High Permeability of Polyunsaturated Lipid Bilayers as Applied to Attoliter Enzyme Reactors

Phospholipid vesicles encapsulated with enzymes have potential application to artificial organelles. A critical problem associated with the compartmentalized enzymes is their low reactivity because of permeability resistance of lipid bilayers to substrates. In the present work, the polyunsaturated bilayers of 1,2-dilinolenoyl-sn-glycero-3-phosphocholine (18:3-PC) were elucidated to be highly permeable to 5(6)-carboxyfluorescein at high temperatures up to 60 °C and applied to fabricate vesicles-based reactive enzyme reactors. D-Amino acid oxidase (DAO) from porcine kidney was encapsulated in 18:3-PC vesicles with each aqueous volume of 3.4 × 10–21 m3 (= 3.4 aL). The DAO-containing vesicles were highly reactive at 40 °C towards D-alanine being added to bulk solution at pH 9.0 and stably catalyzed following two types of reactions. One is the DAO-catalyzed continuous production of H2O2 in the vesicles for 30 min being detected by the free peroxidase-catalyzed oxidation of o-dianisidine in bulk solution. The o...