DECREASED CONSUMPTION OF CA AND P DURING IN-VITRO BIOMINERALIZATION AND BIOLOGICALLY INDUCED DEPOSITION OF NI AND CR IN PRESENCE OF STAINLESS-STEEL CORROSION PRODUCTS

The purpose of this study was to investigate the effects of 316L stain less steel (SS) corrosion products on the in vitro biomineralization p rocess, because tissue necrosis, bone loss, impaired bone mineralizati on, and loosening of orthopedic implants are associated with ions and debris resulting from biodegradation. Rat bone marrow cells were cultu red in experimental conditions that favored the proliferation and diff erentiation of osteoblastic cells and were exposed to SS corrosion pro ducts obtained by electrochemical means for periods ranging from 1 to 21 days. Quantification of total and ionized Ca and P, as well as Fe, Cr, and Ni, ions in the culture media of control and metal added cultu res during the incubation period was performed to study the influence of corrosion products on the Ca and P consumption that occurs during t he mineralization process. Control cultures and metal effects on cultu res were evaluated concerning DNA content, enzymatic reduction of (4,5 -dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and alka line phosphatase (ALP) activity. Histochemical detection of ALP, Ca, a nd phosphate deposition, and examination of the cultures by scanning a nd transmission electron microscopy (SEM and TEM) were also performed. The presence of SS corrosion products resulted in impairment of the n ormal behavior of rat bone marrow cultures. Levels of Cr and Ni in the medium of cultures exposed to 316L SS corrosion products decreased th roughout the incubation period, suggesting a regular deposition of the se species; these results were supported by TEM observation of the cul tures. Cultures exposed to the corrosion products presented lower DNA content, MTT reduction, and ALP activity and failed to form mineralize d areas. These cultures showed negative staining on histochemical reac tions for the identification of calcium and phosphate deposition and S EM and TEM? examination did not show mineral globular structures or mi neralization foci, respectively, which is characteristic of cultures g rown in control conditions. These results suggest that metal ions asso ciated with 316L SS are toxic to osteogenic cells, affecting their pro liferation and differentiation. (C) 1998 John Wiley & Sons, Inc.