Abstract
Purpose: One of the major concerns regarding metal-on-metal prostheses is the biological and biochemical activities of chromium (Cr) ions. Previous studies showed that Cr3+ ions form nanostructures in cell culture media and to date, there has been little attempt to understand the nature of implant-derived metal ions in adjacent tissues or in biofluid. The aim of this work was to determine the nature of proteins present in serum involved in the formation of Cr nanostuctures
Methods: RPMI 1640 and DMEM media supplemented with 5% human serum (HS) or 5% foetal bovine serum (FBS) were incubated for 1h at 37°C in the presence of 50 ppm of Cr3+ (CrCl3). Structures were then isolated and separated by SDS-PAGE. Proteins were stained by Coomassie blue and analyzed by liquid chromatography-quadrupole-time of flight-mass spectrometer (LC-Q-Tof-MS). Data were submitted to Mascot software for a search against the NCBI nonredundant database
Results: Results show that Cr-nanostructures can interact with proteins from both human and bovine serums. On SDS-PAGE, the molecular weights of the proteins were between 40 to 90 kDa. The LC-Q-Tof-MS results suggest that Cr-nanostructures are the result of the interaction with numerous proteins present in serum. However, the complete analysis of results demonstrates that only two proteins (in both RPMI and DMEM) are implicated in these nanostructures: albumin and trans-ferrin. For both proteins, at least 40 peptides matched to the complete sequence of the proteins. The ion scores (“peptide identity score”) were between 79 and 108. Ion scores > 45 indicate identity or extensive homology
Conclusions: Human serum contains more than 400 different proteins. Albumin, the major protein of human serum, has been shown to play a scavenger role by binding and transporting injected and ingested Cr. Albumin could also play an immunological role by addressing signals to defense cells, such as macrophages. Trans-ferrin, known as an iron-carrying protein, also plays a scavenger role for Cr. This suggests that the binding of Cr to these proteins may protect cells from the cytotoxic effect of Cr ions. However, the relation with Cr nano-structures in vivo remains to be determined
Correspondence should be addressed to Cynthia Vezina, Communications Manager, COA, 4150-360 Ste. Catherine St. West, Westmount, QC H3Z 2Y5, Canada
