Programmable CAR-engaging particles rewire human CAR T-cell signaling for sustainable ex vivo expansion

T cell proliferative capacity and persistence determine the therapeutic efficacy of chimeric antigen receptor (CAR) T cells. However, strategies to externally enhance CAR-T cell expansion without genetic rewiring are lacking. Here, we engineer CAREp, programmable DNA-scaffolded PLGA microparticles displaying CAR-targeting antigens and CD28-costimulatory antibodies, to repeatedly stimulate human CD8+ CAR-T cells ex vivo. CAREp sustains a-EGFR CAR-T cell expansion for over 100 days across both 4-1BBζ and CD28ζ constructs, achieving up to 1018-fold cumulative expansion and surpassing tumor-cell or CD3/CD28-Dynabeads stimulation. Expanded cells retain effector function and mitochondrial fitness while exhibiting clonal enrichment, initially preserved memory-associated progenitor states, delayed exhaustion, and transiently activated telomerase delaying telomere attrition. Early transcriptomic responses show coordinated activation of DNA repair, chromatin remodeling, telomere maintenance, and mitochondrial function while restricting differentiation-associated signaling programs, mirroring long-term functional outcomes. These findings demonstrate that nanoscale ligand organization synchronizes acute CAR-T signaling with durable proliferative and metabolic states. T cell proliferative capacity and persistence are key determinants of CAR-T cell therapeutic efficacy. Here, the authors show that CAREp, a microparticle-based platform displaying CAR-targeting antigens and CD28-costimulatory antibodies, selectively and sustainably expands human CD8+ CAR-T cells while maintaining a memory-associated progenitor state and delayed exhaustion.