Development of potentiometric biosensors using electrodeposited polytyramine as the enzyme immobilization matrix

Abstract

The application of electrodeposited polytyramine to the fabrication of potentiometric enzyme electrodes is described. Polytyramine and the enzyme malic acid dehydrogenase were co-deposited onto a pH-sensitive tungsten electrode. The entrapped enzyme was subsequently covalently attached to the polymer film using carbodiimide coupling. Malic acid biosensors fabricated by this method were highly reproducible with good stability, linear detection range between 0.1 and 3.5 mM malic acid and the lowest concentration of malic acid detected was 0.1 mM. Because the acid produced in the enzyme reaction titrates the buffer, the relationship between malic acid concentration and electrode potential is not Nernstian but can be empirically calibrated as a logit function. Electrodeposited polytyramine produces reproducible and stable enzyme electrodes.