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A new lactose biosensor was developed by preparing a suitable copolymer of polypyrrole and poly(3,4-ethylenedioxythiophene) synthesized using the electropolymerization method. Pyrrole and 3,4-ethylenedioxythiophene monomers were deposited in the presence of sodium dodecylbenzene sulphonic acid on a platinum disc electrode, which was used as the working electrode. The sensor is based on the serial reactions of b-galactosidase and galactose oxidase immobilized on a copolymermodified platinum disc electrode. Successful synthesis of the enzyme-immobilized copolymer was confirmed by FT-IR spectrometry, SEM, and electrochemical analysis. The response of the enzyme electrode to lactose was determined by cyclic voltammetry at 1 0.40 V. The response time of the biosensor was found to be from 8 to 10 s, and the upper limit of the linear working portion was found to be at a lactose concentration of 2.30 mM with a detection limit of 1.4 3 10 25 M. The apparent Michaelis-Menten constant was found to be 0.65 mM of lactose. The effects of interferents were also investigated. Lactose concentrations determined by the biosensor were in good agreement with those measured by the reference methods. Our results show that the developed biosensor has a significant potential to the determination of lactose concentration in milk.

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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In this study, surface acoustic wave (SAW) systems are described for the removal of molecules that are unbound to micromotors, thereby lowering the detection limit of the cancer-related biomarker miRNA-21. For this purpose, in the first step, mass production of the Au/Pt bimetallic tubular micromotor was performed with a simple membrane template electrodeposition. The motions of catalytic Au/Pt micromotors in peroxide fuel media were analyzed under the SAW field effect. The changes in the micromotor speed were investigated depending on the type and concentration of surfactants in the presence and absence of SAW streaming. Our detection strategy was based on immobilization of probe dye-labeled single-stranded probe DNA (6-carboxyfluorescein dye-labeled-single-stranded DNA) to Au/Pt micromotors that recognize target miRNA-21. Before/after hybridization of miRNA-21 (for both w/o SAW and SAW streaming conditions), the changes in the speed of micromotors and their fluorescence intensities were studied. The response of fluorescence intensities was observed to be linearly varied with the increase of the miRNA-21 concentration from 0.5 to 5 nM under both w/o SAW and with SAW. The resulting fluorescence sensor showed a limit of detection of 0.19 nM, more than 2 folds lower compared to w/o SAW conditions. Thus, the sensor and behaviors of Au/Pt tubular micromotors were improved by acoustic removal systems.