NIR-II fluorescence membrane probes for rapidly labelling hybrid of probiotic outer membrane vesicles and anti-PD-L1 scFv over-expressing cellular vesicles with targeted photothermal-immunotherapy of colon cancer

Abstract

Lipid-bilayer structured nanovectors (LBSNs) (e.g., liposomes and biomimetic vesicles) are burgeoning for diagnosis and therapy, and fluorescence labelling is often conducted for biodistribution tracing with visible/NIR-I fluorescence membrane probes (MPs). As NIR-II fluorescence imaging exhibits significantly improved fidelity, we synthesize NIR-II emissive donor-acceptor structured BODIPY-based MPs (BMP1-2) to label LBSNs composed of immunogenic probiotic outer membrane vesicles and cellular nanovesicles over-expressing anti-PD-L1 scFv, yielding BMP@Hybrid with tandem-amplified immunotherapy. The compact BMPs contain dodecyl chain and few cationic charges, forming strong electrostatic and hydrophobic interaction with negatively charged LBSNs, respectively. This contributes to features including negligible harm to biofunction of LBSNs, high photothermal conversion capability, good photostability, balanced lipophilicity, fast staining on LBSN within 2 min under mechanical stirring with ultrahigh ON/OFF ratio (>115), which offering wash-free imaging. Notably, BMP1@Hybrid could actively target tumor, facilitating biodistribution tracing, colon cancer diagnosis, and molecular imaging of tumoral microenvironments. Remarkably, BMP1@Hybrid efficiently destructs primary tumor by photothermal effect, blockades PD-1/PD-L1 axis, and modulates tumoral microenvironment with promoting secretion of inflammatory cytokines, M2-to-M1 macrophage repolarization, dendritic cell maturation, local infiltration of CD8⁺ T cells, and boosted therapeutic outcomes. This study provides a new strategy of NIR-II fluorescence membrane probes for the labelling of LBSNs and precise cancer theranostics.