Spatiotemporally controlled pretargeted azide-functionalized M1 macrophage-derived exosome-based Ga/Lu theranostic system for PET imaging and targeted radiotherapy in breast cancer.

Spatiotemporal control of injectable biomaterials is emerging as a powerful strategy to enhance precision theranostics. We report here an injectable, two-step pretargeting system that leverages M1 macrophage-derived exosomes metabolically engineered to display azide groups (M1-Exos-N) and DBCO-functionalized radiopharmaceuticals labeled with Ga or Lu. Following intratumoral accumulation of M1-Exos-N, a temporally controlled intravenous injection of Ga-DOTA-PEG5-C4-DBCO achieves in vivo strain-promoted azide-alkyne cycloaddition (SPAAC) for PET visualization of breast tumors. Subsequent administration of Lu-DOTA-PEG5-C4-DBCO at the optimized time point enables site-specific radionuclide therapy. Confocal microscopy and flow cytometry confirm efficient exosome binding to 4T1 cells, and NIRF imaging pinpoints the optimal 24 h window for probe delivery. PET imaging delineates tumor lesions, and targeted Lu treatment yields significant tumor suppression with minimal off-target toxicity. This spatiotemporally orchestrated, injectable exosome-based platform exemplifies advanced spatial and temporal control in biomaterial design, offering a versatile approach for precision diagnosis and therapy in oncology.