“Cell‐On‐Demand” Digital Microfluidics for Real‐Time Low‐Abundance Single‐Cell Isolation and Sample Analysis

Abstract Studying low‐abundance cells at the single‐cell level is critical for revealing unique biological functions. Efficient single‐cell isolation technology can significantly enhance low‐abundance single‐cell detection sensitivity. However, the lack of individual control over each target cell hinders further bio‐analysis. Here, a “cell‐on‐demand” large‐scale digital microfluidics platform is reported for real‐time low‐abundance single‐cell manipulations. Compared to the conventional strategy that sequentially identifies the target cells among the heterogeneous population, the “cell‐on‐demand” method can conduct targeted‐search‐guided target cell isolation, enabled by on‐demand droplet splitting. The results demonstrate that “cell‐on‐demand” is nearly eightfold more effective compared to the conventional strategy in dealing with low‐abundance (1%) single‐cells. To validate the system's feasibility, heterogenous tumor spheroids samples are used for isolating homogeneous single‐target tumor spheroids, in integration with subsequent drug sensitivity testing and analysis. Drug sensitivity results show significant differences in half‐maximal inhibitory concentration (IC50) for three chemotherapy drugs: Fluorouracil, Irinotecan, and Oxaliplatin, while in high consistency with well‐plate‐based assays. With the capability of processing both high and low‐abundance samples, the proposed platform shows potential in handling various samples and in broader applications.