Loading of myoglobin into layer-by-layer films assembled by concanavalin A and dextran based on their biospecific recognition: An electrochemical study

Lectin protein concanavalin A (Con A) and polysaccharide dextran (Dex) were assembled into {Con A/Dex}n layer-by-layer (LBL) films by biospecific affinity between them. The films were then immersed in myoglobin (Mb) solution to load Mb into the films, designated as {Con A/Dex}n-Mb. Quartz crystal microbalance (QCM), cyclic voltammetry (CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS) were used to monitor the growth of {Con A/Dex}n films and characterize the {Con A/Dex}n-Mb films. The Mb in {Con A/Dex}n-Mb films showed a quasi-reversible CV peak pair for its heme Fe(III)/Fe(II) redox couple, and the Mb-loaded films could be used to electrocatalyze the reduction of oxygen and hydrogen peroxide. The formal potential of Mb (E°′) and the surface concentration of electroactive Mb (Γ*) in the films were affected significantly by the environmental pH. The driving forces of {Con A/Dex}n film assembly and Mb loading into the films were investigated. This model protein-loaded LBL films may guide us to develop novel electrochemical biosensors based on the direct electrochemistry of enzymes.