Generation And Optimization Of Microfluidic Droplet For High-Throughput Screening

Droplet microfluidics, formed in microfluidic devices by manipulated small amounts of liquids, is a new technology in recent years. The use of droplets as individual nanoliter to picoliter reactors, droplets have been used to measure fast enzyme kinetics, for cell-based assays, DNA analysis, protein crystallization. The droplet microfluidic system could generate uniformed droplets with respect to the size and shape. Compared with traditional microtiter plates screening technology, droplet microfluidics has already demonstrated a1000-fold increase in throughput for applications such as the directed evolution of enzymes. Droplet microfluidics technology thus holds great promise as a platform for the next generation of ultrahigh-throughput screening applications. It was still in the stage of basic research in China, little work has been done. In this study, the analysis of the performance metrics-droplet size, droplet generation, throughput, liquid choice, stability, diffusibity and bio-compatibility-of droplet-based assays were developed, and.the applications of droplet microfluidics were explored.In this paper, PDMS-based mcirofluidic chips were designed and fabricated for the research by the moulding. The mineral oil containing3%(V/V) non-ionic surfactant Abil EM90as the continuous phase, the double enzyme coupling fluorescence reaction reagents were added as the water phase. The generated water-in-oil micro-droplets based on the custom-designed mcirofluidic chips, had a controllable size between20to50μm, close to cell diameter between1to20μm, and a throughput about3.6×104to1.8×105droplets per hour. The droplet has a good uniformity and monodispersity in independent experiment.The generated micro-droplets were then used as micro-reactors to encapsulate important amino acids such as glutamic acid, phenylalanine, tryptophan or tyrosine, and characterized for the stability, diffusibity and bio-compatibility for their application in amino acid detection. The results showed after incubationed for20hours at room temperature, more than95%of droplets were remained stable, and the molecular exchange between droplets is less than2%. Based on the custom-designed mcirofluidic system, the droplets encapsulated with amino acids were then examed according to their fluorescence signal. The throughput of detection and sorting is about600mciro-droplets per minute. A good linear relationship between the PMT signal and the glutamic acid concentration (Correlation coefficient0.966).In this paper, this study provides a foundation for the application of droplet-based microfluidic screening system in the directed evolution of enzyme and screening of cell and its metabolites.