Biomimetic Modulation of Calcium Oxalate Growth and Morphology in Hydrogels

Biominerals found in living organisms have diverse biological functions and unique properties arising from the particular structure, orientation, and morphology of the constituent minerals.  A systematic investigation of the morphological evolution of biominerals grown in organic matrices, and the interaction of such matrices with the inorganic crystals are essential for understanding biomineralization processes and for developing bioinspired materials.  We employ here hydrogels as a model organic matrices and a ‘double-diffusion’ method to mimic the formation of calcium oxalate, the major constituent of kidney stones. Gel-mediated crystallization provides a great way to vary the local supersaturation through controlling the diffusion rate of the reacting ions.  We study the nucleation, growth, type of polymorph and orientation of the calcium oxalate crystals as affected by the gel density, reservoir concentrations, molar stock solution ratio, and additives.  The obtained crystals are characterized for their morphology and crystal structure using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), respectively.  We also investigate the possible occlusion of gelatin in calcium oxalate through Thermogravimetric Analysis (TGA).  These findings help our understanding of the mechanism of gelatin incorporation in calcium oxalate crystals, and provide insights into the formation of organic-inorganic composite materials.