Research On Bioactive And Biomimetic Preparation Of Hydroxyapatite Coating On Porous Titanium Surface

In recent years,due to the increasing demand for alternative tissues,research on biomedical implant materials has received increasing attention.At present,biomaterials mainly include bioceramic materials represented by hydroxyapatite(HA)and biometal materials represented by titanium and titanium alloys.HA ceramic material has good biological activity,and it can induce the growth of bone tissue.However,its low strength,high brittleness,can not be used as load-bearing structure.Titanium and titanium alloys have good mechanical properties and are often used as bearing implants.However,the tight titanium elastic modulus does not match with the bone tissue,which may cause stress shielding and lead to implantation failure.The pore structure of porous titanium can make up for the defects in the mechanical properties,and acts as a buffer for decompression.It is also conducive to the transmission of body fluids and promotes the growth of bone tissue on the surfaces and pores of implants.However,it can only form a mechanical lock with the new bone,biological activity needs to be strengthened.In this paper,porous titanium is used as the matrix material,HA coating is prepared on the surface by biomimetic mineralization,The composite samples of Ti/HA coating were obtained.The effect on coating growth is analyzed by different process parameters of biomimetic preparation,deposition solutions and pore size of porous titanium.And the biological activity of the coating material was also studied.According to the results of experiment and test analysis,the following conclusions are obtained.(1)By comparing the morphology of HA coating on different surface pretreatment,the best pretreatment method is obtained,that is acid and alkali treatment.On this basis,the effects of two bionic deposition solutions of HA bionic and saturated calcified solution(SCS)on the growth of the coating were compared.It is found that the supersaturation of the SCS solution is higher,the nucleation free energy is low,the nucleation and growth of the HA crystal isfavorable,the growth speed of the HA crystal is fast,and the crystal size is large.In the HA solution for 7 days,the mass change ratio of the coating reaches1.73%,while the mass change ratio of the coating reaches 2.94% when it is immersed in SCS solution for 4 days.Therefore,SCS solution can shorten the deposition time of HA coating.(2)The effects of deposition temperature,p H and deposition time on the coating were analyzed by single factor experiment.The results show that the coating becomes uniform and dense as the temperature of the deposition liquid increases,but the higher the temperature,the coarser the HA crystal grains,the lower the number of crystal grains,and the looser coating layer.The pH of the deposition solution affects the type of product.When the pH is acidic,the surface deposits are mainly DCPD and HA,the p H value is increased to alkaline,the deposition product is HA coating.As the deposition time increases,the deposition amount of the surface HA coating increases,the coating becomes uniform and dense,the deposition time is too long,and the surface coating will be degraded.(3)The influence of the pore size on the growth of the coating was analyzed.The results showed that within a certain range,the pore size increased and the surface area became relatively larger.After the acid-base treatment,the surface roughness increased,and the nucleation active sites on the substrate surface increased.It is more conducive to the uniform and dense growth of the apatite coating.(4)The biological activity of the material was further studied by simulated body fluid(SBF)soaking experiments and bovine serum albumin(BSA)co-deposition experiments.Experiments show that HA/HA coating samples prepared by HA deposition and SCS solution have new HA after soaking in simulated body fluids,which proves that Ti/HA coating samples have good biological activity;Topographic analysis showed that the soaking time of SBF increased from 3 d to 14 d,and the deposition depth of the coating in the pores increased from 100 ?m to 180 ?m,indicating that prolonged soaking time was beneficial to the growth of HA in the pores.This is important for bone tissue proliferation and differentiation in the well.The addition of BSA makes heterogeneous nucleation more likely to occur,generates a large number ofnuclei,plays a role in grain refinement,and at the same time reduces the HA crystallinity,the crystal size becomes smaller.The formation of nano HA closer to the natural bone,thereby increasing the biological activity of the material,which is beneficial to the clinical application of the coating material.