Study On The Synthesis And Adsorption Properties Of Calcium Oxalate Under Casein Control

Biomineralization principles can guide us to construct artificial multifunctional materials with mesoscopic to macroscopic hierarchically ordered structures. The key lies in the choice of the organic matrix of special structure and the search for reasonable biomimetic synthesis route. In the present work, phosphoproteins-controlled formation and application of calcium oxalate with hierarchical structure will be investigated. This will contribute to not only understanding the biomineralization mechanism deeply, but also providing new theoretical guidance and design basis for materials synthesis. The research mainly includes the following parts:(1) The influence of proteins on the crystallization of calcium oxalate have been investigated in order to determine the roles of amphiphilicity and phosphate groups of proteins in the morphology and the phase control of the calcium oxalate crystals. The crystals obtained are characterized by SEM, FT-IR, XRD, and TGA. The results show that calcium oxalate monohydrate (COM) is obtained in the absence of proteins, while the obtained crystals are calcium oxalate dihydrate (COD) in the presence of casein. Casein can be assumed to take a key role during dumbbell shaped COD formation where it serves as an effective stabilization agent for COD and assembles nanorods into dumbbell COD. Compared to controls containing casein hydrolysate or bovine serum albumin (BSA), the stabilizing effect of casein arises from the electrostatic attraction between phosphate groups as well as carbonate groups (especially the former) and the calcium ions on the COD. The assembling effect of casein mainly comes from the hydrophobic interaction between casein molecules bound on COD nanorod surface. Our studies may contribute to the understanding of the specific role of amphiphilic phosphoprotein in the biomineralization process. In addition, the use of amphiphilic phosphoprotein in CaOx crystallization offers new insights into controlling the polymorphs and morphologies under easily attainable reaction conditions.(2) The regulation mechanism of inorganic mineral crystallization by organic matrix in alcohol-water mixtures has remained unclear. In the present chapter, phosphoproteins-controlled the crystallization of calcium oxalate in alcohol-water mixtures has been investigated systematically. We obtain the calcium oxalate monohydrate (COM) with island structures under the cooperation of casein and ethanol at the appropriate volume ratio of ethanol to water. In addition, the polarity of the alcohol, concentration of casein, ion concentration, reaction temperature and other conditions play key roles in controlling the formation of calcium oxalate monohydrate with island structures. The results show that cooperative effect of casein and ethanol in the (-101) plane of COM leads to the growth process of calcium oxalate crystal and has a significant impact on the control of calcium oxalate crystals morphology. Both the phosphate groups and the amphiphilicity of casein matter much in the cooperation of ethanol and casein.(3) Our previous studies have showed that casein can effectively regulate the crystallization of calcium oxalate at low concentrations of calcium ion. In this chapter, we synthesize the double kiddy-shaped calcium oxalate superstructure under the control of casein at high concentrations of calcium ion, which is determined to be COD and COT mixtures by XRD and FT-IR. By regulating the reaction conditions such as temperature, the pH of the solution, and the concentration of casein, we can control phase transformation and morphology change of calcium oxalate crystals. The results demonstrate that the kinetic and thermodynamic regimes can prominently regulate the polymorphs and morphologies of calcium oxalate mineral in the presence of casein. Also, the double kiddy-shaped calcium oxalate superstructure, as an adsorbent material, has a good adsorption capacity toward anionic dyes. Thus, this research not only uncovers the mechanism adopted by organisms, but also applying them to the synthesis of materials with exquisite morphology and specific textures. Due to the effective permeability and nontoxicity of these synthetic materials, they have wide applications in drug delivery, environmental treatment, catalysis, and biomedical engineering.