Effect of silica nanoparticles on cell membrane fluidity: The role of temperature and membrane composition

The increasing production and application of silica nanoparticles (SiO2 NPs) raise public concern regarding their environmental and health risks. The fluidity of the cell membrane is essential for supporting membrane proteins and regulating membrane transport. Changes in membrane fluidity inevitably influence the physiological activities of cells and even cause biological effects. In this study, the effect of SiO2 NPs on membrane fluidity was studied at 25 °C and 37 °C, and the role of membrane components in SiO2 NP-membrane interactions was investigated using giant plasma membrane vesicles (GPMVs) isolated from RBL-2H3 cells. SiO2 NPs cause a more serious membrane fluidity decrease at 37 °C than at 25 °C, which is revealed by the shift of Laurdan fluorescence emission and further quantified via forster resonance energy transfer (FRET) experiments. In addition, after the removal of 75 % cholesterol from the membrane, SiO2 NPs caused a greater extent of membrane gelation. These results indicate that SiO2 NPs prefer to interact with membranes that are more dynamic and less densely packed. Moreover, fluorescent experiments confirmed that the existence of phosphatidyl ethanolamine (PE) and phosphoinositide (PI) can mitigate NP-induced membrane gelation. Molecular dynamics simulation further demonstrated that SiO2 NPs form hydrogen bonds with the terminal of PE or PI but with the -PO4-- group in the middle of phosphatidylcholine (PC). The bonding that occurs in the terminal gives less restriction of phospholipid movement and a weaker effect on membrane fluidity. This research provides both evidence and mechanisms of SiO2 NP-induced membrane fluidity changes, which are helpful for understanding cell membrane damage and the biological effects of NPs.