Programmable microparticles rewire CAR signaling to enable super-physiological expansion of human T cells in vitro

T cell proliferative capacity and persistence critically determine the therapeutic success of chimeric antigen receptor (CAR) T cells. However, it remains unknown if and how human CAR-T cells can be externally programmed to reach maximal proliferative capacity. Here, we use programmable PLGA microparticles functionalized with CAR-antigens and CD28-costimulatory antibodies (CAREp) to repeatedly stimulate human CD8 ⁺ CAR-T cells in vitro . CAREp-stimulated CAR-T cells expanded continuously for over 100 days-versus ∼30 days with tumor cell stimulation-and achieved up to 10 ¹⁸ -fold cumulative expansion, greatly surpassing CD3/28-Dynabeads. Early-phase transcriptomic responses- upregulation of DNA repair, cell cycle, telomere maintenance, and mitochondrial pathways-aligned with long-term outcomes: massive proliferation, telomere stability, robust respiration, and preserved progenitor phenotype by single-cell sequencing. Differentiation and exhaustion signals were broadly suppressed. Transient telomerase activity further supported physiologic expansion. These findings demonstrate that nanoscale-controlled extracellular cues can rewire intracellular signaling to drive durable, super-physiological expansion of functional CAR-T cells.