Study On The Morphological Control And Performance Of Calcium Phosphate Biomaterials

Calcium phosphate(CaP)materials are optimal candidate biomaterials for bone tissue engineering because of their bioactivity and biocompatibility.The controlled fabrication of CaP materials draws great interest because the size,shape and composition of CaP crystals play critical roles in biological response.In this study,CaP nanowires and microspheres were synthesised via an organic-free hydrothermal process without the assistance of any surfactant or template.The effect of the reaction condition on CaP crystal growth and the drug loading and release performance were investigated.Experimental results showed that the size,shape and composition of the obtained CaP crystals could be manipulated by changing nucleation temperature,reaction temperature,pH value and reaction time.The chemical composition of the obtained crystals had a common change process from dicalcium phosphate dihydrate and dicalcium phosphate anhydrous to hydroxyapatite with the elongation of reaction time.The prenucleation and nucleation temperature before hydrothermal treatment were critical for the growth of CaP crystal.Two typical morphologies of nanowire and microsphere were fabricated under the given reaction condition.The growth mechanisms of the crystals were also discussed in this paper.In vitro results showed that both nanowires and microspheres of CaP exhibited exceptional performance to improve osteoblast proliferation,which endowed them with interesting potential for bone repair.The findings are highly important to develop excellent materials suitable for bone tissue engineering.The research contents and results as follow:1.Study on the preparation and growth mechanism of calcium phosphate microspheresA simple hydrothermal method was used to react with sodium diphosphate as a sodium source and calcium chloride as a calcium source in a simple aqueous solution at the ratio of Ca/P = 5: 3.Under the conditions of nucleation temperature 4?,pH = 4.5,and hydrothermal reaction temperature 140?,the calcium phosphate microspheres with the main components of dicalcium phosphate and hydroxyapatite were prepared,which were assembled with nano rods.In addition,the mechanism study found that the basic structure of calcium phosphate microspheres in the hydrothermal reaction has been formed within 1 h,through the process of dissolution and recrystallization,and the final formation of microspheres is Ostwald ripening mechanism.The microspheres are formed by recrystallization from the slabs of the precursor into interconnected slices.Then the lamellae are self-assembled into globular shape,and the slices are further transformed into needle-like shape after further aging to form the final microspheres.With the extension of the hydrothermal time,the calcium phosphate microspheres were subjected to the transition from calcium hydrogen phosphate dihydrate to calcium hydrogen phosphate and hydroxyapatite.2.Study on the preparation and growth mechanism of calcium phosphate nanowiresUsing the simple hydrothermal method,the reaction was carried out in a simple aqueous solution with disodium hydrogen phosphate as the sodium source and calcium chloride as the calcium source,in the ratio of Ca: P = 5: 3.The main components of nanowires were dibasic calcium phosphate and hydroxyapatite.In addition,the nanowires were also obtained by controlling the nucleation temperature,pH value,hydrothermal reaction temperature and hydrothermal reaction time.The nucleation temperature was the key factor in the formation of products morphology.The optimum preparation conditions of the nanowires were as follows: nucleation temperature 15?,p H=4.5,hydrothermal reaction temperature 140?.It was found that the basic structures of calcium phosphate nanowires have been formed within 1 h after hydrothermal reaction,and they also have been through dissolution and recrystallisation.The crystal growth of nanowire is the oriented attachment.By shortening the hydrothermal reaction time,it was found that the nanowires were recrystallized from the original precursor of nanorods,and then gradually grew into nanowires.At the same time,with the prolongation of the hydrothermal time,the component of nanowires changed from calcium hydrogen phosphate dihydrate to calcium hydrogen phosphate and hydroxyapatite in different stages with microspheres.3.Study on the biocompatibility and drug release of calcium phosphate microspheres and nanowiresCell experiments in vitro showed that calcium phosphate nanowires and nanostructured microspheres not only had no cytotoxicity,but also promote cell proliferation in different degrees,especially the effect of calcium phosphate nanowires was more significant.In addition,the specific surface area of calcium phosphate nanowires and microspheres with nanostructure was very large,which able to load more drug of dexamethasone.Moreover,the loaded dexamethasone could be released sostenuto within 24 h.It was proved that the prepared CaP materials had good sustained release performance in part.