Preparation Of Co-delivery Hydrogel/Microgel And Its Treatment For Orthopedic Implant-related Infections

BackgroundOrthopedic implant-related infection,mainly including periprosthetic infection(PJI)and internal fixation related infection,is a kind of severe bone infection,which still maintains a high rate of relapse despite the extensive surgical debridement and local or systemic antibiotics administration.Such difficulty in the eradication of infection can be explained mainly by the biofilm occurred on the surface of implants and dead bone,and by the intracellular bacterial infection.Currently,the primary strategy to treat the bone infection is to locally apply the polymethyl methacrylate(PMMA)-antibiotic mixtures,which is however limited by the uneven and uncontrollable drug release as well as its non-biodegradable characteristic in vivo.Therefore,there is an urgent need to develop an effective local drug delivery system to disperse mature biofilms and eliminate intracellular bacteria.ObjectiveTo synthesize an injectable hydrogel/microgel co-delivery system for the programmed delivery of lysostaphin enzyme(Ls)and vancomycin(Van),and to verify the characterization,biofilm dispersion ability and synergistic antibacterial effect of the system in vivo and in vitro,and discuss its application in the treatment of implant infection.MethodsVan was encapsulated in gelatin methacryloyl(GelMA)microgel by microfluidic emulsion.Gelatin-oxidized starch hydrogel(GelS)was fabricated through Schiff base reaction,supplemented with Transglutaminase(TG)to stimulate the formation of secondary amide bonds.Van-loaded microgels and lysostaphin(Ls)were then added into the GelS to construct the GelS-based co-delivery system.The Physicochemical properties of the system were characterized,and the biocompatibility in vivo and in vitro were verified.Drug release curves and synergistic antibacterial mechanism in vitro were analyzed.In vitro,biofilm models of Staphylococcus aureus(MSSA)and methicillin-resistant Staphylococcus aureus(MRSA)were constructed on bone plates to verify the ability of co-delivery hydrogels to inhibit and disperse biofilms.The antibacterial efficacy of the co-delivery hydrogel was further tested using a rat tibia infection model.The healing of infection was dynamically observed by imaging,inflammatory cytokine levels,and pathological examinations to evaluate the therapeutic effect of co-delivery hydrogels.ResultsGelS-based hydrogel was crosslinked in situ within one minute at room temperature.In vitro and in vivo degradation experiments showed that the hydrogel maintained continuously for 28 days and had no significant toxicity on cells.The controlled release of encapsulated Ls and Van was observed for at least 7 days and 20 days,respectively.Ls and Van demonstrated the synergistic effect on bactericidal activity and biofilm dispersion against MSS A and MRSA.Animal experiments indicated that one-time injection of Van/Ls-loaded co-delivery system accelerated the disappearance of infection within 4 weeks in vivo.ConclusionGiven the synergistic effect between Van and Ls,the co-delivery hydrogel system has significant effect in solving orthopaedic implant-related infections with significantly shorter treatment time,compared to conventional local or systemic antimicrobial strategies.The co-delivery hydrogel system has a simple fabrication process and good biocompatibility,and exhibits the advantages of injectability,bactericidal,biofilm dispersion,and degradative properties all together.Hence,it has tremendous application potential in clinical treatment.