Osteogenic Mechanism And Osteogenesis Of Silver Nanoparticle/Poly(DL-lactic-co-glycolic Acid)-coated Metal Materials

Osteogenesis effect is the function of stimulating osteoprogenitor cells to differentiate into osteoblasts,and then forming new bone tissue.Bone morphogenetic protein 2 is widely researched osteoinductive protein in biomaterials recently.Based on the disadvantages,scientists are still looking for already existed/new materials or new strategies to improve osteogenesis and for clinic.Electrical force has been found to exert some biological functions for bone osteogenesis and bone regeneration which has inspired the investigation of scientists.However,using electrical force as one property in biomaterials has been barely reported.In this study,we fabricated nanosilver/PLGA coated stainless steel implant,investigated the physicochemical properties for the potential osteogenic mechanism.Also,in vitro cell culture experiments and in vivo animal experiments were used for evaluating the bioactivity of the materials.First,nanosilver was wrapped by PLGA with different proportion(0%,10%or 20%).Then,electro-spraying method was used to prepare nanosilver/PLGA coated metal materials to get SNPSA or SNPT.Scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),atomic force microscopy(AFM)and Kelvin probe microscopy(KPFM)were used for investigating the physicochemical properties of the six groups of materials.MC3T3-EI cells were cultured on the materials for 6,9 or 21 days,antibacterial and osteogenic differentiation properties were investigated based on the contamination probability,ALP staining,etc.A femoral intramedullary rod(FIR)model in Spargue-Dawley(SD)rats was chosen.After 8 weeks from the surgery,rats were sacrificed for MicroCT scanning and histological section for studying the osteogenesis in vivo.In the study,although SNPSA and SNPT materials had similar surface morphology,the hygrophlic-hydrophobic property,chemical state and surface potential revealed that higher surface oxidation state and surface potential on the SNPSA materials than the SNPT materials.In vitro and in vivo experiments had demonstrated that SNPSA materials could improve osteogenic differentiation and osteogenesis.The result also demonstrated that nanosilver had antibacterial property.Our current study not only distinguished the physicochemical properties and bioactivity of SNPSA and SNPT materials,but also firstly revealed the petntial mechanism of the SNPSA bone forming activity that SNPSA materials could provide higher micro-galvanic effect to stimulate calcium and phosphate ions deposited around the implants and thus promoting bone formation.Our findings indicated the possibilities of biomaterials designed to achieve osteogenesis by topographical and electrochemical properties.Based on the coating method,SNPSA obtained a novel function to constitute micro-galvanic cells,which open the door of investigating important features of biomaterials to obtain a specific biological effect in clnic applications.