Abstract
Lactose sensors were fabricated by an avidin/biotin method. Biotinylated glucose oxidase (GOx) and β-galactosidase (β-Gal) formed bienzyme membrane on a Pt electrode by a layer-by-layer deposition of avidin and the biotinylated enzymes. The modified electrode functioned satisfactorily as a lactose sensor, in which two enzymatic reactions were coupled. Ten layers of GOx were deposited on the electrode, and then β-Gal layers were deposited step by step on the GOx layer. The response current of the sensor to lactose increased with increasing the number of depositions of β-Gal; Imax values were 8.4 nA for 2 layers, and 81.3 nA for 12 layer of β-Gal.Three types of arrangement of the enzymes in the membrane were prepared; (5x GOx)+(5x β-Gal), (5x β-Gal)+(5x GOx) and 5x (GOx+β-Gal). The sensor modified with the alternate layers of GOx and β-Gal, 5x (GOx+β-Gal), exhibited a highest signal for lactose. The avidin/biotin method was shown to be useful to optimize composition of the bienzyme membrane.
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