| Chitosan is a natural polymer material with good antibacterial properties,biocompatibility and film-forming ability,and the chitosan membrane is degradable,which is one of the most promising antibacterial materials.However,its solubility is very weak,and it can't dissolve in neutral solutions,and the biological environment is generally neutral or weakly alkaline,which greatly limits the application of chitosan in the biological environment.In addition,chitosan material is difficult to meet the clinically complex antibacterial requirements.Therefore,it is usually necessary to combine chitosan with other antibacterial agents to increase its antibacterial properties.Among many antibacterial agents,nano silver has strong antibacterial properties,can inhibit the growth of most bacteria and will not produce drug resistance,and has become one of the most intensively studied and widely used antibacterial additives.However,nano silver has potential cytotoxicity which greatly limits its application in vivo.Therefore,it is necessary to develop a composite material that can be dissolved in neutral or alkaline solutions,has strong antibacterial properties and low cytotoxicity.This study intends to chemically modify chitosan with catechol,and then use modified chitosan to reduce silver nitrate in situ to produce nano-silver.We studied its application in antibacterial film and titanium implant surface coating.The specific research contents are as follows:Modified chitosan(CSCT)was prepared by grafting small molecule catechol onto chitosan molecule through Mannich reaction.Using modified chitosan as reducing agent and stabilizer,composite nano silver(CSCT-AgNPs)was prepared by one-step method.The chemical structure of CSCT was studied using nuclear magnetic resonance spectrometer and Fourier transform infrared spectrometer.The morphology and structure of CSCT-AgNPs were characterized by X-ray diffractomer and transmission electron microscope.The cytotoxicity test and inhibition zone test were employed to investigate its biocompatibility and antibacterial properties.The results show that CSCT has good water solubility,and the grafting rate of catechol is 22%;CSCT-AgNPs are nearly spherical particles,with an average particle size of about 8.05 nm,small particle size distribution and no agglomeration.When the concentration is lower than 25?g/m L,it is grade 1 for EA.Hy926 cytotoxicity,and CSCT-AgNPs have good antibacterial effects against E.coli and S.aureus.Antibacterial composite films were prepared by blending CSCT-AgNPs and gelatin(G)into CSCT-based films,The morphology and structure of the composite films were characterized by fourier transform infrared spectrometer,scanning electron microscope and ultraviolet spectrophotometer,etc.The mechanical properties of the composite film were tested by texture analyzer,and the antibacterial properties were explored by the inhibition zone test.The results showed that when the addition amount of CSCT-AgNPs was 0.5 g,the tensile strength reached 25.38±0.98 MPa,the elongation at break was 25.32±0.35%,the water vapor transmission coefficient was 0.20±0.07 g·mm·m-2h-1k Pa-1 and water solubility was 41.84%,the inhibition rates against E.coli and S.aureus were69%and 64%,respectively,film antibacterial was contact antibacterial.An antibacterial coating containing CSCT-AgNPs was constructed on the surface of titanium by electrodeposition and spin coating.The microscopic morphology of the coating was observed by SEM,the corrosion resistance and adhesion of the coating were tested with electrochemical and 3M tape,respectively,and the antibacterial ability of the coating was tested by the plate colony counting method.The results show that the dense surface of the coating is smooth without delamination,and the thickness of the coating is 23?m.The adhesion between the coating and the titanium substrate can be rated as 5B level,the corrosion potential of the coating is mentioned as-0.6053 V,the relative antibacterial rate of the coating to E.coli and S.aureus is 99%and 96%. |
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