Rapid and sensitive galactose oxidase-peroxidase biosensor for galactose detection with prolonged stability

Galactose oxidase was co-immobilised with peroxidase by drop-coating on the surface of a graphite electrode with adsorbed ferrocene. This system offers low detection limit - 0.51 mg galactose l(-1) and fast response: 44 s in phosphate buffer or 25 s in borate buffer. Optimal working potential for galactose detection was 150 mV vs. SCE (saturated calomel electrode) with optimal pH of 7.85. The storage stability was highly improved, more than 12 times in comparison to control without stabilisers, by addition of DEAE-dextran and inositol. During repeated assays for 5.25 h, signal dropped only to 95% of original one. The response was linear in phosphate buffer in the range 1-110 mg l(,)(-1) while in borate buffer linear range was extended to 3-210 mg l(-1) because of chelating effect of borate.