Construction of novel xanthine biosensor by using polymeric mediator/MWCNT nanocomposite layer for fish freshness detection

• Preparation of poly(GMA-co-VFc)/MWCNT/Xo bio nanocomposite for biosensor construction.
• Highly sensitive and selective amperometric biosensor is developed for the determination of xanthine.
• The biosensor was used to determine the xanthine in real sample with satisfactory results.

A novel nanocomposite host matrix for enzyme immobilization of xanthine oxidase was developed by incorporating MWCNT in poly(GMA-co-VFc) copolymer film. In the food industry fish is a product with a very low commercial life, and a high variability as well elevated level of xanthine is an important biomarker as a sign of spoilage. The fabricated process was characterized by scanning electron microscopy (SEM), and the electrochemical behaviors of the biosensor were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The prepared enzyme electrodes exhibited maximum response at pH 7.0 and 45 °C +0.35 V and reached 95% of steady-state current in about ∼4 s and its sensitivity was 16 mAM−1. Linear ranges (2–28 μM, 28–46 and 46–86 μM), analytical performance and a low detection limit 0.12 μM obtained from the xanthine biosensor gives reliable results in measuring xanthine concentration in the fish meat. All the results indicating that the resulting biosensor exhibited a good response to xanthine that was related to the addition of MWCNT in the polymeric mediator film which played an important role in the biosensor performance. In addition, the biosensor exhibited high good storage stability and satisfactory anti-interference ability.