Pure Zinc Oral Barrier Membrane With Different Surface Roughness Regulates Degradation Behavior And Biological Adaptation In Vitro Study

Background and ObjectiveGuided bone regeneration(GBR)is an effective therapy to solve the deficiency of peri-implant bone tissue.The GBR barrier membrane establishes a physical barrier space for new bone formation to prevent the growth of surrounding epithelial cells and connective tissue cells.Currently,GBR barrier membrane materials commonly used in clinical practice cannot fully meet the ideal requirements of barrier membrane in terms of mechanical properties,degradation properties,biological activity and clinical operability.Biodegradable zinc-based metals have a suitable degradation rate and excellent biocompatibility,showing great potential for clinical transformation in domestic and foreign studies.After the barrier membrane is implanted in vivo,the immune system is activated and generates an immune microenvironment around the implanted material.As one of the first cells to respond to the immune response,the surface phenotype of macrophages(M1 pro-inflammatory&M2 anti-inflammatory)greatly affects the process of bone integration and bone regeneration around the implant material.Relevant studies have shown that appropriate zinc ion concentration can effectively promote macrophages to polarize into M2 phenotype and secrete related cytokines to promote bone tissue repair and regeneration.At the same time,the degradation products of zinc-based metal soft tissue surface during the degradation process can inhibit the metabolism of bacteria.The degradability of zinc-based metals causes them to be in an unstable state in the degradation process,and the initial surface roughness may affect the degradation behavior and bioactivity of metal materials.At present,the relationship between surface roughness and degradation behavior of zinc-based metal materials,and the effect of degradation behavior on cytocompatibility,immune response and antibacterial properties have not been studied.Starting from the clinical application of GBR barrier film,this study aims to explore the degradation behavior of degradable pure zinc metals with different surface roughness in a simulated oral environment and its mediated initial biological response.Methods1.Pure zinc metal with different surface roughness was prepared,and the morphologic characteristics of pure zinc surface were detected by scanning electron microscope and white light interference 3D profilometer.2.Artificial saliva was used to simulate the degradation behavior of pure zinc metal in oral saliva environment.The corrosion morphology was observed by scanning electron microscopy,and the degradation performance of pure zinc metal was evaluated by potential polarization curve detection and weight loss.The antibacterial properties of pure zinc with different surface roughness were evaluated by live/dead bacteria fluorescent staining and absorbance value.3.Simulated body fluids were prepared to simulate the degradation behavior of pure zinc metal in oral tissue fluid environment.The corrosion morphology was observed by scanning electron microscopy,and the degradation performance of pure zinc metal was evaluated by potential polarization curve detection and weight loss.Cell Counting Kit-8(CCK-8),Lactate dehydrogenase(LDH)test kit and live/dead cell fluorescence staining were used to analyze the cytocompatibility of the pure zinc sample extracts.The expression of macrophage M1/M2 surface markers was analyzed by flow cytometry.Result1.Three representative roughness scales were formed on the surface of pure zinc after mechanical grinding,namely Micron(Sa>1.0μm),Submicron(Sa:0.51.0μm)and Nano(Sa<0.1μm).Peaks and valleys could be observed on the surface of Micron and Submicron groups.Nano surface was smooth and uniform.2.The pure zinc samples immersed in artificial saliva all showed patchy corrosion,and with the increase of roughness,the corrosion pits were deeper and wider.In vitro antibacterial property showed that pure zinc with Micron and Submicron surface had stronger antibacterial property within 6 h.3.The pure zinc samples immersed in simulated body fluids showed pitting corrosion on the rough surface,while the Nano group showed extensive corrosion,and the degradation rate of Nano group decreased significantly.The extracts of Micron,Submicron and Nano groups showed good biocompatibility to different cell lines,and no significant difference in cytotoxicity was observed between the groups.When macrophages were co-cultured with pure zinc on Nano surface,macrophages were promoted to polarize into pro-inflammatory phenotypes.Conclusion1.The pure zinc metals with different surface roughness was successfully prepared by mechanical grinding treatment.2.Simulating the environment of different body fluids in the oral,deep and extensive corrosion pits appeared on the rough surface of pure zinc samples,and patchy corrosion was formed on the smooth surface.In the simulated humoral environment,the degradation rate of smooth surface decreased significantly.3.Pure zinc metal showed certain antibacterial properties,surface with micron and submicron scale has stronger antibacterial properties in 6 h.4.The surface roughness of pure zinc metal had no significant difference in cytotoxicity,but the smooth surface of pure zinc metal promoted the M1 phenotype of macrophages.