LACTATE AMPEROMETRIC BIOSENSOR BASED ON AN ELECTROSYNTHESIZED BILAYERFILM WITH COVALENTLY IMMOBILIZED ENZYME

An alternative approach to the fabrication of an amperometric biosenso r, which combines electrochemical polymerization of a bilayer film and covalent binding of the enzyme, is presented, A Pt electrode modified by an anti-interferent poly(pyrrole) layer is covered by a poly(tyram ine) film, exposing amino groups that are then used for the covalent a ttachment of lactate oxidase after activation with glutaraldehyde, In this way, a fabrication procedure is obtained that combines the advant ages of electrochemical polymerization (high spatial control, no restr ictions in electrode shape and dimension, reproducible film thickness even in the sub-micrometre range) with those of covalent binding of th e enzyme (no enzyme loss, higher response stability and increased life time of the sensor), The interferent rejection efficiency is dictated by the diffusional barrier provided by the bilayer membrane and by the degree of permselectivity that can be built up in the poly(pyrrole) f ilm, A peculiar property was displayed by the bilayer, i.e., the abili ty to separate L-lactate and residual interferent responses in the tim e domain in both flow injection and batch addition experiments, The re sulting L-lactate amperometric biosensor was characterized in terms of sensitivity, response time, linear response range, stability and reje ction of electroactive interferents.