Continuous measurement of enzymatic kinetics in droplet flow for point-of-care monitoring.

Droplet microfluidics is ideally suited to continuous biochemical analysis, requiring low sample volumes and offering high temporal resolution. Many biochemical assays are based on enzymatic reactions, the kinetics of which can be obtained by probing droplets at multiple points over time. Here we present a miniaturised multi-detector flow cell to analyse enzyme kinetics in droplets, with an example application of continuous glucose measurement. Reaction rates and Michaelis-Menten kinetics can be quantified for each individual droplet and unknown glucose concentrations can be accurately determined (errors <5%). Droplets can be probed continuously giving short sample-to-result time (∼30 s) measurement. In contrast to previous reports of multipoint droplet measurement (all of which used bulky microscope-based setups) the flow cell presented here has a small footprint and uses low-powered, low-cost components, making it ideally suited for use in field-deployable devices.