Surface Modification And Properties Of Porous Calcium Phosphate Bioceramics

Porous calcium phosphate ceramics are an inorganic biomaterial widely applied in the field of biomedical materials,due to their good biocompatibility,osteoconductivity and osseointegration.In this study,porous calcium phosphate ceramics with a total porosity of about 70%were prepared by combination of extrusion and porogen burnout technique;subsequently,the surfaces of the porous calcium phosphate ceramics were coated with bioactive glass?BG?and silk fibroin?SF?by dipping in the solution under a negative pressure environment.The effects of BG surface modification with low and high temperature sintering temperatures,and SF surface modification on the physicochemical properties and biological properties of porous calcium phosphate ceramics were investigated.BG has excellent bioactivity.After implantation in the human body,BG undergoes a series of reactions and forms a layer of carbonated hydroxyapatite,which promotes the bonding of the material to the implant tissue.The BG was prepared by a sol-gel method,and the porous calcium phosphate ceramics were immersed in the BG sol under different negative pressures,and the modified porous calcium phosphate ceramics were obtained after drying and subsequent sintering at 600°C.It was proved that BG was not only absorbed on the surface of macropores,but also penetrated into the internal micropores of the ceramics under the negative pressure;after low-temperature sintering,the BG modified porous calcium phosphate ceramics had little change in porosity,and their compressive strength decreased with increasing negative pressure.BG modification with low temperature sintering improved the mineralization ability of porous calcium phosphate ceramics.Modification with an appropriate negative pressure?0.05 MPa?improved the osteogenic differentiation ability of porous calcium phosphate ceramics.Low-temperature sintering of BG surface-modified porous calcium phosphate ceramics released a large amount of Ca²⁺and Si⁴⁺in the early stage of degradation,resulting in excessively high local pH of the body fluid.In order to reduce the degradation rate of BG and fully exert the bone-promoting ability of Si in BG,the porous calcium phosphate ceramics were immersed in the BG sol under different negative pressures,and then dried,and the modified porous calcium phosphate ceramics were obtained by sintering at 1200°C.It was proved that BG began to devitrify at around 948°C.After surface modification,BG reacted with calcium phosphate at high temperature and formed a new phase of Ca₅?PO₄?₂SiO₄.After modification,greater negative pressure showed smaller effect on the porosity of the porous calcium ceramics,but almost no effect on the compressive strength.When coculturing with mouse bone mesenchymal stem cells?mBMSCs?,the modified porous calcium ceramics continuously released Si.The modified porous ceramics sintered at high temperature promoted the expression of ALP activity and osteogenic differentiation of mBMSCs.The modified porous ceramics treated with different negative pressures differed in affecting the in vitro osteogenic performances.Zn²⁺has the ability to promote bone formation,and SF is capable of improving osteogenesis and angiogenesis.The porous calcium phosphate ceramics were modified by Zn²⁺doping in conjunction with SF dipping under a negative pressure of-0.05 MPa.After surface modification,the total porosity of porous calcium phosphate ceramics decreased and the open porosity did not change,and the compressive strength increased by nearly three times.The SF layer on porous calcium phosphate ceramics reduced the proliferation rate of mBMSCs,but Zn²⁺doping and SF surface modification synergistically promoted the osteogenic properties of porous calcium phosphate ceramics.Human umbilical vein endothelial cells?HUVECs?were cultured using real-time extracts of modified porous calcium phosphate ceramics.The results showed that SF surface modification effectively increased the proliferation and in vitro angiogenesis of HUVECs.