Multistage Biobarrier-Adaptive Peptide Radiosensitizer with Low-Dose X-ray Augments Glioblastoma Radiotherapy via Destabilizing Lysosomal Homeostasis

Glioblastoma (GBM) radiotherapy is hampered by intrinsic radioresistance. Current radiosensitizers face two unresolved hurdles: inability to dynamically traverse sequential physiological barriers of GBM and lack of multitargeted action against the pathways driving radioresistance. Here, we developed h-Pep-MTZ, a biobarrier-adaptive peptide-radiosensitizer addressing both. This system undergoes smart multistage transformations to overcome key delivery barriers: It first circulates as large, negatively charged nanoparticles to prolong plasma half-life; then converts to small, positively charged particles via tumor-overexpressed heparanase for deep tumor penetration; and finally assembles into long nanofibers triggered by lysosomal cathepsin B and acidity to extend tumor retention. Importantly, the nanofibers mechanically disrupt lysosomes, increasing lysosomal membrane permeability, inhibiting AKT activation, reducing autophagy, and impairing cytoskeletal integrity─synergistically sensitizing tumors to radiation. This strategy combined with 6 Gy radiation achieved 82.5% tumor suppression in conventional U251 models and 60.4% in radioresistant U87 models, significantly outperforming the clinical radiosensitizer sodium glycididazole. This strategy provides a paradigm for overcoming GBM radioresistance by leveraging bioresponsive nanoscale transformations and lysosomal targeting.