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 various samples, including cells, bacteria, embryos, and spheroids. Handling thousands of such small volumes in parallel is essential but presents substantial challenges. In this study we utilize the open format of the DMA for controlled and highly parallel high-throughput liquid manipulations using the sandwich technique. We demonstrate high-throughput medium replacement at nanoliter-scale, maintaining high viability of cells 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. We also demonstrate highly parallel uptake aliquots from nanoliter droplets, which we use for non-destructive cell viability assessment. Additionally, the presented method enables the controlled parallel transfer of cell spheroids between different DMAs, enabling both transfer and pooling of spheroids in seconds without their damage. These advances significantly enhance the capabilities of DMA, enabling long-term cell culture in thousands of nanoliter droplets and allowing parallel sampling and high-throughput cell or spheroid manipulation for various screening applications. This broadens the potential applications of the DMA platform in the fields such as cell-based high-throughput screening, formation of complex 3D cell models for drug screening, and microtissue engineering.