In vitro calcification model (2): Apatite formation on segmented polyurethane thin films by using an alternate soaking process: The effect of adsorbed serum proteins on calcification

In the present study, the effect of serum proteins on the calcification (ap atite deposition) of commercially available polyurethane (PU) films, Pellet hane(R) 2363-80AE, Pellathane(R) 2363-55DE, and K-III, was evaluated by usi ng an alternating soaking process. Bovine serum albumin, gamma-globulin and fibrinogen were used as typical serum proteins. After the proteins were ad hered to PU films, the films were used in the apatite formation process. Th e thin-film X-ray diffraction spectra of a fibrinogen adhered K-III sample, after 200 calcification sequences, showed HAp formation. The calcium conte nt on the surface of all films to which protein adhered was greater than th at of films incubated in protein free solutions. The films to which fibrino gen adhered showed remarkable apatite formation, though the amount of adher ed fibrinogen was much smaller than the amounts of the other proteins. K-II I films to which fibrinogen had adhered showed small globular apatite aggre gations, whereas the Pellethane(R) 2363 series films showed confetti-shaped apatite. Different morphologies exhibited by the deposits depended on the types of serum protein and on the substrate chemistry. The reason for the d ifferent apatite morphology on different PU films is not clear, however, th e kind of serum protein seems to play an important role in the calcificatio n of a PU.