Effect of chain length of imidazolium ionic liquids on the l-phenylalanine induced phospholipid vesicle membranes: Fluorescence lifetime imaging microscopy study.

Phenylketonuria, a congenital metabolic defect, has been identified as a consequence of the formation of toxic l-phenylalanine fibrillar self-assembly under millimolar concentration in blood. Here, we have studied the influence of l-phenylalanine on the model lipid membrane like 1,2-diacyl-sn-glycero-phosphocholine and 1,2-dimyristoyl-sn-glycero-3-phosphocholine in the aqueous medium with millimolar concentration. The bilayers of the phospholipid vesicles are deformed after the interaction with phenylalanine, which is monitored through the fluorescence lifetime imaging microscopic study. The rigidity and shape of the phospholipid vesicles are recovered after the introduction of a short hydrocarbon chain containing imidazolium ionic liquid, 1-ethyl-3-methylimidazolium hexafluorophosphate ([C2mim]PF6). The long-chain imidazolium ionic liquid, 1-methyl-3-nonylimidazolium hexafluorophosphate (C9mim]PF6), further distorted, fused, and decreased the rigidity of the vesicle bilayer.