The discovery that hypobromous acid (HOBr) can regulate the activity of collagen IV has attracted great attention. However, HOBr as an important reactive small molecule has hardly ever been studied using a detection method suitable for organisms. Herein, a high-quantum-yield mitochondria-targeting near-infrared (NIR) fluorescent probe for HOBr, RhSN-mito, was designed. RhSN-mito was easily obtained by the Suzuki cross-coupling reaction. The test results show that RhSN-mito can rapidly respond to HOBr with ultrasensitivity and high selectivity. The achievement of ultrasensitivity lies in the high signal-to-noise ratio and the highest fluorescence quantum yield of the reaction product (ΦF = 0.68) in the near-infrared region, as far as we know. RhSN-mito is successfully applied to image native HOBr in mitochondria of HepG2 cells and zebrafish. Thus, RhSN-mito is a powerful tool for detecting native HOBr in vivo and is expected to provide a method to further study the physiological and pathological functions related to HOBr.

Hydrogen selenide (H2Se) is an important metabolite of dietary Se compounds and has been implicated in various pathological and physiological processes. The development of highly sensitive and selective methods for the sensing of H2Se is therefore very important. Herein, we developed a fluorescent probe (hemicyanine (Hcy)-H2Se) for detecting H2Se based on a new H2Se-specific receptor unit, 1,2-dithiane-4,5-diol. Hcy-H2Se showed high selectivity toward H2Se over thiols (RSH), hydrogen sulfide (H2S), and selenocysteine (Sec) and was further exploited for the fluorescence imaging of H2Se both in living cells and in vivo. Furthermore, with the aid of Hcy-H2Se, we demonstrated that H2Se can be generated and gradually accumulated in HepG2 cells under hypoxic conditions and in the solid tumor after treatment with Na2SeO3.

Hydrogen selenide (H2Se), a highly reactive Se species, is an important selenium metabolism intermediate involved in many physiological and pathological processes. This compound is of scientific interest with regard to the real-time monitoring of H2Se in living cells and in vivo to understand the anti-cancer mechanism of selenium. However, monitoring H2Se in living cells is still challenging due to the lack of straight forward, highly selective and rapid methods. Here, we developed a novel small-molecule fluorescent probe, NIR-H2Se, for imaging endogenous H2Se. NIR-H2Se exhibited high selectivity toward H2Se over selenocysteine (Sec), H2S and small molecule thiols and was successfully used to image the H2Se content in HepG2 cells during Na2SeO3-induced apoptosis. Increased H2Se content and reduced ROS levels were observed under hypoxic conditions compared to normoxic conditions, which indicated that the cell apoptosis induced by Na2SeO3 under a hypoxic environment is via a non-oxidative stress mechanism. Thus, this probe should serve as a powerful tool for exploring the physiological function of H2Se and Se anticancer mechanisms in a variety of physiological and pathological contexts.

Based on the rapid substitution reaction of the Au–S bond by selenol, we designed and synthesized a nanoprobe 5-FAM-peptide-AuNPs for selenol. Real-time imaging shows that this probe together with the molecular probe QCy7-H2O2 is able to simultaneously and differentially monitor the concentrations of selenol and H2O2 in living cells and in vivo.

To reduce the side effects of chemotherapy, nontoxic prodrugs activated by the tumor microenvironment are urgently required for use in cancer treatment. In this work, we developed prodrug 4 for tumor-targeting treatment and imaging of the anticancer drug release in vivo. Taking advantage of the high glutathione (GSH) concentration in cancer cells, the disulfide bond in prodrug 4 was cleaved, resulting in the release of an active anticancer drug and a near-infrared (NIR) fluorescence dye turn-on. Furthermore, contrast to the free anticancer drug, the prodrug exhibited higher cytotoxicity to hepatoma cells than that to normal HL-7702 cells. Thus, prodrug 4 is a promising platform for specific tumor-activatable drug delivery system, because of its favorable features of in situ and in vivo monitoring of the drug release and therapeutic efficacy.

Selenol is a key metabolite of Na2SeO3 and plays an important role in many physiological and pathological processes. The real-time monitoring of selenol is of scientific interest for understanding the anti-cancer mechanism of Na2SeO3. Based on selenol's ability to specifically break AuS bonds and form more stable AuSe bonds on the surfaces of gold nanoparticles (AuNPs), we developed a novel near-infrared fluorescent nanosensor (Cy5.5-peptide-AuNPs) for detecting selenol. The nanosensor exhibited rapid response to selenol with high selectivity and sensitivity, and it was successfully used to image changes in the selenol level in HepG2 cells during Na2SeO3-induced apoptosis. Moreover, in vivo fluorescence imaging of selenol was obtained from H22 tumor-bearing mice injected with both the nanosensor and sodium selenite. The results showed that the tumor cell apoptosis induced by Na2SeO3 is correlated with high-level of selenol under hypoxic conditions. We believe that this nanosensor could serve as a powerful tool for monitoring selenol and exploring the physiological function of selenol in a variety of physiological and pathological contexts and that the probe-designed strategy will provide a new platform for research on relevant selenium chemistry.Download high-res image (232KB)Download full-size image

Vitamin C (ascorbic acid; AA) is a well-known reducing agent and has been evaluated for its antitumor activity. However, the mechanism for its antitumor action remains unclear. Tracking the metabolism of AA may help to elucidate its antitumor mechanism. In this study, a near-infrared fluorescent probe (Arg-Cy) for monitoring the metabolic products of AA in living cells was developed based on the reaction of the guanidine group in Arg-Cy with the adjacent diketone involved in the metabolites of AA. Consequently, the probe can respond to l-xylosone, a metabolite of AA, with high selectivity and sensitivity and was successfully used to visualize the real-time changes of l-xylosone levels in living cells incubated under normoxic conditions. Considering that the tumor microenvironment suffers from hypoxia, the l-xylosone levels in the process of HepG2 cell death induced by pharmacological doses of AA were also monitored under hypoxic conditions. Surprisingly, no obvious fluorescence change appeared during this process. Furthermore, detection of the intracellular redox state using a reported H2O2 probe confirmed that AA can be metabolized to l-xylosone only under normoxic conditions due to the oxidative stress, but not under hypoxic conditions. Therefore, we hypothesize that the mechanism for cell death induced by AA under hypoxia is different from that under normoxia. Thus, the developed probe can provide a tool for monitoring the metabolism of AA and may help to clarify the mechanism for the antitumor activity of vitamin C in the tumor microenvironment.

Hydrogen selenide (H2Se), a highly reactive Se species, is an important selenium metabolism intermediate involved in many physiological and pathological processes. This compound is of scientific interest with regard to the real-time monitoring of H2Se in living cells and in vivo to understand the anti-cancer mechanism of selenium. However, monitoring H2Se in living cells is still challenging due to the lack of straight forward, highly selective and rapid methods. Here, we developed a novel small-molecule fluorescent probe, NIR-H2Se, for imaging endogenous H2Se. NIR-H2Se exhibited high selectivity toward H2Se over selenocysteine (Sec), H2S and small molecule thiols and was successfully used to image the H2Se content in HepG2 cells during Na2SeO3-induced apoptosis. Increased H2Se content and reduced ROS levels were observed under hypoxic conditions compared to normoxic conditions, which indicated that the cell apoptosis induced by Na2SeO3 under a hypoxic environment is via a non-oxidative stress mechanism. Thus, this probe should serve as a powerful tool for exploring the physiological function of H2Se and Se anticancer mechanisms in a variety of physiological and pathological contexts.

Based on the rapid substitution reaction of the Au–S bond by selenol, we designed and synthesized a nanoprobe 5-FAM-peptide-AuNPs for selenol. Real-time imaging shows that this probe together with the molecular probe QCy7-H2O2 is able to simultaneously and differentially monitor the concentrations of selenol and H2O2 in living cells and in vivo.