Dr. Todd Duncombe and co-authors published in Analytical Chemistry

Authors: Todd A. Duncombe, Aaron Ponti, Florian P. Seebeck, and Petra S. Dittrich

Abstract: We introduce the UV–vis spectra-activated droplet sorter (UVADS) for high-throughput label-free chemical identification and enzyme screening. In contrast to previous absorbance-based droplet sorters that relied on single-wavelength absorbance in the visible range, our platform collects full UV–vis spectra from 200 to 1050 nm at up to 2100 spectra per second. Our custom-built open-source software application, “SpectraSorter,” enables real-time data processing, analysis, visualization, and selection of droplets for sorting with any set of UV–vis spectral features. An optimized UV–vis detection region extended the absorbance path length for droplets and allowed for the direct protein quantification down to 10 μM of bovine serum albumin at 280 nm. UV–vis spectral data can distinguish a variety of different chemicals or spurious events (such as air bubbles) that are inaccessible at a single wavelength. The platform is used to measure ergothionase enzyme activity from monoclonal microcolonies isolated in droplets. In a label-free manner, we directly measure the ergothioneine substrate to thiourocanic acid product conversion while tracking the microcolony formation. UVADS represents an important new tool for high-throughput label-free in-droplet chemical analysis.

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