The first enzymatic biosensor made its appearance almost 60 years ago and has become one of the most widely used sensors today – the blood glucose biosensor. Since then, great progress has been made in the development of biosensors for health-monitoring applications; however, few have made it to the commercial sector. In many cases, the limiting factor is the biofluid. Oftentimes, analytes—such as proteins and hormones—maintain biologically relevant concentrations much lower than the detectable range of current sensor technologies making them useless outside of a lab setting. All sensors within fluid environments pose a unique challenge where the target analyte must compete with neighboring solutes, as well as the solvent itself. The result is an increase in background noise that drives up detection limits. Research has often focused on improving the sensor to solve these issues, such as developing new probes (aptamers, antibodies, etc.) to increase analyte specificity. However, even perfectly selective probes such as enzymes do not solve this background issue, limiting operation to µM to mM analyte concentrations. We present multiple strategies to remove the effects of redox interferent and water background currents in enzymatic sensor systems. Our methods include sophisticated filtering methods, electrode chemistry, and active approaches to mitigate redox active interferents, resulting in up to 100x reduction in detection limits. As a result, with an enzyme in hand, nM level detection becomes a real possibility, including enzymatic detection with 11-beta hydroxysteroid dehydrogenase. Importantly, our methods for reducing background current are highly generalizable, allowing enzymatic sensors to address a much wider spectrum of analytes beyond current µM to mM concentrations.

Enabling nanomolar enzymatic sensors by removal of redox-active interferents

ACS Fall 2021

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