Mechano-Chemical Coordination of Nanoparticle-Based Artificial Antigen-Presenting Cells Synergistically Tunes T Cell Activation and Expansion Phenotypes.

Particle-based artificial antigen-presenting cells (aAPCs) are widely used for ex vivo T cell activation, but rigid, high-avidity stimulation can promote differentiation and exhaustion, reducing therapeutic efficacy. Because T cells sense mechanical forces through the T cell receptor, we engineered nanocapsule aAPCs with three stiffness regimes, spanning MPa to GPa Young's moduli, and two αCD3/αCD28 ligand densities to define how mechanical and biochemical cues shape primary human T cell responses. Across six formulations benchmarked against Dynabeads, stiffness and ligand density acted as orthogonal but synergistic design parameters. Expansion increased with both variables, and the stiff, high-density nanocapsules matched or exceeded Dynabead-mediated expansion by day 8. However, unlike Dynabeads, enhanced expansion did not coincide with strong exhaustion or terminal differentiation. Nanocapsules maintained CD8+ PD-1+ frequencies near baseline, mitigated Dynabead-associated CD4+ bias, and promoted CD8 enrichment, with CD8/CD4 ratios reaching approximately 2.7. They also produced transient, tunable CD25 upregulation, reduced granzyme B expression, and preserved TCF-1+ stem-like populations depending on signal strength. These results establish mechano-chemically tunable nanocapsule aAPCs as a versatile platform for generating expanded, CD8-enriched T cell products with reduced exhaustion-associated phenotypes for adoptive cell therapy manufacturing and provide a rational framework for programmable T cell product design ex vivo applications.