Preparation And Antimicrobial Activity Of Polyhydroxyalkanoate Block Copolymer Based Antibacterial Complexes

Biomaterial-related infection has become a major problem in the modern medicine because the incidence of the infection has been increasing with the wide use of biomaterials year by year.The infection is uncontrollable once the adhered bacterial proliferate and form a biofilm.The sole antibacterial,bactericidal surfaces,or bacterial remove surfaces can effectively prevent infections caused by short-term bacterial adhesion,but fail in long term adhesion and proliferation of bacterial.Dual-or multi-functional antibacterial surfaces is the key to the development of antimicrobial materials.Poly[?3-hydroxybutyrate?-co-?3-hydroxyvalerate?]?PHBV?are a family of thermoplastic biopolyesters produced by microorganisms as energy and carbon storage in cells.They possess good biocompatibility and biodegradability,but the characteristics of strong hydrophobicity,brittleness,and biological inertia limit their wide potential application in the biomedical field greatly.In this work,biocompatible PEG was chosen as a hydrophilic segment to synthesize PEG-PHBV-PEG amphiphilic triblock copolymer.A bacteriostatic-bactericidal dual-functional nanocompositesl was prepared via introducing the antibacterial nanoparticles into the block compolymer.The main contents include:Firstly,PEG-PHBV-PEG amphiphilic triblock copolymers were designed and synthesized.The results showed that the molecular weight of PHBV-diol being prepared via alcoholysis reaction decreased with the increase of the reaction time.The molecular weight distribution was narrow with a polydispersity coefficient between 1.1¹.6.The molecular weight of PEG-PHBV-PEG block copolymer being synthesized by the chain extension reaction increased with the increasing molecular weights of PHBV-diol and PEG segments,and the feed ratio of PEG to PHBV-diol.The crystallization of PHBV and PEG segments in the copolymers affected each other and there may be a eutectic structure dominated by one phase.The initial thermal-degradation temperature of PHBV segment in the triblock copolymer was higher than that of PHBV.PEG-PHBV-PEG block copolymer self-assembled,into rod-shape micelles at the concentration of 0.25 mg/m L,and the critical micelle concentration was approximately 1.05×10^-3 g/L in aqueous solution.Secondly,the antibacterial nanocomposites were prepared by mixing PEG-PHBV-PEG amphiphilic triblock copolymer with ZnO NPs or Ag-ZnO NPs?5 wt%,10 wt%?via a solvent-precipitation method.ZnO NPs and Ag-ZnO NPs were proven to affect the growth of PHBV crystals,and reduce the thermal degradation temperature of PHBV segment significantly.Rod-shape Ag-Zn O NPs was uniformly dispersed in the pores of the surface of PEG-PHBV-PEG.The nanocomposites exhibited various micelles while using selectived solvents to allow self-assembly.The block copolymer-Ag-ZnO and block copolymer-ZnO nanocomposites at a concentration of 50 mg/L did not influence cell viability and proliferation of ATDC5 significantly,but possesed good antibacterial activity against both E.coli and S.aureus with a sterilization rate upto 92%.Moreover,the nanocomposites were shown to be more sensitive to E.coli.Finally,graphene oxide?GO?being prepared by the modified Hummers method was modified with isocyanate,and then reacted with PEG-PHBV-PEG block copolymer to synthesize the block copolymer grafted graphene.The results confirmed that PEG-PHBV-PEG block copolymer was grafted on and between the GO sheets,leading to an increase in interlamellar spacing of GO sheets.The ordered instructure of GO disturbed in some extent,but the block copolymer was amorphous.