Study Of The Biomimetic Mineralization Of Calcium Phosphate In A Galatin Hydroocl-based System

The problems of osteoporosis and its complications become more and more serious with the accelerated aging trend of the population, whereas complementing calcium and vitamin can just prevent osteoporosis to some extent and the effect is not satisfactory. In recent years, the trace element was began to bring into focus, some people want to prevent or treat osteoporosis with taking in trace elements. If we can establish a biomimetic system and add different kinds of elements into this system to study the effect to the bone materials, the role of trace element in bone mineralization and demineralization can be revealed and new drugs or materials to treat osteoporosis and fracture will be developed.The composition of the bone can be divided into organic and inorganic parts, the inorganic part contains hydroxyapatite, water and trace elements, and the organic part consists of collagen and extracellular matrix. Nowadays researchers use seven levels of hierarchical structure to describe the bone formation, this model underlines the combination of organic and inorganic parts, and tells us to introduce organic part into the materials when synthesize inorganic calcium phosphate. In the bone tissue there are various kinds of trace elements, such as silicon, strontium, zinc and magnesium that would influence the growth and metabolism of bone tissue. It is significance to introduce trace elements into the synthesis of calcium phosphate in order to study the influence of trace elements to the bone substitute materials.This article investigated the synthesis of calcium phosphate in a biomimetic system and the effect of trace elements. At first we use calcium acetate and sodium phosphate to synthesize calcium phosphate in a gelatin system, and investigate the self-assembly mechanism of CaP by adjusting pH and adding different trace elements, try to explore how the bone materials produced when organic and inorganic parts interacted. Then we take SBF as human liquid environment, gelatin as collagen to synthesize calcium phosphate in a biomimetic method under the condition of37℃and7.4pH, and study the effect of trace elements in this system. The main results are as follows:1. In the gelatin system, calcium phosphate is synthesized using sodium phosphate and calcium acetate, and we investigated the influence of different pH adjusted methods. The research suggests that the morphology of product would be amorphous and its phase would be whitlockite and monetite when pH was directly adjusted to4, whereas the morphology would be sphere and the phase was hydroxyapatite and octacalcium phosphate when two steps pH adjusted method was employed. This article explains this result by the change of zeta potential with different pH adjusted methods.2. In the gelatin-sodium phosphate system, we use the two-steps pH adjusted method to synthesize spheres and add different trace elements to investigate its effect. When different content of element is added, it shows from ICP analysis that Si can hardly combine into the product, whereas Sr can combine into the product to5%at most and the content of Zn in product will increase gradually with the increased addition. The phase of product changes little when different elements are added, and the morphology and porosity will change regularly.3. A biomimetic system is established within the homemade reactor. In this system we take SBF as human liquid environment, gelatin as collagen to synthesize calcium phosphate under the condition of37℃and7.4pH. Then the pH will be turned down in order to study the demineralization in biomimetic environment. The research find that the size of product would increase with the extension of reaction time and the size of product would be decreased in the stage of degradation when no trace element is added. When Si is added, the variation trend of product size will be the same. The degradation will be restrained when Sr is added and the crystal growth will be restrained obviously if Zn is added to the system. The phase and function group of product are detected by XRD and FTIR, it shows that the phase is hydroxyapatite when no gelatin is added and the product comes to be gelatin-HA composite when gelatin is added. The phase and function group change little when different trace elements are added.In conclusion, the pH adjusted method and trace element have a great effect on the synthesis of calcium phosphate in the gelatin or biomimetic system and the reason for it is different conditions influence the self-assembly of the crystal. The research of calcium phosphate synthesis in biomimetic system would help to study the mechanism of the bone formation, and is significance to the development of drugs to treat osteoporosis and bone substitution materials.