Er3+ Sensitized 1530 nm to 1180 nm Second Near‐Infrared Window Upconversion Nanocrystals for In Vivo Biosensing

Abstract Fluorescent bioimaging in the second near‐infrared window (NIR‐II) can probe deep tissue with minimum auto‐fluorescence and tissue scattering. However, current NIR‐II fluorophore‐related biodetection in vivo is only focused on direct disease lesion or organ bioimaging, it is still a challenge to realize NIR‐II real‐time dynamic biosensing. A new type of Er 3+ sensitized upconversion nanoparticles are presented with both excitation (1530 nm) and emission (1180 nm) located in the NIR‐II window for in vivo biosensing. The microneedle patch sensor for in vivo inflammation dynamic detection is developed based on the ratiometric fluorescence by combining the effective NIR‐II upconversion emission and H 2 O 2 sensing organic probes under the Fenton catalysis of Fe 2+ . Owing to the large anti‐Stokes shifting, low auto‐fluorescence, and tissue scattering of the NIR‐II upconversion luminescence, inflammation can be dynamically evaluated in vivo at very high resolution (200×200 μm).