Electropolymerised o-phenylenediamine film as means of immobilising lactate oxidase for a L-lactate biosensor

Abstract

The immobilisation of L-lactate oxidase at a platinum electrode was achieved by entrapping the enzyme within an o-phenylenediamine film at 0.65 V ( vs. Ag/AgCl). Anodic detection of the product of the enzymatic reaction, i.e., hydrogen peroxide, at 0.75 V ( vs. Ag/AgCl) was employed for the quantification of L-lactate using amperometric batch and flow injection methods. This technique allows the enzyme to be entrapped in a strongly adherent thin membrane. The sensor exhibits a very fast response time, an active enzyme loading of 5 mU/cm 2 electrode surface, and high sensitivity with a detection limit of 2.46 × 10 −7 M. A sample throughput of 180/hr, precision of 3.53% for 25 injections and linearity up to 1.5m M were obtained in flow injection analysis studies. The one-step procedure for sensor preparation requires 20 min, and the discriminative properties of the polymer film show great promise as a means of excluding interfering compounds commonly found in serum.