Programmable microparticles rewire CAR signaling to enable super-physiological expansion of human T cells ex vivo

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, compared to about 30 days with tumor cell stimulation, and achieved up to 10^18-fold cumulative expansion, greatly surpassing CD3/28 Dynabeads. Early-phase transcriptomic responses, including 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 as shown by single-cell sequencing. Differentiation and exhaustion signals were broadly suppressed. Transient telomerase activity further supported physiologic expansion. These findings demonstrate that nanoscale-programmed extracellular cues can rewire CAR-T cell signaling to drive durable, super-physiological expansion, providing a mechanistic framework for next-generation T cell programming.