Synthesis And Properties Of Silicon-calcium Phosphate Microspheres

Traditional calcium phosphate based materials such as hydroxyapatite（HA）and tricalcium phosphate（TCP）are similar to the inorganic components in natural bone and have good osteoinductivity,biocompatibility and degradability,which have been widely used in bone repair,drug delivery and other biological fields.However,the clinical results revealed it had insufficient bioactivity and undesirable degradability.As a trace element in the human body,silicon promotes osteogenic differentiation and new bone mineralization.In addition,microsphere materials with nano-micro structures have attracted attention in the field of drug delivery due to their large specific surface area and nano-sized pore channels.In this work,silicon-calcium phosphate microspheres were synthesized by hydrothermal synthesis.The effects of silicon sources,hydrothermal temperature,hydrothermal time,and the dosage of template agent on the physicochemical properties,degradation and drug release behavior of the obtained silicon-calcium phosphate microspheres.The main results indicate that:（1）Silicon-calcium phosphate microspheres were successfully synthesized using TEOS,Ca Cl₂,（NH₄）₂HPO₄as the sources of silicon,calcium and phosphorus and EDTA-2Na as the template agent by hydrothermal synthesis at 100℃/12 h.The silicon content of the microspheres was 0.44 at.%,which had high sphericity,homogeneous size（about 15μm）,good dispersion and apatite crystal structure.（2）The effects of hydrothermal temperature and hydrothermal time on the synthesis of silicon-calcium phosphate microspheres were investigated.The results showed that the size of microspheres decreased with the increase of the hydrothermal temperature,and the structure of microspheres transformed from dense to loose.The effect of hydrothermal time on the morphology of microspheres was not significant.The optimum preparation conditions were 100℃/12 h.（3）The addition of template agent EDTA-2Na was beneficial to the formation of microsphere morphology.With the increasing dosage of EDTA-2Na,the size of microspheres gradually decreased,the surface sheet structure changed from long sheet to short sheet,the structure changed from loose to dense,and the specific surface area gradually became larger but decreased in pore size.When the dosage of EDTA-2Na was higher than 0.05 g,the trend of influence on the morphology of microspheres became weaker.（4）The degree of degradation and drug loading/release behavior of silicon-calcium phosphate microspheres varied due to the different surface morphology.Microspheres with larger specific surface area showed higher degradation and higher drug loading capacity.However,the drug release showed an opposite trend,and the microspheres could achieve a slow and sustained release behavior for both model drugs.（5）Under the same preparation conditions,the doping of silicon had a modulating effect on the morphology of microspheres.Compared with Ca P microspheres,silicon-calcium phosphate microspheres were smaller in size（around15μm,Ca P microspheres around 30μm）and consisted of short sheet with a dense structure,larger in specific surface area and have better degradability and higher drug loading capacity.