Mytilus edulis Adhesive Protein (MAP) as an Enzyme Immobilization Matrix in the Fabrication of Enzyme-Based Electrodes

A simple enzyme immobilization technique using an adhesive protein isolated from Mytilus edulis blue mussels was optimized for constructing a glucose oxidase (GOD) based electrode. Owing to the presence of 10-15% of 3,4-dihydroxyphenylalanine residues, the mussel adhesive protein (MAP) was easily oxidized to form a stable protein film on platinum, gold and glassy carbon electrodes. Covalent attachment of glucose oxidase to adhesive protein modified electrodes was attained since the oxidized form of the L-Dopa moieties was very reactive towards various compounds containing amino, alcohol and thiol groups. Glucose detection was performed using MAP/GOD modified electrodes at +0.8 V in 0.1 M phosphate buffer, pH 5. Platinum modified electrodes (Pt/MAP/GOD) exhibited a considerably higher sensitivity (1.28 μA/mM) in comparison to its gold (Au/ MAP/GOD, 2.92nA/mM) or glassy carbon (GC/MAP/GOD, 2.62nA/mM) counterparts. Tetrachloro-1,4-benzoquinone (TCBQ), an oxidation product of pentachlorophenol, was detected using MAP/GOD modified electrodes at +0.45 V in a deaerated 0.1 M tartaric acid buffer, pH 3.5 containing 40 mM glucose. In steady state, the current response of the Au/MAP/GOD electrode was higher (6.62 nA nM^-1cm^-2, t₉₅, = 83 s, 5 nM) than the GC/MAP/GOD electrode (3.78 nA nM^-1 cm^-2, 8 nM). In flow injection analysis, GC/MAP/GOD electrodes exhibited a linear response for TCBQ ranging from 10 nM to 1 μM (3.96 nAs nM^-1) with a detection limit of 10 nM. The modified glassy carbon enzyme based electrode retained 90 % and 87 % of its activity after 150 and 250 repeated injections.