Multidrug resistance protein P-glycoprotein does not recognize nanoparticle C60: experiment and modeling

Organisms have evolved stress-inducible defense responses such as the P-glycoprotein (P-gp)-mediated efflux system to maintain chemical homeostasis in cells for both endogenous and xenobiotic compounds. However, despite the extensive focus on the potential interactions of P-gp with small molecules, the effect of nanoparticles on this transporter is scarcely reported. Thus in this work, in vitro experiments combined with molecular dynamics (MD) simulations were carried out to investigate the interactions of the multidrug resistance (MDR) protein P-gp with fullerene (C60), one of the most important nano-drug carriers. Upon exposure to fluorescence-labeledC60 (0–70 μg mL−1) for 2 h, significant accumulation of C60 is found in both the K562S and K562R cells, suggesting the incapability of P-gp to induce the efflux of this nanoparticle. In addition, in vitro inhibition assays also reveal that C60 does not obviously hinder P-gp-mediated rhodamine-123 transport in both K562S and K562R cells. The theoretical simulations further reveal the mechanism involved in C60-P-gp interactions, i.e., the binding of C60 barely induces the conformational changes of P-gp with RMSD of ∼4.8 Å and radius of gyration of ∼41.5 Å, and also no theoretical evidence shows that the C60 acts as a substrate or inhibitor of P-glycoprotein. These results demonstrate the potential of C60 as a good carrier candidate for MDR-targeted drug delivery, since organisms probably have not evolved to recognize this nanoparticle.