Nanohybrid electrochemical enzyme sensor for xanthine determination in fish samples.

An amperometric biosensor for xanthine was designed, based on covalent immobilization of xanthine oxidase (XO) of Bacillus pumilus RL-2d onto a screen-printed multi-walled carbon nanotubes gold nanoparticle-based electrodes (Nano-Au/c-MWCNT). The carboxyl groups at the electrode surface were activated by the use of 1-Ethyl-3-(3-dimethylaminopropyl carbodiimide) (EDC) and N-hydroxysuccinimide (NHS). The working electrode was then coated with 6 μL of xanthine oxidase (0.273 U/mg protein). The cyclic voltammetry (CV) study was done for the characterization of the sensor using [K3Fe(CN)6] as an artificial electron donor. The sensitivity (S) and the limit of detection (LOD) of the biosensor were 2388.88 µA/cm2/nM (2.388 µA/cm2/µM) and 1.14 nM, respectively. The developed biosensor was used for determination of fish meat freshness.