Interactions between C60 and vesicles: A coarse-grained molecular dynamics simulation

The interaction of fullerene with biological systems has been an issue of great research interest for the past decade. Mechanisms of C60 penetrating and disrupting cell membranes have been widely investigated but are not fully understood. Here we report on coarse grained molecular dynamics (CGMD) simulations of the translocation of monomeric C60 and a fullerene pair across a model DPPC (dipalmitoylphosphatidylcholine) vesicle. Our simulations suggest that monomeric C60 tends to dwell between the head groups of the inner leaflet of the vesicle. This characteristic can be verified from the PMF profiles and the Lennard-Jones interaction energy analysis. The fullerene pair can enter the vesicle membrane as a whole, then disaggregate on a nanosecond timescale inside the membrane. To study the toxicity of C60 on the vesicle, the interactions of the fullerene aggregations with the vesicle are also examined in our simulations. Small fullerene aggregations can penetrate into the vesicle membrane, and do not cause significant mechanical damage to the vesicle membrane. However, as the size of the aggregations increases to greater than the thickness of the vesicle membrane, this can induce a change in the structure of the vesicle membrane or even lead to rupture of the vesicle. Our simulations describe the mechanism for the interactions of C60 with the vesicle, and point out the potential toxicity of fullerenes on the vesicle. These results may provide a useful blue print for drug or gene delivery, and improve our understanding of fullerene cytotoxicity.