Preparation And Application Of Polymeric Multifunctional Antimicrobial Hydrogel

Bacterial infection is one of the most common diseases,which badly affects our living quality,and still remains a serious threat to human health in clinics.The wound infection caused by surgeries would result in the delayed wound healing,and could casue sepsis in severe cases,and might even be a threat to life.While the infection caused by implanted medical devices would lead to the implantation failure,and could possibly have several complications.Since antimicrobial hydrogels have been widely investigated and used as wound dressings,medical device coatings and so on,they are regarded as one of the most important novel antimicrobial materials.Whereas,the reported antimicrobial hydrogels usually do not combine the antimicrobial potency,good thixotropic property,excellent biocompatibility,and on-demand release of antibacterial agents,thus their clinical application has been limited.The bactericidal effect of silver nanoparticles is influenced by the particle size-the smaller the nanoparticle,the greater the antibacterial activity.However,small-sized silver nanoparticles are not stable,which are easily oxidized to silver ions or aggregate into large particles,and usually require frequent application.As a result,silver nanoparticles are usually used in combination with cationic polymers to improve its stability and antibacterial activity.However,the reported hydrogels with combined silver nanoparticles and cationic polymers ususally release the antimicrobial agents through uncontrollable diffusion,thus reducing their biocompatibility and long-term antibacterial ability and hindering their application.Therefore,it is quite desirable to design an on-demand release hydrogel.In this dissertation,we design a novel cationic polymer/silver nanocomposite hydrogel with on-demand release and potent antibacterial property.The hydrogel is formed via a Schiff base linkage between oxidized polysaccharides and cationic dendrimers encapsulated with silver nanoparticles.The Schiff base is acid-sensitive,which allows the development of pH-responsive antibacterial materials.The cationic dendrimer is used as a template to synthesize 3-4 nm Ag particles with good stability and bactericidal activity,and it also exhibits antimicrobial effect itself.The acid-labile property of the Schiff base enables the antibacterial components(cationic dendrimer and silver species)to release from the hydrogel matrix in response to acidity generated by growing bacteria.In vitro antibacterial experiment proves its antibacterial ability against both Gram-negative bacteria(E.coli and P.aeruginosa)and Gram-positive bacteria(S.epidermidis and S.aureus).Meanwhile the gel could be applied as an antimicrobial coating and exhibits potent efficacy in long-term study.In vivo infection study shows that the bactericidal activity of the hydrogel is superior to antibacterial gels containing cationic polymers only or commercial Ag hydrogels at the same Ag concentration.Moreover,good thixotropic property and excellent biocompatibility of the hydrogel expects its potential application as a surgical wound dressing or a medical device coating.To summarize,this dissertation provides a facile and promising strategy to develop smart hydrogels to treat local bacterial infections.We use the acid microenvironment generated by growing bacteria to promote the degradation of hydrogel and to accelerate the release of silver ions from silver nanoparticles.Therefore,the on-demand controlled release of antimicrobial components is allowed,and the potent antimicrobial efficacy is enabled by the synergistic effect of silver nanoparticle and cationic polymer.The multifunctional hydrogel is supposed to solve the multi-challenges in antibacterial process and should to be applicable in future.