Excretable IR-820 for in vivo NIR-II fluorescence cerebrovascular imaging and photothermal therapy of subcutaneous tumor

Rationale: Cerebrovascular diseases, together with malignancies, still pose a huge threat to human health nowadays. With the advantages of its high spatial resolution and large penetration depth, fluorescence bioimaging in the second near-infrared spectral region (NIR-II, 900-1700 nm) and its related imaging-guided therapy based on biocompatible fluorescence dyes have become a promising theranostics method. Methods: The biocompatibility of IR-820 we used in NIR-II fluorescence bioimaging was verified by long-term observation. The model of the mouse with a cranial window, the mouse model of middle cerebral artery occlusion (MCAO) and a subcutaneous xenograft mouse model of bladder tumor were established. NIR-II fluorescence cerebrovascular functional imaging was carried out by IR-820 assisted NIR-II fluorescence microscopy. Bladder tumor was treated by NIR-II fluorescence imaging-guided photothermal therapy. Results: We have found that IR-820 has considerable NIR-II fluorescence intensity, and shows increased brightness in serum than in water. Herein, we achieved real time and in vivo cerebrovascular functional imaging of mice with high spatial resolution and large penetration depth, based on IR-820 assisted NIR-II fluorescence microscopy. In addition, IR-820 was successfully employed for NIR-II fluorescence imaging and photothermal therapy of tumor in vivo, and the subcutaneous tumors were inhibited obviously or eradicated completely. Conclusion: Due to the considerable fluorescence intensity in NIR-II spectral region and the good photothermal effect, biocompatible and excretable IR-820 holds great potentials for functional angiography and cancer theranostics in clinical practice.