Smart Droplet Microfluidic System for Single-Cell Selective Lysis and Real-Time Sorting Based on Microinjection and Image Recognition

Single-cell analysis has important implications for understandingthe specificity of cells. To analyze the specificity of rare cellsin complex blood and biopsy samples, selective lysis of target singlecells is pivotal but difficult. Microfluidics, particularly dropletmicrofluidics, has emerged as a promising tool for single-cell analysis.In this paper, we present a smart droplet microfluidic system thatallows for single-cell selective lysis and real-time sorting, aidedby the techniques of microinjection and image recognition. A customprogram evolved from Python is proposed for recognizing target dropletsand single cells, which also coordinates the operation of variousparts in a whole microfluidic system. We have systematically investigatedthe effects of voltage and injection pressure applied to the oil-waterinterface on droplet microinjection. An efficient and selective dropletinjection scheme with image feedback has been demonstrated, with anefficiency increased dramatically from 2.5% to about 100%. Furthermore,we have proven that the cell lysis solution can be selectively injectedinto target single-cell droplets. Then these droplets are shiftedinto the sorting area, with an efficiency for single K562 cells reachingup to 73%. The system function is finally explored by introducingcomplex cell samples, namely, K562 cells and HUVECs, with a successrate of 75.2% in treating K562 cells as targets. This system enablesautomated single-cell selective lysis without the need for manualhandling and sheds new light on the cooperation with other detectiontechniques for a broad range of single-cell analysis.