A Digital Microfluidic Electroporation Platform for Low-input CRISPR Genome Editing and mRNA Transfection In Suspension T Cells and 3D Cell Models

Digital microfluidic (DMF) electroporation enables precise, low-volume genetic manipulation of mammalian cells while minimizing cellular input by up to 100x and preserving viability. This study presents a high-throughput DMF-based transfection workflow for CRISPR-mediated knockout of the TRAC locus in primary human suspension T cells and for mRNA transfection of three-dimensional HEK293T spheroids. Using spatially deposited CRISPR guide RNAs and on- cartridge ribonucleoprotein (RNP) assembly, efficient TRAC locus disruption was achieved in both CD4⁺ and CD8⁺ T-cell populations using only 10,000 cells per condition, with post-editing viabilities exceeding 85%. Biophysical characterization using flow-induced and Taylor dispersion analyses revealed that polymer additives stabilize Cas9-sgRNA complexes under electroporation buffer conditions, supporting reproducible editing at sub microliter volumes. The workflow was further adapted for 3D applications by delivering EGFP mRNA into intact HEK293T spheroids, resulting in robust and spatially uniform fluorescence without impairing spheroid growth or morphology. Together, these results demonstrate that DMF electroporation enables efficient genome editing and mRNA delivery across both suspension immune cells and multicellular spheroids. This platform provides a scalable and low-input solution for applications in CAR-T cell therapy, functional genomics, and advanced 3D cellular models.