Effects of SiO2 nanoparticles on phospholipid membrane integrity and fluidity.

Silicon nanoparticles (NPs) are widely used nanomaterials and reported to have pathogenicity. Effects of five different SiO 2 NPs on the membrane integrity and fluidity were studied using giant unilamellar vesicles (GUVs) as model cell membranes. GUVs were made from 1,2-dioleoyl- sn -glycero-3-phosphocholine (DOPC) by gentle hydration method, and adjusted to be positively- or negatively-charged by adding charged lipids into vesicles. SiO 2 NPs caused more serious damage to oppositely-charged membrane because electrostatic attraction favored the hydrogen bonding to the phospholipids. Increase in NP exposure dose/time and NP sedimentation process aggravated the membrane damage. The membrane phases were evaluated applying the fluorescent probe Laurdan and the calculated generalized polarization (GP) values. Anionic SiO 2 NPs increased the GP value and induced membrane gelation. Cationic SiO 2 NPs did not change the phase of positively-charged GUV and pure DOPC vesicles, but induced the gelation of negatively-charged GUV. Break of membrane integrity and change in membrane phase are possible mechanisms of cytotoxicity because cellular physiological activities require a separated intracellular environment and a fluid membrane phase to support proteins and regulate molecular transport. [ABSTRACT FROM AUTHOR]