Effect of platelet-poor plasma additive on the formation of biocompatible calcium phosphates

Abstract

Biocompatible calcium phosphates were synthesized by mixing calcium- and phosphate-containing solutions in medium with various pH value, which contained up to 6 vol.% of platelet-poor plasma (PPP). Depending on the pH of precipitation medium, the influence of PPP components favored the formation of calcium-deficient hydroxyapatites with varying composition. In neutral medium, dicalcium phosphate dihydrate (DCPD) was the predominant phase but the buffering properties of PPP favored formation up to 24 wt.% of apatitic tricalcium phosphate. In alkaline medium, negatively charged surface of the PPP component macromolecules inhibited Ca2+ diffusion, which in turn lowered the Ca/P molar ratio of the formed hydroxyapatite from 1.67 to 1.62. After soaking in simulated body fluid (SBF), DCPD underwent hydrolysis yielding 29 wt.% of octacalcium phosphate and 19 wt.% of apatitic tricalcium phosphate and hydrolyzed DCPD/PPP sample contained 9 wt.% and 42 wt.% of octacalcium phosphate and apatitic tricalcium phosphate. Calcium-deficient hydroxyapatite in HA/PPP sample consumed the ions of SBF with an increase of its Ca/P molar ratio from 1.62 up to 1.66. In both cases, the Ca/P molar ratio of the calcium phosphates increased, indicating the apatite forming ability of the obtained calcium phosphates. Obtained results seem to be promising in development of new generation of hybrid composites based on calcium phosphates and blood components.