Formation of lipid membrane-incorporated small π-molecules bearing hydrophilic groups

Abstract

Nineteen poorly water-soluble π-conjugated molecules were evaluated in terms of their ability to be stably incorporated into lipid membranes. The resulting lipid membrane-incorporated π-conjugated guest molecules (LMIGs) were classified into four categories, including (i) those that formed stable LMIGs; (ii) those where some of the guest molecules precipitated; (iii) those that formed small self-aggregates consisting of lipids and/or guest molecules; and (iv) those that leaked some of the guest molecules into the bulk water. Compounds belonging to category (ii) were confirmed by UV-vis absorption analysis. In contrast, compounds belonging to categories (i), (iii) and (iv) were discriminated based on their ¹H NMR spectra and the broadening or disappearance of the peaks of the guest molecules and the lipids in LMIGs and large liposomes. Several LMIGs could be converted from one category to another using other lipids. Furthermore, the guest molecules belonging to category (iv) were successfully predicted using the octanol–water partition coefficient, which was calculated by simulation.