Development and characterization of calcium phosphate cements containing collagen

Reference	Presenter	Authors (Institution)	Abstract
02-041	Christiane Ribeiro	Ribeiro, C.(Universidade Federal do ABC (SP), BRAZIL); Lima, V.A.(Universidade Federal do ABC); Setz, L.F.(Universidade Federal do ABC);	In recent years, calcium phosphate ceramics have been explored also as injectable materials to repair bone tissue, due to its molding capabilities, biocompatibility and osteoconduction characteristics successfully. Therefore, new formulations are increasingly suggest for calcium phosphate cements (CPCs) or pastes as injectable ceramics through minimally invasive means. In the present study, a calcium phosphate cement was developed in the absence and presence of collagen in its composition and their characteristics evaluated. The starting materials were characterized by X-ray diffraction, FTIR spectroscopy and scanning electron microscopy (SEM). For the liquid phase, a solution of phosphoric acid (3.0M) was used, and mixed with the solid phase of tricalcium phosphate, at a 1:1 (wt.%) ratio. Different concentrations of collagen were analyzed and the pH, temperature and setting times of the cements were monitored. The cements were characterized by isothermal calorimetry tests and were also assessed by XRD, FTIR, apparent porosity and SEM, as well as mechanical assay to determine the elastic modulus. No secondary phases were observed in the starting material. The concentration of 20 wt% collagen showed suitable hardening time. Monetite was the majoritary phase in cement, favored by the methodology used. The presence of the collagen covered the calcium phosphate particles, which slowed the setting time and minimized the heat accumulated in the samples, influencing the dissolution reaction and formation of other phases in the cement, besides preserving a residual amount of the original ceramic phase. The collagen also decreased the apparent porosity, due to the coating of the crystals of dicalcium phosphate and filled the microporosity. The elastic modulus values obtained were comparable to those reported in the literature, but the presence of collagen altered its mechanical performance to elastic modulus values between the cortical and trabecular bone range.
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