Calcium Phosphate Mineralization of Hydrogels, their Microstructure and Mechanical Behavior

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This grant supports research that advances knowledge of the manufacturing process promoting both the progress of science and national health. Every year, over half a million patients need bone defect repairs in the U.S. and advanced manufacturing methods of materials for bone replacement and regeneration are needed. A promising method is the use of calcium phosphate mineralization of hydrogel materials. Calcium phosphate is the mineral component of bone and mineralized hydrogels could yield both suitable biomimetic properties and mechanical strength as a bone defect replacement material. Despite the significant advance in understanding mineralization, knowledge of the relation between the mineralization pathway, the microstructure and the mechanical response of these hybrid materials is still lacking, which hinders advances in manufacturing science. This grant supports fundamental research to provide that needed knowledge for the development of mineralization processes of hydrogels that allow control of their structure-mechanical property relation. The gained knowledge will be applicable to advance manufacturing of biomaterials via abiotic mineralization for bone replacement. Furthermore, the gained insight will be also relevant to control biotic mineralization pathways, and hence, for bone regeneration based on tissue engineering. Therefore, results from this research will benefit the U.S. society. This research involves several disciplines including materials science and engineering, chemistry, and mechanics and will contribute to the development of workforce in the U.S. The multi-disciplinary research will help broaden participation of underrepresented groups in research and positively impact engineering education.The overall objective of this research is to comprehend, quantify and model the relation between mineralization pathways of calcium phosphate in the presence of amorphous calcium carbonate (ACC) precursors, the microstructure of the mineralized hydrogel and its mechanical response. This grant supports the research that will elucidate i) how the mineralization pathway is affected by the presence of ACC in the hydrogels, ii) the relation between polymer properties (charge density, chemical crosslinks vs. physical entanglements and self-assembly capability), mineralization mechanisms and microstructure, iii) the effect of the solution chemistry on the mineralization rate, and iv) the relation between microstructure and rheology of mineralized hydrogels. The findings of this work will be used to develop a conceptual framework to predict strengthening mechanisms of hydrogels via calcium phosphate mineralization as a function of solution composition and hydrogel properties. Experiments are designed to examine specific underlying mechanisms and test the posed hypotheses concerning issues such as the initial formation of a liquid-phase precursor en route to mineralization, the induced polymer-mineral interaction strength, and the nanoparticle aggregation in the hydrogel.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.