Photoinduced, polyelectrolyte-driven release of contents of phosphatidylcholine bilayer vesicles

We report herein a new approach to the photoinduced release of contents of lipid bilayer vesicles. The method builds on prior work from this laboratory, in which it was shown that adsorption of the hydrophobic polyelectrolyte poly(2-ethylacrylic acid) (PEAA, 1) on phosphatidylcholine (PC, 2) membranes causes conversion of the lipid from vesicular to mixed micellar form. The adsorption of PEAA and the attendant vesicle-to-micelle transition are driven by increasing proton concentration, such that PC vesicles that are resistant to leakage at pH 7.4 can be induced to release their contents rapidly and quantitatively upon mild acidification. In the work described herein, we have used 3,3’-dicarboxydiphenyliodonium salts (3) as water-soluble, photosensitive proton sources. Irradiation of vesicular PC suspensions prepared in dilute aqueous solutions of 1 and 3 results in rapid loss of vesicle contents