Latest ArticlesUnder the public spotlight, uranyl (UO22+) ions has attracted considerable attention for the extreme radioactive and chemical toxicity to ourselves and our environment. Herein, we present a simple and effective ratiometric fluorescence imaging method for the visualizing and quantitative detection UO22+ ions by cellphone-based optical platform. The sensing solution was prepared by mixing label-free red carbon dots (r-CDs) and blue carbon dots (b-CDs) together with a fixed photoluminescence intensity ratio of 4:1. When UO22+ ions were added, the fluorescence of r-CDs can be selectively quenched, while the fluorescence of b-CDs remains stable without spectral changes. With the gradually increase the amounts of UO22+ ions, the different response of dual-color CDs resulted in a signification color evolution from deep red to dark purple under the ultraviolet (UV) light illumination. Then, a cellphone-based optical platform was constructed for directly imaging the color change of the samples, and the built-in Colorpicker APP quickly output the red, green and blue (RGB) channel values of these images within one second. Interesting, there was a linear relationship between the ratio of red and blue (R/B) channel values and UO22+ ions concentration from 0 μmol/L to 30.0 μmol/L (R2 = 0.92804) with the detection limit of ~8.15 μmol/L (signal-to-noise ratio of 3). In addition, the optical platform has also been applied to the quantification of UO22+ ions in tap water and river water sample. With the advantage of low-cost, portable, easy to operation, we anticipate that this method would greatly improve the accessibility of UO22+ ions detection even in resource-limited areas.
Room temperature phosphorescence (RTP) generated by small molecules has attracted great attention due to their unique potentials for biosensor, bioimaging and security protection. While, the design of RTP materials is extremely challenging for organic small molecules in non-crystalline solid state. Herein, we report a new strategy for achieving non-crystalline organic small molecules with RTP emission by modifying different phosphors onto diphenylalanine or phenylalanine derivatives. Benefiting from the skeletal structure of the amino acid derivatives, there are intermolecular hydrogen bond formation and rigidification effect, thereby minimizing the intermolecular motions and enhancing their RTP performance
A highly sensitive fluorescent sensor ZnDN was designed, synthesized and used for tracking intracellular zinc ions in various living cells and direct imaging of prostatic tissue in mice. ZnDN was prepared from the heterocyclic-fused naphthalimide fluorophore, and the zinc receptor, N, N-bis(2-pyridylmethyl)ethylenediamine (BPEN). Upon addition of Zn2+ to the solutions of ZnDN, a remarkable fluorescence enhancement was observed, which could be attributed to the photo-induced electron transfer (PET) mechanism. Since ZnDN exhibited high sensitivity toward Zn2+ in phosphate buffer solution, with a limit of detection of 4.0×10-9 mol/L, it was further applied for the imaging of exogenous and endogenous Zn2+ in different living cells. Living cells imaging experiments suggested that ZnDN could image the changes of intracellular free zinc ions, and could be used for two-photon imaging. Moreover, flow cytometry suggested that ZnDN could distinguish cancerous prostate cells from normal cells. Animal experiments indicated that ZnDN had the potential in imaging prostate tissue in vivo.
Monitoring dynamics of mitochondria has become an essential approach to explore the function of mitochondria in living cells with the emergence of super-resolution fluorescence microscopy. However, long-term super-resolution imaging of mitochondria is still challenging due to the lack of photostable fluorescent probes and stable mitochondria-specific markers which are not affected by the changes of mitochondrial membrane potential. Here, we introduce a method for long-term imaging mitochondrial dynamic through the SNAP-tag fluorogenic probe based on 4-azetidinyl-naphthalimide derivatives. Using structured illumination microscopy (SIM), we observed the fusion and fission of mitochondria over a course of 16 min at 109 nm resolution. Furthermore, the interactions as well as fusion between mitochondria and lysosomes were studied during mitophagy at the nanoscale. Convincingly, the combination of SNAP-tag fluorogenic probes and super-resolution fluorescence microscopy will offer a new way to monitor dynamic mitochondria in living cells.
Iron is one of the essential trace elements in the human body. It plays an important role in human biology and pathology. Deregulation of iron levels in cells is associated with disease development. In this work, we synthesized a novel near-infrared intramolecular charge transfer (ICT) based ratiometric fluorescent probe to detect Fe2+, by using naphthalimide and indole moieties as building blocks. Our work showed that the radiometric probe has excellent selectivity, sensitivity and rapid response. Moreover, we could successfully perform real-time monitoring of Fe2+ in HeLa cells and C. elegans.
Cytochrome P450 1A1 (CYP1A1), a heme-containing monooxygenase, is of particular importance for human health because of its vital roles in the metabolic activation of pro-carcinogenic compounds to the carcinogens. Deciphering the relevance of CYP1A1 to human diseases and screening of CYP1A1 modulators require reliable tool(s) for probing this key enzyme in complex biological matrices. Herein, a practical and ultrasensitive fluorescence-based assay for real-time sensing CYP1A1 activities in biological systems has been developed, via designing an isoform-specific fluorogenic sensor for CYP1A1 (CHPO). The newly developed fluorogenic substrate for CYP1A1 has been carefully investigated in terms of specificity, sensitivity, precision, quantitative linear range and the anti-interference ability. The excellent selectivity, strong anti-interference ability and fast response kinetics, making the practicability of CHPO-based CYP1A1 activity assay is better than that of most reported CYP1A1 activity assays. Furthermore, CHPO has been successfully used for imaging CYP1A1 activities in living cells and human tissues, as well as for high-throughput screening of CYP1A1 inhibitors using tissue preparations as enzyme sources. Collectively, this study provided a practical fluorogenic sensor for real-time sensing CYP1A1 in complex biological systems, which would strongly facilitate the investigations on the relevance of CYP1A1 to human diseases and promote high-throughput screening of CYP1A1 modulators for biomedical applications.
For efficient and quantitative DNA detection, fluorescence staining is the most often explored approach, which relies on non-covalent binding of dyes with double stranded DNA (dsDNA). Ethidium bromide (EB) is the most classic DNA stain, but suffers from its high carcinogenicity. A series of less toxic alternatives were developed, many of which contain the core structure of the benzothiazole ring. However, the relationship between the structure and the DNA detection performance was not illustrated. Herein, five benzothiazole dyes, namely thiazole orange, SYBR Green Ⅰ, PicoGreen, SYBR Safe, and thioflavine-T, were compared for DNA detection through direct fluorescence and gel electrophoresis, with particular focus on the structure-performance relationship. It turned out that SYBR Green Ⅰ is currently the best choice for DNA detection. The results in this work may be useful for future DNA-staining dye developments.
A ratiometric probe (HBT-HBZ) bearing 2-hydrazino benzothiazole and 3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylbenzaldehyde for sensing hypochlorous acid (HClO) with high selectivity and sensitivity is reported in this article. The fluorescence intensity ratios (I470 nm/I572 nm) of the probe with different concentrations of analyte showed excellent selectivity and a linear response to minor changes in HClO. The detection limit of 24 nmol/L suggests that the sensor is very sensitive to HClO. According to the series of performed experiments, HBT-HBZ has practical applications, such as the detection of HClO residues in tap water, which has been rarely reported. In addition, confocal laser microscopy experiments confirmed that HBT-HBZ can selectively recognize HClO in HeLa cells. A ratiometric probe (HBT-HBZ) for sensing HClO with high selectivity and sensitivity is reported in this article. The probe exhibited high selectivity for HClO among other ROS, RNS and anions. In addition, HBTHBZ has some practical applications such as the analysis of the HClO content in tap water. Furthermore, confocal fluorescence microscopy imaging showed that HBT-HBZ can be applied for detecting HClO in living cells.
Three fluorescent BINOL-Si complexes (FS1, FS2 and FS3) were rationally designed and synthesized to detect diethyl chlorophosphate (DCP), a mimic of lethal nerve agents. These three fluorescent probes showed green, yellow and orange fluorescence, respectively. Moreover, the series of fluorescent probes has the characteristics of fast response time (≤4 s), low detection limit (0.0097 μmol/L), high sensitivity and naked eye detection. More important, a fiber optic sensor capable of detecting DCP vapor in real time was also prepared for the first time, the lowest detection limits (down to 4.4 ppb) were all lower than that of the IDLH (immediately dangerous to life or health) concentration of Sarin (7.0 ppb).
In the active layer of organic solar cells (OSCs), the lifetime of triplet excitons is one of the decisive factors in the diffusion length and therefore has important impact on the power conversion efficiency of the devices. Herein, we have investigated singlet excited state relaxation dynamics and their triplet exciton lifetimes of two thiophene-coupled perylene diimides (PDI) dyads (2PDI-Th and fused-2PDI-Th), in order to provide a unique explanation in depth on their different performances in OSC devices. From the transient absorption (TA) spectra, the singlet excitons of 2PDI-Th form excimers in the time scale of 1.5 ps. Then the excimers go into the triplet state via intersystem crossing (ISC). In fused-2PDI-Th, triplet excitons are generated directly from the singlet excited excitons via the efficient ISC. Density functional theory (DFT) calculations further support the formation of excimers. DFT results indicate that 2PDI-Th exhibits an H-typed molecular configuration which is beneficial to form the excimers, while fused-2PDI-Th gives a twisted X-shaped configuration in the optimized ground and excited state. In steady-state emission spectra, 2PDI-Th shows abroad and featureless spectral characteristics of the excimers with a decay time of 840 ps, which is much shorter than those of PDI (5.5 ns) and fused-2PDI-Th (3.3 ns). The triplet lifetime (67 μs) of fused-2PDI-Th is factor of 3 longer than that of 2PDI-Th (22 μs). These results demonstrate that ring-fused structure is an efficient strategy to eliminate excimer formation and prolong the lifetime of triplet excitons, which provides a new insight for design of optoelectronic molecules for high efficiency organic solar cells.
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