Fibrinogen clot induced by gold-nanoparticle in vitro

The biomedical applications of gold nanoparticle (GNP) are extraordinarily promising due to its special optical properties. However, before transforming into real clinical test, a systematic understanding of the physiological interactions of GNP becomes imperative. For example, protein-GNP interactions and their biological consequences are the most fundamental and exigent for the related studies in cell level. In this study, we report on our findings that the interaction of GNP and fibrinogen (fg) could induce blood clot, one important blood protein, under near-physiological conditions. Firstly, through different characterization methods, namely, UV spectrum, dynamic lighter scattering (DLS) and atomic force microscopy (AFM), fg-GNP clots with the microm size were found to be formed and their average size is time- and concentration dependent. Besides, the dissociation constant was calculated to be 1.36 - 2.05 microg/mL (nM level), suggesting that the interaction between fg and GNP is very strong. Finally, by scrutinizing the fg sequences, this strong binding was found to originate from many Cys residues distributed in alpha, beta, and gamma chains of fg through Au-S bond. Most of these Cys residues are in the form of disulfide bonds, which locate at the central E domain and flank parts of C-terminal and N-terminal in the coil-coil region.