CAT and glioblastoma: Similarly, in glioblastoma multiforme (GBM), where the blood-brain barrier (BBB) restricts drug accumulation, BBB-penetrating nanoparticles loaded with chlorin e6 and catalase demonstrated dual functionality: they alleviated hypoxia via H2O2 decomposition while achieving deep-tissue PDT activation under MRI guidance (Wu C. et al., 2024).