Effects of Bisphenol A on DOPC/Cholesterol Binary Mixtures: Implications for Cell Membrane Integrity

This study explored the effects of bisphenol A (BPA), a residual contaminant derived from plastic materials, on binary mixtures of the phospholipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and cholesterol (Chol). These mixtures were structured into bilayers, forming giant unilamellar vesicles (GUVs), and monolayers, forming Langmuir films, whose compositions and phases are relevant for mimicking the cell plasma membrane in eukaryotic cells. The composition of the binary mixture of DOPC/Chol 8:2, representing the proportion of the primary lipid groups found in cells, was effective in inducing inward buddings when exposed to BPA, in addition to the multiple shape transformations observed for DOPC vesicles. In monolayers, BPA induced the π-A isotherm expansion of DOPC, Chol, and the binary mixtures, also mainly in the DOPC/Chol 8:2 monolayers. Consistently, polarization-modulated infrared reflection absorption spectroscopy measurements revealed more pronounced interactions between BPA and the DOPC headgroup (hydrogen bonding from the hydrogen of the BPA phenol group and the nitrogen from the DOPC choline group, preferentially) in the DOPC/Chol 8:2 monolayer compared to that in individual DOPC monolayer. The presence of Chol appears to make the DOPC headgroups more accessible for interaction, even in bilayers. These results emphasize the substantial impact of BPA on the DOPC/Chol binary mixture, highlighting its critical role in predicting the potential damage to human cell membranes.