Development of electrochemical biosensor with nano-interface for xanthine sensing – A novel approach for fish freshness estimation

Highly sensitive, selective and mediator-free electrochemical biosensor with nano-interface for sensing xanthine using xanthine oxidase (XOx) has been developed. Towards the preparation of nano-interface, Fe3O4 nanoparticles were synthesized by thermal co-precipitation method and structural, morphological characterizations were carried out using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and field emission transmission electron microscope (FE-TEM) respectively. The modified electrode with the covalently linked XOx was confirmed by FT-IR. With the modified electrode as working electrode, electrochemical studies were carried out. The linear range was found to be from 0.4 to 2.4 nM. The biosensor exhibited an optimum response in less than 2 s and was not prone to interferences from ascorbic acid, urea and sucrose. The Michaelis–Menten constant (Km) was found to be 1.3 nM. The limit of detection is found to be 2.5 pM and limit of quantification as 8.3 pM. The developed biosensor was used for the real time measurement of fish freshness.