The quantification of cellular viability and inflammatory response to stainless steel alloys.

The biocompatibility of metallic alloys is critical to the success of many orthopedic therapies. Corrosion resistance and the immune response of the body to wear debris products ultimately determine the performance of these devices. The establishment of quantitative tests of biocompatibility is an important issue for biomaterials development. We have developed an in vitro model to measure the pro-inflammatory cytokine production and in this study investigated the cellular responses induced by nitrogenated and 316L stainless steel alloys in both particulate and solid form. We utilized a murine macrophage cell line, RAW 264.7, to characterize and compare the mRNA profiles of TNF-alpha and IL-1beta in these cells using real time-polymerase chain reaction (RT-PCR). Fluorescence microscopy and flow cytometry were used to probe the viability of the population and to examine the apoptotic pathway. The goals of this work were to develop improved measurement methods for the quantification of cellular inflammatory responses to biomaterials and to obtain data that leads to an enhanced understanding of the ways in which the body responds to biomaterials. Using these techniques, we observed evidence for an association between the upregulation of IL-1beta and reversible apoptosis, and the upregulation of TNF-alpha and irreversible apoptosis.