation of pig blood mononuclear...... cells. Compared to monomeric MDP, MDP-dendrimers induced a markedly enhanced production of IL-12 p40, IL-1β and IL-6 and completely down-regulated surface expression of B7 and MHC class II. These results suggest a possible novel strategy based on controlled multimerization of minimal PAMP motifs...... on dendrimers for preparing molecularly defined immunostimulators with predictable bioactivities....

  19. Dendrimer encapsulated Silver nanoparticles as novel catalysts for reduction of aromatic nitro compounds

    Science.gov (United States)

    Asharani, I. V.; Thirumalai, D.; Sivakumar, A.

    2017-11-01

    Polyethylene glycol (PEG) core dendrimer encapsulated silver nanoparticles (AgNPs) were synthesized through normal chemical reduction method, where dendrimer acts as reducing and stabilizing agent. The encapsulated AgNPs were well characterized using TEM, DLS and XPS techniques. The synthesized AgNPs showed excellent catalytic activity towards the reduction of aromatic nitro compounds with sodium borohydride as reducing agent and the results substantiate that dendrimer encapsulated AgNPs can be an effective catalyst for the substituted nitro aromatic reduction reactions. Also the kinetics of different nitro compounds reductions was studied and presented.

  20. Interactions of Poly(amidoamine) Dendrimers with Human Serum Albumin: Binding Constants and Mechanisms

    OpenAIRE

    Giri, Jyotsnendu; Diallo, Mamadou S.; Simpson, André J.; Liu, Yi; Goddard, William A., III; Kumar, Rajeev; Woods, Gwen C.

    2011-01-01

    The interactions of nanomaterials with plasma proteins have a significant impact on their in vivo transport and fate in biological fluids. This article discusses the binding of human serum albumin (HSA) to poly(amidoamine) [PAMAM] dendrimers. We use protein-coated silica particles to measure the HSA binding constants (K_b) of a homologous series of 19 PAMAM dendrimers in aqueous solutions at physiological pH (7.4) as a function of dendrimer generation, terminal group, and core chemistry. To g...

  1. Stable silver nanoclusters electrochemically deposited on nitrogen-doped graphene as efficient electrocatalyst for oxygen reduction reaction

    Science.gov (United States)

    Jin, Shi; Chen, Man; Dong, Haifeng; He, Bingyu; Lu, Huiting; Su, Lei; Dai, Wenhao; Zhang, Qiaochu; Zhang, Xueji

    2015-01-01

    Metal nanoclusters exhibit unusually high catalytic activity toward oxygen reduction reaction (ORR) due to their small size and unique electronic structures. However, controllable synthesis of stable metal nanoclusters is a challenge, and the durability of metal clusters suffers from the deficiency of dissolution, aggregation, and sintering during catalysis reactions. Herein, silver nanoclusters (AgNCs) (diameter , which is vital in high performance fuel cells, batteries and nanodevices.

  2. Stabilizing Protein Effects on the Pressure Sensitivity of Fluorescent Gold Nanoclusters

    Science.gov (United States)

    2016-01-13

    affected by the environment of the stabilizing protein, allowing these hybrid systems to act as sensors in many applications.2,9,14–19 This has led...Biosens Bioelectron. 2012;32:297–299. 8. Joseph D, Geckeler KE. Synthesis of highly fluorescent gold nanoclusters using egg white proteins. Colloids Surf...Chang HW, Chien YC, Hsiao JK, Cheng JT, Chou PT. Insulin -directed synthesis of fluorescent gold nanoclusters: preservation of insulin bioactivity and

  3. Kernel Tuning and Nonuniform Influence on Optical and Electrochemical Gaps of Bimetal Nanoclusters.

    Science.gov (United States)

    He, Lizhong; Yuan, Jinyun; Xia, Nan; Liao, Lingwen; Liu, Xu; Gan, Zibao; Wang, Chengming; Yang, Jinlong; Wu, Zhikun

    2018-03-14

    Fine tuning nanoparticles with atomic precision is exciting and challenging and is critical for tuning the properties, understanding the structure-property correlation and determining the practical applications of nanoparticles. Some ultrasmall thiolated metal nanoparticles (metal nanoclusters) have been shown to be precisely doped, and even the protecting staple metal atom could be precisely reduced. However, the precise addition or reduction of the kernel atom while the other metal atoms in the nanocluster remain the same has not been successful until now, to the best of our knowledge. Here, by carefully selecting the protecting ligand with adequate steric hindrance, we synthesized a novel nanocluster in which the kernel can be regarded as that formed by the addition of two silver atoms to both ends of the Pt@Ag 12 icosohedral kernel of the Ag 24 Pt(SR) 18 (SR: thiolate) nanocluster, as revealed by single crystal X-ray crystallography. Interestingly, compared with the previously reported Ag 24 Pt(SR) 18 nanocluster, the as-obtained novel bimetal nanocluster exhibits a similar absorption but a different electrochemical gap. One possible explanation for this result is that the kernel tuning does not essentially change the electronic structure, but obviously influences the charge on the Pt@Ag 12 kernel, as demonstrated by natural population analysis, thus possibly resulting in the large electrochemical gap difference between the two nanoclusters. This work not only provides a novel strategy to tune metal nanoclusters but also reveals that the kernel change does not necessarily alter the optical and electrochemical gaps in a uniform manner, which has important implications for the structure-property correlation of nanoparticles.

  4. Iron/iron oxide core-shell nanoclusters for biomedical applications

    International Nuclear Information System (INIS)

    Qiang You; Antony, Jiji; Sharma, Amit; Nutting, Joseph; Sikes, Daniel; Meyer, Daniel

    2006-01-01

    Biocompatible magnetic nanoparticles have been found promising in several biomedical applications for tagging, imaging, sensing and separation in recent years. Most magnetic particles or beads currently used in biomedical applications are based on ferromagnetic iron oxides with very low specific magnetic moments of about 20-30 emu/g. Here we report a new approach to synthesize monodispersed core-shell nanostructured clusters with high specific magnetic moments above 200 emu/g. Iron nanoclusters with monodispersive size of diameters from 2 nm to 100 nm are produced by our newly developed nanocluster source and go to a deposition chamber, where a chemical reaction starts, and the nanoclusters are coated with iron oxides. HRTEM Images show the coatings are very uniform and stable. The core-shell nanoclusters are superparamagnetic at room temperature for sizes less than 15 nm, and then become ferromagnetic when the cluster size increases. The specific magnetic moment of core-shell nanoclusters is size dependent, and increases rapidly from about 80 emu/g at the cluster size of around 3 nm to over 200 emu/g up to the size of 100 nm. The use of high magnetic moment nanoclusters for biomedical applications could dramatically enhance the contrast for MRI, reduce the concentration of magnetic particle needs for cell separation, or make drug delivery possible with much lower magnetic field gradients

  5. Optical properties of multicomponent antimony-silver nanoclusters formed in silica by sequential ion implantation

    International Nuclear Information System (INIS)

    Zuhr, R.A.

    1995-11-01

    The linear and nonlinear optical properties of nanometer dimension metal colloids embedded in a dielectric depend explicitly on the electronic structure of the metal nanoclusters. The ability to control the electronic structure of the nanoclusters may make it possible to tailor the optical properties for enhanced performance. By sequential implantation of different metal ion species multi-component nanoclusters can be formed with significantly different optical properties than single element metal nanoclusters. The authors report the formation of multi-component Sb/Ag nanoclusters in silica by sequential implantation of Sb and Ag. Samples were implanted with relative ratios of Sb to Ag of 1:1 and 3:1. A second set of samples was made by single element implantations of Ag and Sb at the same energies and doses used to make the sequentially implanted samples. All samples were characterized using RBS and both linear and nonlinear optical measurements. The presence of both ions significantly modifies the optical properties of the composites compared to the single element nanocluster glass composites. In the sequentially implanted samples the optical density is lower, and the strong surface plasmon resonance absorption observed in the Ag implanted samples is not present. At the same time the nonlinear response of the these samples is larger than for the samples implanted with Sb alone, suggesting that the addition of Ag can increase the nonlinear response of the Sb particles formed. The results are consistent with the formation of multi-component Sb/Ag colloids

  6. Photoluminescent Gold Nanoclusters in Cancer Cells: Cellular Uptake, Toxicity, and Generation of Reactive Oxygen Species.

    Science.gov (United States)

    Matulionyte, Marija; Dapkute, Dominyka; Budenaite, Laima; Jarockyte, Greta; Rotomskis, Ricardas

    2017-02-10

    In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. Therefore, the assessment of the biocompatibility and potential toxicity of gold nanoclusters is of major importance before their clinical application. In this study, the cellular uptake, cytotoxicity, and intracellular generation of reactive oxygen species (ROS) of bovine serum albumin-encapsulated (BSA-Au NCs) and 2-(N-morpholino) ethanesulfonic acid (MES)capped photoluminescent gold nanoclusters (Au-MES NCs) were investigated. The results showed that BSA-Au NCs accumulate in cells in a similar manner as BSA alone, indicating an endocytotic uptake mechanism while ultrasmall Au-MES NCs were distributed homogeneously throughout the whole cell volume including cell nucleus. The cytotoxicity of BSA-Au NCs was negligible, demonstrating good biocompatibility of such BSA-protected Au NCs. In contrast, possibly due to ultrasmall size and thin coating layer, Au-MES NCs exhibited exposure time-dependent high cytotoxicity and higher reactivity which led to highly increased generation of reactive oxygen species. The results demonstrate the importance of the coating layer to biocompatibility and toxicity of ultrasmall photoluminescent gold nanoclusters.

  7. Photoluminescent Gold Nanoclusters in Cancer Cells: Cellular Uptake, Toxicity, and Generation of Reactive Oxygen Species

    Directory of Open Access Journals (Sweden)

    Marija Matulionyte

    2017-02-01

    Full Text Available In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. Therefore, the assessment of the biocompatibility and potential toxicity of gold nanoclusters is of major importance before their clinical application. In this study, the cellular uptake, cytotoxicity, and intracellular generation of reactive oxygen species (ROS of bovine serum albumin-encapsulated (BSA-Au NCs and 2-(N-morpholino ethanesulfonic acid (MEScapped photoluminescent gold nanoclusters (Au-MES NCs were investigated. The results showed that BSA-Au NCs accumulate in cells in a similar manner as BSA alone, indicating an endocytotic uptake mechanism while ultrasmall Au-MES NCs were distributed homogeneously throughout the whole cell volume including cell nucleus. The cytotoxicity of BSA-Au NCs was negligible, demonstrating good biocompatibility of such BSA-protected Au NCs. In contrast, possibly due to ultrasmall size and thin coating layer, Au-MES NCs exhibited exposure time-dependent high cytotoxicity and higher reactivity which led to highly increased generation of reactive oxygen species. The results demonstrate the importance of the coating layer to biocompatibility and toxicity of ultrasmall photoluminescent gold nanoclusters.

  8. Study of the interactions of PAMAM-NH2 G4 dendrimer with selected natural amino acids in aqueous solutions

    International Nuclear Information System (INIS)

    Buczkowski, Adam; Palecz, Bartlomiej

    2014-01-01

    Highlights: • Calorimetric titration and dilution calorimetry show strong interactions between PAMAM-NH 2 G4 dendrimer and amino acids. • The more polar the amino acid side chain, the more exothermic the effects of the direct interactions with dendrimer. • Macromolecule of PAMAM-NH 2 G4 dendrimer can coordinate 20 to 40 molecules of amino acid. -- Abstract: The interactions of PAMAM-NH 2 G4 dendrimer with selected natural amino acids (Gly, Ala, Val, Leu, Ile, Phe, Ser, Thr, Met, Asn, Gln, Pro and Trp) in aqueous solutions were measured with the use of the techniques of calorimetric titration and dilution calorimetry. The results of calorimetric measurements show strong interactions between PAMAM-NH 2 G4 dendrimer and amino acids with polar substituents. A macromolecule of PAMAM-NH 2 G4 dendrimer can coordinate 20 to 40 molecules of amino acid

  9. Dendrimer-based Macromolecular MRI Contrast Agents: Characteristics and Application

    Directory of Open Access Journals (Sweden)

    Hisataka Kobayashi

    2003-01-01

    Full Text Available Numerous macromolecular MRI contrast agents prepared employing relatively simple chemistry may be readily available that can provide sufficient enhancement for multiple applications. These agents operate using a ~100-fold lower concentration of gadolinium ions in comparison to the necessary concentration of iodine employed in CT imaging. Herein, we describe some of the general potential directions of macromolecular MRI contrast agents using our recently reported families of dendrimer-based agents as examples. Changes in molecular size altered the route of excretion. Smaller-sized contrast agents less than 60 kDa molecular weight were excreted through the kidney resulting in these agents being potentially suitable as functional renal contrast agents. Hydrophilic and larger-sized contrast agents were found better suited for use as blood pool contrast agents. Hydrophobic variants formed with polypropylenimine diaminobutane dendrimer cores created liver contrast agents. Larger hydrophilic agents are useful for lymphatic imaging. Finally, contrast agents conjugated with either monoclonal antibodies or with avidin are able to function as tumor-specific contrast agents, which also might be employed as therapeutic drugs for either gadolinium neutron capture therapy or in conjunction with radioimmunotherapy.

  10. Synthetic Strategies towards Fullerene-Rich Dendrimer Assemblies

    Directory of Open Access Journals (Sweden)

    Jean-François Nierengarten

    2012-02-01

    Full Text Available The sphere-shaped fullerene has attracted considerable interest not least due to the peculiar electronic properties of this carbon allotrope and the fascinating materials emanating from fullerene-derived structures. The rapid development and tremendous advances in organic chemistry allow nowadays the modification of C60 to a great extent by pure chemical means. It is therefore not surprising that the fullerene moiety has also been part of dendrimers. At the initial stage, fullerenes have been examined at the center of the dendritic structure mainly aimed at possible shielding effects as exerted by the dendritic environment and light-harvesting effects due to multiple chromophores located at the periphery of the dendrimer. In recent years, also many research efforts have been devoted towards fullerene-rich nanohybrids containing multiple C60 units in the branches and/or as surface functional groups. In this review, synthetic efforts towards the construction of dendritic fullerene-rich nanostructures have been compiled and will be summarized herein.

  11. Direct Synthesis and Morphological Characterization of Gold-Dendrimer Nanocomposites Prepared Using PAMAM Succinamic Acid Dendrimers: Preliminary Study of the Calcification Potential

    Directory of Open Access Journals (Sweden)

    E. Vasile

    2014-01-01

    Full Text Available Gold-dendrimer nanocomposites were obtained for the first time by a simple colloidal approach based on the use of polyamidoamine dendrimers with succinamic acid terminal groups and dodecanediamine core. Spherical and highly crystalline nanoparticles with dimensions between 3 nm and 60 nm, and size-polydispersity depending on the synthesis conditions, have been generated. The influence of the stoichiometric ratio and the structural and architectural features of the dendrimers on the properties of the nanocomposites has been described. The self-assembling behaviour of these materials produces gold-dendrimer nanostructured porous networks with variable density, porosity, and composition. The investigations of the reaction systems, by TEM, at two postsynthesis moments, allowed to preliminary establish the control over the properties of the nanocomposite products. Furthermore, this study allowed better understanding of the mechanism of nanocomposite generation. Impressively, in the early stages of the synthesis, the organization of gold inside the dendrimer molecules has been evidenced by micrographs. Growth and ripening mechanisms further lead to nanoparticles with typical characteristics. The potential of such nanocomposite particles to induce calcification when coating a polymer substrate was also investigated.

  12. Direct synthesis and morphological characterization of gold-dendrimer nanocomposites prepared using PAMAM succinamic acid dendrimers: preliminary study of the calcification potential.

    Science.gov (United States)

    Vasile, E; Serafim, A; Petre, D; Giol, D; Dubruel, P; Iovu, H; Stancu, I C

    2014-01-01

    Gold-dendrimer nanocomposites were obtained for the first time by a simple colloidal approach based on the use of polyamidoamine dendrimers with succinamic acid terminal groups and dodecanediamine core. Spherical and highly crystalline nanoparticles with dimensions between 3 nm and 60 nm, and size-polydispersity depending on the synthesis conditions, have been generated. The influence of the stoichiometric ratio and the structural and architectural features of the dendrimers on the properties of the nanocomposites has been described. The self-assembling behaviour of these materials produces gold-dendrimer nanostructured porous networks with variable density, porosity, and composition. The investigations of the reaction systems, by TEM, at two postsynthesis moments, allowed to preliminary establish the control over the properties of the nanocomposite products. Furthermore, this study allowed better understanding of the mechanism of nanocomposite generation. Impressively, in the early stages of the synthesis, the organization of gold inside the dendrimer molecules has been evidenced by micrographs. Growth and ripening mechanisms further lead to nanoparticles with typical characteristics. The potential of such nanocomposite particles to induce calcification when coating a polymer substrate was also investigated.

  13. Morphological and structural characterizations of dendrimer-mediated metallic Ti and Al thin film nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Curry, M. [Center for Materials for Information Technology, University of Alabama, Tuscaloosa, AL 35487-0209 (United States); Department of Chemistry, University of Alabama, Tuscaloosa, AL 35487-0209 (United States); Li, X. [Center for Materials for Information Technology, University of Alabama, Tuscaloosa, AL 35487-0209 (United States); Department of Metallurgical and Materials Science and Engineering, University of Alabama, Tuscaloosa, AL 35487-0209 (United States); Zhang, J. [Center for Materials for Information Technology, University of Alabama, Tuscaloosa, AL 35487-0209 (United States); Department of Chemistry, University of Alabama, Tuscaloosa, AL 35487-0209 (United States); Weaver, M.L. [Center for Materials for Information Technology, University of Alabama, Tuscaloosa, AL 35487-0209 (United States); Department of Metallurgical and Materials Science and Engineering, University of Alabama, Tuscaloosa, AL 35487-0209 (United States); Street, S.C. [Center for Materials for Information Technology, University of Alabama, Tuscaloosa, AL 35487-0209 (United States) and Department of Chemistry, University of Alabama, Tuscaloosa, AL 35487-0209 (United States)]. E-mail: sstreet@bama.ua.edu

    2007-02-26

    Evidence is presented here for significant influence on the surface topography of Ti and Al films in the presence of poly(amidoamine) dendrimer monolayers [generations G(4-8)] on SiO {sub x}. X-ray photoelectron spectroscopy analysis clearly indicates formation of nitrides and carbides for Ti metal grown on dendrimer monolayers. In addition, obvious trends in measured correlation lengths and crystalline growth modes of Ti films indicate grain sizes tracking the intrinsic roughness of dendrimer monolayers. No formation of metal nitride is observed for Al depositions. Atomic force microscopy analyses show significant changes in rms vertical roughness and aggregation of as-deposited Ti or Al in presence of dendrimer monolayers.

  14. Unusual concentration-dependent microscopic dynamics of dendrimers in aqueous solution

    International Nuclear Information System (INIS)

    Wong, Kaikin; Wu, Chin Ming; Lam, Hak Fai; Chathoth, Suresh M.

    2016-01-01

    Dendrimers are novel three-dimensional, hyperbranched globular nanopolymeric macromolecules. The nanoscopic size, narrow polydispersity index, excellent control over molecular structure, availability of multiple functional groups at the periphery, and cavities in the interior made them very attractive candidate for drug delivery. In this communication, we have studied the microscopic dynamics of tetra-acid and pentaerythritol glycidyl ether dendrimers dissolved in aqueous solution with different concentrations. The effects of concentration and temperature to their long-range diffusion process are investigated by dynamic light scattering. Experimental results show a huge variation in the translational diffusion coefficient for the two dendrimers samples. Besides, the dependence of diffusion coefficients on concentration is unusually different in these dendrimer samples. Although the diffusion process follows Arrhenius relation with the temperature in both systems, the activation energy for the diffusion process has a distinct concentration dependence.

  15. Unusual concentration-dependent microscopic dynamics of dendrimers in aqueous solution

    Science.gov (United States)

    Wong, Kaikin; Wu, Chin Ming; Lam, Hak Fai; Chathoth, Suresh M.

    2016-05-01

    Dendrimers are novel three-dimensional, hyperbranched globular nanopolymeric macromolecules. The nanoscopic size, narrow polydispersity index, excellent control over molecular structure, availability of multiple functional groups at the periphery, and cavities in the interior made them very attractive candidate for drug delivery. In this communication, we have studied the microscopic dynamics of tetra-acid and pentaerythritol glycidyl ether dendrimers dissolved in aqueous solution with different concentrations. The effects of concentration and temperature to their long-range diffusion process are investigated by dynamic light scattering. Experimental results show a huge variation in the translational diffusion coefficient for the two dendrimers samples. Besides, the dependence of diffusion coefficients on concentration is unusually different in these dendrimer samples. Although the diffusion process follows Arrhenius relation with the temperature in both systems, the activation energy for the diffusion process has a distinct concentration dependence.

  16. Effect of viologen-phosphorus dendrimers on acetylcholinesterase and butyrylcholinesterase activities.

    Science.gov (United States)

    Ciepluch, Karol; Weber, Monika; Katir, Nadia; Caminade, Anne-Marie; El Kadib, Abdelkrim; Klajnert, Barbara; Majoral, Jean Pierre; Bryszewska, Maria

    2013-03-01

    The inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) is the first step in checking whether new compounds can be considered as drugs for treating neurodegenerative diseases. The effect of viologen-phosphorus dendrimers on AChE and BChE activities was studied. The results show that the effects on the cholinesterase activities depend on dendrimer type and size. Viologen dendrimers can interact with the enzymes in two ways: they can bind either to a peripheral site of the enzyme or to amino acids located near the active site, inhibiting catalysis by both cholinesterases. All tested non-toxic viologen-phosphorus dendrimers inhibited the activities of both cholinesterases, showing their potential as new drugs for treating neurodegenerative diseases. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Unusual concentration-dependent microscopic dynamics of dendrimers in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Kaikin; Wu, Chin Ming; Lam, Hak Fai; Chathoth, Suresh M., E-mail: smavilac@cityu.edu.hk [City University of Hong Kong, Department of Physics and Materials Science (Hong Kong, People’s Republic of China) (China)

    2016-05-15

    Dendrimers are novel three-dimensional, hyperbranched globular nanopolymeric macromolecules. The nanoscopic size, narrow polydispersity index, excellent control over molecular structure, availability of multiple functional groups at the periphery, and cavities in the interior made them very attractive candidate for drug delivery. In this communication, we have studied the microscopic dynamics of tetra-acid and pentaerythritol glycidyl ether dendrimers dissolved in aqueous solution with different concentrations. The effects of concentration and temperature to their long-range diffusion process are investigated by dynamic light scattering. Experimental results show a huge variation in the translational diffusion coefficient for the two dendrimers samples. Besides, the dependence of diffusion coefficients on concentration is unusually different in these dendrimer samples. Although the diffusion process follows Arrhenius relation with the temperature in both systems, the activation energy for the diffusion process has a distinct concentration dependence.

  18. Brain Targeting of a Water Insoluble Antipsychotic Drug Haloperidol via the Intranasal Route Using PAMAM Dendrimer.

    Science.gov (United States)

    Katare, Yogesh K; Daya, Ritesh P; Sookram Gray, Christal; Luckham, Roger E; Bhandari, Jayant; Chauhan, Abhay S; Mishra, Ram K

    2015-09-08

    Delivery of therapeutics to the brain is challenging because many organic molecules have inadequate aqueous solubility and limited bioavailability. We investigated the efficiency of a dendrimer-based formulation of a poorly aqueous soluble drug, haloperidol, in targeting the brain via intranasal and intraperitoneal administration. Aqueous solubility of haloperidol was increased by more than 100-fold in the developed formulation. Formulation was assessed via different routes of administration for behavioral (cataleptic and locomotor) responses, and for haloperidol distribution in plasma and brain tissues. Dendrimer-based formulation showed significantly higher distribution of haloperidol in the brain and plasma compared to a control formulation of haloperidol administered via intraperitoneal injection. Additionally, 6.7 times lower doses of the dendrimer-haloperidol formulation administered via the intranasal route produced behavioral responses that were comparable to those induced by haloperidol formulations administered via intraperitoneal injection. This study demonstrates the potential of dendrimer in improving the delivery of water insoluble drugs to brain.

  19. Aptamer-conjugated dendrimer-modified quantum dots for glioblastoma cells imaging

    International Nuclear Information System (INIS)

    Li Zhiming; Huang Peng; He Rong; Bao Chenchen; Cui Daxiang; Zhang Xiaomin; Ren Qiushi

    2009-01-01

    Targeted quantum dots have shown potential as a platform for development of cancer imaging. Aptamers have recently been demonstrated as ideal candidates for molecular targeting applications. In present work, polyamidoamine dendrimers were used to modify surface of quantum dots and improve their solubility in water solution. Then, dendrimer-modified quantum dots were conjugated with DNA aptamer, GBI-10, can recognize the extracellular matrix protein tenascin-C on the surface of human glioblastoma cells. The dendrimer-modified quantum dots exhibit water-soluble, high quantum yield, and good biocompatibility. Aptamer-conjugated quantum dots can specifically target U251 human glioblastoma cells. High-performance aptamer-conjugated dendrimers modified quantum dot-based nanoprobes have great potential in application such as cancer imaging.

  20. Synthesis of Dendrimer Containing Dialkylated-fluorene Unit as a Core Chromophore via Click Chemistry

    International Nuclear Information System (INIS)

    Han, Seung Choul; Lee, Jae Wook; Jin, Sung Ho

    2012-01-01

    The convergent synthetic strategy for the emissive dendrimers having the chromophore at core via the coppercatalyzed 1,3-dipolar cycloaddition reaction between alkyne and azide was described. 2,7-Diazido-9,9-dioctyl- 9H-fluorene, designed to serve as the core in dendrimer, was stitched with the alkyne-functionalized Frechettype and PAMAM dendrons by the click chemistry leading to the formation of the corresponding fluorescent dendrimers in high yields. The preliminary photoluminescence studies indicated that 2,7-diazido-9,9-dioctyl- 9H-fluorene showed no fluorescence due to the quenching effect from the electron-rich α-nitrogen of the azido group but the dendrimers fluoresced due to the elimination of the quenching through the formation of the triazole ring

  1. Dendrimers as tunable vectors of drug delivery systems and biomedical and ocular applications

    Science.gov (United States)

    Kalomiraki, Marina; Thermos, Kyriaki; Chaniotakis, Nikos A

    2016-01-01

    Dendrimers are large polymeric structures with nanosize dimensions (1–10 nm) and unique physicochemical properties. The major advantage of dendrimers compared with linear polymers is their spherical-shaped structure. During synthesis, the size and shape of the dendrimer can be customized and controlled, so the finished macromolecule will have a specific “architecture” and terminal groups. These characteristics will determine its suitability for drug delivery, diagnostic imaging, and as a genetic material carrier. This review will focus initially on the unique properties of dendrimers and their use in biomedical applications, as antibacterial, antitumor, and diagnostic agents. Subsequently, emphasis will be given to their use in drug delivery for ocular diseases. PMID:26730187

  2. Kinetic and thermodynamic study of the transfer of anionic polyamidoamine dendrimers across two immiscible liquids

    International Nuclear Information System (INIS)

    Gonzalez-Fuentes, Miguel A.; Manriquez, J.; Antano-Lopez, R.; Godinez, Luis A.

    2011-01-01

    The kinetics and thermodynamics for the phase transfer of carboxyl-terminated polyamidoamine (PAMAM) dendrimers across the water/dichloroethane interface were analyzed by cyclic voltammetry and electrochemical impedance spectroscopy. A three phase junction was employed by inserting a cylindrical gold electrode through the liquid-liquid interface. The reversible redox species decamethylferrocene (DMFc) was used in the organic phase in order to promote dendrimer transfer. It was found that the electrochemical behaviour of DMFc at the gold/dichloroethane interface depends on the generation and concentration of the dendrimer species in the aqueous phase. In addition, it was observed that the electrochemically driven transfer of these macromolecules corresponds to a quasi-reversible process. The data obtained from thermodynamic studies indicate that dendrimers are transferred between the two phases under study by an entropy controlled process.

  3. Dendrimers as tunable vectors of drug delivery systems and biomedical and ocular applications

    Directory of Open Access Journals (Sweden)

    Kalomiraki M

    2015-12-01

    Full Text Available Marina Kalomiraki,1 Kyriaki Thermos,2 Nikos A Chaniotakis1 1Laboratory of Analytical Chemistry, Department of Chemistry, 2Department of Pharmacology, School of Medicine, University of Crete Voutes, Heraklion, Greece Abstract: Dendrimers are large polymeric structures with nanosize dimensions (1–10 nm and unique physicochemical properties. The major advantage of dendrimers compared with linear polymers is their spherical-shaped structure. During synthesis, the size and shape of the dendrimer can be customized and controlled, so the finished macromolecule will have a specific “architecture” and terminal groups. These characteristics will determine its suitability for drug delivery, diagnostic imaging, and as a genetic material carrier. This review will focus initially on the unique properties of dendrimers and their use in biomedical applications, as antibacterial, antitumor, and diagnostic agents. Subsequently, emphasis will be given to their use in drug delivery for ocular diseases. Keywords: nanoparticles, ocular diseases, encapsulation, macromolecule, diagnostic agent

  4. Iodine-Containing Mass-Defect-Tuned Dendrimers for Use as Internal Mass Spectrometry Calibrants

    Science.gov (United States)

    Giesen, Joseph A.; Diament, Benjamin J.; Grayson, Scott M.

    2018-03-01

    Calibrants based on synthetic dendrimers have been recently proposed as a versatile alternative to peptides and proteins for both MALDI and ESI mass spectrometry calibration. Because of their modular synthetic platform, dendrimer calibrants are particularly amenable to tailoring for specific applications. Utilizing this versatility, a set of dendrimers has been designed as an internal calibrant with a tailored mass defect to differentiate them from the majority of natural peptide analytes. This was achieved by incorporating a tris-iodinated aromatic core as an initiator for the dendrimer synthesis, thereby affording multiple calibration points ( m/z range 600-2300) with an optimized mass-defect offset relative to all peptides composed of the 20 most common proteinogenic amino acids. [Figure not available: see fulltext.

  5. Effect of methotrexate conjugated PAMAM dendrimers on the viability of MES-SA uterine cancer cells

    Directory of Open Access Journals (Sweden)

    Samreen Khatri

    2014-01-01

    Full Text Available The aim of this work was to synthesize methotrexate (MTX-polyamidoamine (PAMAM dendritic nanoconjugates and to study their effect on cell viability in uterine sarcoma cells. The amide-bonded PAMAM dendrimer-MTX conjugates were prepared by conjugation between the amine-terminated G5 dendrimer and the carboxylic groups of the MTX using a dicyclohexylcarbodiimide coupling reaction. The formation of conjugates was evaluated by ultraviolet (UV and 1 H nuclear magnetic resonance ( 1 H NMR spectroscopy studies. The cell survival of MES-SA cells, a uterine sarcoma cell line, was evaluated in the presence of the dendrimer-MTX nanoconjugate, using appropriate controls. The UV and 1 H NMR study confirmed the formation of covalent bonds between the drug and the dendrimer. The cell viability study indicated that the nanoconjugates had significantly improved cell killing compared to the free MTX.

  6. Interactive transport of guanidinylated poly(propylene imine)-based dendrimers through liposomal and cellular membranes.

    Science.gov (United States)

    Tsogas, Ioannis; Sideratou, Zili; Tsiourvas, Dimitris; Theodossiou, Theodossis A; Paleos, Constantinos M

    2007-10-15

    The ability of guanidinylated poly(propylene imine) dendrimers to translocate across lipid bilayers was assessed by employing either a model phosphate-bearing liposomal membrane system or A549 human lung carcinoma cells. Two dendrimer generations, differing in the number of surface guanidinium groups, were employed, while surface acetylation or the use of spacers affected the binding of the guanidinium group to the phosphate moiety and finally the transport efficiency. Following adhesion of dendrimers with liposomes, fusion or transport occurred. Transport through the liposomal bilayer was observed at low guanidinium/phosphate molar ratios, and was enhanced when the bilayer was in the liquid-crystalline phase. For effective transport through the liposomal membrane, an optimum balance between the binding strength and the degree of hydrophobicity of the guanidinylated dendrimer is required. In experiments performed in vitro with cells, efficient penetration and internalization in subcellular organelles and cytosol was observed.

  7. Phosphorus-Based Dendrimer ABP Treats Neuroinflammation by Promoting IL-10-Producing CD4(+) T Cells.

    Science.gov (United States)

    Hayder, Myriam; Varilh, Marjorie; Turrin, Cédric-Olivier; Saoudi, Abdelhadi; Caminade, Anne-Marie; Poupot, Rémy; Liblau, Roland S

    2015-11-09

    Dendrimers are polyfunctional nano-objects of perfectly defined structure that can provide innovative alternatives for the treatment of chronic inflammatory diseases, including multiple sclerosis (MS). To investigate the efficiency of a recently described amino-bis(methylene phosphonate)-capped ABP dendrimer as a potential drug candidate for MS, we used the classical mouse model of MOG35-55-induced experimental autoimmune encephalomyelitis (EAE). Our study provides evidence that the ABP dendrimer prevents the development of EAE and inhibits the progression of established disease with a comparable therapeutic benefit as the approved treatment Fingolimod. We also show that the ABP dendrimer redirects the pathogenic myelin-specific CD4(+) T cell response toward IL-10 production.

  8. Molecular dynamics study of the structure and interparticle interactions of polyethylene glycol-conjugated PAMAM dendrimers.

    Science.gov (United States)

    Lee, Hwankyu; Larson, Ronald G

    2009-10-08

    We performed molecular dynamics (MD) simulations of one or two copies of polyethylene glycol of molecular weight 550 (PEG550) and 5000 (PEG5000) daltons, conjugated to generation 3 (G3) to 5 (G5) polyamidoamine (PAMAM) dendrimers with explicit water using a coarse-grained model. We found the radii of gyration of these dendrimer-PEG molecules to be close to those measured in experiments by Hedden and Bauer (Hedden , R. C. ; Bauer , B. J. Macromolecules 2003 , 36 , 1829.). Densely grafted PEG ligands (>50% of the dendrimer surface) extend like brushes, with layer thickness in agreement with theory for starlike polymers. Two dendrimer-PEG complexes in the box drift away from each other, indicating that no aggregation is induced by either short or long PEG chains, conflicting with a recent view that the cytotoxicity of some PEGylated particles might be due to particle aggregation for long PEG lengths.

  9. Fate and transformation products of amine-terminated PAMAM dendrimers under ozonation and irradiation

    International Nuclear Information System (INIS)

    Santiago-Morales, Javier; Rosal, Roberto; Hernando, María D.; Ulaszewska, Maria M.; García-Calvo, Eloy; Fernández-Alba, Amadeo R.

    2014-01-01

    Highlights: • We detected transformation products from dendrimer under ozonation and irradiation. • Retro-Michael fragmentation pathway with highly oxygenated structures. • High toxicity of G3 PAMAM dendrimer for green algae. • Reactive oxygen species were associated with the toxic damage. • Transformation mixtures could be more toxic than the parent dendrimer. -- Abstract: This article deals with the degradation of a third-generation (G3) poly(amidoamine) (PAMAM) dendrimer under ozonation and irradiation. The identification and quantification of G3 PAMAM dendrimer and its transformation products has been performed by liquid chromatography–electrospray ionization-hybrid quadrupole time-of-flight-mass spectrometry. The dendrimer was completely depleted by ozone in less than 1 min. The effect of ultraviolet irradiation was attributed to hydroxyl-mediated oxidation. The transformation products were attributed to the oxidation of amines, which resulted in highly oxidized structures with abundance of carboxylic acids, which started from the formation of amine oxide and the scission of the C-N bond of the amide group. We studied the toxicity of treated mixtures for six different organisms: the acute toxicity for the bacterium Vibrio fischeri and the microcrustacean Daphnia magna, the multigenerational growth inhibition of the alga Pseudokirchneriella subcapitata, and the seed germination phytotoxicity of Licopersicon esculentum, Lactuca sativa and Lolium perenne. Ozonation and irradiation originated transformation products are more toxic than the parent dendrimer. The toxicity of the dendrimer for the green alga was linked to a strong increase of intracellular reactive oxygen species with intense lipid peroxidation

  10. Fate and transformation products of amine-terminated PAMAM dendrimers under ozonation and irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Santiago-Morales, Javier [Department of Chemical Engineering, University of Alcalá, 28871 Alcalá de Henares, Madrid (Spain); Rosal, Roberto, E-mail: roberto.rosal@uah.es [Department of Chemical Engineering, University of Alcalá, 28871 Alcalá de Henares, Madrid (Spain); Advanced Study Institute of Madrid, IMDEA Agua, Parque Científico Tecnológico, 28805 Alcalá de Henares, Madrid (Spain); Hernando, María D. [Spanish National Institute for Agricultural and Food Research and Technology – INIA, Crta. de la Coruña, km 7.5, 28040 Madrid (Spain); Ulaszewska, Maria M. [Advanced Study Institute of Madrid, IMDEA Agua, Parque Científico Tecnológico, 28805 Alcalá de Henares, Madrid (Spain); García-Calvo, Eloy [Department of Chemical Engineering, University of Alcalá, 28871 Alcalá de Henares, Madrid (Spain); Advanced Study Institute of Madrid, IMDEA Agua, Parque Científico Tecnológico, 28805 Alcalá de Henares, Madrid (Spain); Fernández-Alba, Amadeo R. [Advanced Study Institute of Madrid, IMDEA Agua, Parque Científico Tecnológico, 28805 Alcalá de Henares, Madrid (Spain); Pesticide Residue Research Group, Department of Hydrogeology and Analytical Chemistry, University of Almería, 04120 Almería (Spain)

    2014-02-15

    Highlights: • We detected transformation products from dendrimer under ozonation and irradiation. • Retro-Michael fragmentation pathway with highly oxygenated structures. • High toxicity of G3 PAMAM dendrimer for green algae. • Reactive oxygen species were associated with the toxic damage. • Transformation mixtures could be more toxic than the parent dendrimer. -- Abstract: This article deals with the degradation of a third-generation (G3) poly(amidoamine) (PAMAM) dendrimer under ozonation and irradiation. The identification and quantification of G3 PAMAM dendrimer and its transformation products has been performed by liquid chromatography–electrospray ionization-hybrid quadrupole time-of-flight-mass spectrometry. The dendrimer was completely depleted by ozone in less than 1 min. The effect of ultraviolet irradiation was attributed to hydroxyl-mediated oxidation. The transformation products were attributed to the oxidation of amines, which resulted in highly oxidized structures with abundance of carboxylic acids, which started from the formation of amine oxide and the scission of the C-N bond of the amide group. We studied the toxicity of treated mixtures for six different organisms: the acute toxicity for the bacterium Vibrio fischeri and the microcrustacean Daphnia magna, the multigenerational growth inhibition of the alga Pseudokirchneriella subcapitata, and the seed germination phytotoxicity of Licopersicon esculentum, Lactuca sativa and Lolium perenne. Ozonation and irradiation originated transformation products are more toxic than the parent dendrimer. The toxicity of the dendrimer for the green alga was linked to a strong increase of intracellular reactive oxygen species with intense lipid peroxidation.

  11. Magnetic properties of dendrimer structures with different coordination numbers: A Monte Carlo study

    Science.gov (United States)

    Masrour, R.; Jabar, A.

    2016-11-01

    We investigate the magnetic properties of Cayley trees of large molecules with dendrimer structure using Monte Carlo simulations. The thermal magnetization and magnetic susceptibility of a dendrimer structure are given with different coordination numbers, Z=3, 4, 5 and different generations g=3 and 2. The variation of magnetizations with the exchange interactions and crystal fields have been given of this system. The magnetic hysteresis cycles have been established.

  12. Synthesis of a cationic thermoresponsive dendrimer and its self-assembly with apoferritin protein cage

    OpenAIRE

    Välimäki, Salla

    2015-01-01

    The aim of this work was to synthesize cationic dendrimer with a thermoresponsive polymer tail and complex the dendrimer with negatively charged apoferritin protein nanocage. These kind of systems are developed, for example, for biomedical applications. Spermine dendron with atom transfer radical polymerization initiator in focal point was synthesized successfully. Thermoresponsive poly(di(ethylene glycol) methyl ether methacrylate) was in situ polymerized to the dendron to form the therm...

  13. Epitaxially Grown Ultra-Flat Self-Assembling Monolayers with Dendrimers

    Directory of Open Access Journals (Sweden)

    Takane Imaoka

    2018-02-01

    Full Text Available Mono-molecular films formed by physical adsorption and dendrimer self-assembly were prepared on various substrate surfaces. It was demonstrated that a uniform dendrimer-based monolayer on the subnanometer scale can be easily constructed via simple dip coating. Furthermore, it was shown that an epitaxially grown monolayer film reflecting the crystal structure of the substrate (highly ordered pyrolytic graphite (HOPG can also be formed by aligning specific conditions.

  14. Charge transport properties of carbazole dendrimers in organic field-effect transistors

    Science.gov (United States)

    Mutkins, Karyn; Chen, Simon S. Y.; Aljada, Muhsen; Powell, Ben J.; Olsen, Seth; Burn, Paul L.; Meredith, Paul

    2011-10-01

    We report three generations of p-type dendrimer semiconductors comprised of spirobifluorene cores, carbazole branching units and fluorene surface groups for use in organic field-effect transistors (OFETs). The group of dendrimers are defined by their generation and noted as SBF-(Gx)2, where x is the generation. Top contact-bottom gate OFETs were fabricated by spin-coating the dendrimers onto an n-octyltrichlorosilane (OTS) passivated silicon dioxide surface. The dendrimer films were found to be amorphous. The highest mobility was measured for the first generation dendrimer (SBF-(G1)2), which had an average mobility of (6.6 +/- 0.2) × 10-5 cm2/V s and an ON/OFF ratio of 3.0 × 104. As the generation of the dendrimer was increased there was only a slight decrease in the measured mobility in spite of the significantly different molecular sizes of the dendrimers. The mobility of SBF-(G3)2, which had a hydrodynamic radius almost twice of SBF-(G1)2, still had an average mobility of (4.7 +/- 0.6) × 10-5 cm2/V s and an ON/OFF ratio of 2.7 × 103. Density functional theory calculations showed that the highest occupied molecular orbital was distributed over the core and carbazole units meaning that both intra- and intermolecular charge transfer could occur enabling the hole mobility to remain essentially constant even though the dendrimers would pack differently in the solid-state.

  15. Eco-friendly (green) synthesis of magnetically active gold nanoclusters

    Science.gov (United States)

    Kadasala, Naveen Reddy; Lin, Lu; Gilpin, Christopher; Wei, Alexander

    2017-12-01

    Au-FexOy composite nanoparticles (NPs) are of great technological interest due to their combined optical and magnetic properties. However, typical syntheses are neither simple nor ecologically friendly, creating a challenging situation for process scale-up. Here we describe conditions for preparing Au-FexOy NPs in aqueous solutions and at ambient temperatures, without resorting to solvents or amphiphilic surfactants with poor sustainability profiles. These magnetic gold nanoclusters (MGNCs) are prepared in practical yields with average sizes slightly below 100 nm, and surface plasmon resonances that extend to near-infrared wavelengths, and sufficient magnetic moment (up to 6 emu g-1) to permit collection within minutes by handheld magnets. The MGNCs also produce significant photoluminescence when excited at 488 nm. Energy dispersive X-ray (EDX) analysis indicates a relatively even distribution of Fe within the MGNCs, as opposed to a central magnetic core.

  16. Gold Nanocluster-Mediated Cellular Death under Electromagnetic Radiation.

    Science.gov (United States)

    Cifuentes-Rius, Anna; Ivask, Angela; Das, Shreya; Penya-Auladell, Nuria; Fabregas, Laura; Fletcher, Nicholas L; Houston, Zachary H; Thurecht, Kristofer J; Voelcker, Nicolas H

    2017-11-29

    Gold nanoclusters (Au NCs) have become a promising nanomaterial for cancer therapy because of their biocompatibility and fluorescent properties. In this study, the effect of ultrasmall protein-stabilized 2 nm Au NCs on six types of mammalian cells (fibroblasts, B-lymphocytes, glioblastoma, neuroblastoma, and two types of prostate cancer cells) under electromagnetic radiation is investigated. Cellular association of Au NCs in vitro is concentration-dependent, and Au NCs have low intrinsic toxicity. However, when Au NC-incubated cells are exposed to a 1 GHz electromagnetic field (microwave radiation), cell viability significantly decreases, thus demonstrating that Au NCs exhibit specific microwave-dependent cytotoxicity, likely resulting from localized heating. Upon i.v. injection in mice, Au NCs are still present at 24 h post administration. Considering the specific microwave-dependent cytotoxicity and low intrinsic toxicity, our work suggests the potential of Au NCs as effective and safe nanomedicines for cancer therapy.

  17. Exploring Low Internal Reorganization Energies for Silicene Nanoclusters

    Science.gov (United States)

    Pablo-Pedro, Ricardo; Lopez-Rios, Hector; Mendoza-Cortes, Jose-L.; Kong, Jing; Fomine, Serguei; Van Voorhis, Troy; Dresselhaus, Mildred S.

    2018-05-01

    This paper is a contribution to the Physical Review Applied collection in memory of Mildred S. Dresselhaus. High-performance materials rely on small reorganization energies to facilitate both charge separation and charge transport. Here, we perform density-functional-theory calculations to predict small reorganization energies of rectangular silicene nanoclusters with hydrogen-passivated edges denoted by H-SiNC. We observe that across all geometries, H-SiNCs feature large electron affinities and highly stabilized anionic states, indicating their potential as n -type materials. Our findings suggest that fine-tuning the size of H-SiNCs along the "zigzag" and "armchair" directions may permit the design of novel n -type electronic materials and spintronics devices that incorporate both high electron affinities and very low internal reorganization energies.

  18. A comparison of interatomic potentials for modeling tungsten nanocluster structures

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Jiannan; Shu, Xiaolin, E-mail: shuxlin@buaa.edu.cn; Jin, Shuo; Zhang, Xuesong; Zhang, Ying; Lu, Guang-Hong

    2017-02-15

    Molecular dynamic simulation is utilized to study the nanocluster and the fuzz structure on the PFM surface of tungsten. The polyhedral and linear cluster structures based on the icosahedron, cuboctahedron and rhombic dodecahedron are built up. Three interatomic potentials are used in calculating the relationship between the cluster energy and the number of atoms. The results are compared with first-principles calculation to show each potential’s best application scale. Furthermore, the transition between the icosahedral and the cuboctahedral clusters is observed in molecular dynamic simulation at different temperatures, which follows a critical curve for different numbers of atoms. The linear structures are proved to be stable at experimental temperatures by thermodynamics. The work presents a selection of interatomic potentials in simulating tungsten cluster systems and helps researchers understand the growth and evolution laws of clusters and the fuzz-like structure formation process in fusion devices.

  19. Electrically driven light emission from an array of Si nanoclusters

    International Nuclear Information System (INIS)

    Mazzitello, K I; Martin, H O; Aldao, C M; Roman, H E

    2004-01-01

    Charge transport and light emission properties of an array of silicon nanoclusters (NCs), sandwiched between a p-type and an n-type doped silicon crystal, are studied theoretically by assuming that electrons and holes enter from the opposite sides of the array in response to an applied electric field. The size of the NCs considered ranges from 16 nm down to 3.6 nm and their spatial distribution is optimized so that light emission, resulting from radiative recombinations, is peaked in the visible red around 1.8 eV. The light emission efficiency is limited by the carrier hopping times and is found to be in the range 2-0.5%, for fields ranging from 100 kV cm -1 to 500 kV cm -1 , respectively

  20. Melting of Cu nanoclusters by molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Li; Zhang, Yanning; Bian, Xiufang; Chen, Ying

    2003-04-14

    We present a detailed molecular dynamics study of the melting of copper nanoclusters with up to 8628 atoms within the framework of the embedded-atom method. The finding indicates that there exists an intermediate nanocrystal regime above 456 atoms. The linear relation between the cluster size and its thermodynamics properties is obeyed in this regime. Melting first occurs at the surface of the clusters, leading to T{sub m,N}=T{sub m,Bulk}-{alpha}N{sup -1/3}, dropping from T{sub m,Bulk}=1360 K to T{sub m,456}=990 K. In addition, the size, surface energy as well as the root mean square displacement (RMSD) of the clusters in the intermediate regime have been investigated.

  1. Exploring Low Internal Reorganization Energies for Silicene Nanoclusters

    KAUST Repository

    Pablo-Pedro, Ricardo

    2017-08-17

    High-performance materials rely on small reorganization energies to facilitate both charge separation and charge transport. Here, we performed DFT calculations to predict small reorganization energies of rectangular silicene nanoclusters with hydrogen-passivated edges denoted by H-SiNC. We observe that across all geometries, H-SiNCs feature large electron affinities and highly stabilized anionic states, indicating their potential as n-type materials. Our findings suggest that fine-tuning the size of H-SiNCs along the zigzag and armchair directions may permit the design of novel n-type electronic materials and spinctronics devices that incorporate both high electron affinities and very low internal reorganization energies.

  2. A comparison of interatomic potentials for modeling tungsten nanocluster structures

    International Nuclear Information System (INIS)

    Hao, Jiannan; Shu, Xiaolin; Jin, Shuo; Zhang, Xuesong; Zhang, Ying; Lu, Guang-Hong

    2017-01-01

    Molecular dynamic simulation is utilized to study the nanocluster and the fuzz structure on the PFM surface of tungsten. The polyhedral and linear cluster structures based on the icosahedron, cuboctahedron and rhombic dodecahedron are built up. Three interatomic potentials are used in calculating the relationship between the cluster energy and the number of atoms. The results are compared with first-principles calculation to show each potential’s best application scale. Furthermore, the transition between the icosahedral and the cuboctahedral clusters is observed in molecular dynamic simulation at different temperatures, which follows a critical curve for different numbers of atoms. The linear structures are proved to be stable at experimental temperatures by thermodynamics. The work presents a selection of interatomic potentials in simulating tungsten cluster systems and helps researchers understand the growth and evolution laws of clusters and the fuzz-like structure formation process in fusion devices.

  3. Connections Between Theory and Experiment for Gold and Silver Nanoclusters

    Science.gov (United States)

    Weerawardene, K. L. Dimuthu M.; Häkkinen, Hannu; Aikens, Christine M.

    2018-04-01

    Ligand-stabilized gold and silver nanoparticles are of tremendous current interest in sensing, catalysis, and energy applications. Experimental and theoretical studies have closely interacted to elucidate properties such as the geometric and electronic structures of these fascinating systems. In this review, the interplay between theory and experiment is described; areas such as optical absorption and doping, where the theory-experiment connections are well established, are discussed in detail; and the current status of these connections in newer fields of study, such as luminescence, transient absorption, and the effects of solvent and the surrounding environment, are highlighted. Close communication between theory and experiment has been extremely valuable for developing an understanding of these nanocluster systems in the past decade and will undoubtedly continue to play a major role in future years.

  4. Critical sizes and critical characteristics of nanoclusters, nanostructures and nanomaterials

    International Nuclear Information System (INIS)

    Suzdalev, I.P.

    2005-01-01

    Full text: Critical sizes and characteristics of nanoclusters and nanostructures are introduced as the parameters of nanosystems and nanomaterials. The next critical characteristics are considered: atomic and electronic 'magic number', critical size of cluster nucleation, critical size of melting-freezing of cluster, critical size of quantum (laser) radiation, critical sizes for the single electron conductivity, critical energy and magnetic field for the magnetic tunneling, critical cluster sizes for the giant magnetic resistance, critical size of the first order magnetic phase transition. The critical characteristics are estimated by thermodynamic approaches, by Moessbauer spectroscopy, AFM, heat capacity, SQUID magnetometry and other technique, The influence of cluster-cluster interactions, cluster-matrix interactions and cluster defects on cluster atomic dynamics, cluster melting, cluster critical sizes, Curie or Neel points and the character of magnetic phase transitions were investigated. The applications of critical size and critical characteristic parameters for the nanomaterial characterization are considered

  5. Modeling the photosensitizing properties of thiolate-protected gold nanoclusters.

    Science.gov (United States)

    Azarias, Cloé; Adamo, Carlo; Perrier, Aurélie

    2016-03-21

    An accurate computational strategy for studying the structural, redox and optical properties of thiolated gold nanoclusters (GNCs) using (Time-Dependent) Density Functional Theory is proposed. The influence of the pseudopotential/basis set, solvent description and the choice of the functional has been investigated to model the structural and electronic properties of the Au25(SR)18(-) system, with R being an organic ligand. This study aims to describe with a comparable precision both the GNC and the organic ligands and rationalize the effect of coating on different GNC properties. Two differently coated GNCs have been considered: the system with R = CH2CH2Ph and the GNC coated with 17 alkyl chains (C6H13) and functionalized by one fluorophore pyrene derivative (CH2CH2(NH)(CO)Py). The computational protocol we propose should then be used to design more efficient metal cluster-sensitized solar cells.

  6. Electrical transport properties in Co nanocluster-assembled granular film

    Science.gov (United States)

    Zhang, Qin-Fu; Wang, Lai-Sen; Wang, Xiong-Zhi; Zheng, Hong-Fei; Liu, Xiang; Xie, Jia; Qiu, Yu-Long; Chen, Yuanzhi; Peng, Dong-Liang

    2017-03-01

    A Co nanocluster-assembled granular film with three-dimensional cross-connection paralleled conductive paths was fabricated by using the plasma-gas-condensation method in a vacuum environment. The temperature-dependent longitudinal resistivity and anomalous Hall effect of this new type granular film were systematically studied. The longitudinal resistivity of the Co nanocluster-assembled granular film first decreased and then increased with increasing measuring temperature, revealing a minimum value at certain temperature, T min . In a low temperature region ( T governed the electrical transport process, and the temperature coefficient of resistance (TCR) showed an insulator-type behavior. The thermal fluctuation-induced tunneling conduction progressively increased with increasing temperature, which led to a decrease in the longitudinal resistivity. In a high temperature region, the TCR showed a metallic-type behavior, which was primarily attributed to the temperature-dependent scattering. Different from the longitudinal resistivity behavior, the saturated anomalous Hall resistivity increased monotonically with increasing measuring temperature. The value of the anomalous Hall coefficient ( R S ) reached 2.3 × 10-9 (Ω cm)/G at 300 K, which was about three orders of magnitude larger than previously reported in blocky single-crystal Co [E. N. Kondorskii, Sov. Phys. JETP 38, 977 (1974)]. Interestingly, the scaling relation ( ρx y A ∝ ρx x γ ) between saturated anomalous Hall resistivity ( ρx y A ) and longitudinal resistivity ( ρ x x ) was divided into two regions by T min . However, after excluding the contribution of tunneling, the scaling relation followed the same rule. The corresponding physical mechanism was also proposed to explain these phenomena.

  7. Targeting human liver cancer cells with lactobionic acid-G(4)-PAMAM-FITC sorafenib loaded dendrimers.

    Science.gov (United States)

    Iacobazzi, Rosa Maria; Porcelli, Letizia; Lopedota, Angela Assunta; Laquintana, Valentino; Lopalco, Antonio; Cutrignelli, Annalisa; Altamura, Emiliano; Di Fonte, Roberta; Azzariti, Amalia; Franco, Massimo; Denora, Nunzio

    2017-08-07

    Reported here is the synthesis and biological evaluation of the asialoglycoprotein receptor (ASGP-R) targeted fourth generation poliamidoamine dendrimer (G(4)-PAMAM) loaded with sorafenib. The ASGP-R targeted dendrimer was obtained by conjugation of Lactobionic acid (La) to the G(4)-PAMAM dendrimer, followed by acetylation (Ac) of the free amino groups in order to reduce the non-specific interactions with the cell membrane. Moreover, by additionally grafting fluorescein (FITC), it was easy to characterize the internalization pathway and the intracellular fate of the targeted dendrimer Ac-La-G(4)-PAMAM-FITC. In vitro experiments performed on HepG-2 and HLE cell lines, allowed to study the ability of the dendrimers to affect the cell vitality. Confocal microscopy and cytofluorimetric analysis confirmed higher binding and uptake ability of the Ac-La-G(4)-PAMAM-FITC dendrimer in well differentiated and ASGP-R expressing human liver cancer cell line HepG-2 compared non-expressing HLE cells. Ac-La-G(4)-PAMAM-FITC dendrimer loaded with sorafenib was stable and showed sustained sorafenib release. As evidenced by the cytotoxicity studies, sorafenib included in the dendrimer maintained its effectiveness, and was able to produce a longer lasting effect over the time compared to molar equivalent doses of free sorafenib. This new targeted dendrimer appears to be a suitable carrier for the delivery of sorafenib to liver cancer cells expressing ASGP-R. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Intracellular Ca2+ release mediates cationic but not anionic poly(amidoamine) (PAMAM) dendrimer-induced tight junction modulation.

    Science.gov (United States)

    Avaritt, Brittany R; Swaan, Peter W

    2014-09-01

    Poly(amidoamine) (PAMAM) dendrimers show great promise for utilization as oral drug delivery vehicles. These polymers are capable of traversing epithelial barriers, and have been shown to translocate by both transcellular and paracellular routes. While many proof-of-concept studies have shown that PAMAM dendrimers improve intestinal transport, little information exists on the mechanisms of paracellular transport, specifically dendrimer-induced tight junction modulation. Using anionic G3.5 and cationic G4 PAMAM dendrimers with known absorption enhancers, we investigated tight junction modulation in Caco-2 monolayers by visualization and mannitol permeability and compared dendrimer-mediated tight junction modulation to that of established permeation enhancers. [(14)C]-Mannitol permeability in the presence and absence of phospholipase C-dependent signaling pathway inhibitors was also examined and indicated that this pathway may mediate dendrimer-induced changes in permeability. Differences between G3.5 and G4 in tight junction protein staining and permeability with inhibitors were evident, suggesting divergent mechanisms were responsible for tight junction modulation. These dissimilarities are further intimated by the intracellular calcium release caused by G4 but not G3.5. Based on our results, it is apparent that the underlying mechanisms of dendrimer permeability are complex, and the complexities are likely a result of the density and sign of the surface charges of PAMAM dendrimers. The results of this study will have implications on the future use of PAMAM dendrimers for oral drug delivery.

  9. Nanomedicine for prion disease treatment: new insights into the role of dendrimers.

    Science.gov (United States)

    McCarthy, James M; Appelhans, Dietmar; Tatzelt, Jörg; Rogers, Mark S

    2013-01-01

    Despite their devastating impact, no effective therapeutic yet exists for prion diseases at the symptomatic stage in humans or animals. Progress is hampered by the difficulty in identifying compounds that affect PrP (Sc) and the necessity of any potential therapeutic to gain access to the CNS. Synthetic polymers known as dendrimers are a particularly promising candidate in this area. Studies with cell culture models of prion disease and prion infected brain homogenate have demonstrated that numerous species of dendrimers eliminate PrP (Sc) in a dose and time dependent fashion and specific glycodendrimers are capable of crossing the CNS. However, despite their potential a number of important questions remained unanswered such as what makes an effective dendrimer and how dendrimers eliminate prions intracellularly. In a number of recent studies we have tackled these questions and revealed for the first time that a specific dendrimer can inhibit the intracellular conversion of PrP (C) to PrP (Sc) and that a high density of surface reactive groups is a necessity for dendrimers in vitro anti-prion activity. Understanding how a therapeutic works is a vital component in maximising its activity and these studies therefore represent a significant development in the race to find effective treatments for prion diseases.

  10. Engineering CNDP's of dendrimers containing phosphorous interior compositions to produce new emerging properties

    Science.gov (United States)

    Caminade, Anne-Marie; Majoral, Jean-Pierre

    2018-03-01

    Phosphorus-containing dendrimers are defined as dendrimers having at least one phosphorus atom at each branching point. In this review, we will show how phosphorhydrazone dendrimers can be modified at will at the level of the core and of the branches, to afford specific properties, such as fluorescence to image biological events. Accelerated methods of synthesis of phosphorus (one step for one generation) will be also displayed, as well as the specific reactivity of P=N-P=S linkages obtained in most of these accelerated method of synthesis, which has led to particularly original dendritic architectures, such as dendrons included in dendrimers. Finally, we will display how modifications of the internal structure of a series of dendrimers having the same type and number of terminal functions can deeply modify their biological anti-inflammatory properties. Among the six critical nanoscale design parameters (CNDP), we will show how two of them, i.e., architecture and elemental composition, have been particularly engineered to modify phosphorus-containing dendrimers, in order to fulfill the desired properties.

  11. Cationic Phosphorus Dendrimer Enhances Photodynamic Activity of Rose Bengal against Basal Cell Carcinoma Cell Lines.

    Science.gov (United States)

    Dabrzalska, Monika; Janaszewska, Anna; Zablocka, Maria; Mignani, Serge; Majoral, Jean Pierre; Klajnert-Maculewicz, Barbara

    2017-05-01

    In the last couple of decades, photodynamic therapy emerged as a useful tool in the treatment of basal cell carcinoma. However, it still meets limitations due to unfavorable properties of photosensitizers such as poor solubility or lack of selectivity. Dendrimers, polymers widely studied in biomedical field, may play a role as photosensitizer carriers and improve the efficacy of photodynamic treatment. Here, we describe the evaluation of an electrostatic complex of cationic phosphorus dendrimer and rose bengal in such aspects as singlet oxygen production, cellular uptake, and phototoxicity against three basal cell carcinoma cell lines. Rose bengal-cationic dendrimer complex in molar ratio 5:1 was compared to free rose bengal. Obtained results showed that the singlet oxygen production in aqueous medium was significantly higher for the complex than for free rose bengal. The cellular uptake of the complex was 2-7-fold higher compared to a free photosensitizer. Importantly, rose bengal, rose bengal-dendrimer complex, and dendrimer itself showed no dark toxicity against all three cell lines. Moreover, we observed that phototoxicity of the complex was remarkably enhanced presumably due to high cellular uptake. On the basis of the obtained results, we conclude that rose bengal-cationic dendrimer complex has a potential in photodynamic treatment of basal cell carcinoma.

  12. Molecular dynamics simulations of single siloxane dendrimers: Molecular structure and intramolecular mobility of terminal groups

    Science.gov (United States)

    Kurbatov, A. O.; Balabaev, N. K.; Mazo, M. A.; Kramarenko, E. Yu.

    2018-01-01

    Molecular dynamics simulations of two types of isolated siloxane dendrimers of various generations (from the 2nd to the 8th) have been performed for temperatures ranging from 150 K to 600 K. The first type of dendrimer molecules has short spacers consisting of a single oxygen atom. In the dendrimers of the second type, spacers are longer and comprised of two oxygen atoms separated by a single silicon atom. A comparative analysis of molecular macroscopic parameters such as the gyration radius and the shape factor as well as atom distributions within dendrimer interior has been performed for varying generation number, temperature, and spacer length. It has been found that the short-spacer dendrimers of the 7th and 8th generations have a stressed central part with elongated bonds and deformed valence angles. Investigation of the time evolution of radial displacements of the terminal Si atoms has shown that a fraction of the Si groups have a reduced mobility. Therefore, rather long time trajectories (of the order of tens of nanoseconds) are required to study dendrimer intramolecular dynamics.

  13. Molecular Determinants of the Cellular Entry of Asymmetric Peptide Dendrimers and Role of Caveolae.

    Directory of Open Access Journals (Sweden)

    Prarthana V Rewatkar

    Full Text Available Caveolae are flask-shaped plasma membrane subdomains abundant in most cell types that participate in endocytosis. Caveola formation and functions require membrane proteins of the caveolin family, and cytoplasmic proteins of the cavin family. Cationic peptide dendrimers are non-vesicular chemical carriers that can transport pharmacological agents or genetic material across the plasma membrane. We prepared a panel of cationic dendrimers and investigated whether they require caveolae to enter into cells. Cell-based studies were performed using wild type or caveola-deficient i.e. caveolin-1 or PTRF gene-disrupted cells. There was a statistically significant difference in entry of cationic dendrimers between wild type and caveola-deficient cells. We further unveiled differences between dendrimers with varying charge density and head groups. Our results show, using a molecular approach, that (i expression of caveola-forming proteins promotes cellular entry of cationic dendrimers and (ii dendrimer structure can be modified to promote endocytosis in caveola-forming cells.

  14. COMPUTER SIMULATION OF LOCAL MOBILITY IN DENDRIMERS WITH ASYMMETRIC BRANCHING BY BROWNIAN DYNAMICS METHOD

    Directory of Open Access Journals (Sweden)

    O. V. Shavykin

    2016-09-01

    Full Text Available The Brownian dynamics method has been used to study the effect of the branching asymmetry on the local orientational mobility of segments and bonds in dendrimers in good solvent. “Coarse-grained” models of flexible dendrimers with different branching symmetry but with the same average segment length were considered. The frequency dependences of the rate of the spin-lattice relaxation nuclear magnetic resonance (NMR [1/T1H(H] for segments or bonds located at different distances from terminal monomers were calculated. After the exclusion of the contribution of the overall dendrimer rotation the position of the maxima of the frequency dependences [1/T1H(ωH] for different segments with the same length doesn’t depend on their location inside a dendrimer both for phantom models and for models with excluded volume interactions. This effect doesn’t depend also on the branching symmetry, but the position of the maximum [1/T1H(ωH] is determined by the segment length. For bonds inside segments the positions of the maximum [1/T1H(ωH] coincide for all models considered. Therefore, the obtained earlier conclusion about the weak influence of the excluded volume interactions on the local dynamics in the flexible symmetric dendrimers can be generalized for dendrimers with an asymmetric branching.

  15. Effect of increased surface hydrophobicity via drug conjugation on the clearance of inhaled PEGylated polylysine dendrimers.

    Science.gov (United States)

    Haque, Shadabul; McLeod, Victoria M; Jones, Seth; Fung, Sandy; Whittaker, Michael; McIntosh, Michelle; Pouton, Colin; Owen, David J; Porter, Christopher J H; Kaminskas, Lisa M

    2017-10-01

    PEGylated polylysine dendrimers are attractive and well tolerated inhalable drug delivery platforms that have the potential to control the release, absorption kinetics and lung retention time of conjugated drugs. The clinical application of these systems though, would likely require partial substitution of surface PEG groups with drug molecules that are anticipated to alter their lung clearance kinetics and clearance pathways. In the current study, we therefore evaluated the impact of increased surface hydrophobicity via substitution of 50% surface PEG groups with a model hydrophobic drug (α-carboxyl OtButylated methotrexate) on the lung clearance of a Generation 5 PEGylated polylysine dendrimer in rats. PEG substitution with OtBu-methotrexate accelerated lung clearance of the dendrimer by increasing polylysine scaffold catabolism, improving systemic absorption of the intact dendrimer and low molecular weight products of scaffold catabolism, and enhancing mucociliary clearance. These results suggest that the conjugation of hydrophobic drug on the surface of a PEGylated dendrimer is likely to accelerate lung clearance when compared to a fully PEGylated dendrimer. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

  16. A combinatorial approach of inclusion complexation and dendrimer synthesization for effective targeting EGFR-TK.

    Science.gov (United States)

    Shende, Pravin; Patil, Sampada; Gaud, R S

    2017-07-01

    The aim of the present study was to use a combinatorial approach of inclusion complexation and dendrimer synthesization of gefitinib using solvent-free technique for targeting EGFR-TK to treat Non-Small-Cell Lung Cancer (NSCLC). The inclusion complex of gefitinib with β-cyclodextrin was prepared by trituration method. This complex encapsulated G4 PAMAM dendrimers were synthesized by Michael addition and amidation reactions using green chemistry and then PEGylated by conjugation reaction. FTIR and DSC confirmed the formation of inclusion complex of gefitinib and β-cyclodextrin and PEGylation of G4 PAMAM dendrimers. Gefitinib showed higher solubility, encapsulation efficiency and controlled release profile from PEGylated dendrimers compared to inclusion complex. The PEGylated dendrimers of inclusion complex of gefitinib were found to reduce hemolytic toxicity and lesser GI 50 value on Human lung cancer cell line A-549 by effective targeting EGFR-TK. A combinatorial approach of inclusion complexation and dendrimer synthesization is one of the alternative advanced approaches to treat NSCLC. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Supramolecular assembly of a series of chiral dendrimers in interfacial films

    International Nuclear Information System (INIS)

    Yuan Jing; Deng Guojun; Fan Qinghua; Liu Minghua

    2004-01-01

    Supramolecular assembly and interfacial properties of a series of novel binaphthyl containing dendrimers from generation 1 through generation 4 have been investigated at the air/water interface and in solid substrates. Due to the lack of either long alkyl chains or strong hydrophilic groups, the dendrimer molecules tend to aggregate together to form stable two-dimensional ultrathin films, as verified by π-A and A-t measurements. Atomic force microscope (AFM) measurements of the transferred one-layer ultrathin films indicate that all the dendrimers show disk-like morphologies, which could be varied in particle size upon changing the surface pressure. The height profiles reveal that the height of the disks is between that of a monolayer and a bilayer, indicating that they are formed due to the aggregation of dendrimers with a distortion and/or partial overlapping. Circular dichroism (CD) spectra of the transferred multilayer films show Cotton effects due to the exciton couplet of the aromatic moieties adjacent to the bis(diphenylphosphino)-binaphthyl moiety, which is an active catalytic site for the dendrimer. With the increment of the generation, the intensity of the Cotton effects increased, suggesting that the optical active site of the dendrimer can be controlled by the outside wedge

  18. Dendrimer Nanoscaffolds for Potential Theranostics of Prostate Cancer with a Focus on Radiochemistry

    Science.gov (United States)

    Lo, Su-Tang; Kumar, Amit; Hsieh, Jer-Tsong; Sun, Xiankai

    2013-01-01

    Dendrimers are a class of structurally defined macromolecules featured with a central core, a low-density interior formed by repetitive branching units, and a high-density exterior terminated with surface functional groups. In contrast to their polymeric counterparts, dendrimers are nano-sized and symmetrically shaped, which can be reproducibly synthesized in a large scale with monodispersity. These unique features have made dendrimers of increasing interest for drug delivery and other biomedical applications as a nanoscaffold system. Intended to address the potential use of dendrimers for the development of theranostic agents, which combines therapeutics and diagnostics in a single entity for personalized medicine, this review focuses on the reported methodologies of using dendrimer nanoscaffolds for targeted imaging and therapy of prostate cancer. Of particular interest, relevant chemistry strategies are discussed due to their important roles in the design and synthesis of diagnostic and therapeutic dendrimer-based nanoconjugates and potential theranostic agents, targeted or non-targeted. Given the developing status of nanoscaffolded theranostics, major challenges and potential hurdles are discussed along with the examples representing current advances. PMID:23294202

  19. Precise localization of metal nanoparticles in dendrimer nanosnakes or inner periphery and consequences in catalysis

    Science.gov (United States)

    Liu, Xiang; Gregurec, Danijela; Irigoyen, Joseba; Martinez, Angel; Moya, Sergio; Ciganda, Roberto; Hermange, Philippe; Ruiz, Jaime; Astruc, Didier

    2016-10-01

    Understanding the relationship between the location of nanoparticles (NPs) in an organic matrix and their catalytic performances is essential for catalyst design. Here we show that catalytic activities of Au, Ag and CuNPs stabilized by dendrimers using coordination to intradendritic triazoles, galvanic replacement or stabilization outside dendrimers strongly depends on their location. AgNPs are found at the inner click dendrimer periphery, whereas CuNPs and AuNPs are encapsulated in click dendrimer nanosnakes. AuNPs and AgNPs formed by galvanic replacement are larger than precursors and only partly encapsulated. AuNPs are all the better 4-nitrophenol reduction catalysts as they are less sterically inhibited by the dendrimer interior, whereas on the contrary CuNPs are all the better alkyne azide cycloaddition catalysts as they are better protected from aerobic oxidation inside dendrimers. This work highlights the role of the location in macromolecules on the catalytic efficiency of metal nanoparticles and rationalizes optimization in catalyst engineering.

  20. Molecular Determinants of the Cellular Entry of Asymmetric Peptide Dendrimers and Role of Caveolae.

    Science.gov (United States)

    Rewatkar, Prarthana V; Parekh, Harendra S; Parat, Marie-Odile

    2016-01-01

    Caveolae are flask-shaped plasma membrane subdomains abundant in most cell types that participate in endocytosis. Caveola formation and functions require membrane proteins of the caveolin family, and cytoplasmic proteins of the cavin family. Cationic peptide dendrimers are non-vesicular chemical carriers that can transport pharmacological agents or genetic material across the plasma membrane. We prepared a panel of cationic dendrimers and investigated whether they require caveolae to enter into cells. Cell-based studies were performed using wild type or caveola-deficient i.e. caveolin-1 or PTRF gene-disrupted cells. There was a statistically significant difference in entry of cationic dendrimers between wild type and caveola-deficient cells. We further unveiled differences between dendrimers with varying charge density and head groups. Our results show, using a molecular approach, that (i) expression of caveola-forming proteins promotes cellular entry of cationic dendrimers and (ii) dendrimer structure can be modified to promote endocytosis in caveola-forming cells.

  1. Synthesis of New Functionalized Citric Acid-based Dendrimers as Nanocarrier Agents for Drug Delivery

    Directory of Open Access Journals (Sweden)

    Sanaz Motamedi

    2011-06-01

    Full Text Available Introduction: Citric acid-polyethylene glycol-citric acid (CPEGC triblock dendrimers can serve as potential delivery systems. Methods: In this investigation, CPEGC triblock dendrimers were synthesized and then imidazole groups were conjugated onto the surface of the G1, G2 and G3 of the obtained dendrimers. In order to study the type of the interactions between the functionalized dendrimers and a drug molecule, Naproxen which contains acidic groups, was examined as a hydrophobic drug in which the interactions would be of the electrostatic kind between its acidic groups and the lone pair electrons of nitrogen atom in imidazole groups. The quantity of the trapped drug and also the amount of its release were measured with UV spectrometric method in pH 1, 7.4 and 10. The average diameter of the nanocarriers was measured by Dynamic Light Scattering (DLS technique Results: The size range of particles was determined to be 16-50 nm for different generations. The rate of the release increased in pH=10 in all generations due to the increase in Naproxen solubility and the hydrolysis of the esteric bonds in the mentioned pH. The results showed that the amount of the trapped drug increased with the increase in the generation of the dendrimer and pH. Conclusion: Based on our findings, we suggest CPEGC triblock dendrimers possess great potential to be used as drug/gene delivery system.

  2. Interactions of PAMAM dendrimers with SDS at the solid-liquid interface.

    Science.gov (United States)

    Arteta, Marianna Yanez; Eltes, Felix; Campbell, Richard A; Nylander, Tommy

    2013-05-14

    This work addresses structural and nonequilibrium effects of the interactions between well-defined cationic poly(amidoamine) PAMAM dendrimers of generations 4 and 8 and the anionic surfactant sodium dodecyl sulfate (SDS) at the hydrophilic silica-water interface. Neutron reflectometry and quartz crystal microbalance with dissipation monitoring were used to reveal the adsorption from premixed dendrimer/surfactant solutions as well as sequential addition of the surfactant to preadsorbed layers of dendrimers. PAMAM dendrimers of both generations adsorb to hydrophilic silica as a compact monolayer, and the adsorption is irreversible upon rinsing with salt solution. SDS adsorbs on the dendrimer layer and at low bulk concentrations causes the expansion of the dendrimer layers on the surface. When the bulk concentration of SDS is increased, the surfactant layer consists of aggregates or bilayer-like structures. The adsorption of surfactant is reversible upon rinsing, but slight changes of the structure of the preadsorbed PAMAM monolayer were observed. The adsorption from premixed solutions close to charge neutrality results in thick multilayers, but the surface excess is lower when the bulk complexes have a net negative charge. A critical examination of the pathway of adsorption for the interactions of SDS with preadsorbed PAMAM monolayers and premixed PAMAM/SDS solutions with hydrophilic silica revealed that nonequilibrium effects are important only in the latter case, and the application of a thermodynamic model to such experimental data would be inappropriate.

  3. ANTI-INFLAMMATORY EFFECT OF ANTI-TNF-ALPHA siRNA CATIONIC PHOSPHOROUS DENDRIMERS NANOCOMPLEXES ADMINISTERED INTRANASALLY IN A MURINE ACUTE LUNG INJURY MODEL

    DEFF Research Database (Denmark)

    Bohr, Adam; Tsapis, Nicolas; Andreana, Ilaria

    2017-01-01

    lung injury model. To achieve this goal, two different types of phosphorus-based dendrimers with either pyrrolidinium or morpholinium as terminal protonated amino groups were selected for their better biocompatibility compared to other dendrimers. Dendriplexes containing pyrrolidinium surface groups...

  4. Small Angle Neutron Scattering Studies of the Counterion Effects on the Molecular Conformation and Structure of Charged G4 PAMAM Dendrimers in Aqueous Solutions

    International Nuclear Information System (INIS)

    Chen, Wei-Ren

    2007-01-01

    The structural properties of generation 4 (G4) poly(amidoamine) starburst dendrimers (PAMAM) with an ethylenediamine ne (EDA) central core in D O 2 solutions have been studied by small angle neutron scattering. Upon the addition of DCl , SANS patterns show a pronounced inter-particle 2 correlation peaks due to the strong repulsion introduced by the protonation of the amino groups of the dendrimers. By solving the Ornstein-Zernike integral equation (OZ) with hypernetted chain closure (HNC), the dendrimer-dendrimer er structure factor S(Q) is determined and used to fit the experimental data. Quantitative information such as the effective charge per dendrimer and its conformational change at different conditions can be obtained. The results obtained show clear evidence that significant counterion association occurs, strongly mediating the inter-dendrimer interaction. The influence of interplay between counterions and molecular protonation of dendrimers has strong effect on the dendrimer conformation and effective interaction.

  5. Electrical transport properties in Fe-Cr nanocluster-assembled granular films

    Science.gov (United States)

    Wang, Xiong-Zhi; Wang, Lai-Sen; Zhang, Qin-Fu; Liu, Xiang; Xie, Jia; Su, A.-Mei; Zheng, Hong-Fei; Peng, Dong-Liang

    2017-09-01

    The Fe100-xCrx nanocluster-assembled granular films with Cr atomic fraction (x) ranging from 0 to 100 were fabricated by using a plasma-gas-condensation cluster deposition system. The TEM characterization revealed that the uniform Fe clusters were coated with a Cr layer to form a Fe-Cr core-shell structure. Then, the as-prepared Fe100-xCrx nanoclusters were randomly assembled into a granular film in vacuum environments with increasing the deposition time. Because of the competition between interfacial resistance and shunting effect of Cr layer, the room temperature resistivity of the Fe100-xCrx nanocluster-assembled granular films first increased and then decreased with increasing the Cr atomic fraction (x), and revealed a maximum of 2 × 104 μΩ cm at x = 26 at.%. The temperature-dependent longitudinal resistivity (ρxx), magnetoresistance (MR) effect and anomalous Hall effect (AHE) of these Fe100-xCrx nanocluster-assembled granular films were also studied systematically. As the x increased from 0 to 100, the ρxx of all samples firstly decreased and then increased with increasing the measuring temperature. The dependence of ρxx on temperature could be well addressed by a mechanism incorporated for the fluctuation-induced-tunneling (FIT) conduction process and temperature-dependent scattering effect. It was found that the anomalous Hall effect (AHE) had no legible scaling relation in Fe100-xCrx nanocluster-assembled granular films. However, after deducting the contribution of tunneling effect, the scaling relation was unambiguous. Additionally, the Fe100-xCrx nanocluster-assembled granular films revealed a small negative magnetoresistance (MR), which decreased with the increase of x. The detailed physical mechanism of the electrical transport properties in these Fe100-xCrx nanocluster-assembled granular films was also studied.

  6. A scalable synthesis of highly stable and water dispersible Ag 44(SR)30 nanoclusters

    KAUST Repository

    AbdulHalim, Lina G.; Ashraf, Sumaira; Katsiev, Khabiboulakh; Kirmani, Ahmad R.; Kothalawala, Nuwan; Anjum, Dalaver H.; Abbas, Sikandar Zameer; Amassian, Aram; Stellacci, Francesco; Dass, Amala; Hussain, Irshad; Bakr, Osman

    2013-01-01

    We report the synthesis of atomically monodisperse thiol-protected silver nanoclusters [Ag44(SR)30] m, (SR = 5-mercapto-2-nitrobenzoic acid) in which the product nanocluster is highly stable in contrast to previous preparation methods. The method is one-pot, scalable, and produces nanoclusters that are stable in aqueous solution for at least 9 months at room temperature under ambient conditions, with very little degradation to their unique UV-Vis optical absorption spectrum. The composition, size, and monodispersity were determined by electrospray ionization mass spectrometry and analytical ultracentrifugation. The produced nanoclusters are likely to be in a superatom charge-state of m = 4-, due to the fact that their optical absorption spectrum shares most of the unique features of the intense and broadly absorbing nanoparticles identified as [Ag44(SR) 30]4- by Harkness et al. (Nanoscale, 2012, 4, 4269). A protocol to transfer the nanoclusters to organic solvents is also described. Using the disperse nanoclusters in organic media, we fabricated solid-state films of [Ag44(SR)30]m that retained all the distinct features of the optical absorption spectrum of the nanoclusters in solution. The films were studied by X-ray diffraction and photoelectron spectroscopy in order to investigate their crystallinity, atomic composition and valence band structure. The stability, scalability, and the film fabrication method demonstrated in this work pave the way towards the crystallization of [Ag44(SR)30]m and its full structural determination by single crystal X-ray diffraction. Moreover, due to their unique and attractive optical properties with multiple optical transitions, we anticipate these clusters to find practical applications in light-harvesting, such as photovoltaics and photocatalysis, which have been hindered so far by the instability of previous generations of the cluster. © 2013 The Royal Society of Chemistry.

  7. Peptide Dendrimer/Lipid Hybrid Systems Are Efficient DNA Transfection Reagents: Structure–Activity Relationships Highlight the Role of Charge Distribution Across Dendrimer Generations

    Science.gov (United States)

    2013-01-01

    Efficient DNA delivery into cells is the prerequisite of the genetic manipulation of organisms in molecular and cellular biology as well as, ultimately, in nonviral gene therapy. Current reagents, however, are relatively inefficient, and structure–activity relationships to guide their improvement are hard to come by. We now explore peptide dendrimers as a new type of transfection reagent and provide a quantitative framework for their evaluation. A collection of dendrimers with cationic and hydrophobic amino acid motifs (such as KK, KA, KH, KL, and LL) distributed across three dendrimer generations was synthesized by a solid-phase protocol that provides ready access to dendrimers in milligram quantities. In conjunction with a lipid component (DOTMA/DOPE), the best reagent, G1,2,3-KL ((LysLeu)8(LysLysLeu)4(LysLysLeu)2LysGlySerCys-NH2), improves transfection by 6–10-fold over commercial reagents under their respective optimal conditions. Emerging structure–activity relationships show that dendrimers with cationic and hydrophobic residues distributed in each generation are transfecting most efficiently. The trigenerational dendritic structure has an advantage over a linear analogue worth up to an order of magnitude. The success of placing the decisive cationic charge patterns in inner shells rather than previously on the surface of macromolecules suggests that this class of dendrimers significantly differs from existing transfection reagents. In the future, this platform may be tuned further and coupled to cell-targeting moieties to enhance transfection and cell specificity. PMID:23682947

  8. Synthesis of biocompatible AuAgS/Ag2S nanoclusters and their applications in photocatalysis and mercury detection

    International Nuclear Information System (INIS)

    Zhao, Qian; Chen, Shenna; Zhang, Lingyang; Huang, Haowen; Liu, Fengping; Liu, Xuanyong

    2014-01-01

    In this paper, a facile approach for preparation of AuAgS/Ag 2 S nanoclusters was developed. The unique AuAgS/Ag 2 S nanoclusters capped with biomolecules exhibit interesting excellent optical and catalytic properties. The fluorescent AuAgS/Ag 2 S nanoclusters show tunable luminescence depending on the nanocluster size. The apoptosis assay demonstrated that the AuAgS/Ag 2 S nanoclusters showed low cytotoxicity and good biocompatibility. Therefore, the nanoclusters can be used not only as a probe for labeling cells but also for their photocatalytic activity for photodegradation of organic dye. Moreover, a highly selective and sensitive assay for detection of mercury including Hg 2+ and undissociated mercury complexes was developed based on the quenching fluorescent AuAgS/Ag 2 S nanoclusters, which provides a promising approach for determining various forms of Hg in the mercury-based compounds in environment. These unique nanoclusters may have potential applications in biological labeling, sensing mercury, and photodegradation of various organic pollutants in waste water.Graphical Abstract

  9. Aqueous synthesis of ZnTe/dendrimer nanocomposites and their antimicrobial activity: implications in therapeutics

    Science.gov (United States)

    Ghosh, S.; Ghosh, D.; Bag, P. K.; Bhattacharya, S. C.; Saha, A.

    2011-03-01

    The present strategy proposes a simple and single step aqueous route for synthesizing stable, fluorescent ZnTe/dendrimer nanocomposites with varying dendrimer terminal groups. In these hybrid materials, the fluorescence of the semiconductor combines with the biomimetic properties of the dendrimer making them suitable for various biomedical applications. The ZnTe nanocomposites thus obtained demonstrate bactericidal activity against enteropathogenic bacteria without having toxic effects on the human erythrocytes. The average size of the ZnTe nanoparticles within the dendrimer matrix was in the range of 2.9-6.0 nm, and they have a good degree of crystallinity with a hexagonal crystal phase. The antibacterial activities of the ZnTe/dendrimer nanocomposites (ZnTe DNCs) as well other semiconductor nanocomposites were evaluated against enteropathogenic bacteria including multi-drug resistant Vibrio cholerae serogroup O1 and enterotoxigenic Escherichia coli (ETEC). ZnTe DNCs had significant antibacterial activity against strains of V. cholerae and ETEC with minimum inhibitory concentrations ranging from 64 to 512 μg ml-1 and minimum bactericidal concentrations ranging from 128 to 1000 μg ml-1. Thus, the observed results suggest that these water-soluble active nanocomposites have potential for the treatment of enteric diseases like diarrhoea and cholera.The present strategy proposes a simple and single step aqueous route for synthesizing stable, fluorescent ZnTe/dendrimer nanocomposites with varying dendrimer terminal groups. In these hybrid materials, the fluorescence of the semiconductor combines with the biomimetic properties of the dendrimer making them suitable for various biomedical applications. The ZnTe nanocomposites thus obtained demonstrate bactericidal activity against enteropathogenic bacteria without having toxic effects on the human erythrocytes. The average size of the ZnTe nanoparticles within the dendrimer matrix was in the range of 2.9-6.0 nm, and they

  10. Analysis of Biotinylated Generation 4 Poly(amidoamine (PAMAM Dendrimer Distribution in the Rat Brain and Toxicity in a Cellular Model of the Blood-Brain Barrier

    Directory of Open Access Journals (Sweden)

    Heather A. Bullen

    2013-09-01

    Full Text Available Dendrimers are highly customizable nanopolymers with qualities that make them ideal for drug delivery. The high binding affinity of biotin/avidin provides a useful approach to fluorescently label synthesized dendrimer-conjugates in cells and tissues. In addition, biotin may facilitate delivery of dendrimers through the blood-brain barrier (BBB via carrier-mediated endocytosis. The purpose of this research was to: (1 measure toxicity using lactate dehydrogenase (LDH assays of generation (G4 biotinylated and non-biotinylated poly(amidoamine (PAMAM dendrimers in a co-culture model of the BBB, (2 determine distribution of dendrimers in the rat brain, kidney, and liver following systemic administration of dendrimers, and (3 conduct atomic force microscopy (AFM on rat brain sections following systemic administration of dendrimers. LDH measurements showed that biotinylated dendrimers were toxic to cell co-culture after 48 h of treatment. Distribution studies showed evidence of biotinylated and non-biotinylated PAMAM dendrimers in brain. AFM studies showed evidence of dendrimers only in brain tissue of treated rats. These results indicate that biotinylation does not decrease toxicity associated with PAMAM dendrimers and that biotinylated PAMAM dendrimers distribute in the brain. Furthermore, this article provides evidence of nanoparticles in brain tissue following systemic administration of nanoparticles supported by both fluorescence microscopy and AFM.

  11. Interaction of poly(amidoamine) dendrimers with supported lipid bilayers and cells: hole formation and the relation to transport.

    Science.gov (United States)

    Hong, Seungpyo; Bielinska, Anna U; Mecke, Almut; Keszler, Balazs; Beals, James L; Shi, Xiangyang; Balogh, Lajos; Orr, Bradford G; Baker, James R; Banaszak Holl, Mark M

    2004-01-01

    We have investigated poly(amidoamine) (PAMAM) dendrimer interactions with supported 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayers and KB and Rat2 cell membranes using atomic force microscopy (AFM), enzyme assays, flow cell cytometry, and fluorescence microscopy. Amine-terminated generation 7 (G7) PAMAM dendrimers (10-100 nM) were observed to form holes of 15-40 nm in diameter in aqueous, supported lipid bilayers. G5 amine-terminated dendrimers did not initiate hole formation but expanded holes at existing defects. Acetamide-terminated G5 PAMAM dendrimers did not cause hole formation in this concentration range. The interactions between PAMAM dendrimers and cell membranes were studied in vitro using KB and Rat 2 cell lines. Neither G5 amine- nor acetamide-terminated PAMAM dendrimers were cytotoxic up to a 500 nM concentration. However, the dose dependent release of the cytoplasmic proteins lactate dehydrogenase (LDH) and luciferase (Luc) indicated that the presence of the amine-terminated G5 PAMAM dendrimer decreased the integrity of the cell membrane. In contrast, the presence of acetamide-terminated G5 PAMAM dendrimer had little effect on membrane integrity up to a 500 nM concentration. The induction of permeability caused by the amine-terminated dendrimers was not permanent, and leaking of cytosolic enzymes returned to normal levels upon removal of the dendrimers. The mechanism of how PAMAM dendrimers altered cells was investigated using fluorescence microscopy, LDH and Luc assays, and flow cytometry. This study revealed that (1) a hole formation mechanism is consistent with the observations of dendrimer internalization, (2) cytosolic proteins can diffuse out of the cell via these holes, and (3) dye molecules can be detected diffusing into the cell or out of the cell through the same membrane holes. Diffusion of dendrimers through holes is sufficient to explain the uptake of G5 amine-terminated PAMAM dendrimers into cells and is consistent

  12. Synthesis of indium nanoclusters and formation of thin film contacts on plastic substrates for organic and flexible electronics applications

    International Nuclear Information System (INIS)

    Shi, Frank F; Bulkowski, Michal; Hsieh, K C

    2007-01-01

    In this work, we described the processes of synthesizing free-standing indium nanoclusters using inverse micelles and microemulsions as well as synthesizing organic-encapsulated indium nanoclusters using alkanethiols as the organic encapsulants. The synthesized organic-encapsulated indium nanoclusters have demonstrated the feasibilities to be used as plastic compatible soft metal contacts for emerging organic devices. The homogeneously distributed indium nanoclusters with sizes of 10-30 nm have been fabricated on a few different plastic substrates. By changing the alkanethiol carbon chain length and the sizes of the indium nanoclusters, the annealing temperature required to form low-resistance indium thin film conductors has been reduced to 80-100 deg. C, which is acceptable for a variety of organic thin films

  13. Real-time transmission electron microscope observation of gold nanoclusters diffusing into silicon at room temperature

    International Nuclear Information System (INIS)

    Ishida, Tadashi; Nakajima, Yuuki; Fujita, Hiroyuki; Endo, Junji; Collard, Dominique

    2009-01-01

    Gold diffusion into silicon at room temperature was observed in real time with atomic resolution. Gold nanoclusters were formed on a silicon surface by an electrical discharge between a silicon tip and a gold coated tip inside an ultrahigh-vacuum transmission electron microscope (TEM) specimen chamber. At the moment of the gold nanocluster deposition, the gold nanoclusters had a crystalline structure. The crystalline structure gradually disappeared due to the interdiffusion between silicon and gold as observed after the deposition of gold nanoclusters. The shape of the nanocluster gradually changed due to the gold diffusion into the damaged silicon. The diffusion front between silicon and gold moved toward the silicon side. From the observations of the diffusion front, the gold diffusivity at room temperature was extracted. The extracted activation energy, 0.21 eV, matched the activation energy in bulk diffusion between damaged silicon and gold. This information is useful for optimizing the hybridization between solid-state and biological nanodevices in which gold is used as an adhesive layer between the two devices.

  14. Self-trapping nature of Tl nanoclusters on the Si(111)-7x7 surface

    International Nuclear Information System (INIS)

    Hwang, C G; Kim, N D; Lee, G; Shin, S Y; Kim, J S; Chung, J W

    2008-01-01

    We have studied properties of thallium (Tl) nanoclusters formed on the Si(111)-7x7 surface at room temperature (RT) by utilizing photoemission spectroscopy (PES) and high-resolution electron-energy-loss spectroscopy (HREELS) combined with first principles calculations. Our PES data reveal that the surface states stemming from the Si substrate remain quite inert with Tl adsorption producing no Tl-induced state until saturation at Tl coverage θ=0.21 monolayers. Such a behavior, in sharp contrast with the extremely reactive surface states upon the formation of Na or Li nanoclusters, together with the presence of a unique Tl-induced loss peak in HREELS spectra suggests no strong Si-Tl bonding, and is well understood in terms of gradual filling of Si dangling bonds with increasing θ. Our calculation further indicates the presence of several metastable atomic structures of Tl nanoclusters at RT rapidly transforming from one to another faster than 10 10 flippings per second. We thus conclude that the highly mobile Tl atoms form self-trapped nanoclusters within the attractive basins of the Si substrate at RT with several metastable phases. The mobile and multi-phased nature of Tl nanoclusters not only accounts for all the existing experimental observations available at present, but also provides an example of self-trapping of atoms in a nanometre-scale region

  15. Synthesis and Optical Properties of Au-Ag Alloy Nanoclusters with Controlled Composition

    Directory of Open Access Journals (Sweden)

    J. F. Sánchez-Ramírez

    2008-01-01

    Full Text Available Colloidal solid-solution-like Au-Ag alloy nanoclusters of different compositions were synthesized through citrate reduction of mixed metal ions of low concentrations, without using any other protective or capping agents. Optical absorption of the alloy nanoclusters was studied both theoretically and experimentally. The position of the surface plasmon resonance (SPR absorption band of the nanoclusters could be tuned from 419 nm to 521 nm through the variation of their composition. Considering effective dielectric constant of the alloy, optical absorption spectra for the nanoclusters were calculated using Mie theory, and compared with the experimentally obtained spectra. Theoretically obtained optical spectra well resembled the experimental spectra when the true size distribution of the nanoparticles was considered. High-resolution transmission electron microscopy (HREM, high-angle annular dark field (HAADF imaging, and energy dispersive spectroscopy (EDS revealed the true alloy nature of the nanoparticles with nominal composition being preserved. The synthesis technique can be extended to other bimetallic alloy nanoclusters containing Ag.

  16. Macromolecular and dendrimer-based magnetic resonance contrast agents

    Energy Technology Data Exchange (ETDEWEB)

    Bumb, Ambika; Brechbiel, Martin W. (Radiation Oncology Branch, National Cancer Inst., National Inst. of Health, Bethesda, MD (United States)), e-mail: pchoyke@mail.nih.gov; Choyke, Peter (Molecular Imaging Program, National Cancer Inst., National Inst. of Health, Bethesda, MD (United States))

    2010-09-15

    Magnetic resonance imaging (MRI) is a powerful imaging modality that can provide an assessment of function or molecular expression in tandem with anatomic detail. Over the last 20-25 years, a number of gadolinium-based MR contrast agents have been developed to enhance signal by altering proton relaxation properties. This review explores a range of these agents from small molecule chelates, such as Gd-DTPA and Gd-DOTA, to macromolecular structures composed of albumin, polylysine, polysaccharides (dextran, inulin, starch), poly(ethylene glycol), copolymers of cystamine and cystine with GD-DTPA, and various dendritic structures based on polyamidoamine and polylysine (Gadomers). The synthesis, structure, biodistribution, and targeting of dendrimer-based MR contrast agents are also discussed

  17. Controlled doping by self-assembled dendrimer-like macromolecules

    Science.gov (United States)

    Wu, Haigang; Guan, Bin; Sun, Yingri; Zhu, Yiping; Dan, Yaping

    2017-02-01

    Doping via self-assembled macromolecules might offer a solution for developing single atom electronics by precisely placing individual dopants at arbitrary location to meet the requirement for circuit design. Here we synthesize dendrimer-like polyglycerol macromolecules with each carrying one phosphorus atom in the core. The macromolecules are immobilized by the coupling reagent onto silicon surfaces that are pre-modified with a monolayer of undecylenic acid. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) are employed to characterize the synthesized macromolecules and the modified silicon surfaces, respectively. After rapid thermal annealing, the phosphorus atoms carried by the macromolecules diffuse into the silicon substrate, forming dopants at a concentration of 1017 cm-3. Low-temperature Hall effect measurements reveal that the ionization process is rather complicated. Unlike the widely reported simple ionization of phosphorus dopants, nitrogen and carbon are also involved in the electronic activities in the monolayer doped silicon.

  18. Thiophene dendrimer-based low donor content solar cells

    Science.gov (United States)

    Stoltzfus, Dani M.; Ma, Chang-Qi; Nagiri, Ravi C. R.; Clulow, Andrew J.; Bäuerle, Peter; Burn, Paul L.; Gentle, Ian R.; Meredith, Paul

    2016-09-01

    Low donor content solar cells containing polymeric and non-polymeric donors blended with fullerenes have been reported to give rise to efficient devices. In this letter, we report that a dendrimeric donor can also be used in solution-processed low donor content devices when blended with a fullerene. A third generation dendrimer containing 42 thiophene units (42T) was found to give power conversion efficiencies of up to 3.5% when blended with PC70BM in optimized devices. The best efficiency was measured with 10 mole percent (mol. %) of 42T in PC70BM and X-ray reflectometry showed that the blends were uniform. Importantly, while 42T comprised 10 mol. % of the film, it made up 31% of the film by volume. Finally, it was found that solvent annealing was required to achieve the largest open circuit voltage and highest device efficiencies.

  19. Light-fuelled transport of large dendrimers and proteins.

    Science.gov (United States)

    Koskela, Jenni E; Liljeström, Ville; Lim, Jongdoo; Simanek, Eric E; Ras, Robin H A; Priimagi, Arri; Kostiainen, Mauri A

    2014-05-14

    This work presents a facile water-based supramolecular approach for light-induced surface patterning. The method is based upon azobenzene-functionalized high-molecular weight triazine dendrimers up to generation 9, demonstrating that even very large globular supramolecular complexes can be made to move in response to light. We also demonstrate light-fuelled macroscopic movements in native biomolecules, showing that complexes of apoferritin protein and azobenzene can effectively form light-induced surface patterns. Fundamentally, the results establish that thin films comprising both flexible and rigid globular particles of large diameter can be moved with light, whereas the presented material concepts offer new possibilities for the yet marginally explored biological applications of azobenzene surface patterning.

  20. Transport of optical excitations on dendrimers in the continuum approximation

    International Nuclear Information System (INIS)

    Vlaming, S.M.; Heijs, D.J.; Knoester, J.

    2005-01-01

    We study the incoherent transport of optical excitations created at the rim of a dendritic molecule to a trap occurring at the core. The corresponding discrete random walk is treated in a continuum approximation, resulting in a diffusion-like process which admits semi-analytical solutions. The thus obtained arrival time distribution for the excitation at the trap is compared with the one for the original, discrete problem. In the case of an inward bias or even a weak outward one, the agreement is very good and the continuum approximation provides a good alternative description of the energy transfer process, even for small dendrimers. In the case of a strong outward bias, the mean trapping time, which sets the time scale for the entire distribution, depends exponentially on the number of generations in both approaches, but with a different base. The failure of the continuum approximation for this case is explained from the peaked behavior of the excitation density near the rim

  1. Simulation of bulk phases formed by polyphilic liquid crystal dendrimers

    Directory of Open Access Journals (Sweden)

    J.M. Ilnytskyi

    2010-01-01

    Full Text Available A coarse-grained simulation model for a third generation liquid crystalline dendrimer (LCDr is presented. It allows, for the first time, for a successful molecular simulation study of a relation between the shape of a polyphilic macromolecular mesogen and the symmetry of a macroscopic phase. The model dendrimer consists of a soft central sphere and 32 grafted chains each terminated by a mesogen group. The mesogenic pair interactions are modelled by the recently proposed soft core spherocylinder model of Lintuvuori and Wilson [J. Chem. Phys, 128, 044906, (2008]. Coarse-grained (CG molecular dynamics (MD simulations are performed on a melt of 100 molecules in the anisotropic-isobaric ensemble. The model LCDr shows conformational bistability, with both rod-like and disc-like conformations stable at lower temperatures. Each conformation can be induced by an external aligning field of appropriate symmetry that acts on the mesogens (uniaxial for rod-like and planar for disc-like, leading to formation of a monodomain smectic A (SmA or a columnar (Col phase, respectively. Both phases are stable for approximately the same temperature range and both exhibit a sharp transition to an isotropic cubic-like phase upon heating. We observe a very strong coupling between the conformation of the LCDr and the symmetry of a bulk phase, as suggested previously by theory. The study reveals rich potential in terms of the application of this form of CG modelling to the study of molecular self-assembly of liquid crystalline macromolecules.

  2. Formation of functionalized nanoclusters by solvent evaporation and their effect on the physicochemical properties of dental composite resins.

    Science.gov (United States)

    Rodríguez, Henry A; Giraldo, Luis F; Casanova, Herley

    2015-07-01

    The aim of this work was to study the effect of silica nanoclusters (SiNC), obtained by a solvent evaporation method and functionalized by 3-methacryloxypropyltrimethoxysilane (MPS) and MPS+octyltrimethoxysilane (OTMS) (50/50wt/wt), on the rheological, mechanical and sorption properties of urethane dimethylacrylate (UDMA)/triethylenglycol dimethacrylate (TEGDMA) (80/20wt/wt) resins blend. Silica nanoparticles (SiNP) were silanized with MPS or MPS+OTMS (50/50wt/wt) and incorporated in an UDMA-isopropanol mix to produce functionalized silica nanoclusters after evaporating the isopropanol. The effect of functionalized SiNC on resins rheological properties was determined by large and small deformation tests. Mechanical, thermal, sorption and solubility properties were evaluated for composite materials. The UDMA/TEGDMA (80/20wt/wt) resins blend with added SiNC (ca. 350nm) and functionalized with MPS showed a Newtonian flow behavior associated to their spheroidal shape, whereas the resins blend with nanoclusters silanized with MPS+OTMS (50/50wt/wt) (ca. 400nm) showed a shear-thinning behavior due to nanoclusters irregular shape. Composite materials prepared with bare silica nanoclusters showed lower compressive strength than functionalized silica nanoclusters. MPS functionalized nanoclusters showed better mechanical properties but higher water sorption than functionalized nanoclusters with both silane coupling agents, MPS and OTMS. The solvent evaporation method applied to functionalized nanoparticles showed to be an alternative way to the sinterization method for producing nanoclusters, which improved some dental composite mechanical properties and reduced water sorption. The shape of functionalized silica nanoclusters showed to have influence on the rheological properties of SiNC resin suspensions and the mechanical and sorption properties of light cured composites. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  3. Microglial migration and interactions with dendrimer nanoparticles are altered in the presence of neuroinflammation.

    Science.gov (United States)

    Zhang, Fan; Nance, Elizabeth; Alnasser, Yossef; Kannan, Rangaramanujam; Kannan, Sujatha

    2016-03-22

    Microglial cells have been implicated in neuroinflammation-mediated injury in the brain, including neurodevelopmental disorders such as cerebral palsy (CP) and autism. Pro-inflammatory activation of microglial cells results in the impairment of their neuroprotective functions, leading to an exaggerated, ongoing immune dysregulation that can persist long after the initial insult. We have previously shown that dendrimer-mediated delivery of an anti-inflammatory agent can attenuate inflammation in a rabbit model of maternal inflammation-induced CP and significantly improve the motor phenotype, due to the ability of the dendrimer to selectively localize in activated microglia. To elucidate the interactions between dendrimers and microglia, we created an organotypic whole-hemisphere brain slice culture model from newborn rabbits with and without exposure to inflammation in utero. We then used this model to analyze the dynamics of microglial migration and their interactions with dendrimers in the presence of neuroinflammation. Microglial cells in animals with CP had an amoeboid morphology and impaired cell migration, demonstrated by decreased migration distance and velocity when compared to cells in healthy, age-matched controls. However, this decreased migration was associated with a greater, more rapid dendrimer uptake compared to microglial cells from healthy controls. This study demonstrates that maternal intrauterine inflammation is associated with impaired microglial function and movement in the newborn brain. This microglial impairment may play a role in the development of ongoing brain injury and CP in the offspring. Increased uptake of dendrimers by the "impaired" microglia can be exploited to deliver drugs specifically to these cells and modulate their functions. Host tissue and target cell characteristics are important aspects to be considered in the design and evaluation of targeted dendrimer-based nanotherapeutics for improved and sustained efficacy. This ex

  4. Development of Tat-Conjugated Dendrimer for Transdermal DNA Vaccine Delivery.

    Science.gov (United States)

    Bahadoran, Azadeh; Moeini, Hassan; Bejo, Mohd Hair; Hussein, Mohd Zobir; Omar, Abdul Rahman

    In order to enhance cellular uptake and to facilitate transdermal delivery of DNA vaccine, polyamidoamine (PAMAM) dendrimers conjugated with HIV transactivator of transcription (TAT) was developed. First, the plasmid DNA (pIRES-H5/GFP) nanoparticle was formulated using PAMAM dendrimer and TAT peptide and then characterized for surface charge, particle size, DNA encapsulation and protection of the pIRES-H5/GFP DNA plasmid to enzymatic digestion. Subsequently, the potency of the TAT-conjugated dendrimer for gene delivery was evaluated through in vitro transfection into Vero cells followed by gene expression analysis including western blotting, fluorescent microscopy and PCR. The effect of the TAT peptide on cellular uptake of DNA vaccine was studied by qRT-PCR and flow cytometry. Finally, the ability of TAT-conjugated PAMAM dendrimer for transdermal delivery of the DNA plasmid was assessed through artificial membranes followed by qRT-PCR and flow cytometry. TAT-conjugated PAMAM dendrimer showed the ability to form a compact and nanometre-sized polyplexes with the plasmid DNA, having the size range of 105 to 115 nm and a positive charge of +42 to +45 mV over the N/P ratio of 6:1(+/-).  In vitro transfection analysis into Vero cells confirms the high potency of TAT-conjugated PAMAM dendrimer to enhance the cellular uptake of DNA vaccine.  The permeability value assay through artificial membranes reveals that TAT-conjugated PAMAM has more capacity for transdermal delivery of the DNA compared to unmodified PAMAM dendrimer (Pdendrimer is a promising non-viral vector for transdermal use.This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

  5. Anticancer copper(II) phosphorus dendrimers are potent proapoptotic Bax activators.

    Science.gov (United States)

    Mignani, Serge; El Brahmi, Nabil; Eloy, Laure; Poupon, Joel; Nicolas, Valérie; Steinmetz, Anke; El Kazzouli, Said; Bousmina, Mosto M; Blanchard-Desce, Mireille; Caminade, Anne-Marie; Majoral, Jean-Pierre; Cresteil, Thierry

    2017-05-26

    A multivalent phosphorus dendrimer 1G 3 and its corresponding Cu-complex, 1G 3 -Cu have been recently identified as agents retaining high antiproliferative potency. This antiproliferative capacity was preserved in cell lines overexpressing the efflux pump ABC B1, whereas cross-resistance was observed in ovarian cancer cell lines resistant to cisplatin. Theoretical 3D models were constructed: the dendrimers appear as irregularly shaped disk-like nano-objects of about 22 Å thickness and 49 Å diameter, which accumulated in cells after penetration by endocytosis. To get insight in their mode of action, cell death pathways have been examined in human cancer cell lines: early apoptosis was followed by secondary necrosis after multivalent phosphorus dendrimers exposure. The multivalent plain phosphorus dendrimer 1G 3 moderately activated caspase-3 activity, in contrast with the multivalent Cu-conjugated phosphorus dendrimer 1G 3 -Cu which strikingly reduced the caspase-3 content and activity. This decrease of caspase activity is not related to the presence of copper, since inorganic copper has no or little effect on caspase-3. Conversely the potent apoptosis activation could be related to a noticeable translocation of Bax to the mitochondria, resulting in the release of AIF into the cytosol, its translocation to the nucleus and a severe DNA fragmentation, without alteration of the cell cycle. The multivalent Cu-conjugated phosphorus dendrimer is more efficient than its non-complexed analog to activate this pathway in close relationship with the higher antiproliferative potency. Therefore, this multivalent Cu-conjugated phosphorus dendrimer 1G 3 -Cu can be considered as a new and promising first-in-class antiproliferative agent with a distinctive mode of action, inducing apoptosis tumor cell death through Bax activation pathway. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  6. Prevention of Synaptic Alterations and Neurotoxic Effects of PAMAM Dendrimers by Surface Functionalization

    Directory of Open Access Journals (Sweden)

    Felipe Vidal

    2017-12-01

    Full Text Available One of the most studied nanocarriers for drug delivery are polyamidoamine (PAMAM dendrimers. However, the alterations produced by PAMAM dendrimers in neuronal function have not been thoroughly investigated, and important aspects such as effects on synaptic transmission remain unexplored. We focused on the neuronal activity disruption induced by dendrimers and the possibility to prevent these effects by surface chemical modifications. Therefore, we studied the effects of fourth generation PAMAM with unmodified positively charged surface (G4 in hippocampal neurons, and compared the results with dendrimers functionalized in 25% of their surface groups with folate (PFO25 and polyethylene glycol (PPEG25. G4 dendrimers significantly reduced cell viability at 1 µM, which was attenuated by both chemical modifications, PPEG25 being the less cytotoxic. Patch clamp recordings demonstrated that G4 induced a 7.5-fold increment in capacitive currents as a measure of membrane permeability. Moreover, treatment with this dendrimer increased intracellular Ca2+ by 8-fold with a complete disruption of transients pattern, having as consequence that G4 treatment increased the synaptic vesicle release and frequency of synaptic events by 2.4- and 3-fold, respectively. PFO25 and PPEG25 treatments did not alter membrane permeability, total Ca2+ intake, synaptic vesicle release or synaptic activity frequency. These results demonstrate that cationic G4 dendrimers have neurotoxic effects and induce alterations in normal synaptic activity, which are generated by the augmentation of membrane permeability and a subsequent intracellular Ca2+ increase. Interestingly, these toxic effects and synaptic alterations are prevented by the modification of 25% of PAMAM surface with either folate or polyethylene glycol.

  7. Nanocrystals and Nanoclusters as Cocatalysts for Photocatalytic Water Splitting

    KAUST Repository

    Sinatra, Lutfan

    2016-12-04

    studied for the photocatalytic H2 production in order to explore the synergistic effect of the plasmonic resonance from the Au nanoparticles and pn-junction between Cu2O and TiO2. Additionally, the plasmonic effect of the Au films was also studied and utilized in order to improve the PWS. Secondly, the nanoscaling of cocatalysts was studied in order to improve the efficiency thereof and to reduce the cost of the cocatalyst materials. Moreover, it is sought to explore the quantum size effect on the properties of the cocatalyst and their effect on the photocatalytic reaction. Atomically precise Au and Ni nanoclusters were employed in these studies. Au nanoclusters were studied in relation to the cocatalysts in the photocatalytic water splitting, and Ni nanoclusters were studied in relation to the cocatalysts in the electrocatalytic water oxidation. The results of these studies will provide new insights in relation to the strategy used in order to develop efficient cocatalysts for the purpose of photocatalytic water splitting.

  8. Charge-dependent conformations and dynamics of pamam dendrimers revealed by neutron scattering and molecular dynamics

    Science.gov (United States)

    Wu, Bin

    Neutron scattering and fully atomistic molecular dynamics (MD) are employed to investigate the structural and dynamical properties of polyamidoamine (PAMAM) dendrimers with ethylenediamine (EDA) core under various charge conditions. Regarding to the conformational characteristics, we focus on scrutinizing density profile evolution of PAMAM dendrimers as the molecular charge of dendrimer increases from neutral state to highly charged condition. It should be noted that within the context of small angle neutron scattering (SANS), the dendrimers are composed of hydrocarbon component (dry part) and the penetrating water molecules. Though there have been SANS experiments that studied the charge-dependent structural change of PAMAM dendrimers, their results were limited to the collective behavior of the aforementioned two parts. This study is devoted to deepen the understanding towards the structural responsiveness of intra-molecular polymeric and hydration parts separately through advanced contrast variation SANS data analysis scheme available recently and unravel the governing principles through coupling with MD simulations. Two kinds of acids, namely hydrochloric and sulfuric acids, are utilized to tune the pH condition and hence the molecular charge. As far as the dynamical properties, we target at understanding the underlying mechanism that leads to segmental dynamic enhancement observed from quasielstic neutron scattering (QENS) experiment previously. PAMAM dendrimers have a wealth of potential applications, such as drug delivery agency, energy harvesting medium, and light emitting diodes. More importantly, it is regarded as an ideal system to test many theoretical predictions since dendrimers conjugate both colloid-like globular shape and polymer-like flexible chains. This Ph.D. research addresses two main challenges in studying PAMAM dendrimers. Even though neutron scattering is an ideal tool to study this PAMAM dendrimer solution due to its matching temporal and

  9. Charge Carrier Dynamics at Silver Nanocluster-Molecular Acceptor Interfaces

    KAUST Repository

    Almansaf, Abdulkhaleq

    2017-07-01

    A fundamental understanding of interfacial charge transfer at donor-acceptor interfaces is very crucial as it is considered among the most important dynamical processes for optimizing performance in many light harvesting systems, including photovoltaics and photo-catalysis. In general, the photo-generated singlet excitons in photoactive materials exhibit very short lifetimes because of their dipole-allowed spin radiative decay and short diffusion lengths. In contrast, the radiative decay of triplet excitons is dipole forbidden; therefore, their lifetimes are considerably longer. The discussion in this thesis primarily focuses on the relevant parameters that are involved in charge separation (CS), charge transfer (CT), intersystem crossing (ISC) rate, triplet state lifetime, and carrier recombination (CR) at silver nanocluster (NCs) molecular-acceptors interfaces. A combination of steady-state and femto- and nanosecond broadband transient absorption spectroscopies were used to investigate the charge carrier dynamics in various donor-acceptor systems. Additionally, this thesis was prolonged to investigate some important factors that influence the charge carrier dynamics in Ag29 silver NCs donor-acceptor systems, such as the metal doping and chemical structure of the nanocluster and molecular acceptors. Interestingly, clear correlations between the steady-state measurements and timeresolved spectroscopy results are found. In the first study, we have investigated the interfacial charge transfer dynamics in positively charged meso units of 5, 10, 15, 20-tetra (1- methyl-4-pyridino)-porphyrin tetra (p-toluene sulfonate) (TMPyP) and neutral charged 5, 10, 15, 20-tetra (4-pyridyl)-porphyrin (TPyP), with negatively charged undoped and gold (Au)- doped silver Ag29 NCs. Moreover, this study showed the impact of Au doping on the charge carrier dynamics of the system. In the second study, we have investigated the interfacial charge transfer dynamics in [Pt2 Ag23 Cl7 (PPh3

  10. Principal Physicochemical Methods Used to Characterize Dendrimer Molecule Complexes Used as Genetic Therapy Agents, Nanovaccines or Drug Carriers.

    Science.gov (United States)

    Alberto, Rodríguez Fonseca Rolando; Joao, Rodrigues; de Los Angeles, Muñoz-Fernández María; Alberto, Martínez Muñoz; Manuel Jonathan, Fragoso Vázquez; José, Correa Basurto

    2017-08-30

    Nanomedicine is the application of nanotechnology to medicine. This field is related to the study of nanodevices and nanomaterials applied to various medical uses, such as in improving the pharmacological properties of different molecules. Dendrimers are synthetic nanoparticles whose physicochemical properties vary according to their chemical structure. These molecules have been extensively investigated as drug nanocarriers to improve drug solubility and as sustained-release systems. New therapies such as gene therapy and the development of nanovaccines can be improved by the use of dendrimers. The biophysical and physicochemical characterization of nucleic acid/peptide-dendrimer complexes is crucial to identify their functional properties prior to biological evaluation. In that sense, it is necessary to first identify whether the peptide-dendrimer or nucleic aciddendrimer complexes can be formed and whether the complex can dissociate under the appropriate conditions at the target cells. In addition, biophysical and physicochemical characterization is required to determine how long the complexes remain stable, what proportion of peptide or nucleic acid is required to form the complex or saturate the dendrimer, and the size of the complex formed. In this review, we present the latest information on characterization systems for dendrimer-nucleic acid, dendrimer-peptide and dendrimer-drug complexes with several biotechnological and pharmacological applications. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  11. Charge inversion of dendrimers in complexes with linear polyelectrolytes in the solutions with low pH

    NARCIS (Netherlands)

    Larin, S.V.; Lyulin, S.V.; Lyulin, A.V.; Darinskii, A.A.

    2009-01-01

    Complexes of fully ionized third-generation dendrimers with oppositely charged linear polyelectrolyte chains are studied by the Brownian dynamics method. A freely jointed model of a dendrimer and a linear chain is used. Electrostatic interactions are considered within the Debye-Hückel approximation

  12. Modified PAMAM dendrimer with 4-carbomethoxypyrrolidone surface groups reveals negligible toxicity against three rodent cell-lines

    DEFF Research Database (Denmark)

    Janaszewska, Anna; Ciolkowski, Michal; Wróbel, Dominika

    2013-01-01

    Modification of the surface groups of dendrimers is one of the methods to improve their biocompatibility. This article presents results of experiments related to the toxicity of a modified polyamidoamine (PAMAM) dendrimer of the fourth generation with 4-carbomethoxypyrrolidone surface groups (PAM...

  13. Synthesis of Novel Hydrocarbon Soluble Multifunctional Anionic Initiators: Tools for Synthesis of Novel Dendrimer and Molecular Brush Polymer Architectures

    Science.gov (United States)

    2015-02-09

    Synthesis of Novel Dendrimer and Molecular Brush Polymer Architectures. Research Area:7.4 The views, opinions and/or findings contained in this report...journals: Final Report: Synthesis of Novel Hydrocarbon Soluble Multifunctional Anionic Initiators: Tools for Synthesis of Novel Dendrimer and Molecular

  14. Formation and growth of embedded indium nanoclusters by In2+ implantation in silica

    International Nuclear Information System (INIS)

    Santhana Raman, P.; Nair, K.G.M.; Kesavamoorthy, R.; Panigrahi, B.K.; Dhara, S.; Ravichandran, V.

    2007-01-01

    Indium nanoclusters are synthesized in an amorphous silica matrix using an ion-implantation technique. Indium ions (In 2+ ) with energy of 890 keV are implanted on silica to fluences in the range of 3 x 10 16 -3 x 10 17 cm -2 . The formation of indium nanoclusters is confirmed by optical absorption spectrometry and glancing incidence X-ray diffraction studies. A low frequency Raman scattering technique is used to study the growth of embedded indium nanoclusters in the silica matrix as a function of fluence and post-implantation annealing duration. Rutherford backscattering spectrometry studies show the surface segregation of implanted indium. Photoluminescence studies indicate the formation of a small quantity of indium oxide phase in the ion-implanted samples. (orig.)

  15. Cluster-to-cluster transformation among Au6, Au8 and Au11 nanoclusters.

    Science.gov (United States)

    Ren, Xiuqing; Fu, Junhong; Lin, Xinzhang; Fu, Xuemei; Yan, Jinghui; Wu, Ren'an; Liu, Chao; Huang, Jiahui

    2018-05-22

    We present the cluster-to-cluster transformations among three gold nanoclusters, [Au6(dppp)4]2+ (Au6), [Au8(dppp)4Cl2]2+ (Au8) and [Au11(dppp)5]3+ (Au11). The conversion process follows a rule that states that the transformation of a small cluster to a large cluster is achieved through an oxidation process with an oxidizing agent (H2O2) or with heating, while the conversion of a large cluster to a small one occurs through a reduction process with a reducing agent (NaBH4). All the reactions were monitored using UV-Vis spectroscopy and ESI-MS. This work may provide an alternative approach to the synthesis of novel gold nanoclusters and a further understanding of the structural transformation relationship of gold nanoclusters.

  16. Fabrication and modification of metal nanocluster composites using ion and laser beams

    International Nuclear Information System (INIS)

    Haglund, R.F. Jr.; Osborne, D.H. Jr.; Magruder, R.H. III; White, C.W.; Zuhr, R.A.; Townsend, P.D.; Hole, D.E.; Leuchtner, R.E.

    1994-12-01

    Metal nanocluster composites have attractive properties for applications in nonlinear optics. However, traditional fabrication techniques -- using melt-glass substrates -- are severely constrained by equilibrium thermodynamics and kinetics. This paper describes the fabrication of metal nanoclusters in both crystalline and glassy hosts by ion implantation and pulsed laser deposition. The size and size distribution of the metal nanoclusters can be modified by controlling substrate temperature during implantation, by subsequent thermal annealing, or by laser irradiation. The authors have characterized the optical response of the composites by absorption and third-order nonlinear-optical spectroscopies; electron and scanning-probe microscopies have been used to benchmark the physical characteristics of the composites. The outlook for controlling the structure and nonlinear optical response properties of these nanophase materials appears increasingly promising

  17. Extension of the radiative lifetime of Wannier-Mott excitons in semiconductor nanoclusters

    International Nuclear Information System (INIS)

    Kukushkin, V. A.

    2015-01-01

    The purpose of the study is to calculate the radiative lifetime of Wannier-Mott excitons in three-dimensional potential wells formed of direct-gap narrow-gap semiconductor nanoclusters in wide-gap semiconductors and assumed to be large compared to the exciton radius. Calculations are carried out for the InAs/GaAs heterosystem. It is shown that, as the nanocluster dimensions are reduced to values on the order of the exciton radius, the exciton radiative lifetime becomes several times longer compared to that in a homogeneous semiconductor. The increase in the radiative lifetime is more pronounced at low temperatures. Thus, it is established that the placement of Wannier-Mott excitons into direct-gap semiconductor nanoclusters, whose dimensions are of the order of the exciton radius, can be used for considerable extension of the exciton radiative lifetime

  18. XAFS studies of monodisperse Au nanoclusters formation in the etching process

    International Nuclear Information System (INIS)

    Yang, Lina; Huang, Ting; Liu, Wei; Bao, Jie; Huang, Yuanyuan; Cao, Yuanjie; Yao, Tao; Sun, Zhihu; Wei, Shiqiang

    2016-01-01

    Understanding the formation mechanism of gold nanoclusters is essential to the development of their synthetic chemistry. Here, by using x-ray absorption fine-structure (XAFS) spectroscopy, UV-Vis and MS spectra, the formation process of monodisperse Au 13 nanoclusters is investigated. We find that a critical step involving the formation of smaller Au 8 -Au 11 metastable intermediate clusters induced by the HCl + HSR etching of the polydisperse Au n precursor clusters occurs firstly. Then these intermediate species undergo a size-growth to Au 13 cores, followed by a slow structure rearrangement to reach the final stable structure. This work enriches the understanding of cluster formation chemistry and may guide the way towards the design and the controllable synthesis of nanoclusters. (paper)

  19. Synthesis of hydrophobic gold nanoclusters: growth mechanism study, luminescence property and catalytic application

    International Nuclear Information System (INIS)

    Selvam, Tamil Selvi; Chi, Kai-Ming

    2011-01-01

    One-pot synthesis of well dispersed, size-controlled gold nanoparticles with the average size of 10–15 nm and luminescent gold nanoclusters with average size of 1.7–2.0 nm were successfully achieved by thermal decomposition of gold organometallic precursor CH 3 AuPPh 3 in the presence of thiol surfactants in o-xylene. Only difference between the preparations of two types of Au nanoparticles is the amount of thiol surfactant employed. The mechanistic study of formation of gold nanoparticles was carried out by analyzing the samples at different reaction time intervals and revealed that two-staged growth process was involved. The nanoclusters showed strong red emission with the maximum intensity at about 600 nm. The maximum room temperature photoluminescence quantum yield was measured as 1.2%. The catalytic ability of the Au nanoclusters to promote Suzuki–Miyaura coupling involving the C–C bond formation was also investigated.

  20. Nanocluster metal films as thermoelectric material for radioisotope mini battery unit

    International Nuclear Information System (INIS)

    Borisyuk, P.V.; Krasavin, A.V.; Tkalya, E.V.; Lebedinskii, Yu.Yu.; Vasiliev, O.S.; Yakovlev, V.P.; Kozlova, T.I.; Fetisov, V.V.

    2016-01-01

    The paper is devoted to studying the thermoelectric and structural properties of films based on metal nanoclusters (Au, Pd, Pt). The experimental results of the study of single nanoclusters’ tunneling conductance obtained with scanning tunneling spectroscopy are presented. The obtained data allowed us to evaluate the thermoelectric power of thin film consisting of densely packed individual nanoclusters. It is shown that such thin films can operate as highly efficient thermoelectric materials. A scheme of miniature thermoelectric radioisotope power source based on the thorium-228 isotope is proposed. The efficiency of the radioisotope battery using thermoelectric converters based on nanocluster metal films is shown to reach values up to 1.3%. The estimated characteristics of the device are comparable with the parameters of up-to-date radioisotope batteries based on nickel-63.