Preparation Of Mg-substituted Beta-tricalcium Phosphate And The Application In Skeletal Drug Controlled Delivery System

Because of their excellent biocompatibility and osteoconductivity,calcium phosphates(CaP)are attractive as biomaterials for bone substitute and skeletal drug delivery systems,especially the resorbable and biodegradable ?-TCP biomaterials.Among various morphologies of CaP,porous and hollow structures of CaP are more advantageous for skeletal drug controlled delivery due to the large surface area and high surface activity.However,biological apatite is somehow different from the synthetic one in that the former contains other ions other than calcium and phosphate ions,such as magnesium ions.In biological conditions,magnesium ions have an impending role on the bone metabolism,the deficiency of magnesium in hard tissues may result in some skeletal diseases such as osteoporosis.Moreover,magnesium substituted beta-tricalcium phosphate(?-TCMP)is one of the native biological apatite.Therefore,the preparation of ?-TCMP porous nanoparticles is significant for their application in biomedical fields and bone engineering.The most common methods to prepare ?-TCMP are solid-state reaction at an elevated temperature and chemical precipitation following on a calcination process.Nevertheless,the calcination process causes the collapse of pre-formed nanostructures and the specific surface area decreases.Alternatively,porous and hollow inorganic structures have been spontaneously assembled by mesoscale transformation of metastable inorganic aggregates without the calcination process.The interaction between the organic molecules and the surface of inorganic particles is the main drive force to prepare special morphology of inorganic particles.In this paper,we report the fabrication of ?-TCMP porous nanospheres by the self-assembly and transformation of metastable precursor involving EDTA ions.Generally,?-TCP can not form in aqueous solution as the involvement of proton and hydroxyl ions,however,the substitution of magnesium can stabilize ?-TCP in the mineralization process.Moreover,it has been demonstrated that the guiding effect of the EDTA ions is crucial for the formation of ?-TCMP porous nanospheres.Importantly,the particle size and special surface area of the obtained porous nanospheres were tuned by a simple approach.