Preparation, Characterization And Antibacterial Properties Of Silver/Chitosan Nanocomposites

Chitosan is a nontoxic natural polymeric material with good biocompatibility andbroad-spectrum antimicrobial properties, which is widely used in the field ofbiomaterials. However, the antibacterial properties of chitosan in neutral and alkalineconditions are weakened, thus we hope to develop chitosan-based biomaterials withboth antibacterial properties and good biocompatibility in physiological conditions.Firstly, we researched the relationship between the antibacterial properties of chitosanand its morphology, and then two kinds of silver/chitosan nanoconposites with bothantibacterial properties and good biocompatibility were prepared. The resultsprovided an experimental basis for their application in wound dressing and tissueengineering.Chitosan nanofibers (CsNF) and chitosan microfibers (CsMF) were prepared byphase separation, and chitosan hydrogels were prepared by physical cross-linkingmethod. The antibacterial properties against e.coli and s.aureus of those samples weretested by shaking flask method. The results showed that the antibacterial properties ofchitosan were affected by its structure and morphology, and CsNF possessed the bestantibacterial properties.Silver nanoparticles were prepared by in situ reducing silver nitrate with ascorbicacid in chitosan hydrogels. The existence of nano-silver was confirmed by UV-visiblespectra, XRD diffraction patterns and TEM images. High resolution TEM images anddiffraction patterns proved the crystalline state of nano-silver was not uniform.Particle size analysis showed that the mean size of silver nanoparticles was about30nm. Cytotoxicity and antibacterial experiments showed that the anti-bacterialproperties of chitosan hydrogels could be improved by introduction of nano-silver,with the increase of nano-silver content, the antibacterial properties increased, but cellcompatibility decreased.0.1wt%Ag/Cs nano-composite hydrogels maintained both antibacterial properties and good cell compatibility.Silver nanoparticles were also in situ prepared by UV irradiation in chitosannanofibers. TEM images confirmed the existence of nano-silver. High resolution TEMimages and diffraction patterns proved the crystalline state of nano-silver was notuniform. Particle size analysis showed that the mean size of silver nanoparticles wasabout22nm. SEM images showed Ag/Cs composite nanofibers had the samemorphology with CsNF. Cytotoxicity experiment showed that the introduction ofnano-silver would reduce the cell compatibility of CsNF. Shaking flask methodexperiment showed that nano-silver can improve the anti-bacterial properties of CsNF.Overall, antibacterial efficiency of0.1wt%Ag/Cs composite nano-fibers against s.aureus and e. coli increased about16%and27.7%, while cell compatibilitymaintained.