Molecular mechanism of coating carbon black nanoparticles with polycyclic aromatic hydrocarbons on the binding to serum albumin and the related cytotoxicity

Abstract

Ultrafine particles (UFPs) have emerged as the main components of particulate pollutants in urban and industrial air. One of the major organic compounds absorbed on these particles are polycyclic aromatic hydrocarbons (PAHs), which play essential roles in the toxicity of UFPs. Nonetheless, the impact of PAHs on the interactions of UFPs with proteins and the mechanisms underlying these interactions remain unclear. In this study, the toxic impact of ultrafine carbon black nanoparticles (CBNPs) in the presence and absence of two PAHs, namely phenanthrene (Phe) and pyrene (Pyr), on the binding to human serum albumin (HSA) as well as the related cytotoxicity were determined by various spectroscopic methods as well as transmission electron microscopy (TEM) and isothermal titration calorimetry (ITC). From the fluorescence results, we found that HSA could bind to well-dispersed CBNPs and CBNP-PAHs to form moderately stable bioconjugates, predominantly through hydrophobic forces. Moreover, the binding of both CBNPs and CBNP-PAHs to HSA not only resulted in the conformational and functional alterations of protein, but also reduced their cytotoxicity due to the formation of complexes." The present work provides quantitative evidence for elucidating the toxicity of UFPs in vivo.