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

ABSTRACT

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.