Construction And Characterization Of Antibacterial And Osteogenetic Functional Biomimetic Scaffolds

Bone defects caused by tumors,infections or other diseases are common disease in clinical.Artificial bone implant has become the main method for the treatment of bone defects due to the limited sources and a series of complications of autologous and allogeneic bone grafts.However,infection and insufficient osteogenesis-promoting ability be regarded as the two major problems of implant failure.Biomaterials that possess excellent osteogenic and antibacterial properties as well as promote in situ inflammatory cells to fight microbial infection are considered ideal orthopedic implants.Traditional therapeutics for infections are surgical debridement and antibiotics,however,abuse of antibiotics may lead to colonization of drug-resistant bacteria and other adverse effects.Therefore,it is necessary to rationally design multifunctional bone repair biomaterials with comprehensive bone treatment and regeneration functions.The immune environment plays an important role in the bone healing process and the reconstruction of large bone defects by bioactive materials without exogenous cells or growth factors remains a substantial clinical challenge.At present,the materials for treating bone defects do not have regenerative endogenous stem cells that can promote immune regulation,cell recruitment,vascularization,angiogenesis and osteogenic differentiation,and cannot completely repair large bone defects in a short period of time（three months）.Aiming at the problem of antibacterial and osteogenesis-promoting in bone reparation,in this article,antibacterial and osteogenesis-promoting effects in vitro and in vivo of three-dimensional（3D）bioprinted titanium alloy scaffolds cooperate with intelligent bioactive hydrogels were carried out.Meanwhile,functional composite scaffolds can manipulate a lower inflammatory level in situ by polarizing macrophages to M2 phenotype,resulting in superior efficacy of mature new bone regeneration.The design and preparation of functional composite scaffolds and the research on in vitro and in vivo application properties are mainly carried out as follows:In order to improve the surface biological properties of titanium alloys,copper（Cu）and zinc（Zn）as well as phosphorus（P）were co-doped into a Ti–6Al–4V alloy via micro-arc oxidation（MAO）in a special electrolyte system consists of EDTA-Cu Na₂,KOH,phytic acid,and EDTA-Zn Na₂.The copper-zinc-titanium alloy treated by micro-arc oxidation can exert antibacterial effect and excellent biocompatibility.3D printing technology improves the mechanical support of titanium alloy and promotes bone conduction properties.However,the biological inertness of titanium alloys still limits its ability to induce osteogenesis.Thus,we designed a bioactive smart polysaccharide hydrogel that can release dual cytokines composited with 3D printed titanium alloy to evaluate the physicochemical properties of this hybrid scaffold and its ability to promote osteogenic differentiation and proliferation of human bone marrow mesenchymal stem cells（h BMSCs）.Polysaccharide hydrogels provide a suitable matrix for cell adhesion,differentiation and proliferation which could mimic the dynamic mechanical property,chemical composition and interior microstructure of natural ECM.IL-4 and BMP-2 were encapsulated in the hydrogel and sustainedly delivered in vivo to polarize macrophages into M2-type for inducing local anti-inflammatory response,and accelerate the differentiation of osteoblasts,respectively.The transformation of macrophages to M2 phenotype accelerates bone regeneration.Moreover,the hydrogel showed antibacterial activity that could potentially combat the infection during scaffold implantation and bone growth.In order to solve the problems of non-degradability and uncontrollable factor release of titanium alloy scaffolds,and to simulate the role of ECM hydrogels and M2macrophage pathways in immunoregulatory osteogenesis,we further designed a biodegradable Here,synthetic fibrous glycopeptide hydrogel(GR^gel)self-assembled byβ-sheet RADA16-grafted glucomannan was designed to mimic the glycoprotein composition and the fibrillar architecture of natural extracellular matrix（ECM）,which was non-covalently composited with 3D-printed polycaprolactone/nano hydroxyapatite（PCL/n HA）scaffold for cranial bone regeneration.The glycopeptide hydrogel significantly promoted the proliferation,osteogenic differentiation of bone mesenchymal stem cells（BMSCs）,which was further augmented by GR^gel-induced macrophage M2-phonotype polarization and the effective M2 macrophage-BMSC crosstalk.The repair of critical-size skull bone defect in rat indicated a superior efficacy of PCL/n HA@GR^gel implant on bone regeneration and osseointegration,with an average bone area of 83.3%throughout the defect location at 12 weeks post treatment.Furthermore,the GR^gel increased percentage of anti-inflammatory M2macrophages and osteoblasts and high-level vascularization.Collectively,the composite scaffold developed here with macrophage polarization-mediated osteo-immunomodulation may represent a promising implant for expediting in situ bone regeneration by providing biochemical and osteoinductive cues at the injured tissue.