Luminescence Lifetime–Based In Vivo Detection with Responsive Rare Earth–Dye Nanocomposite

For years, luminescence lifetime imaging has served as a quantitative tool in indicating intracellular components and activities. However, very few studies involve the in vivo study of animals, especially in vivo stimuli-responsive activities of animals, as both excitation and emission wavelengths should fall into the near-infrared (NIR) optical transparent window (660-950 and 1000-1500 nm). Herein, this work reports a lifetime-responsive nanocomposite with both excitation and emission in the NIR I window (800 nm) and lifetime in the microsecond region. The incorporation of Tm3+ -doped rare-earth nanocrystals and NIR dye builds an efficient energy transfer pathway that enables a tunable luminescence lifetime range. The NaYF4 :Tm nanocrystal, which absorbs and emits photons at the same energy level, is found to be 33 times brighter than optimized core-shell upconversion nanocrystals, and proved to be an effective donor for NIR luminescence resonance energy transfer (LRET). The anti-interference capability of luminescence lifetime signals is further confirmed by luminescence and lifetime imaging. In vivo studies also verify the lifetime response upon stimulation generated in an arthritis mouse model. This work introduces an intriguing tool for luminescence lifetime-based sensing in the microsecond region.