Preparation And Properties Of Spherical Calcium Sulphate-based Composites For Bone Repair

Bioceramic materials are often used to repair tissue defects,replace lost or failed tissues,parts or all of organs due to their excellent biocompatibility,degradability,bone conductivity,and potential osteoinductive properties.The calcium sulfate,calcium phosphate materials are commonly used bone repair materials.Calcium sulfate/strontium-doped(3-TCP composite materials have more advantages than single materials in terms of bioactivity,degradability and so on,and have been more widely used.Among them,the stirring spray drying method was applied to prepare the calcium sulfate/strontium doped ?-TCP composite spherical materials.At the same time,in order to meet the requirements of bone tissue engineering for porous biological materials,theobtained composite sphericalmaterialswere combined with silica,gelatin,sodium carboxymethyl cellulose,respectively,to getporous?SiO₂,gelatin and sodium carboxymethyl cellulose?/composite spheral scaffold materials.The composition,structure and the properties of the porous scaffolds were investigated and the results were shown as following.The strontium-doped(3-tricalcium phosphate powder was prepared by precipitation method using the raw materials calcium of carbonate?CaCO₃?,strontium nitrate?Sr?NO₃?₂?and phosphoric acid?H3PO₄?.And the main phase of the powder is ?-TCP?acccounts for 86.7wt%?;The grain size of the powder is between 10?m-100?m,the grain size of the powder after ball milling is 0.5?m?10?m.and the amount of strontium has little effect on the size of the powder.At the same time,strontium doped with ?-TCP formed a replacement solid solution,but the amount of strontiumhas little effect on the crystal structure.The cytotoxicity tests showed the The strontium-doped ?-tricalcium phosphate powder had no cytotoxic effect.The optimum technological scheme for the preparation of composite spherical pellets was selected by orthogonal design,that is,when the CaSO₄ powder was added to 2.5g,the concentration of the binderwas 10wt%,?-TCP concentration was 10wt%andthe content of strontium in?-TCP reached 30wt%,respectively,it can make the pelleting rate to 75%,andthe pellets size isbetween 0.95 mm and 1.35mm.The cytotoxicity tests showed the composite spherical pellets had no cytotoxic effect.?SiO₂,gelatin and sodium carboxymethyl celllulose?/composite spherical scaffoldwere prepared by stirring spray drying method using silica gel,gelatin and sodium carboxymethyl cellulose.The results show that the porosity of the three kinds of composite scaffolds is almost the same,which is about 60%.The three kinds of composite scaffolds have irregular pore structure with pore size between 0.2 and 1.0mm,The pore size of SiO₂/composite spherical scaffold is mainly distributed in 100-300?m.The pore size of gelatin/composite spherical scaffold was mainly distributed in the range of 100-500?m.The pore size of the sodium carboxymethyl cellulose/composite spherical scaffold was mainly distributed in the range of 50-300?m.The average compressive strength of gelatin/composite spherical scaffold was about 6.3Mpa.The average resistance of carboxymethyl cellulose/composite spherical scaffold was about 0.7Mpa.The in vitro biodegradation experiments showed that the three kinds of stents immersed in the process of SBF are apatite deposition,indicating that they have a good bioactivity.The degradation period of gelatin/composite pellet scaffold was the longest and was not completely degraded within 80 days.The degradation period of carboxymethyl cellulose/composite pellet was about 40 days,SiO₂/composite spherical scaffolds were completely degraded withinabout 80 days.The cytotoxicity tests showed thethree kinds of composite scaffolds had no cytotoxic effect.