In-VitroDevelopment and Characterisation of a Superoxide Dismutase-Based Biosensor.

Abstract

A first generation amperometric biosensor for the detection of superoxide (O2−) was constructed utilising a dip-coating approach for immobilising the enzyme superoxide dismutase (SOD, 200 U/mL) onto a Pt electrode. Several dip-coating procedures were investigated, incorporating styrene, glutaraldehyde, bovine serum albumin and polyethylenimine at various concentrations, in order to develop a simple and reproducible coating method to maximise the sensitivity of the sensor to O2−. The optimised design was produced using 5 dip-coatings and a composite containing 200 U/mL SOD, 0.5 % glutaraldehyde and 2 % polyethylenimine (Sty-(SOD-0.5 %GA-2 %PEI)5). This sensor displayed excellent permselective characteristics with negligible signals produced by 12 of the most common electroactive species present in brain extracellular fluid, including uric acid (UA) which is produced as a by-product of the O2− generating xanthine-xanthine oxidase calibration method. In addition, it had a response time of ca. 1 s, high sensitivity to O2− (0.91 ± 0.02 nA/μM), and an in-vitro limit of detection of ca. 0.063 μM, thus suggesting potential use for neurochemical monitoring of O2− in-vivo.