The Preparation Of Polysaccharide-based Silver Nano-materials And Its Synergistic Antibacterial Research

Bacterial resistance has become a major threat to human health and safety due to the misuse of antibiotics.As a kind of antibacterial material,nano-silver is favored because of its good antibacterial performance,wide antibacterial spectrum,and does not lead to bacterial resistance.However,the inherent biotoxicity of silver nanoparticles limits their use in the antimicrobial field.Therefore,how to reduce the biological toxicity of nano-silver antibacterial materials has attracted more and more attention.As a kind of material with excellent biocompatibility,natural polysaccharides are most suitable for the preparation of low toxicity nano-silver antibacterial materials.At the same time,the use of materials with antibacterial properties in cooperation with silver nanoparticles can reduce the amount of silver nanoparticles,so as to reduce the biological toxicity of silver nanoparticles.In this paper,four kinds of nanometer silver-based synergistic antibacterial composites based on polysaccharides were designed and prepared,and their synergistic antibacterial properties and mechanisms were systematically studied,which successfully promoted the healing of bacteria-infected wounds.The details are as follows:(1)In this study,a novel antibacterial agent was developed based on chitin nanofbrous microspheres loaded with AgNPs and Fe3O4 nanoparticles(Ag-Fe3O4-NMs)for synergistic antibacterial activity and wound healing.AgFe3O4-NMs was prepared via an in situ synthetic method which showed an excellent porosity and wettability.Moreover,Ag-Fe3O4-NMs were capable of sustained release of Ag+ and catalysed the decomposition of low H2O2 concentrations to generate hydroxyl radical(.OH).The OH and Ag+ showed higher antibacterial activity and inhibited the toxicity with high dose of AgNPs and H2O2.In vitro biocompatibility results suggested that AgFe3O4-NMs have low toxicity and low hemolysis.Thus,a novel antibacterial agent with enhanced synergistic antibacterial activity was obtained by combination of Ag-Fe3O4-NMs and H2O2 at a low and biologlically safe dosage,which could facilitate fbroblast growth,accelerate epithelialization,and promote the healing rate of infected wounds.(2)A hyaluronic acid/AgNPs/gentamicin composite material(HB/Ag/g)was prepared by simple self-assembly method using hyaluronic acid as the carrier.The prepared HB/Ag/g showed the slow and controlled release performance of Ag and gentamicin in response to pH or hyaluronidase(HAase),and had the highly effective synergistic antibacterial ability.In addition,HB/Ag/g was fixed on the surface of dopamine-modified chitin hydrogel(CPH)by a simple dipping and drying process to obtain a new wound dressing named HB/Ag/g@CPH.HB/Ag/g@CPH has a strong inhibitory effect on the growth and adhesion of bacteria,and does not affect the growth of cell adhesion.Most importantly,HB/Ag/g@CPH inhibited the growth of S.aureus in rat wounds and accelerated wound healing.(3)Silver nanoparticles(CEP-AgNPs)were synthesized by using pectin(CEP)extracted from Akebia trifoliata var.australis peel as reducing agent and stabilizer.CEP-AgNPs showed sustained release of Ag+ and significant antibacterial activity.Subsequently,CEP-AgNPs was further processed into CEP-Ag antibacterial sponge.The antibacterial sponge not only has excellent water absorption and long-term water retention,but also promotes cell adhesion and proliferation.Most importantly,CEP-Ag sponges inhibit bacterial growth and provide the moist environment needed for wound healing,speeding up the healing of infected wounds.(4)CEP-Ag@AgCl/ZnO nanocomposites were synthesized by green two-step method using CEP as the carrier.After the preparation of CEP-Ag@AgCl/ZnO,there was no obvious destruction of molecular structure except the change of crystallinity.CEP-Ag@AgCl/ZnO showed the characteristics of pH response releasing Zn2+ and low metering releasing Ag+.This selective release property not only satisfies the antibacterial requirements,but also avoids the biological toxicity caused by the high dose of Ag+.Antibacterial experiments have shown that the simultaneous use of Ag and Zn can reduce the measurement of the two elements while ensuring the antibacterial performance.In addition,CEP-Ag@AgCl/ZnO also showed good photocatalytic antibacterial activity.