High diversity droplet microfluidic libraries generated with a commercial liquid spotter

Christian A Siltanen,Chen Sun,Jesse Q Zhang,Adam R Abate,Kai-Chun Chang,Zev J Gartner,Russell H Cole,Ata Dolatmoradi

doi:10.1038/s41598-021-83865-y

Abstract

Droplet libraries consisting of many reagents encapsulated in separate droplets are necessary for applications of microfluidics, including combinatorial chemical synthesis, DNA-encoded libraries, and massively multiplexed PCR. However, existing approaches for generating them are laborious and impractical. Here, we describe an automated approach using a commercial array spotter. The approach can controllably emulsify hundreds of different reagents in a fraction of the time of manual operation of a microfluidic device, and without any user intervention. We demonstrate that the droplets produced by the spotter are similarly uniform to those produced by microfluidics and automate the generation of a ~ 2 mL emulsion containing 192 different reagents in ~ 4 h. The ease with which it can generate high diversity droplet libraries should make combinatorial applications more feasible in droplet microfluidics. Moreover, the instrument serves as an automated droplet generator, allowing execution of droplet reactions without microfluidic expertise.

Highlights

Droplet libraries consisting of many reagents encapsulated in separate droplets are necessary for applications of microfluidics, including combinatorial chemical synthesis, DNA-encoded libraries, and massively multiplexed PCR
In enzyme screening, the sample can consist of microbes expressing variants from a library[6], while in single cell genomics, it can consist of cells with distinctive molecular features[7]
Drug screens test hundreds of compounds, individually or in combination, against model systems to elicit a desired response[11]. Such combinatorial applications would greatly benefit from the speed and efficiency of droplet microfluidics, but have been limited by the difficulty of rapidly generating libraries of distinct reagent droplets

Summary

Introduction

Droplet libraries consisting of many reagents encapsulated in separate droplets are necessary for applications of microfluidics, including combinatorial chemical synthesis, DNA-encoded libraries, and massively multiplexed PCR. Droplet microfluidics uses micron-scale water-in-oil emulsions to conduct assays at high throughput and using minimal reagents. Such combinatorial applications would greatly benefit from the speed and efficiency of droplet microfluidics, but have been limited by the difficulty of rapidly generating libraries of distinct reagent droplets.

Results

Conclusion