Activated NIR-? Rare Earth Fluorescence Nanoprobe For Detecting GSH In An Organism

Fluorescence imaging with the features of real-time tracking,high temporal-spatial resolution,and noninvasiveness has been extensively studied and holds great promise for monitoring biological substances and processes in vivo.Especially,near-infrared fluorescence imaging in the second biological window(NIR-?),has evoked considerable attention for bioimaging because of its unparalleled spatial resolution and signal-to-background ratio,benefiting from the negligible autofluorescence as well as the reduced photon absorption and scattering by biosamples.Lanthanide-doped nanoparticles(LnNPs)as a new kind of promising NIR-? luminescent materials with high photostability,long luminescence lifetime,narrow emission peaks and low toxicity have received increasing interest in fields of chemical and biomedical science.Because the LnNPs excitation light is located in the near infrared region,it can avoid the interference of background fluorescence in biological tissue and improve the penetration depth of fluorescence imaging.Because of the lack of flexible design strategies,it is still a challenge to construct an activatable NIR-? nanoprobes based on LnNPs.Owing to the shortage of energy acceptors with absorption in NIR-? region,fluorescence resonance energy transfer(FRET)process is not suitable for fabricating LnNPs-based nanoprobe with emission in NIR-? region.Herein,we proposed a strategy of target-triggered dye-sensitization process to build an activatable NIR-? LnNPs-based nanoprobe.The faint absorptivity of lanthanide ions leads to a rather low photoluminescence effificiency of LnNPs.Through the introduction of an organic dye with strong NIR absorption as an antenna,it is possible to increase the utilizing effificiency of excitation light and enhance the luminescence of LnNPs.With GSH as a proof-of-concept target,an organic dye was designed and synthesized as both the recognition motif for GSH and a potential antenna,with the LnNPs assembly to build the NIR-? nano probe.Through the specific recognition of probe and target,the sensitization process of dye to LnNPs is controlled,and the quantitative detection of GSH is realized.This nanoprobe not only showed superior detection performance in buffer solution,but also exhibited excellent biocompatibility and responsive ability.In addition,it was able to track the fluctuation of GSH level in liver and lymphatic drainage and provide clear images with high contrast and resolution in vivo.This strategy can be generalized to construct NIR-? probes for various analytes by simply changing the recognition motif of the dye,greatly promoting the application of LnNPs in biomedical feild.