Amperometric dimethyl sulfoxide sensor using dimethyl sulfoxide reductase from Rhodobacter sphaeroides

An amperometric dimethyl sulfoxide (DMSO) sensor was constructed based on DMSO reductase (DMSO-R). DMSO-R from Rhodobacter sphaeroides f. sp. denitrificans was immobilized by BSA-glutaraldehyde cross-linking at the surface of a glassy carbon electrode. Mediators were added to the sample solution in a free form. Several mediators (methyl viologen (MV), benzyl viologen (BV), neutral red (NR), safranin T (ST), FMN, phenazine methosulfate (PMS)), which can donate electrons to DMSO-R, were examined with the DMSO-R immobilized electrode. Among them MV was selected as a model mediator because of its wide linear response range and fast response time. The response current was effected by the measurement temperature but hardly effected by the pH of the sample solution. The response current was increased with the measurement temperature up to 50 degrees C. A response current was observed at 1 microM DMSO and the response time was 20 s under the optimum conditions. The response was observed for approximately 2 weeks. By the reduction of Schiff base in the cross-linking layer the response range became narrower but most of the response current was retained at 300 microM of DMSO for more than 5 weeks.