| Natural biominerals often contain small amount of acidic macromolecules. These soluble macromolecules are thought to play a very important role in regulating the biomineralization process. By using synthetic acidic biopolymer and natural proteins extracted from biominerals to mimic these acidic macromolecules, the Polymer-Induced Liquid-Precursor (PILP) process is proposed to have great relevance to biomineralization. Like some biominerals, the minerals formed by the PILP process have both non-equilibrium morphology (e.g., "molded" crystal morphologies, films, rods, and tablets) and non-equilibrium composition (e.g., high magnesian calcite).; Our goal was to study the formation of calcium carbonate and calcium phosphate formation by the PILP process. By using fluorescence labeling, in-situ observation, and TEM study, we examined the formation of liquid-precursor and polymer-mineral association (exclusion, occlusion). The cooperation of Mg and polymer leads to pronounced amorphous-crystalline transition and formation of thin films incorporating high amount of impurity comparable to biominerals. By taking advantage of amorphous-crystalline transition in the PILP process, calcium carbonate amorphous liquid precursors are molded inside a porous hydrogel and transform to crystalline calcite. After removal of the organic mold, a calcite scaffold with complex morphology is formed.; Natural soluble proteins are extracted from nacre. Our in-vitro crystallization studies using these proteins show similar amorphous-crystalline transition and thin film morphology in the presence of Mg. The combination of organic substrate and nacre proteins leads to thin aragonite films.; Finally we studied the formation of calcium phosphate using our in-vitro crystallization model. As in the calcium carbonate system, thin films were formed on organic substrate and glass slides in the presence of polymer. We also successfully prepared PHEMA-CaP and collagen-HA organic inorganic composites for tissue-engineering applications.; By the above studies, we hope to unveil the role of the acidic proteins in biomineralization. We hope that our in vitro model system can show how different substrates and impurities influence the deposition and transformation of amorphous phases generated with the soluble polymeric process-directing agent. We believe that this new approach to mimicking biomineralization will allow fabrication of novel biomimetic materials from mild conditions. |
