Orthogonal Near-Infrared-II Imaging Enables Spatially Distinguishing Tissues Based on Lanthanide-Doped Nanoprobes.

Multichannel near-infrared (NIR)-II imaging provides more precise and detailed information for studying complex biological processes. When studying specific biological processes, a separated single signal and multisignals are essential but difficult to obtain by traditional multichannel NIR-II imaging methods. Taking advantage of the unique optical properties of lanthanide ions, especially in atom-like absorbance and emission spectroscopy in the NIR region, in this study, we synthesized two lanthanide-doped nanoprobes, NaYF4:Gd@NaYF4:Nd@NaYF4 (cssNd) and NaYF4:Gd@NaYF4:Er@NaYF4 (cssEr). These two nanoprobes show orthogonal NIR-II emissions (1064 and 1330 nm for cssNd and 1550 nm for cssEr) under 730 and 980 nm excitation, respectively. The feasibility of cssNd and cssEr for multichannel NIR-II imaging was proven in vitro. Under different methods of administering the nanoprobes, in vivo multichannel NIR-II imaging with both the separated single signal and multisignals was successfully performed and could spatially distinguish tissues under two different excitation sources. Our results provide a new method for multichannel NIR-II imaging with separable signals, which is promising for precisely studying complex biological processes precisely.