One-step Potentiostatic Laccase-polydopamine Deposition for Amperometric Biosensors

Electrochemical biosensors have a tremendous potential to become cheap, fast and reliable analytic tools in clinical, industrial, environmental and agricultural analyses, eliminating the need of expensive equipment, highly trained personnel and time-consuming steps [1]. Achieving such level of routinely usage requires effective biofunctionalization strategies and biocompatible materials which ensure the maintenance of the recognition performance under appropriate operational conditions. This is the case of mussel-inspired chemistry that relies on aminocatechol moieties to mimetize the high adhesion of mussels to wet surfaces [2]. It is widely known that dopamine undergoes oxidative polymerization in aerated basic medium, covering virtually any type of surface with a quinone-enriched matrix (polydopamine, PDA) that displays reactivity towards amine functions. Recently, we have demonstrated the suitability of thin PDA films (ca. 3 nm) to immobilize biologically active Glucose Oxidase and Laccase on graphite electrodes [3]. Although far less explored than the chemical route, electrochemical polymerization of dopamine, by potentiodynamic mode, is also gaining importance in the literature [4]. Hereby, we present a successful one-step electrode modification where the enzyme Laccase is co-immobilized during the potentiostatic deposition of a polydopamine film on carbon electrodes. The morphology, wettability, optical and electrochemical properties of modified electrodes with distinct concentration of enzyme and electrodeposition time, were accessed by atomic force microscopy, water contact angle, ellipsometry and cyclic voltammetry. The catalytic performance of the Laccase-polymer modified electrodes was evaluated by chronoamperometry, and optimized for 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) detection, a well-known substrate of Laccase. There is a clear improvement of the analytical parameters (apparent Michaelis-Menten constant and sensitivity) achieved for the one-step modified electrodes regarding those prepared in two steps: immobilization of Laccase on chemically or electrochemically pre-synthesized polydopamine films. The fast and efficient one-pot procedure proposed in this work is further explored in the detection of phenolic compounds.