Formation, stability, and pH sensitivity of free-floating, giant unilamellar vesicles using palmitic acid-cholesterol mixtures

Despite the fact that palmitic acid (PA) and cholesterol (Chol) do not form fluid bilayers once hydrated individually, giant unilamellar vesicles (GUVs) were formed from a mixture of palmitic acid and cholesterol, 30/70 mol/mol. These free-floating GUVs were stable over weeks, did not aggregate and were shown to be highly stable in alkaline pH compared to conventional phospholipid-based GUVs. Acidic pH-triggered payload release from the GUVs was associated with the protonation state of palmitic acid that dictated the mixing lipid properties, thus affecting the stability of the fluid lamellar phase. The successful formation of PA-Chol GUVs reveals the possibility to create monoalkylated amphiphile-based GUVs with distinct pH stability/sensitivity.