The Role of Cholesterol on the Stability of Phospholipid Bilayers under the Action of DMSO

-glycero-3-phosphocholine (DOPC)-cholesterol (CHOL) bilayers were conducted in the presence of DMSO at varying concentrations and two different levels of hydration. The presence of CHOL was found, as expected, to have a condensing effect on these lipid bilayers, causing a reduction in overall area per lipid (APL) with increasing CHOL content. For fully hydrated conditions, APL values remained unaffected in the presence of dilute DMSO concentrations (0-19.2 mol %). Under dehydrated conditions, the condensing effect of CHOL counteracts the expansive action of DMSO on the bilayer. The pronounced increase in APL previously reported for dehydrated pure DOPC bilayers was reduced in 2DOPC:1CHOL bilayers at low DMSO content (0-10 mol %), while 1DOPC:1CHOL bilayers remained largely unaffected by the addition of DMSO across all concentrations investigated (0-52.6 mol %). Increased DMSO penetration correlated with the increase in APL for 2DOPC:1CHOL bilayers at 0-10.0 mol % DMSO. Counterintuitively, increasing CHOL content did not hinder the capacity of DMSO to penetrate the bilayers. Instead, DMSO penetration was enhanced at high concentrations (21.7-52.6 mol %) in 1DOPC:1CHOL bilayers, despite its greater condensation. These findings indicate that CHOL modulates and mitigates the structural effects of DMSO on DOPC bilayers without impeding its penetration, a behavior relevant to its role as a cell-penetrating CPA.