Study On The Preparation And Properties Of Hydroxyapatite/Sodium Alginate/Chitosan Composite Microspheres

The prosthodontic treatment of bone defects is a very tricky problem to be solved in orthopaedics.The fabrication of the biocompatible and multi-functional bone graft substitutes is a research focus in bone tissue engineering.Hydroxyapatite(HA),the major inorganic component of vertebrate tooth and bone,has good properties of biocompatibility and osteoconduction.Up to now,researchers have developed various synthetic methods to prepare HA,however,there are some disadvantages in these conventional synthetic methods,including long preparation time,and tedious process.Therefore,developing a novel synthetic method with convenient,efficient and environmentally friendly to obtain HA will contribute to the promotion and application of HA.However,HA obtained from artificial synthetic method has the disadvantages of slow degradation rate,poor plasticity and easy to agglomeration.Besides,the irregular-shaped materials implanted into the body are easy to cause secondary damage to the damaged part.To overcome these difficulties,the HA and polymer materials were used to prepare composite materials with regular shape to obtain better performance in this paper.In order to provide methods for the application of composite microspheres in bone tissue engineering and drug delivery system,the preparation and properties of hydroxyapatite/sodium alginate/chitosan composite microspheres were investigated.The main contents and conclusions are as follows:(1)The dual frequency ultrasound was applied to prepare HA nanoparticles.To obtain the best preparation conditions,the effect of ultrasonic power and time on HA nanoparticles were investigated.Furthermore,the possible influencing mechanism of acoustic cavitation effect yield on HA crystal was briefly explored.The result showed that the dual frequency ultrasound could be utilized successfully to prepare rod-shaped HA nanoparticles.The dual frequency ultrasound significantly enhanced the acoustic cavitation effect over single frequency ultrasound,the further enhanced acoustic cavitation effect can improve the dispersity of particles and reduce the particle sizes.Compared with the conventional synthetic methods,the dual frequency ultrasonic method exhibits remarkable characteristics of time-saving and environmentally friendly,it may be expected to become an efficient and environmentally friendly synthetic technology to obtain HA nanoparticles.(2)The emulsion crosslink method was applied to prepare hydroxyapatite/sodium alginate/chitosan(HA/SA/CS)composite microspheres with three dimensional space structure,the effect of preparation conditions on morphology and dispersity of composite microspheres were investigated.The results showed that the morphology and dispersity of microspheres were significantly effected by the concentration of sodium alginate,the ratio of water to oil,the content of HA and emulsifier,and the rotate speed.(3)Hydrochloric acid doxorubicin(Dox·HCl)was used as the drug model to study the drug loading efficiency and encapsulation efficiency of HA nanoparticles,HA/SA composite microspheres and HA/SA/CS composite microspheres.The in-vitro drug release behavior of HA/SA/CS/Dox composite microspheres was investigated in different simulation environment,and drug release curves were fitted using model equation.The results showed that the drug loading and encapsulation efficiency of HA nanoparticles were(1.18 mg Dox/20 mg HA)and 11.77% respectively,while were(9.37 mg Dox /20 mg HA/SA/CS)and 93.72% respectively in HA/SA/CS composite microspheres.The drug loading efficiency of HA nanoparticles was less than HA/SA/CS composite microspheres,indicating that the three-dimensional network structure of HA/SA/CS composite microspheres was contributed to improve the quantity of loaded drugs.The drug release behavior of HA/SA/CS/Dox composite microspheres has PH-sensitivity and slow release feature.The drug release behavior in different PH release media was more fitted to the first-order kinetics equation.(4)The biocompatibility of HA,HA/SA and HA/SA/CS were investigated,the results showed that the hemolysis ratio of HA,HA/SA and HA/SA/CS was less than 5% within the experimental concentration,the toxicity to normal bronchial epithelial cells(16HBE)was very small,indicating these materials meeting the requirements of medical biomaterials.The adhesion and proliferative capacity of osteoblast cells(MG-63)on HA/SA/CS composite microspheres were higher than that of the HA nanoparticles and HA/SA microspheres.It was attributed to that three dimensional network structure and the rough surface of HA/SA/CS microspheres were more conducive to cells adhesion and proliferation.The HA/SA/CS composite microspheres are expected to become a new-type composite microspherical bone repair materials with double functions of bone reconstruction and drug sustained release properties,which will possess potential application prospects in drug delivery system and bone tissue engineering.