Highly Parallel and High-Throughput Nanoliter-Scale Liquid, Cell, and Spheroid Manipulation on Droplet Microarray

The droplet microarray (DMA) platform is a powerful tool for high-throughput biological and chemical applications, enabling miniaturization and parallelization of experimental processes. Capable of holding hundreds of nanoliter droplets, it facilitates the screening and analysis of samples, such as cells, bacteria, embryos, and spheroids. Handling thousands of small volumes in parallel presents significant challenges. In this study, we utilize the open format of the DMA for controlled, parallel high-throughput liquid manipulations using the sandwich technique. We demonstrate high-throughput medium replacement at nanoliter-scale, maintaining high cell viability on DMA for up to 7 days; for HeLa-CLL2 cells (adherent) and SU-DHL4 cells (suspension), and up to 14 days for HEK293 spheroids. Additionally, we achieve highly parallel aliquot uptake from nanoliter droplets, enabling non-destructive cell viability assessments. Furthermore, the presented method enables the parallel transfer of cell spheroids between different DMAs, allowing transfer and pooling of spheroids in seconds without damage. These advances significantly enhance the capabilities of the DMA platform, enabling long-term cell culture in nanoliter droplets and parallel sampling for high-throughput cell or spheroid manipulation. This broadens the scope of DMA's potential applications in fields such as cell-based high-throughput screening, formation of complex 3D cell models for drug screening, and microtissue engineering.