Microfluidic ER‐Targeted Photodynamic Vesicles Overcome Radioresistance and Boost Antitumor Immunity via Organelle Stress Amplification

Radioresistance remains a significant obstacle in oncology, underpinned by adaptive cellular stress responses that attenuate radiation efficacy. We present microfluidically engineered, endoplasmic reticulum (ER)‐targeted photodynamic vesicles designed to surmount radioresistance through a spatiotemporally controlled, phototriggered reactive oxygen species (ROS) cascade. Upon 660 nm irradiation, these vesicles elicit an organelle‐confined oxidative burst, initiating a self‐amplifying cycle of calcium efflux and acute proteotoxic stress. This photodynamic priming achieves a superior sensitization enhancement ratio (SER = 1.35 ± 0.16) versus non‐targeted vesicles (SER = 1.01 ± 0.03), drastically reducing clonogenic survival to 1.3 ± 0.6% at 6.0 Gy X‐ray. Mechanistically, this synergy disrupts multiple resistance pathways by exacerbating genomic instability, depleting glutathione defenses, and inducing concurrent apoptosis and pyroptosis. Transcriptomic analysis reveals the regulation of radiosensitivity‐associated genes, confirming comprehensive reprogramming of cellular stress responses. Crucially, this cascade induces immunogenic cell death (ICD), elevating dendritic cell maturation to 39.5 ± 5.5% in tumor‐draining lymph nodes. Combined with localized radiotherapy, this approach profoundly amplifies systemic antitumor immunity, increasing intratumoral CD8 + T cell infiltration and robustly suppressing distant metastasis. This work establishes organelle‐targeted ROS cascade amplification as a paradigm‐shifting radiosensitization strategy that extends beyond conventional DNA‐centric approaches, thereby unveiling novel therapeutic avenues for intractable malignancies.