Functionalized Modification Of Natural Polysaccharides For Antimicrobial Study

At present,the incidence rate of hospital acquired infection is increasing year by year,and most of nosocomial infections are related to implantable or indwelling catheters.Formation of biofilms is an important reason for the high incidence of catheter-related infections.Antibiotic treatment is the most important treatment for bacterial infection.However,when bacteria form biofilms on the surface of the catheter,their tolerance to antibiotics is greatly enhanced,which reduces the efficacy of antibiotics.Therefore,it is very important to make functional coatings on the surface catheters,which could kill bacterial and inhibit the formation of biofilms.Natural polysaccharides are ubiquitous among plants,animals and microorganisms,which can regulate a variety of biological functions.Therefore,polysaccharides and their derivatives as a potential antimicrobial agent have attached much attention.In Chapter 2 of this thesis,taking advantage of the biocompatibility and easy chemical modification of natural polysaccharides,based on layer-by-layer strategy,we designed a bacteria-responsive polymer coating for antibacterial and antibiofilm properties on polyvinyl chloride(PVC)surface,using oxidized dextran(ODex),polymyxin B(PMB)and D-Tyrosine(D-Tyr).As biofilmdispersal signal molecules,the introduction of D-Tyr can make the coating antibiofilm.PMB is a kind of polypeptide antibiotic,which can provide antibacterial property for the coating.At the same time,its polyamino structure can react with ODex to fabricate polymer coating with multilayer structure by Schiff base reaction.When bacteria colonize the surface,the metabolic activities of bacteria will lead to the decrease of local pH,which will hydrolyze the Schiff base bond in the coating and release the bactericidal(PMB)and biofilm-dispersal signal molecules(D-Tyr).For mild infections,PMB can directly kill the bacteria in the microenvironment;when severe infections occur,PMB and D-Tyr can inhibit the formation of biofilm.In Chapter 3 of this thesis,we explored the application of functionalized modification of natural polysaccharides for anti marine microorganisms.Based on layer-by-layer strategy,we designed an antialgae coating on glass surface using heparin,quaternized polyethyleneimine(QPEI)and cupric nitrate(Cu(NO3)2).Heparin is a negatively charged natural polysaccharide containing abundant carboxyl and sulfonic groups,which could react with QPEI to fabricate a functional coating with multilayer structure by amidation reaction.In addition,copper(?)ions were introduced into heparin by cation exchange.When the coating is in water,the copper(?)ions were released to inhibit the growth of algae.Finally,we proved the anti-algae function of this coating by culturing the with Chlorella and Anabaena.