Engineering NIR-II luminescent lanthanide nanoprobes for imaging brain diseases in vivo

Brain research is a cutting-edge topic but it remains challenging to achieve noninvasive sensitive diagnosis of brain diseases. Lanthanide nanocrystals (NCs) with near-infrared II (NIR-II) photoluminescence (PL) have shown great promise for noninvasive through-skull high-resolution imaging. Currently, it still lacks a systematic review discussing the emerging spectroscopic and nanoprobe engineering of NIR-II luminescent lanthanide NCs for specific imaging of brain diseases. Herein, we comprehensively review recent development of NIR-II lanthanide nanoprobes for brain disease imaging in vivo. We first summarize luminescence regulation strategies aiming to enhance the NIR-II PL efficiency of lanthanide NCs. Then, the design strategies of lanthanide nanoprobes are introduced with the effort to improve their brain delivery efficacy and NIR-II PL imaging specificity and sensitivity in the brain. In particular, we comprehensively detail the latest tailoring of lanthanide nanoprobes for NIR-II PL imaging of brain diseases such as brain injuries and tumors. Finally, we propose future opportunities and challenges in the exploration of NIR-II lanthanide nanoprobes and practical imaging studies of brain diseases. This review is anticipated to motivate future engineering of lanthanide nanoprobes for the diagnosis and treatment of brain diseases.