An electrochemical wearable sensor for levodopa quantification in sweat based on a metal–Organic framework/graphene oxide composite with integrated enzymes

Levodopa (L-dopa) is an effective medication for Parkinson's disease. However, excess intake from overdose or the intake of natural sources of L-dopa can be dangerous, causing, for example, tardive dyskinesia. Therefore, in medicated individuals, it is important to monitor the levels of L-dopa in the body. In this paper, we report a simple, wearable, noninvasive, and portable metal−organic framework (MOF)-based electrochemical sensor with integrated enzymes for monitoring the concentration of levodopa in sweat, which can be used as a proxy for L-dopa levels in the body. Zeolitic imidazolate framework/graphene oxide (ZIF-8/GO) composites were prepared by the in-situ growth of ZIF-8 nanoparticles on the surface of GO, and, subsequently, tyrosinase was loaded onto the composite to yield the sensor. Integration with a wireless electronic circuit enabled communication between the sensor and a smartphone application for continuous analysis. The sensor was found to have a wide linear response range from 1 to 95 µM, a low limit of detection of 0.45 µM, satisfactory reproducibility, and excellent selectivity. In addition, the sensor showed high sensitivity and good stability as a result of the anchoring of the enzyme. Thus, the sensor shows promise for continuous, noninvasive point-of-care drug monitoring and management.