Proteins incorporated into biomimetically prepared calcium phosphate coatings modulate their mechanical strength and dissolution rate

In a previous investigation, we demonstrated that when bovine serum albumin (BSA) is biomimetically co-precipitated with Ca2+ and PO43− ions upon titanium-alloy implants, it becomes incorporated into the crystal lattice and is not merely deposited on its surface. Moreover, the protein elicited a change in crystal structure from an octacalcium phosphate type to a carbonated apatite one, which bears a closer resemblance to natural bone mineral. In the present study, we investigated the dissolution rate and mechanical strength of such BSA-containing coatings as a function of protein concentration within the bathing medium (10 ng/ml to 1.0 mg/ml). BSA-containing coatings released Ca2+ ions more slowly (5 ppm/min) than did non-BSA-containing ones (10 ppm/min), but this rate did not change as a function of protein concentration within the bathing medium. In contrast, the strength of coatings increased almost linearly as a function of protein concentration within the bathing medium, indicating that BSA incorporated into the crystal lattice enhances its mechanical strength in a concentration-dependent manner.