Quantification of C-induced membrane disruption using a quartz crystal microbalance.

Direct contact between fullerene C nanoparticles (NPs) and cell membranes is one of mechanisms for its cytotoxicity. In this study, the influence of C NPs on lipid membranes was investigated. Giant unilamellar vesicles (GUVs) were used as model cell membranes to observe the membrane disruption after C exposure. C NPs disrupted the positively charged GUVs but not the negatively charged vesicles, confirming the role of electrostatic forces. To quantify the C adhesion on membrane and the induced membrane disruption, a supported lipid bilayer (SLB) and a layer of small unilamellar vesicles (SUVs) were used to cover the sensor of a quartz crystal microbalance (QCM). The mass change on the SLB (Δ ) was caused by the C adhesion on the membrane, while the mass change on the SUV layer (Δ ) was the combined result of C adhesion (mass increase) and SUV disruption (mass loss). The surface area of SLB ( ) was much smaller than the surface area of SUV ( ), but Δ was larger than Δ after C deposition, indicating that C NPs caused remarkable membrane disruption. Therefore a new method was built to quantify the degree of NP-induced membrane disruption using the values of Δ /Δ and / . In this way, C can be compared with other types of NPs to know which one causes more serious membrane disruption. In addition, C NPs caused negligible change in the membrane phase, indicating that membrane gelation was not the mechanism of cytotoxicity for C NPs. This study provides important information to predict the environmental hazard presented by fullerene NPs and to evaluate the degree of membrane damage caused by different NPs.