Phase separation-driven modulation of cell membrane interactions with benzo[<i>a</i>]pyrene-bearing graphene nanosheets: molecular insights into combined toxicity

The interface between nanoparticles and cell membranes is a critical site for nano-bio interactions that determine the fate and toxicity of nanoparticles within biological systems. However, understanding these interactions is often hindered by the dual complexity of environmental and biological systems. In this study, we employed a computational approach for elucidating the pivotal role of phase separation in modulating cell membrane interactions with graphene nanosheets (GNs) preloaded with benzo[<i>a</i>]pyrene (BaP), a common environmental contaminant. Our results reveal that pristine GNs, unlike their oxidized counterparts, can spontaneously insert into cell membranes, preferentially localizing in the liquid-disordered (<i>L</i>_d) phase region. BaP molecules adsorbed on GNs are effectively solubilized within the membrane through competitive interactions with lipids, and they predominantly adopt random orientations in the <i>L</i>_d phase. In contrast, the liquid-ordered (<i>L</i>_o) phase, or lipid raft, resists GN insertion and traps BaPs in a unique lying conformation between leaflets. These interactions disrupt membrane fluidity and mechanical properties, solidify phase separation, and impair membrane functions reliant on dynamic phase transitions. Our findings highlight the importance of considering membrane phase separation when evaluating the combined effects of nanoparticles and coexisting contaminants on cellular behavior, providing critical insights into risk assessment and design of safer nanomaterials.