| Background:Since the 1970s,titanium implants have been increasingly used in clinical treatments.Compared with traditional materials,titanium implants have lower density,lower elastic modulus,higher strength and better biocompatibility as well as better corrosion resistance.However,titanium is an inert metal,its osteoinductive and osseointegration properties cannot achieve satisfactory results,so it needs to be modified.At present,the main clinical practice is to perform sandblasting and acid etching(SLA)on titanium.Sandblasting and acid etching technology can increase the roughness,contact area and contact method of the titanium surface.In recent years,many studies have adopted different treatment processes to improve the biological,chemical properties and osteogenesis of titanium,including ion implantation,micro-arc oxidation,etc.,but these methods have various shortcomings and it is necessary to find a new method.The phosphate chemical conversion method refers to the process of contacting the metal surface with an acidic solution containing phosphate,then forming a stable and insoluble inorganic compound coating through a chemical and electrochemical process.The preparation technology of phosphate chemical conversion method is simple and can be doped with biological functional elements.The coating has the characteristics of promising corrosion resistance and wear resistance.Strontium(Sr)and zinc(Zn)are both essential trace elements for the human body.They play an important role in many biological processes and can promote the differentiation of osteoblasts and bone growth.Purpose:In this study,the phosphate chemical conversion method was used to prepare titanium sheets with different micro-nano structure characteristics of strontium zinc phosphate chemical conversion coatings,and to conduct a comparative study on the differentiation of osteoblasts.Method:1.The surface of titanium was treated with phosphate chemical conversion method to prepare different micro-nano structure of titanium sheets(Sr-Zn-P-a,Sr-Zn-P-b,Sr-Zn-P-c,Sr-Zn-P-d),and a smooth titanium sheet was as the control group.Through scanning electron microscopy,fourier infrared absorption spectroscopy,X-ray energy spectrometer,laser confocal microscope and other methods,the crystal morphology,phase composition and physical and chemical properties of the different titanium coatings were tested,observed and analyzed.2.Through the CCK-8 experiment,fluorescence staining and scanning electron microscopy to detect each group of titanium plates,we observed the proliferation and adhesion of MC3T3-E1 cells on different micro-nano-structured strontium zinc phosphate coatings.3.Through alkaline phosphatase(ALP)experiment and alizarin red(ARS)experiment and detection the expression of osteogenic related genes(ALP,Runx2,COL-1),we evaluated the osteogenic differentiation of MC3T3-E1 cells on different micro-nano structure strontium zinc phosphate coatings.Results:1.SEM showed that from the Sr-Zn-P-a group to the Sr-Zn-P-d group,coatings are complete and dense,and the microscopic and crystal morphology of coatings changed regularly,gradually from irregular granular crystals to regular morphology.Finally,a stable cubic block crystal was formed.Elemental composition analysis showed that the Ti element content of Sr-Zn-P-a to Sr-Zn-P-c group gradually decreases,while the Sr-Zn-P-d group did not contain Ti element.The coating thickness of Sr-Zn-P-c group and Sr-Zn-P-d group had no significant difference,but they were greatly higher than Sr-Zn-P-a group and Sr-Zn-P-b group.From Sr-Zn-P-a group to Sr-Zn-P-d group,sample wettability,roughness and the corrosion resistance was constantly improved.2.Vitro experiments have proved that the strontium zinc phosphate conversion coatings had good biocompatibility.MC3T3-E1 cells could adhere,grow,proliferate and differentiate on the membrane surface as well as promote the expression of osteogenic related genes(ALP,Runx2,COL-1).The Sr-Zn-P-d coating significantly promoted the osteogenic differentiation of MC3T3-E1 cells compared with other groups.Conclusions:In this study,the strontium zinc phosphate conversion coating which is prepared by the phosphate chemical conversion method improved the material and bone formation properties of titanium.Through comparative studies,we could find that in the four groups of different micro-nano structured zinc strontium phosphate coatings,Sr-Zn-P-d coating has a more stable and regular crystal morphology,better wetting performance,higher corrosion resistance,and can more effectively promote the proliferation and differentiation of osteoblasts.It provides important experimental basis and theory for the surface modification of titanium implants and its further clinical application. |
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