Alginate Film Preparation, Characterization And Electrochemical Study

In this work, a novel two-step construction strategy for protein assembly films was proposed. The first step was the preparation of porous calcium alginate (CA) films by spraying calcium chloride (CaCl2) solution over the mixture surface of sodium alginate (SA) and polyethylene glycol (PEG) on various solid substrates. The second step involved the cast of myoglobin (Mb) onto the porous CA films and then formed the electroactive porous Mb-CA films. The nitrogen adsorption desorption isotherm, scanning electron microscope (SEM), alternating current impendence (A.C. impendence) and cyclic voltammetry (CV) were used to characterize the porous films. Fully hydrated porous CA films had nearly90wt%water contents and UV-vis showed that Mb in the porous films retained its near native conformation at medium pH. The stable films modified on glassy carbon (GC) electrode demonstrated good electroactivity in protein-free buffer, which was originated from protein heme Fe(III)/Fe(II) redox couples. The electrochemical parameters such as apparent heterogeneous electron transfer rate constant (ks) and formal potential (E°) were estimated by fitting the data of square-wave voltammetry (SWV) with nonlinear regression analysis. The formal potential of the Mb Fe(III)/Fe(II) couple in porous CA films shifted linearly between pH4.0and11.0with a slope of-52.7mV pH-suggesting that one proton transfer is coupled to each electron transfer in the electrochemical reaction. Porous Mb-CA films showed the electrocatalytic activity toward dioxygen, hydrogen peroxide and nitrite with significant decreases in the electrode potential required, and exhibited good operational and storage stability, reproducibility and fast response time for H2O2detection. It is showing the possible future application of the films for biosensors and biocatalysis.