Electrosynthesis of polydopamine films - tailored matrices for laccase-based biosensors

This work explores the electrosynthesis of bio-inspired polydopamine thin films (ePDA), a route that is still overlooked in polycatecholamine coatings formation, aiming at the construction of prime matrices for biosensor applications. A combination of surface characterization techniques attests the electrochemical and optical properties, wettability, morphology, thickness and chemical composition of the ePDA films. ePDA coatings exhibit structural differences from the chemically synthesized polymers unveiling distinct polymerization pathways. We propose that fast electropolymerization forms a co-polymer enriched by chains of dopamine in the open form, in detriment of indole moieties, yielding more organized and conducting polymeric matrices. For thin coatings (ca. 3 nm), ePDA presents high electroactivity of pendent quinone groups, appropriate for covalent biomolecule interaction. The suitability of the functional ePDA films towards electrochemical biosensing was demonstrated through the catalytic activity of immobilized laccase. A clear improvement of transducing performances towards 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) detection was achieved when using the more electroactive ePDA thin film as supporting matrix, reaching a sensitivity of 342 mA M−1 cm−2. The new structural insights presented in this work, undoubtedly prove the advantage of electrosynthesis regarding molecular oxygen-driven polymerization to prepare more reproducible and organized polycatecholamines for amperometric sensors.