A highly selective and instantaneous upconversion fluorescent nanoprobe for ascorbic acid detection in biological samples

Ascorbic acid（AA） serves as a key coenzyme in many metabolic pathways. Enough daily AA supplements from different dietary sources are the only way for human to maintain their AA levels in body.Determination of AA content in different foods guides to build healthy diet, which is of great biomedical significance. Hence, developing a highly selective and instantaneous fluorescent nanoprobe for the detection of AA in biological samples is highly needed. Here we present a novel turn-on fluorescent nanoprobe using lanthanide-doped upconversion nanoparticles（UCNPs） and cobalt oxyhydroxide（Co OOH） nanoflakes for monitoring AA in fruit samples. In this nanosystem, the UCNPs can be adsorbed onto the Co OOH nanoflakes, leading to a remarkable fluorescence decrease through Fo？rster resonance energy transfer. Furthermore, the AA could trigger the disassembly of the Co OOH to liberate the upconverted fluorescence. The UCNPs-based nanoprobe can provide an effective platform for highly selective and rapid detection of AA in biological samples.

A NIR ratiometric fluorescent biosensor for sensitive detection and imaging of α-L-fucosidase in living cells and HCC tumor-bearing mice

Detection and imaging of α-L-fucosidase(AFU)is of great value to understand its roles in hepatocellular carcinoma(HCC)and tumor early diagnosis,but ideal assays are still lacking.Herein,a near-infrared(NIR)fluorescent biosensor(α-Fuc-DCM)was elaborately designed and synthesized for rapid and ratiometric detection of AFU activity in cells and HCC tumor mouse models.In the presence of AFU,this biosensor shows an enhancement in NIR emission in a ratiometric manner,which significantly improves the detection accuracy with the limit of detection as low as 4.8 mU/mL.Taking advantage of these merits,the activity of AFU in lysosomes could be visualized using ratiometric and NIR dual modality in living cells.Furthermore,its remarkable application for monitoring of endogenous AFU activity in HCC tumor-bearing mouse model is also demonstrated with bright fluorescence signal,which indicated that the biosensor could clearly monitor the liver tumor in the early stage.Importantly,the α-Fuc-DCM probe can be utilized to detect the AFU in serum from HCC patients.This strategy offers a promising biosensor system for early diagnosis of HCC and studying the roles of AFU in cancers.

Simultaneous bioimaging of MMP-2 and MMP-7 via Au-Se constructed fluorescence nanoprobe

Au-Se bond strategy has been applied to construct fluorescence nanoprobe that is being used to simultaneously dual-image the tumor markers matrix metalloproteinase-2(MMP-2)and matrix metalloproteinase-7(MMP-7)in vitro.The two Se-terminating ligand peptide chains respectively labeled with fluorescein isothiocyanate(FITC)and 5-Carboxytetramethylrhodamine(5-TAMRA)dyes are attached to the surface of Au nanoparticles(NPs).The nanoprobe can be specifically cut off by MMP-2 and MMP-7 respectively to carry out significant enhanced fluorescence recovery for simultaneously imaging both markers.The nanoprobe not only displays high selectivity and sensitivity towards MMP-2 and MMP-7,but also has strong anti-interference stability against biothiols and enhanced fidelity for avoiding"false positive"results.This approach offers new perspectives in designing tumor-related early diagnosis approaches and also provides strategies for clinical applications.

Theranostic gold cluster nanoassembly for simultaneous enhanced cancer imaging and photodynamic therapy

As one of near-infrared（NIR） fluorescent（FL） nanoprobes, gold nanoclusters（Au NCs） are delicated to passive-targeting tumors for NIR FL imaging, but which easily cleared by the kidneys for the small size（〈1.5 nm）. Herein, the well-defined gold clusters nanoassembly（Au CNA） was synthesized by the selfassembly of Au NCs based on protein cross-linking approach. The as-prepared Au CNA demonstrated highly effective cellular uptake and precise tumor targeting compared to that of Au NCs. Moreover, with the irradiation of 660 nm laser, Au CNA generated largely reactive oxygen species（ROS） for photodynamic therapy（PDT）. In vitro and [39TD$IF]in vivo PDT revealed that Au CNA exhibited largely cell death and significantly tumor removal at a low power density of 0.2 W/cm^2. It could be speculated that the laser-excited Au CNA produced photon energy, which further obtained electron from oxygen to generate radical species.Therefore, Au CNA as a photosensitizer could realize NIR FL imaging and NIR laser induced PDT.