In this study, a new lactose biosensor has been developed in which the 3,4-ethylenedioxythiophene/thiophene (EDOT/Th) copolymer is used as a transducer. The EDOT/Th copolymer was deposited on the glassy carbon electrode to be used as the working electrode. In addition to the working electrode, the three-electrode system was used in both the electrochemical synthesis and in the biosensor measurements. Lactase (β-galactosidase) that catalyzes the breakdown of lactose into monosaccharides (glucose and galactose) and galactose oxidase that catalyzes the oxidation of the resulting galactose were attached to the copolymer by a cross-linker on the modified working electrode. The response of the enzyme electrode to lactose was determined by cyclic voltammetry (CV) at +0.12 V. Enzyme electrode optimization parameters (pH, temperature, enzyme concentration, etc.) were performed. Fourier transform infrared spectroscopy, scanning electron microscopy and CV methods were used to support copolymer formation. In addition, the characteristics of the enzyme electrode prepared in this study (Km, 0.02 mM; activation energy Ea, 38 kJ/mol; linear working range, up to 1.72 mM; limit of detection, 1.9 × 10−5 M and effects of interferents [uric acid and ascorbic acid]) were determined.

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A low-cost and sensitive amperometric biosensor was developed for the determination of α-amylase activity. The biosensor was constructed by immobilizing glucose oxidase-gelatin via glutaraldehyde on the Au electrode surface. Measurements were carried out chronoamperometrically at -0.7 V. Several parameters such as glucose oxidase activity, gelatin amount, and glutaraldehyde percentage for cross-linking were optimized. Optimum pH, optimum temperature, repeatability, and storage stabilities of the biosensor were identified. Under the optimum experimental conditions, a linear calibration curve was obtained for α-amylase between 0.819 and 13.110 U/ml. Sample analyses were carried out by detecting α-amylase activities in baker's yeast samples.

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