A critical evaluation of the purification of biominerals by hypochlorite treatment.

The quantitative deproteination of calcific deposits from surgically explanted heart valve bioprostheses was carried out by both hypochlorite and hydrazine extraction to establish which is the better procedure for preparing purified mineral suitable for detailed chemical and structural characterization. Hypochlorite treatment resulted in a material with a higher Ca/PO4 ratio than that of the untreated deposits. The hydrazine treatment did not produce such an effect. A systematic comparison of x-ray diffraction patterns of calcific deposits showed an increase in crystallinity of hypochlorite-treated versus native material, while the crystallinity of hydrazine-treated materials did not change. One other result of the hypochlorite treatment was a pronounced disaggregation of well-ground calcific deposits into a particle populations ranging from 50-300 nm in size, as shown by scanning electron microscopy. Results comparable to the above findings were also obtained when the two treatments were applied to other bioapatites. On the other hand, mineral solubilities were comparable, regardless of which deproteination treatment was used. The principal conclusion from this study is that hydrazine deproteination is preferable to hypochlorite extraction in isolating pathologic mineral deposits from bioprosthetic materials for further study.