Synthesis And Self-assembly Of Bioactive Nano-hydroxyapatite

In recent years,with the continuous improvement of living standards,people are more care of their personal health.Therefore,the medical and health care industry began to develop rapidly,and the development of new medical materials had become a hot spot in current research.Among them,the field of biomaterials has shown unprecedented development prospects due to its huge market demand.Existing biomaterials such as bioceramics,biopolymer materials and bioactive glass etc.are far from satisfactory,so there is a need to develop new biomaterials for medical needs.Hydroxyapatite(HA)is a biocompatible biomaterial that is a major component of human bones and teeth.The bones and teeth in the living body have great hardness,pressure resistance and wear resistance due to their special internal appearance and structure of HA.The main contents and conclusions of this study are as follows:(1)Synthesis of nano-HA with controlled particle size.Nano-HA was synthesized by co-precipitation method using partially hydrolyzed keratin as template.The effect of the concentration of templating agent on the particle size of synthetic HA was studied,the sizes are compared with the HA extracted from grass carp scales,and the reason for this effect was also investigated.Finally,in vitro cell co-culture was carried out to test their Biocompatibility.The results showed the size of the synthetic HA gradually decreases as the concentration of partially hydrolyzed keratin increases.In addition,cell experiments demonstrate that HA synthesized by this method have good biocompatibility.(2)Synthesis of porous sheet-like HA.HA was synthesized by hydrothermal method using a small amount of polyvinyl alcohol(PVA)as a template.The effects of the concentration of templating agent on the morphology of synthetic HA were studied,and the possible mechanism was proposed.The mechanism was also verified by comparison with HA synthesized under the same conditions using polyvinylpyrrolidone(PVP)as template.The results show that with the increase of PVA concentration,HA changes from granular to porous sheet-like structure,which may be because PVA provides a periodic arrangement of nucleation sites,which can cause HA to grow around its molecular chain,and The HA synthesized by using PVP as a template is granular or rod-shaped.In addition,the in vitro cytotoxicity of HA synthesized using PVA as a template was also tested,and the results showed that these samples had no cytotoxic.(3)Preparation and compounding of self-assembled HA with enamel-like micro-nano structure.Calcium stearate and calcium oleate were used as calcium sources to synthesize calcium phosphate salt with an ordered structure by hydrothermal method,and the principle of forming a structure was speculated.However,considering the low conversion of raw materials,the products synthesized by these two methods contain a small amount of hard-to-remove organic matter,which will seriously affect the mechanical properties,and the synthesis conditions are harsh,so it is difficult to prepare in large quantities and apply to practice.Therefore,a two-step synthesis method of HA with ordered structure was designed:First,calcium oleate was converted into single crystal calcium phosphate,then the calcium phosphate was used as precursor and converted into HA in alkaline solution.SEM photographs showed that the product do have enamel-like structure.Here,we propose a conjecture of the splitting-self-assembly process of the transformation process.Subsequently,we compounded the self-assembled HA sample with PMMA to test its nano-hardness and modulus,and found that its nano-mechanical strength is very close to that of natural enamel.The organic content of the composites obtained under different conditions was 18.53%-22.91%,which was tested by thermogravimetric analysis.In addition,the in vitro cytotoxicity of HA composite materials was also tested.It was found that HA composite materials had different promoting effects on cell growth.