Screen-printed tyrosinase-containing electrodes for the biosensing of enzyme inhibitors

Disposable amperometric inhibition biosensors have been microfabricated by screen printing a tyrosinase-containing carbon ink. The decrease in the substrate (catechol) steady-state current, caused by the addition of various pesticides and herbicides, offers convenient quantitation of micromolar levels of these pollutants. Unlike esterase-based disposable strips, the tyrosinase thick-film devices can be fabricated by incorporating the enzyme within the carbon ink, and do not require a prolonged incubation step in the presence of the inhibitor. The effect of experimental variables, such as the enzyme loading or substrate concentration, is assessed. Applicability to an untreated river water sample is illustrated. Such use of single-use devices for monitoring toxins addresses the problem of irreversible enzyme inhibition, and holds great promise for on-site field analysis.