Real-time studies of plasma membrane damage trigger cell apoptosis from sulfhydryl nanoparticles to support safety assessment of nanoscale materials

Abstract Background: Sulfhydryl groups are present on the surface of nanoparticles in unburned vehicle exhaust and most air pollutants produced by combustion, which raises the risk for exposure of human. Sulfhydride nanoparticles not only penetrate the skin range from the stratum corneum to pass below the dermis, they also entering the systemis circulation from cell endocytosis pass way. The potential risk of skin and body healthy associated from sulfhydride nanoparticles were attach much attentions. It is important to illuminate the underlying toxicity of sulfhydride nanoparticles to humanbody, but the mechanisms underlying the toxicity of nanoparticles on cells remain unclear, especially the relationship from the damage of cells plasma membrane and the cell cycle.Methods: We performed time-response studies and cells-membrane interaction studies in C6 cells to observe the effects of 50nm and 200nm sulfhydryl nanoparticles on the activities, cell metabolism and cell cycle. The cells were exposed to 0, 10 or 20 Nano particles for 12, 36, 24, 48 or 72h to finish the particle- response studies. On the time of treatment, cells were collected to assess the expression of tight junction-associated proteins, P21, FBW7 and cyclin E. To further investigate the mechanisms underlying nanoparticle-induced dysregulation of tight junction-associated protein, we studied the change of lipid bilayers. Sum frequency generation optic spectrum was carried out to study the membrane change. Results: The results show that the smaller particles penetrate the plasma membrane and without bilayer disruption, whereas the larger one will pilled off one leaflet of the membrane, they are mostly trapped in endosomes. The larger ones result in slow but unrepairable cell necrosis and caused cell cycle regulation disorders via disturbing the expression of p21, cyclin E, and FBW-7. Conclusion: The results suggest that the destruction of membrane structure by the particles will cause irreversible biological damage, and particles entering cells through protein assisted process will increase the expression of cell cycle related proteins and cells self-repair can be observed from the in vitro experiments. From the interactions between mitochondria lipid model and nanoparticles, we deduced that, the efficiencies of nano-scaled drugs could be enhanced by altering the interaction models of nano systems and mitochondria. In the future, mitochondria membrane proteins would also be carefully explored to confirm their roles in the active mitochondrial uptake of nanoparticles and provide new channels for safe and effective mitochondria targeting drug delivery. Real-time studies of plasma membrane damage from sulfhydryl nanoparticles, and analysis the triggering of cell apoptosis, will support safety assessment of nanoscale materials.