Adhesive Polydopamine-based Electrodes for Laccase and Magnetite Nanoparticles Immobilization.

Inspired by the adhesive properties of mussel foot proteins, polydopamine (PDA) spontaneous coatings have emerged as a simple surface modification approach able to cover virtually any organic or inorganic material [1]. PDA is rich in catechol, amines and imines, and its excellent biocompatibility has stimulated its application in different areas, e.g. biosensors. PDA quinone groups display latent reactivity towards primary amines allowing covalent binding of target biomolecules, such as Laccase (Lac), a well-known phenol oxidase, through a Schiff base formation or Michael type addition. The aim of this work is to optimize the catalytic activity of immobilized industrial Lac on PDA films, chemically and electrochemically grown at carbon surfaces. Magnetite nanoparticles (Fe3O4-NPs, ca. 40 nm) were also co-immobilised with Lac envisaging the enhancement of the amperometric signal [2]. PDA films with different thicknesses were grown and their electrochemical properties evaluated. Ellipsometric and AFM measurements allowed to correlate the film optical thickness and morphology, respectively, with the deposition time or growth charge. Chemically or electrochemically synthesized PDA films reveal similar properties, including hydrophilicity, however, electrochemical growth offers a better control over PDA oxidation state. A simple and effective co-immobilization of Lac, PDA and Fe3O4 NPs results in high sensitive responses towards the detection of diammonium 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonate) (ABTS), displaying a great potential to be used in portable phenolic biosensors.