Effects Of Multi-walled Carbon Nanotubes On Model Cell Membranes And Plasma Membrane Vesicles

Carbon nanotubes (CNTs) possess remarkable electronic, mechanical and thermal properties, hence are excellent candidates for many potential applications in capacitors, biosensors, or drug carriers.With the increasing probability of CNTs exposure to the environment, the toxicity of CNTscauses raising concerns.The direct contact between CNTs and cell membranes inducescellar internalization, potentially leading to cytotoxicity. However, effects of CNTs on membrane disruption and the pathways of CNTs across membrane are still open to debate. In this study, the interaction between multi-walled carbon nanotubes (MWCNTs) and membraneswas explored and the mechanism was discussed.Pristine, graphitized, hydroxylated and carboxylated MWCNTs with different surface properties was selected tostudy surface degree and defects of MWCNTs on membrane disruption process through the microscope. MWCNT adhesion on membraneswas monitred quantitatively by a quartz crystal microbalance with dissipation monitoring (QCM-D).Charged large unilamellar vesicles (giant unilamellar vesicles, GUVs) and supported lipid bilayers (SLBs) are applied as model cell membranes.MWCNTs were treated with bovine serum albumin (BSA) to simulate the real extracellular environment.A comprehensive characterization of untreated and BSA adsorbed MWCNTs was conducted. Negatively-charged MWCNTs can adsorb to SLBs1 and induce GUVs+disruption inmediated by electrostatic interaction. The mass loss was detected from theSLBs" after MWCNT exposure, which suggested the extraction of phospholipids.The defective degree of MWCNTs determined their adhesion amount on membranes. Both the oxygenated functional groups and unoxidized dangling carbon bonds were active sites forMWCNT-membrane interactions. The MWCNTs were observed to be engulfed inside GUVs+Carboxylated multi-walled carbon nanotubes interact with cell membrane was observed by microscopy for better understanding the pathways of CNTs across membranes.Giant plasma membrane vesicles (GPMV) were derived from rat basophilic leukemia (RBL) cells and negatively charged GUVs were used as model membranes.Effect of Ca2+ on the interaction of MWCNTswith cells, GPMV and GUVwas also studied.The presence of Ca2+accelerate cellar internalizationof MWCNTs.MWCNT can spontaneously enter GPMV and accumulate inside, but does not disrupt GPMV. However MWCNTs disrupt GUVs" in the presence of Ca2+. It indicates that individual MWCNT can be internalized into cells not only through endocytosis but also possibly through the direct membrane penetrationin the absence of energy supply.