CellTrap: A Microfluidic Platform Enabling Cell-Cell Interactions at Variable Effector to Target Ratios

Immune-cancer cell interactions play a central role in understanding antitumor responses and evaluating immunotherapies. However, long-term, single-cell-level analysis of these interactions remains challenging. To address this, we developed a microfluidic trapping device with 1,024 traps, each equipped with a filter to retain cells, sustain medium flow, minimize cross-talk, and allow precise control of effector-to-target (E:T) ratios. The platform enables continuous monitoring of immune-cancer interactions for up to 14 hours. Device characterization was performed using 10 {micro}m fluorescent beads seeded via hydrostatic flow, with trap occupancy validated by Poisson statistics. Initial experiments using PBMCs against GFP-expressing U87 (U87GFP) glioblastoma cells demonstrated an immune-mediated reduction in GFP intensity, which was interpreted cautiously as a cytotoxic response. To improve reproducibility, we subsequently employed IL-2-stimulated Natural Killer cells (NK92IL2) as standardized effectors and evaluated their interactions with U87GFP glioblastoma cells, K562 chronic myelogenous leukemia cells, and LS174T adenocarcinoma cells. Time-lapse imaging revealed transient intracellular calcium fluxes, consistent with early activation of NK92IL2 cells, followed by a cytotoxic response. Increasing E:T ratios consistently enhanced immune activity, highlighting the utility of this device for dissecting immune-cancer interactions and guiding the development of immunotherapy.