(229bi) High-Throughput Combinatorial Drug Screening of Caenorhabditis Elegans Using Droplet-on-Demand Technology

The nematode Caernorhabditis elegans (C. elegans) is an excellent model organism for research on neurodegenerative disorders. The ability to assay worm behavior in response to multiple cues is important for drug screening to assess potential synergistic or interferential effects. However combinatorial screening is difficult because of the complexity of sample preparation and costs of the drugs. Droplet microfluidic technology can address the cost by reducing volume consumption by several orders of magnitude. However, handling C. elegans in droplets remains challenging due to the animalsâ?? ability to locomotion and interaction with structures on-chip.

Here we present a platform to enable high-throughput combinatorial screening of drugs for C. elegans. Animals are encapsulated in individual droplets and ordered in an array for imaging. The chambers are designed to have a trapping capacity over a wide range of volume, enabling sequential loading of droplets containing worms and stimuli, and to release the droplets on demand. We optimized structured wall design to obtain 100% trapping efficiency. Chemical reagents are mixed on chip to create combinatorial stimuli in an automated way via the actuation of valves and then delivered to the worms. Upon merging of droplets, worm responses are recorded, then the array is flushed, freeing space for the next batch. Videos are subsequently analyzed, screening for specific behaviors. To demonstrate screening capability, we studied worm responses to an anesthetics (tetramisole). Thrashing frequency as a function of drug concentration was analyzed over time to quantify paralysis, using a custom MATLAB program. We demonstrate strong increase of paralysis efficiency with increased drug concentration.

This platform provides a robust method to perform high-throughput combinatorial screening of chemicals in C. elegans, using droplets on demand to create mixtures while minimizing reagent consumption. We envision this platform to be determinant in discovering drugs or deciphering genetic basis of neurodegenerative disorders.