Serum protein albumin and chromium: Mechanistic insights into the interaction between ions, nanoparticles, and protein.

The interaction of human proteins and metal species, both ions and nanoparticles, is poorly understood despite their growing importance. These materials are the by-products of corrosion processes and are of relevance for food and drug manufacturing, nanomedicine, and biomedical implant corrosion. Here, we study the interaction of Cr(III) ions and chromium oxide nanoparticles with bovine serum albumin in physiological conditions. This study combined electrophoretic mobility measurements, spectroscopy, and time-of-flight secondary ion mass spectrometry with principal component analysis. It was determined that neither metal species resulted in global albumin unfolding. The Cr(III) ions interacted strongly with amino acids found in previously discovered metal binding sites, but also were most strongly implicated in the interaction with negatively charged acid residues, suggesting an electrostatic interaction. Bovine serum albumin (BSA) was found to bind to the Cr2O3 nanoparticles in a preferential orientation, due to electrostatic interactions between the positive amino acid residues and the negative chromium oxide nanoparticle surface. These findings ameliorate our understanding of the interaction between trivalent chromium ions and nanoparticles, and biological macromolecules.