Electroactive layer-by-layer films of hemeprotein-coated polystyrene latex beads with poly(styrene sulfonate)

Abstract

In this work, a novel two-step construction strategy for protein layer-by-layer assembly films was proposed. In the first step, positively charged hemoglobin (Hb) or myoglobin (Mb) at pH 5.0 was adsorbed on the negatively charged surface of 500 nm diameter-sized polystyrene (PS) latex beads, forming core-shell structured PS–protein particles. In the next step, the PS–protein particles were further assembled layer by layer with oppositely charged poly(styrene sulfonate) (PSS) on various solid surfaces under suitable conditions. Cyclic voltammetry (CV), quartz crystal microbalance (QCM), and UV-vis spectroscopy were used to monitor the growth of {(PS–protein)/PSS}_n films. The stable {(PS–protein)/PSS}_n films modified on pyrolytic graphite (PG) electrodes demonstrated good electroactivity in protein-free buffer, which was originated from protein heme Fe(III)/Fe(II) redox couples, and the electroactivity extended to six (PS–protein)/PSS bilayers. UV-vis spectroscopy showed that Hb and Mb in the films retained their near-native structure in the medium pH range. {(PS–protein)/PSS}_n films catalyzed electrochemical reduction of oxygen, hydrogen peroxide, trichloroacetic acid (TCA) and nitrite with a significant lowering of overpotential, and displayed better catalytic activity than corresponding cast PS–protein films.