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Jiacong Shen - One of the best experts on this subject based on the ideXlab platform.

  • cell adhesion properties of patterned poly acrylic acid poly allylamine hydrochloride Multilayer Films created by room temperature imprinting technique
    Langmuir, 2008
    Co-Authors: Junqi Sun, Jiacong Shen
    Abstract:

    Patterned poly(acrylic acid) (PAA)/poly(allylamine hydrochloride) (PAH) Multilayer Films with line structures of different lateral size and vertical height were fabricated by a room-temperature imprinting technique, and their cell adhesion properties were investigated. The nonimprinted PAA/PAH Multilayer Films are cytophilic toward NIH/3T3 fibroblasts and HeLa cells whether PAA or PAH is the outer most layer. In contrast, the PAA/PAH Multilayer Films with a 6.5-μm-line/3.5-μm-space pattern structure are cytophobic toward NIH/3T3 fibroblasts and HeLa cells when the height of the lines is 1.29 μm. By either increasing the lateral size of the patters to 69-μm-line/43-μm-space or decreasing the height of the imprinted lines to ∼107 nm, imprinted PAA/PAH Multilayer Films become cytophilic. This kind of transition of cell adhesion behavior derives from the change of the physical pattern size of the PAA/PAH Multilayer Films and is independent of the chemical composition of the Films. The easy patterning of layer...

  • ion triggered exfoliation of layer by layer assembled poly acrylic acid poly allylamine hydrochloride Films from substrates a facile way to prepare free standing Multilayer Films
    Chemistry of Materials, 2007
    Co-Authors: And Junqi Sun, Jiacong Shen
    Abstract:

    A facile way to prepare sheet- and tubelike free-standing Films of poly(acrylic acid) (PAA)/poly(allylamine hydrochloride) (PAH) was developed by exfoliating PAA/PAH Multilayer Films from substrates in acid aqueous solution containing copper ions. The exfoliation of the PAA/PAH film from the substrate was achieved by breaking the electrostatic interaction of the PAA layer with the underlying substrate while keeping the integrity of the resultant Films. Further study shows that thermally cross-linked free-standing PAA/PAH film can be prepared by treating the film in acid aqueous solution with a pH of 2.0. The ion-triggered exfoliation of PAA/PAH Multilayer film provides a simple and flexible way to prepare layer-by-layer (LbL) assembled free-standing Multilayer Films.

  • room temperature imprinting poly acrylic acid poly allylamine hydrochloride Multilayer Films by using polymer molds
    Langmuir, 2007
    Co-Authors: Xiaoling Chen, Junqi Sun, Jiacong Shen
    Abstract:

    Layer-by-layer assembled polyelectrolyte Multilayer Films of poly(acrylic acid) (PAA)/poly(allylamine hydrochloride) (PAH) have been successfully patterned by room-temperature imprinting using a Norland Optical Adhesives (NOA 63) polymer mold. The proper amount of water in the PAA/PAH Multilayer film can decrease the viscosity of the film and facilitate the imprinting. Many factors, such as imprinting pressure, length of imprinting time, and the structure and size of the patterns in the polymer mold, can produce an influence on the final imprinted pattern structures on Multilayer Films. A high imprinting pressure of 100 bar and elongated imprinting time of several hours is needed to achieve a patterned PAA/PAH Multilayer film with a feature size of several tens of micrometers. With a twice imprinting, grid structures can be successfully produced when a NOA 63 mold having line structures is used. Room-temperature imprinting by using polymer NOA 63 mold provides a facile way to fabricate layered polymeric Films with various kinds of pattern structures.

  • construction of antibacterial Multilayer Films containing nanosilver via layer by layer assembly of heparin and chitosan silver ions complex
    Journal of Biomedical Materials Research Part A, 2006
    Co-Authors: Dezeng Fan, Jiacong Shen
    Abstract:

    Antibacterial Multilayer Films containing nanosilver were prepared via layer-by-layer fashion. PET film was aminolyzed with 1,6-hexanediamine to introduce amino groups on PET film surface; chitosan-silver nitrate complex and heparin were alternately deposited onto an aminolyzed PET film surface, and subsequently, the silver ions within the Multilayer Films were reduced with ascorbic acid to form silver nanoparticles. UV-visible spectroscopy and transmission electron microscopy confirmed the formation of well-dispersed nanosilver particles with sizes (10-40 nm) that depended on the initial concentration of silver ions in chitosan solution and the pH of ascorbic acid solution. The chitosan/heparin Multilayer Films were possessed of bactericidal effect on Escherichia coli (E. coli), and this antibacterial effect could be significantly enhanced by the incorporation of silver nanoparticles into the Multilayer Films. The Multilayer Films containing nanosilver were not only effective as antibacterial but also as anticoagulant coating. And cell toxicity evaluation suggested that the Multilayer Films containing nanosilver did not show any cytotoxicity. The Multilayer Films containing nanosilver may have good potentials for surface modification of medical devices, especially for cardiovascular implants.

  • construction of anti adhesive and antibacterial Multilayer Films via layer by layer assembly of heparin and chitosan
    Biomaterials, 2005
    Co-Authors: Weiyong Yuan, Jiacong Shen
    Abstract:

    Chitosan as an antibacterial agent and heparin as an anti-adhesive agent were alternatively deposited onto aminolyzed poly(ethylene terephthalate) (PET) Films to construct anti-adhesive and antibacterial Multilayer Films. The contact-angle and UV data verified the progressive buildup of the Multilayer film by alternate deposition of the polyelectrolytes. The properties of Multilayer Films were investigated by contact angle, atomic force microscopy (AFM), lateral force microscopy (LFM) and UV spectra. The results of initial adhesion of Escherichia coli (E. coli) on PET substrates showed that the number of E. coli adhered onto the control PET was in a much greater extent than onto the chitosan/heparin Multilayer Films, and the number of adhesive bacteria decreased with a decrease in assembly pH. The in vitro antibacterial test indicated that a Multilayer of chitosan/heparin could kill the bacteria effectively. The number of viable bacteria decreased by 7% after 7 h in contact with the control PET Films, but by 46-68% for the Multilayer-modified PET Films. Only 3-8% of the cells were viable for the Multilayer-modified PET Films after 24h. It is interesting to find the assembly pH has a remarkable effect on the antibacterial property of the Multilayer. The number of viable bacteria on the Multilayer assembled at pH = 3.8, 2.9 and 6.0 decreased by 68%, 58% and 46%, respectively. Such an easy processing and shape-independent method to prepare an anti-adhesive and antibacterial surface may have good potential for surface modification of cardiovascular devices.

Shaojun Dong - One of the best experts on this subject based on the ideXlab platform.

  • electrochemical and electrogenerated chemiluminescence of clay nanoparticles ru bpy 32 Multilayer Films on ito electrodes
    Analyst, 2004
    Co-Authors: Zhihui Guo, Yan Shen, Feng Zhao, Mingkui Wang, Shaojun Dong
    Abstract:

    The electrochemical and electrogenerated chemiluminescence of Ru(bpy)32+ immobilized in {clay/Ru(bpy)32+}n Multilayer Films by layer-by-layer assembly were investigated. The stable Multilayer Films of clay and Ru(bpy)32+ were assembled by alternate adsorption of negatively charged clay platelets and positively charged Ru(bpy)32+ from their aqueous dispersions. UV-vis spectroscopy, quartz crystal microbalance (QCM), cyclic voltammetry, and electrogenerated chemiluminescence (ECL) were used to monitor the immobilization of Ru(bpy)32+ and the regular growth of the {clay/Ru(bpy)32+}n Multilayer Films. The Multilayer Films modified electrode was used for the ECL detection of tripropylamine (TPA) and oxalate. The proposed novel immobilized method exhibited good stability, reproducibility and high sensitivity for the determination of TPA and oxalate, which mainly resulted from the contributing of clay nanoparticles with appreciable surface area, special structural features and unusual intercalation properties. Detection limits were 20 and 100 nM for TPA and oxalate, respectively and the linear concentration range extended from 60 nM to 0.66 mM for TPA.

  • layer by layer assembly of Multilayer Films composed of avidin and biotin labeled antibody for immunosensing
    Biosensors and Bioelectronics, 2003
    Co-Authors: Xiaoqiang Cui, Zhenxin Wang, Shaojun Dong, Renjun Pei, Fan Yang, Xiurong Yang
    Abstract:

    Protein Multilayers composed of avidin and biotin-labeled antibody (bio-Ab) were prepared on gold surface by layer-by-layer assembly technology using the high specific binding constant (K-a: approximate to 10(15) M-1) between avidin and biotin. The assembly process of the Multilayer Films was monitored by using real-time BIA technique based on surface plasmon resonance (SPR). The Multilayer Films were also characterized by electrochemical impedance spectroscopy (EIS) and reflection absorption Fourier transform infrared spectroscopy (FTIR). The results indicate that the growth of the Multilayer is uniform. From response of SPR for each layer, the stoichiometry S for the interaction between avidin and bio-Ab is calculated to be 0.37 in the Multilayer whereas 0.82 in the first layer. The protein mass concentration for each layer was also obtained. The schematic figure for the Multilayer assembly was proposed according to the layer mass, concentration and S value. The utility of the mutilayer Films for immunosensing has been investigated via their subsequent interaction with hIgG. The binding ability of the Multilayer increased for one to three layers of antibody, and then reach saturation after the fourth layer. These layer-by-layer constructed antibody Multilayers enhance the binding ability than covalently immobilized monolayer antibody. This technology can be also used for construction of other thin Films for immunosensing and biosensor.

  • Fabrication of layer-by-layer deposited Multilayer Films containing DNA and its interaction with methyl green
    Biophysical Chemistry, 2001
    Co-Authors: Liqiang Luo, Jianyun Liu, Zhenxin Wang, Xiurong Yang, Shaojun Dong, Erkang Wang
    Abstract:

    Multilayer Films were fabricated by layer-by-layer electrostatic deposition techniques between poly(diallyldimethylammonium chloride) (PDDA) and calf thymus DNA (CT DNA) on glassy carbon and quartz substrates. Electrochemical impedance spectroscopy (EIS), Fourier transform infrared (FTIR) spectroscopy and UV-vis spectroscopy demonstrated the uniform assembly of PDDA/DNA Multilayer Films, and X-ray photoelectron spectroscopy confirmed the elemental composition of the Films. Moreover, the interaction of DNA in PDDA/DNA Films with methyl green was investigated by UV-vis spectroscopy and circular dichroism (CD).

  • covalent modification of a glassy carbon surface by 4 aminobenzoic acid and its application in fabrication of a polyoxometalates consisting monolayer and Multilayer Films
    Langmuir, 2000
    Co-Authors: Jianyun Liu, Long Cheng, And Baifeng Liu, Shaojun Dong
    Abstract:

    4-Aminobenzoic acid (4-ABA) was covalently grafted on a glassy carbon electrode (GCE) by amine cation radical formation in the electrooxidation process of the amino-containing compound. X-ray photoelectron spectroscopy measurement proves the presence of 4-carboxylphenylamine monolayer on the GCE. The redox responses of various electroactive probes were investigated on the 4-ABA-modified GCE. Electron transfer to Fe(CN)63- in solutions of various pHs was studied by both cyclic voltammetry and electrochemical impedance analysis on the modified electrode. Changes in the solution pH value result in the variation of the terminal group charge state, based on which surface pKa values are estimated. The 4-ABA-modified GCE was used as a suitable charged substrate to fabricate polyoxometalates-consisting (POM-consisting) monolayer and Multilayer Films through layer-by-layer assembly based on electrostatic attraction. Cyclic voltammetry shows the uniform growth of these three-dimensional Multilayer Films. Taking K10...

  • layer by layer assembly of Multilayer Films consisting of silicotungstate and a cationic redox polymer on 4 aminobenzoic acid modified glassy carbon electrode and their electrocatalytic effects
    Analytica Chimica Acta, 2000
    Co-Authors: Long Cheng, Jianyun Liu, Shaojun Dong
    Abstract:

    A novel 4-aminobenzoic acid (4-ABA) monolayer film is formed on glassy carbon electrode (GCE) by amino cation radical method. Silicotungstic heteropolyanion (SiW12O404-, denoted as SiW12)-containing Multilayer Films have been fabricated on the 4-ABA modified GCE surface by alternate deposition with a quaternized poly(4-vinylpyridine) partially complexed with [Os(bpy)(2)Cl](2+/+) (denoted as QPVP-Os). Cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and X-ray reflectivity (XR) have been used to characterise the as-prepared Multilayer Films. It is proved that the Multilayer Films are uniform and stable. The average thickness for a bilayer of QPVP-Os/SiW12 in the Multilayer film is 30.2 Angstrom. The electrocatalytic activities of the Multilayer Films have been investigated on the reduction of three substrates of important analytical interests, HNO2, BrO3- and H2O2. Especially, the influence of layer number of the Multilayer Films on the electrocatalytic reduction of HNO2 has been investigated in detail. (C) 2000 Elsevier Science B.V. All rights reserved.

Jianyun Liu - One of the best experts on this subject based on the ideXlab platform.

Frank Caruso - One of the best experts on this subject based on the ideXlab platform.

  • stabilization of dna Multilayer Films through oligonucleotide crosslinking
    Small, 2008
    Co-Authors: Angus P R Johnston, Frank Caruso
    Abstract:

    Multilayer Films and capsules synthesized from DNA are of interest because they are biodegradable, biocompatible, and the structure of the Films can be finely controlled by base pairing of the nucleotides. As DNA Films are held together through a balance between the attractive hydrogen bonding and the aromatic stacking of the base pairs and the electrostatic repulsion of the negatively charged phosphate backbones, the Films can be subject to disintegration at low salt concentrations (<200 mM). Enhancement of the stability of the Films is essential if they are to be used in bioapplications. Herein, we describe an approach to form DNA Films and capsules that are stable under a variety of buffer conditions, including low salt concentrations (down to 25 mM NaCl). The Films are assembled using a triblock oligonucleotide system, in which the two outer blocks facilitate the assembly of the film and the middle block can be used to stabilize the Films by hybridizing oligonucleotide sequences that crosslink the Films. Additionally, crosslinked DNA capsules are shown to exhibit significantly different shrinkage properties to those of noncrosslinked capsules, thus demonstrating further control over the capsule properties. These DNA capsules are envisaged to find applications as drug-delivery vehicles, in diagnostics, and as microreactors.

  • polyelectrolyte blend Multilayer Films surface morphology wettability and protein adsorption characteristics
    Langmuir, 2007
    Co-Authors: Anthony Quinn, Elvira Tjipto, Thomas R Gengenbach, Frank Caruso
    Abstract:

    We report the influence of polyelectrolyte (PE) Multilayer Films prepared from poly(styrene sulfonate)−poly(acrylic acid) (PSS-PAA) blends, deposited in alternation with poly(allylamine hydrochloride) (PAH), on film wettability and the adsorption behavior of the protein immunoglobulin G (IgG). Variations in the chemical composition of the PAH/(PSS-PAA) Multilayer Films, controlled by the PSS/PAA blend ratio in the dipping solutions, were used to systematically control film thickness, surface morphology, surface wettability, and IgG adsorption. Spectroscopic ellipsometry measurements indicate that increasing the PSS content in the blend solutions results in a systematic decrease in film thickness. Increasing the PSS content in the blend solutions also leads to a reduction in film surface roughness (as measured by atomic force microscopy), with a corresponding increase in surface hydrophobicity. Advancing contact angles (θ) range from 7° for PAH/PAA Films through to 53° for PAH/PSS Films. X-ray photoelectro...

  • nanoporous block copolymer micelle micelle Multilayer Films with dual optical properties
    Journal of the American Chemical Society, 2006
    Co-Authors: Jinkee Hong, Kookheon Char, Frank Caruso
    Abstract:

    We introduce a novel and versatile approach for preparing self-assembled nanoporous Multilayered Films with tunable optical properties. Protonated polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and anionic polystyrene-block-poly(acrylic acid) (PS-b-PAA) block copolymer micelles (BCM) were used as building blocks for the layer-by-layer assembly of BCM Multilayer Films. BCM film growth is governed by electrostatic and hydrogen-bonding interactions between the opposite BCMs. Both film porosity and film thickness are dependent upon the charge density of the micelles, with the porosity of the film controlled by the solution pH and the molecular weight (Mw) of the constituents. PS7K-b-P4VP28K/PS2K-b-PAA8K Films prepared at pH 4 (for PS7K-b-P4VP28K) and pH 6 (for PS2K-b-PAA8K) are highly nanoporous and antireflective. In contrast, PS7K-b-P4VP28K/PS2K-b-PAA8K Films assembled at pH 4/4 show a relatively dense surface morphology due to the decreased charge density of PS2K-b-PAA8K. Films formed from BCMs with i...

  • dna Multilayer Films on planar and colloidal supports sequential assembly of like charged polyelectrolytes
    Nano Letters, 2005
    Co-Authors: Angus P R Johnston, Elizabeth S Read, Frank Caruso
    Abstract:

    Multilayer Films comprising solely negatively charged polyelectrolytes were sequentially assembled based on DNA hybridization. Films prepared from alternating layers of two-block homopolymeric nucleotides (polyA20G20/polyT20C20) grew linearly with increasing layer number, as verified by quartz crystal microgravimetry, UV−vis spectrophotometry and optical microscopy. Urea treatment of the Films induced morphological changes, while exposure to low ionic strength solutions resulted in film disassembly. DNA Multilayer Films were also formed on silica particles, and DNA hollow capsules were obtained following dissolution of the template core.

  • growth of Multilayer Films of fixed and variable charge density polyelectrolytes effect of mutual charge and secondary interactions
    Macromolecules, 2003
    Co-Authors: Bjoern Schoeler, E Poptoschev, Frank Caruso
    Abstract:

    We report on the effect of mutual polyelectrolyte charge and secondary interactions on the formation of polyelectrolyte Multilayer Films of a lowly charged copolymer of acrylamide and [3-(2-methylpropionamido)propyl]trimethylammonium chloride, AM-MAPTAC 10 (10 mol % of cationic monomers), and poly(acrylic acid) (PAA). These Multilayer Films were constructed on planar substrates by the sequential adsorption of AM-MAPTAC 10 and PAA at different pH conditions. Surface plasmon resonance spectroscopy (SPRS), quartz crystal microbalance (QCM), and atomic force microscopy (AFM) were employed to follow the film formation process. While AM-MAPTAC 10 is permanently charged, the ionization of PAA is adjusted by changing the pH of the adsorption solutions. In contrast with previous studies, it is shown that Multilayer formation with one polyelectrolyte with a charge density of 10 mol % is possible. However, the Multilayer growth follows a different pattern depending on the relative charge density of PAA. At low pH, w...

Guixue Wang - One of the best experts on this subject based on the ideXlab platform.

  • biofunctionalization of titanium surface with Multilayer Films modified by heparin vegf fibronectin complex to improve endothelial cell proliferation and blood compatibility
    Journal of Biomedical Materials Research Part A, 2013
    Co-Authors: H G Wang, Tieying Yin, Qin Zhang, Q L Dong, D X Lei, Daming Sun, Guixue Wang
    Abstract:

    In-stent restenosis and subsequent thrombosis remain a significant complication following the implantation of coronary stents. Different approaches have been used in developing novel coronary stents to protect against thrombosis and minimize restenosis. In the present study, we designed a biomacromolecular layer-by-layer coating with heparin, vascular endothelial growth factor (VEGF), and fibronectin onto nickel-free titanium surface to improve blood compatibility and endothelial cell proliferation. The Multilayer assembling process was monitored by water contact angle and surface plasmon resonance, respectively. With increasing the number of layers, the deposition of polyelectrolyte as self-assembled ultrathin Multilayer Films showed linear growth of absorbance. In vitro blood compatibility results revealed that the fabricated layers prolonged activated partial thrombin time and prothrombin time, reduced platelets activation and aggregation, and reduced blood hemolysis rate. Cell adhesion and growth results showed that the assembled Multilayer Films significantly promoted cell attachment and growth, and the endothelialization property of the Multilayer Films was preferable compared with the untreated titanium disk. In conclusion, these results suggest that titanium surface modification using biofunctional Multilayer Films composed of heparin, VEGF, and fibronectin may serve as a potential approach to inhibit thrombosis and promote re-endothelialization of cardiovascular stents.

  • biofunctionalization of titanium surface with Multilayer Films modified by heparin vegf fibronectin complex to improve endothelial cell proliferation and blood compatibility
    Journal of Biomedical Materials Research Part A, 2013
    Co-Authors: H G Wang, Qin Zhang, Shuping Ge, Qinglei Dong, Guixue Wang
    Abstract:

    In-stent restenosis and subsequent thrombosis remain a significant complication following the implantation of coronary stents. Different approaches have been used in developing novel coronary stents to protect against thrombosis and minimize restenosis. In the present study, we designed a biomacromolecular layer-by-layer coating with heparin, vascular endothelial growth factor (VEGF), and fibronectin onto nickel-free titanium surface to improve blood compatibility and endothelial cell proliferation. The Multilayer assembling process was monitored by water contact angle and surface plasmon resonance, respectively. With increasing the number of layers, the deposition of polyelectrolyte as self-assembled ultrathin Multilayer Films showed linear growth of absorbance. In vitro blood compatibility results revealed that the fabricated layers prolonged activated partial thrombin time and prothrombin time, reduced platelets activation and aggregation, and reduced blood hemolysis rate. Cell adhesion and growth results showed that the assembled Multilayer Films significantly promoted cell attachment and growth, and the endothelialization property of the Multilayer Films was preferable compared with the untreated titanium disk. In conclusion, these results suggest that titanium surface modification using biofunctional Multilayer Films composed of heparin, VEGF, and fibronectin may serve as a potential approach to inhibit thrombosis and promote re-endothelialization of cardiovascular stents. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.