Low Electro-Polymerization Potentials of Natural Phenols Can Improve Sensing Performances of Derived Films

Often first-generation amperometric biosensor designs are based on Red-Ox reactions that commonly generate H2O2. Unfortunately, at this potential other naturally occurring molecules such as ascorbic acid (AA) or dopamine (DA) can be oxidized. Phenylendiamines (PPD) are commonly used to avoid this problem: when these compounds are electro-deposited on the transducer surface, a highly selective membrane is formed1. Unfortunately PPD monomers are considered carcinogenic. Aim of this work was to evaluate the suitability of natural phenols as non-toxic alternatives to the ortho isomer of PPD. The electro-synthesis over Pt-Ir electrodes of natural 2-methoxy phenols such as guaiacol, eugenol and isoeugenol, and hydroxylated biphenyls like dehydrodieugenol and magnolol were fully assessed. They showed quite good values of permselectivity for biosensor application, but not as good as PPDs3. In order to improve permselectivity of films several electro-polymerization potentials were applied by means of constant potential amperometry4. The electropolymerization potentials used are significantly lower than values commonly applied and better permselective properties were obtained. The electrodes coated with phenols were stable and responsive throughout two weeks. Among the tested compounds, isoeugenol and magnolol proved as permselective as poly-ortho-PPD and may be considered as effective polymeric alternatives. Also a biosensor based on acetylcholine esterase and choline oxidase enzymes was electro-coated with a poly-magnolol film in order to prove feasibility of this newly electro-synthetized films in a first generation amperometric biosensor.