Self-propelled cellular translocation of Janus-shaped graphene quantum dots: A molecular dynamics simulation and thermodynamic analysis

Abstract

Although spatially heterogeneous oxidation is pivotal to the cellular translocation process of graphene quantum dots (GQDs), the dynamical road to the thermodynamically stable translocation conformation remains hazy. In this study, we illuminate the bio-interface doctrine involving the cellular translocation of Janus-shaped oxidized GQDs by performing multi-dimensional pathway computations predicated on coupled microsecond-long molecular dynamics and well-tempered metadynamics simulations. The oxidation nanodomains of Janus-shaped GQDs spontaneously yield hydrogen-bonds with polar lipid heads, while their pristine graphene nanodomains hydrophobically associate with nonpolar lipid tails, and thus respond as self-propelled nanomotors across biological membranes. Hydrophobic-associations and hydrogen-bondings are found to be competitively coordinated, which dictates the dynamic pathway and thermodynamic states for cellular translocation, particularly modulating the adaptive self-propelling activity. The translocational phase diagram is drawn, demonstrating that GQDs with moderately square-patterned oxidation and thin thickness facilitate excellent translocation and minimal biological nanotoxicity. Importantly, intermolecular mechanochemistry is discovered to play a crucial role in energy transduction and nanomechanical interactions, which in turn affect the spatial rotation pathways of GQDs, as well as the membrane perturbations. Overall, this study provides an intuitive insight into the dynamics and thermodynamics of spontaneously translocating GQDs, opening up brand-new avenues for developing GQD-enabled nanocarriers or antibiotics.