Effect of Coordinated Solvent Molecules in Cu-MOF on Enzyme Free Sensing of Glucose and Lactate in Physiological pH

Developing a nonenzymatic sweat sensor for selective determination of glucose and lactate holds great significance in clinical diagnostics. Among various catalysts, transition metal-based metal-organic frameworks (MOF) have recently drawn more attention due to their tunable porosity and enhanced electrocatalytic activity. The presence of the solvent molecule in the framework can influence both structural and electrochemical properties. In the present work, Copper-terephthalate (CuBDC) MOF was synthesized in a solvothermal method with different time durations. The effect of the coordinated solvent molecules on the metal centre on structural and electrocatalytic properties was systematically investigated using various characterization techniques. As most of the copper-based composites reported so far showed performance in an alkaline medium, we demonstrate the detection of glucose and lactate in a neutral medium that enables direct analyte measurement from the body fluid. Electrochemical studies indicate that the solvated structure shows superior sensitivity to the desolvated MOF for glucose and lactate. The high sensitivity of the solvated MOF is attributed to the favourable solvent exchange mechanism and ion diffusion through the channels of the MOF. Furthermore, CuBDC12E and CuBDC48E show negligible interference toward competing analytes. The proposed sensor also exhibits good sensing performance in artificial sweat, making it suitable for a non-invasive, practical sweat sensor.