Toward hybrid proteo-polymeric vesicles generating a photoinduced proton gradient forbiofuel cells

Abstract

We describe our efforts towards constructing a hybrid protein–polymer vesicle device based onthe photoactive protein, bacteriorhodopsin (BR), for applications in the area of biosensorsand biofuel cells. Successful protein incorporation into biomimetic polymer vesicles is aprerequisite for developing hybrid ‘nano–bio’ integrated devices. We suggest a systematicprocedure for creating energy transducing, protein-incorporating, functional vesicles, basedon the morphological ternary diagram. First, we constructed the morphologicalternary diagram of the water/ethanol/polymer system with a size distribution ofvesicles. The polymer used was an ABA triblock copolymer, PEtOz–PDMS–PEtOz[poly(2-ethyl-2-oxazoline)-b-poly(dimethylsiloxane)-b-poly(2-ethyl-2-oxazoline)]. Second, we incorporated BR in the form of purple membrane(PM) into polymer vesicle membranes under several different conditions, based on themorphological ternary diagram. Generation of electrochemical energy by BR protonpumping was checked by monitoring the pH change in parallel with transmission electronmicroscope analysis. The morphology of the polymer vesicles changed very little with theaddition of PM. This work shows that the morphological ternary diagram provides asystematic method for constructing successful hybrid BR-incorporating biomimeticpolymer vesicles.