The influence of different pH values between assembly and application environment on the surface properties of layer-by-layer assembled heparin and chitosan multilayer films was investigated.The high adsorption amount of cationic dye and high wettability on the chitosan terminated multilayer films at high environment pH may indicate the excess of free sulfate group existed on the chitosan surface.Since the ionization degree of chitosan decreased with increasing of pH,the multilayer films assembled at low pH will lead to some excess free unpaired sulfate group in higher pH application environment,which paired with ionized amino group under prepared conditions.The blood-compatibility tests performed with these films clearly demonstrated that the good anticoagulant activity of low pH assembled heparin/chitosan even on the chitosan-terminated surface.Such an easy and controlled processing by the difference of pH values between assembly and application environment may have a good potential for fabrication of biomedical device coating.
A water soluble hydroxy-capped comb-like poly(ethylene glycol)(CPEG) was prepared via atom transfer radical polymerization(ATRP).A stable CPEG coating was obtained via dip-coating followed by curing at 70℃ for 48 h.The CPEG-modified surface was proved to be stable in both aqueous environment and ambient according to contact angle behavior and weight decrement testing.The coating forming mechanism was investigated through FTIR,the spectra data demonstrated the stability of CPEG coating derived from its hydrogen bond of inter-molecules and intra-molecules.Platelet experiment showed CPEG modified surface reacted extremely weakly with platelet and showed excellent thrombus resistance than that of both on the pure PET surface and PET surface modified with linear PEG.The model drug RD6G was applied to fabricate a drug-buried CPEG coating surface.The drug-releasing curve demonstrated the stability of the CPEG coating and the controlled-release behavior of RD6G.The unique property of CPEG coating surface provided the potential application in the immobilization and release of aqueous drug,including protein and peptide.
The synthesis of norvancomycin (NVan)-capped silver nanoparticles (Ag@NVan) and their notable in vitro antibacterial activities against E. coli, a Gram-negative bacterial strain (GNB), are reported here. Mercaptoacetic acid-stabilized spherical silver nanoparticles with a diameter of 16±4 nm are prepared by a simple chemical reaction. The formation process of the silver nanoparticles is investigated by UV-visible (UV-vis) spectroscopy and transmission electron microscopy (TEM). NVan is then grafted to the terminal carboxyl of the mercaptoacetic acid in the presence of N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDAC). The TEM images of single bacteria treated with Ag@NVan show that plenty of Ag@NVan aggregate in the cell wall of E. coli. A possible antibacterial mechanism is proposed that silver nanoparticles may help destroy the stability of the outer membrane of E. coli, which makes NVan easier to bind to the nether part of the peptidoglycan structure. The antibacterial activities of silver nanoparticles on their own, together with the rigid polyvalent interaction between Ag@NVan and cell wall, enables Ag@NVan to be an effective inhibitor of GNB. This kind of bionanocomposites might be used as novel bactericidal materials and we also provide an effective synthesis method for preparing functional bioconjugated nanoparticles here.
Novel amphiphilic polymers,cholesterol-end-capped poly(2-methacryloyloxyethyl phosphorylcholine)(CMPC) was specially designed as the drug delivery systems.Cytotoxicity of this novel amphiphiles was not observed as indicated by cell culture.Anti-cancer drug adriamycin(ADR) was incorporated into the micelles by oil-in-water method.The release of ADR from the nanosphere continued over 7 d.The drug-loaded micelles could effectively restrain the growth of cancer cell.These results suggest that the drug loaded nanoparticles could be a good candidate for injectable drug delivery carrier.
Biodegradable multilayer films of alternating poly- L -lysine(PLL) and deoxyribonucleic acid(DNA) layers were fabricated onto quartz substrates by the layer-by-layer(LbL) self-assembly method. UV-Visible spectra showed that PLL and DNA can successfully be adsorbed and form multilayer films via LbL. Degradation experiments were carried out with enzymes. AFM was utilized to measure the changes of thickness of multilayer films. The gradual decrease of thickness of multilayer films with the increase of degradation time was observed. In our experiments, about 85% of films was degraded in 35 h. Our study provided a novel gene delivery system using LbL method,which may be applied to gene therapy.
