Berna Dalkıran

Electrochemical biosensing of galactose based on carbon materials: graphene versus multi-walled carbon nanotubes

In this study, two enzyme electrodes based on graphene (GR), Co3O4 nanoparticles and chitosan (CS) or multi-walled carbon nanotubes (MWCNTs), Co3O4 nanoparticles, and CS, were fabricated as novel biosensing platforms for galactose determination, and their performances were compared. Galactose oxidase (GaOx) was immobilized onto the electrode surfaces by crosslinking with glutaraldehyde. Optimum working conditions of the biosensors were investigated and the analytical performance of the biosensors was compared with respect to detection limit, linearity, repeatability, and stability. The MWCNTs-based galactose biosensor provided about 1.6-fold higher sensitivity than its graphene counterpart. Moreover, the linear working range and detection limit of the MWCNTs-based galactose biosensor was superior to the graphene-modified biosensor. The successful application of the purposed biosensors for galactose biosensing in human serum samples was also investigated.

Graphene and tricobalt tetraoxide nanoparticles based biosensor for electrochemical glutamate sensing.

Abstract An amperometric biosensor based on tricobalt tetraoxide nanoparticles (Co3O4), graphene (GR), and chitosan (CS) nanocomposite modified glassy carbon electrode (GCE) for sensitive determination of glutamate was fabricated. Scanning electron microscopy was implemented to characterize morphology of the nanocomposite. The biosensor showed optimum response within 25 s at pH 7.5 and 37 °C, at +0.70 V. The linear working range of biosensor for glutamate was from 4.0 × 10−6 to 6.0 × 10−4 M with a detection limit of 2.0 × 10−6 M and sensitivity of 0.73 μA/mM or 7.37 μA/mMcm2. The relatively low Michaelis–Menten constant (1.09 mM) suggested enhanced enzyme affinity to glutamate. The glutamate biosensor lost 45% of its initial activity after three weeks.