Simultaneous Detection of Dopamine and Xanthine in Human Sweat by Ultrasensitive MoB-MBene/PVA Sponge-like Hydrogel Grown on a Porous Nickel Substrate

Dopamine and xanthine are essential biomolecules for neurological disorders and oxidative stress, respectively, and their abnormal concentrations are associated with Parkinson's disease, schizophrenia, Alzheimer's disease, and renal dysfunction. To overcome the limitations of invasive conventional diagnostics, a flexible MoB/PVA hydrogel on nickel foam is fabricated for the simultaneous, non-invasive electrochemical detection of dopamine and xanthine in human sweat. It is prepared through selective alkali etching and solvothermal synthesis. Characterization of the optimized MoB-MBene hydrogel (7 wt %), such as FTIR, confirms characteristic Mo-B vibrational bands, while SEM analysis reveals a sponge-like porous morphology favorable for rapid ion transport and enhanced electroactive sites. Using the DPV technique, the MoB/PVA hydrogel/NF sensor, which has a higher active surface area, demonstrates the simultaneous detection of dopamine, with a linear range from 50 nM to 500 μM, detection limit of 0.35 nM, and sensitivity of 158 μA nM-1 cm-2, and xanthine, with a linear range of 100 nM to 1 mM, detection limit of 0.098 nM, and sensitivity of 95.2 μA nM-1 cm-2, with a peak separation (ΔEp) of 285 mV. The superior electrochemical performance is attributed to the synergistic effect arising from abundant active sites in the ion-rich MoB/PVA hydrogel, facilitating higher charge-transfer kinetics and resulting in enhanced peak currents and well-resolved peaks for simultaneous sensing with 99.6-101.3% recovery for dopamine and 99.3-101.4% recovery for xanthine. Repeatability tests (N = 4) yielded dopamine with a 0.6% RSD and xanthine with a 1.93% RSD. The flexible sensor exhibits excellent selectivity and stability for up to 4 weeks and holds potential for point-of-care and flexible wearable devices.