Colorimetric and Electrochemical Dual-Mode Biosensor Based on MnCu@N-Ti₃C₂T_x for Ultrasensitive Detection of Xanthine

Accurate quantification and monitoring of xanthine are vital for assessing human health. Herein, a novel dual-mode electrochemical-colorimetric cascade sensing platform based on a MnCu-decorated nitrogen-doped Ti₃C₂T_x nanosheet (MnCu@N-Ti₃C₂T_x, T_x = -OH, -F, and -O^-) was developed for xanthine detection. In this cascade system, xanthine acts as the initiator, activating xanthine oxidase (XOD) to produce H₂O₂ (enzymatic reaction I), which subsequently triggers the peroxidase-like activity of MnCu@N-Ti₃C₂T_x to generate •OH (enzymatic reaction II), establishing an efficient enzymatic cascade. Furthermore, the MnCu@N-Ti₃C₂T_x provided a quick electron transfer pathway for the oxidation of xanthine. The dual-mode sensing platform integrating both electrochemical and colorimetric readouts achieved impressive detection limits of 37.6 nM (electrochemical) and 81.9 nM (colorimetric), with effectively eliminated interference from competing reactive pathways coupled with enhanced detection accuracy. Practical validation of sensor performance in real serum samples demonstrated excellent recovery rates (92.2-105.8%), confirming the precision and suitability for real-world applications. Overall, the accurate and ultrasensitive determination of xanthine by the proposed novel sensing method makes it promising for advanced sensing applications and personalized medicine.