Biomimetic Synthesis Of Inorganic Bioactive Materials Using Gelatin As Organic Matix

The general principles of biomineralization are introduced into the synthesis process of inorganic materials. Simulating the biomineralization process of inorganic materials with novel performance and structure and interpreting the organic matrix modulation mechanism, have important implications and a wide range of prospects. In this paper, a biomimetic synthesis method using gelatin as matrix was used to obtain hydroxyapatite, calcium carbonate and zinc oxide. Taking advantage of its molecular structure characteristics and self-assembly performance in outer environment was modulated to inorganic bioactive materials and its formation mechanisms. The specific work includes the following:Hydroxyapatite (HA) has good bioactivity and biocompatibility; it is one of the ideal implant materials in hard tissues. Based on the basic principles of biomineralization, hydroxyapatite was synthesized under the control of gelatin used as the organic matrix. The mineralization mechanism and self-assembly process of HA nanoparticles were discussed and the bioactivity and ion exchange of the product were investigated. The results indicate that adsorption of static electricity of side-chain group of gelatin macromolecules reacts with Ca2+ ions in solution, which is capable of controlling the nucleation and growth of HA crystals and plays a key role of the process of self-assembly of hydroxyapatite particles. The concentration ratio of Ca2+ and gelatin has a great impact on HA morphology. As the concentration ratio increasing, the morphologies of products comprise some units of nanoparticles, nanorods and nano-flakes. In the ion-exchange experiments Cd2+ ions are replace by Ca2+ ions among the hydroxyapatite crystals, the rate reach to 80.2%.Strontium-substituted Hydroxyapatite can improve the crystalline, solubility and biodegradable property of hydroxyapatite material. Calcium strontium phosphate hydroxide hollow nanospheres were synthesized using gelatin as organic substrate. Impacting on the morphology of the products the concentration ratio of Ca2+ ions and Sr2+ ions was discussed. The results show that the hollow nanosphere products with 50-100 nm in diameter can be obtained when the concentration ratio is 1:1. Its formation process is the heterogeneous nucleation of crystals on the gelatin molecular side chain and the solid spheres are formed. Further mineralization process, the crystals of the solid spheres constantly produce dissolution and deposition in the solution, and the hollow nanospheres are formed by Ostwald crystallization. Methylene Blue (MB) as a model drug is loaded in the hollow nanospheres, and the maximum is 105 mg/g. In the release process, the cumulative released amount in 2 h is 18.9%, it reaches 90% after the release of 48h. The hollow spherical structure material is suitable for drug release as a drug carrier. The strontium-calcium apatite was biomineralized in the present of gelatin solution and the morphology and structure of the product affected by the concentration of gelatin and Sr2+ ions were discussed. The nanobelts, nanotablets and nanostructure balls were synthesized in the different concentration of gelatin.As a major component of shells, calcium carbonate is another important biological material. Calcium carbonate was synthesized by mineralization using gelatin for a matrix. The influences of factors, namely the concentration of gelatin and Ca2+ ions, the aging time, the reaction temperature, on the composition and structure, were investigated. The results show that the structures of product are controlled by the ratio of the concentration of gelatin and calcium ions. As the ratio of concentration of gelatin and calcium ions gradually decreases, the compact spherical CaCO3 can change to the double-snail-like, analogous spherical-like and loose spherical CaCO3 aggregation. In addition, vaterite is stable in the solution due to the effect of gelatin in the first phase, and the concave hole CaCO3 appears for the phase transformation from vaterite to calcite in the end. In addition, a comparative study of other substrates, such as PEG, PVP, CTAB, and SDS on the effects of calcium carbonate products morphology was in progress. Studies show that ionic surfactant has a large impact on morphology of product. It may be the changes of gelatin molecular conformation caused by the ionic surfactant.At the same time, magnesium carbonate, strontium carbonate, barium carbonate and other series of carbonates were formed by biomineralization, and impacting on the morphology of the product the sizes of positive ionic radius was discussed. The results indicate that the larger the positive ionic radius, the sizes of the product get smaller and the structures of the product get more divergent. It may be the changes of the gelatin molecule conformation accused by the sizes of positive ionic radius. As the size of ionic radius increases, gelatin molecule conformation shapes from poly group and converts to a decentralized state, which affects the morphology of the products, such as from the compact "nest"-like structure and sphere to the dumbbell-shaped structure and dendritic structure. Furthermore, nanorods carbonated nickel and cobalt carbonate, dumbbell-shaped manganese carbonate and spherical cadmium carbonate were obtained. It indicates that the gelatin conformation of molecules is also limited by the effects of atomic weight.The results of series of phosphate and carbonate mineralized in gelatin solution provide guidance for biomimetic synthesis other inorganic materials. Zinc oxide was synthesized by the biomimetic process in the gelatin solution at low temperature, and the nucleation, growth and self-assembly of ZnO crystals in the course of mineralization synthesis was studied. The results indicate that the gelatin concentration, the zinc ion concentration, the mineralization time, the temperature and precipitation agent of mineralization on mineralization process and products have a larger impact on the product. With the extension of time for mineralization, the sheet-like, flower-like, peanut-like zinc oxide is changed to dumbbell-like zinc oxide. A different structure ZnO producing the effect of UV blue shift due to the effect of nanometer was found. Gas performance test results indicate that the peanut-like zinc oxide have a better of sensing properties on alcohol. The sensitivity reaches 25 when the concentration of ethanol is 40ppm.