Engineered MSC-Derived Nanovesicles Delivering Cascade-Responsive Self-Assembling Gd-Based Contrast Agents for Enhanced T2-Weighted MRI of Glioblastoma

The clinical management of glioblastoma (GBM) remains severely constrained by the blood−brain barrier (BBB), which impedes both diagnostic and therapeutic interventions. Here, we present an innovative bioengineered platform (hMSC-NV-Gd-CBT) based on human mesenchymal stem cell-derived nanovesicles (hMSC-NVs) that are covalently modified with a self-assembling, small-molecule Gd-based contrast agent (N3-Gd-CBT). These nanovesicles retain the inherent BBB-penetrating capacity of their parent cells while offering substantially higher production yields than conventional hMSC-derived exosomes. Furthermore, the incorporation of glutathione/cathepsin B (CTSB) cascade-responsive self-assembling probe N3-Gd-CBT enables tumor-specific aggregation and accumulation of contrast agents, significantly enhancing T2-weighted MRI contrast in GBM. Systematic evaluation at 9.4 T reveals that hMSC-NV-Gd-CBT generates superior MRI contrast for GBM compared with the free N3-Gd-CBT probe, hMSC-NV-Gd-CBT co-treated with a CTSB inhibitor, and commercial Gd-DTPA. This strategy not only provides a novel diagnostic tool for brain tumors and other neurodegenerative diseases but also opens new avenues for developing next-generation T2-weighted MRI contrast agents.