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In this study, radiolytic functionalization of fullerene in methanol/1,2-dichlorobenzene mixtures and its applications with respect to biosensor support materials were studied. To obtain supports for biosensors for electron transfer, fullerene was functionalized by c-irradiation in a methanol/1,2-dichlorobenzene mixture solution. The hydroxyl group-modified fullerene, F-fullerene, was characterized by Fourier-transform infrared, Raman spectroscopy, MALDI-TOF mass spectroscopy, and elemental analysis. As a result, the main hydroxyl group was successfully introduced on the surface of fullerene. F-fullerene was found to disperse well in water by ultrasonication. The results indicated that F-fullerene is a good candidate for use in biological systems as a biosensor support material. A biosensor based on F-fullerene was prepared by hand-casting the mixture of tyrosinase, F-fullerene, and 2% chitosan solution on an ITO electrode. Furthermore, the prepared biosensor was optimized pH and temperature. The prepared biosensor was then evaluated for its ability to analyze phenolic compounds contained in commercial red wines. The total phenolic concentration was determined to be in the range of 397-895 mg/L. From these results, the electron transfer ability of F-fullerene was improved on an enzyme biosensor.

Electrochemical DNA (E-DNA) biosensors were fabricated by the physical immobilization of probe DNA, 5 0 -GGA GCT GCT GGC ATT ATT GAA-3 0 , on ionicliquid-multiwalled carbon nanotubes (IL-MWNTs) modified with indium tin oxide (ITO) electrodes to detect Salmonella typhi (S. typhi). IL-MWNTs were prepared by the introduction of 1-butylimidazole bromide onto an epoxy group on poly(GMA)-grafted MWNTs, which were synthesized by radiation-induced graft polymerization of glycidyl methacrylate (GMA) onto MWNTs in aqueous solution. Subsequently, IL-MWNTs were coated onto the ITO electrode surface, and then the physical immobilization of the probe DNA performed in probe DNA solution at room temperature for 1 h. The IL-MWNTs were characterized by elemental analysis, XPS, and TGA. The electron transfer resistance (R et ) of the E-DNA biosensor was evaluated after hybridization of the probe DNA and target DNA using elec-trochemical impedance spectroscopy. The R et increased after the hybridization of probe DNA and target DNA. The DNA used was complementary DNA: 5 0 -TTC AAT AAT GCC AGC AGC TCC-3 0 , single-base mismatch DNA: 5 0 -TTC AAT AAT GGC AGC AGC TCC-3 0 and three-base mismatch DNA: 5 0 -TTC ATT AAT GGC AGC ACG TCC-3 0 . The dynamic detection range for the sequence-specific DNA of target DNA was from 1.0 Â 10 À13 to 1.0 Â 10 À10 mol L À1 with a regression equation R et (X) ¼ 18.6 C þ 128 and regression coefficient (c) of 0.996. The detection limit was determined to be 3.1 Â 10 À14 mol L À1 . The results demonstrated that the sensitivity of this impedance-based DNA sensor was sufficient for the target DNA sequence detection.

A biosensor comprisingtyrosinaseimmobilized on bifunctionalized multiwalled carbon nanotube (MWNT) supports was prepared for the detection of phenolic compounds in drinks such as red wine and juices. The MWNT supports were prepared by radiation-induced graft polymerization (RIGP) of epoxy-containing glycidyl methacrylate (GMA), to covalently immobilize thetyrosinase, and vinyl ferrocene (VF), which can act as an electron transfer mediator via redox reactions. The bifunctionalized MWNTs were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). Electrodes prepared with the MWNTs showed increased current with increasing VF content. A biosensor comprisingtyrosinaseimmobilized on the bifunctionalized MWNTs could detect phenol at 0.1–20 mM. Phenolics in red wine and juices were determined using the biosensor after its calibration.

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