In this paper, we designed and synthesized three benzothiazole-based fluorescent probes L1, L2, and L3 for zinc ion detection. Among various metal ions, only the zinc ion exhibited fluorescence enhancement at 475 nm accompanied by the blue-shift emission wavelength in HEPES buffer solution containing probes. Through titration experiment, the detection limit of L1 for zinc ion sensing was calculated to be as low as 7 nM, which showed a high sensitivity. Furthermore, the confocal laser scanning micrographs of HeLa cells demonstrate good cell permeability of probe L1 and selective detection of zinc ion in living cells. The L1–Zn2+ complex was further used for pyrophosphate (PPi) sensing in HEPES buffer solution, the limit of detection was calculated to be as low as 60 nM. L1–Zn2+ can monitor the enzyme catalyzed degradation process of PPi, thus providing a meaningful way for tracking of zinc ion and pyrophosphate in biological systems.

Developing highly sensitive and selective methods for HOCl/OCl– detection is of significant interest. In this work, two fluorescent probes based on mono- and bis-formylated fluorescein, FN-1 and FN-2, were developed. The probes exhibit rapid response and high selectivity to HOCl/OCl– over other reactive oxygen species (ROS)/reactive nitrogen species (RNS). Furthermore, a good linearity between the fluorescent intensity at 529 nm and the concentration of HOCl/OCl– in the range 0–10 μM were presented. The probes FN-1 and FN-2 showed detection limits as low as 0.21 and 0.23 μM, respectively. The confocal laser scanning micrographs of HeLa cells confirmed cell permeability of the two probes and their abilities to detect HOCl/OCl– in living cells. Compared to compound FN-1, FN-2 has lower background fluorescence and a higher speed of the reaction with HOCl/OCl– which made it a better option for the detection of HOCl/OCl– in aqueous solution.

•A ratiometric fluorescence probe is developed for detection of hypochlorite.•This probe can detect hypochlorite with a detection limit of 8.9 nM.•The probe is applicable for monitoring hypochlorite produced in living cells.We have developed a ratiometric fluorescent probe for hypochlorite detection with high selectivity and sensitivity. The probe 1 can rapidly turn into an oxidized form accompanied by the fluorescence changes from yellow to blue only upon the addition of hypochlorite among various reactive oxygen species (ROS) and reactive nitrogen species (RNS). The limit of detection was calculated to be as low as 8.9 nM, which showed good sensitivity to hypochlorite. Furthermore, the confocal laser scanning micrographs of HeLa cells confirmed good cell permeability of probe 1 and its application to selective detecting hypochlorite in living cells.

Hypochlorous acid (HOCl) plays a vital role in many physiological and pathological processes as one of reactive oxygen species (ROS). Developing highly sensitive and selective methods for HOCl detection is of significant interest. In this work, we developed a benzothiazole based probe 1 for ratiometric fluorescence detection of hypochlorite in living cells. The probe can detect HOCl with high selectivity, fast response (within 30 s) as well as low detection limit (0.18 mmol/L). Fluorescence co-localization studies demonstrated that probe 1 was a mitochondria-targeted fluorescent probe. Furthermore, confocal fluorescence images of HeLa cell indicated that probe 1 could be used for monitoring intracellular HOCl in living cells. Finally, test strips experiment suggests that the probe 1 can detect the hypochlorous acid in tap water accompanied by remarkable color change.Download high-res image (114KB)Download full-size image

•ESIPT-based fluorescent probes with large Stocks shifts are developed for detection of Pd2+.•The probes exhibited good selectivity to Pd2+ among various metal ions.•The high sensitivity of probes 1 and 2 with detection limits of 285 nM and 15 nM were determined, respectively.•The portable test strips prepared by the probe molecules can detect the lowest possible ppm levels of Pd2+.Highly sensitive and selective fluorescent probes 1 and 2 for detection of palladium ions (Pd2+) were synthesized based on excited-state intramolecular proton transfer process (ESIPT) using 2-(2′-hydroxy-)benzothiazole moiety. Different metal ions were used to optimize their sensitivity and selectivity but best results were obtained with Pd2+. Probe 1 produced green fluorescence with Stokes shift of about 163 nm upon addition of Pd2+, whereas probe 2 displayed red fluorescence with a large Stokes shift of about 217 nm under similar conditions. The detection limits of 1 and 2 to Pd2+ were found to be 285 nM and 14.6 nM, respectively. Mechanistic aspects of probes 1 and 2 were discussed to account for the optical changes leading to the strong ESIPT fluorescence in very short duration. Furthermore, the portable test strips were also prepared by direct deposition of the probe molecules onto the filter paper to detect the lowest possible ppm levels of Pd2+.Two 2-(2′-hydroxyphenyl)benzothiazole-based fluorescent probes 1 and 2 were designed and exhibited strong fluorescence in short duration upon exposure to Pd2+. The portable test strips were also prepared by direct deposition of the probe molecules onto the filter paper to detect the lowest possible ppm levels of Pd2+.Download high-res image (141KB)Download full-size image

Polydiacetylenes (PDAs) have received increasing attention as smart materials owing to their unique properties. Upon addition of various stimuli, blue PDAs can undergo a colorimetric transition from blue to red along with a change from non-fluorescent to fluorescent. The optical changes can be readily detected by the naked eye and by using absorption and fluorescence spectrometers. These properties make PDAs excellent materials for use in platforms for sensing chemical or biological targets. In recent years, a number of biosensors and chemosensors based on the optical responses of polydiacetylenes have been reported. In this review, recent advances made in this area were discussed following a format based on different cognizing targets, including temperature, metal ions, anions, surfactants, amines, water, gas, sugars, hydrocarbons, neomycin, heparin, virus, enzymes, bacteria, and cancers. Emphasis is given to the methods used to prepare PDA sensing systems as well as their sensing performance.

A novel naphthalimide-based fluorescent probe employing a sulfonamide unit as a thiol-responsive group is reported. It is capable of efficiently distinguishing GSH from cysteine and homocysteine. Bioimaging shows that it has high selectivity in living cells and can visualize the level of GSH in lysosomes. It is worth mentioning that different groups on the imide unit can affect the selectivity and reaction dynamics of the probe towards thiols.

•A highly selective fluorescent probe based on ESIPT is developed for GSH detection.•The probe is operated by a GSH-induced nucleophilic substitution reaction.•This probe is applicable for monitoring GSH in living cells.In this paper, highly sensitive and selective fluorescent probe 1 for GSH is designed and synthesized based on modulation of the excited-state intramolecular proton transfer (ESIPT) process of 2-(2′-hydroxy-3′-ethoxyphenyl)benzothiazole. Upon introducing GSH in neutral solution containing CTAB micelles, dinitrophenyl, the protecting group of the probe, is removed via the nucleophilic substitution, thereby retrieving the ESIPT process of 2-(2′-hydroxy-3′-ethoxyphenyl)benzothiazole, which results in a fluorescence enhancement at 485 nm. Additionally, the fluorescence intensity of the probe is linearly proportional to GSH concentration ranging from 0 to 100 μM and the obtained detection limit is as low as 0.81 μM. The enhanced selectivity toward GSH over Cys and Hcy is also attributed to one more carboxyl group in GSH. Importantly, the probe is successfully utilized for monitoring GSH in living HeLa cells.

•A new metal complex-based chemosensor for PPi was synthesized.•This new metal complex-based chemosensor exhibited highly selective and sensitive response toward PPi in aqueous solution.•The new complex was applied to monitoring the hydrolysis reaction of PPi and the polymerase chain reaction in DNA synthesis, respectively.A new dinuclear-copper(II) complex (Cu-L2) with two ammonium arms based on bis-2-((pyridin-2-ylmethylamino)methyl)phenol as the coordinated unit was synthesized. The complex exhibited high affinity with pyrophosphate (PPi) in aqueous solution. Using pyrocatechol violet (PV) as a colorimetric indicator, the indicator displacement assay (IDA) was carried out to determine the binding constant between the complex and PPi. A ca. 784-fold enhancement was founded when compared Cu-L2 to ammonium-free counterpart (Cu-L1). The new dinuclear complex was successfully used to monitor the hydrolysis of PPi catalyzed by pyrophosphatase (PPase). Furthermore, by employing esculetine as a fluorescent indicator, the complex was also used to detect PPi released during polymerase chain reaction (PCR).Graphical abstract for “A dinuclear-copper(ii) complex-based sensor for pyrophosphate and its applications to detecting pyrophosphatase activity and monitoring polymerase chain reaction”

•A ECL sensor was assembled by rGO-BaYF5: Yb, Er prepared in situ hydrothermal.•ECL intensity of rGO-BaYF5: Yb, Er modified by AuNPs was enhanced 4-fold.•Immunosensor exhibited high selectivity to CEA with low detection limit.•The immunosensor was applied to a real sample (human serum samples).•The immunosensor has advantageous potential for future clinical analysis.We reported a novel ECL immunosensor for detection of carcinoembryonic antigen (CEA) based on the reduced graphene Oxide-BaYF5:Yb, Er (rGO-BaYF5:Yb, Er) nanocomposites. The rGO-BaYF5:Yb, Er nanocomposites, used as electrode luminescence materials, were prepared by in situ hydrothermal method, and characterized by TEM, XRD, UV–vis spectra, and upconversion fluorescence spectra. Further, poly (diallyldimethylammonium chloride) (PDDA), Au nanoparticles (AuNPs), and Anti-CEA were successively assembled on the surface of rGO-BaYF5:Yb, Er nanocomposites modified-electrode for fabricating ECL immunosensor. The results of the ECL measurements of CEA indicated that this novel ECL immunosensor exhibited high sensitive response to CEA in a linear range of 0.001–80 ng mL−1 with a low detection limit of 0.87 pg mL−1, good selectivity and satisfactory stability.

Electrochemiluminescence (ECL) property of nitroolefin-based fluorescein was investigated and reported for the first time. Its ECL behaviors in acetonitrile (CH3CN) system and aqueous system were studied, respectively. Results indicated that nitroolefin-based fluorescein showed reversible reduction peaks on cycling voltammetric (CV) spectrum and produced ECL emission with the presence of benzoyl peroxide (BPO) as a coreactant in CH3CN solution. Reduction potential peaks of the substance can be observed in water solution in CV, and the intensity of ECL emission is much lower in water than that of in CH3CN solution. However, the ECL property of nitroolefin-based fluorescein can be used for the detection of cysteine (Cys) by using potassium persulfate (K2S2O8) as coreactant in aqueous solution. Under optimum conditions, the ECL intensity has a linear relationship with the concentration of cysteine in the range of 10−9 to 10−8 mol L−1 and a detection limit of 4.2 × 10−10 mol L−1. It has a lower detection limit than the fluorescence method. Our investigation demonstrated that the proposed method provides an elegant platform for fabrication of new generation of biosensors with ultrahighsensitivity, and might have potentially broad applications in amino acids diagnostics and bioassay.

A perylene-based probe was developed for uridine diphosphate (UDP) sensing and cell imaging. The probe presented about 4-fold fluorescence enhancement in the presence or absence of 100 equiv UDP. The selectivity toward UDP over other phosphor-containing anions was observed. The selective UDP sensing was speculated to be related to the binding affinities of Zn2+ ions in sensor with the uridine and phosphate moieties of UDP. Furthermore, this probe was also applied to image of UDP in living cells.A perylene-based fluorescent probe was developed for the detection of UDP with high selectivity.

The presence of cyanide ions in surface water is not only caused by industrial waste but also by biological processes. Owing to the extreme toxicity of cyanide in physiological systems and its widespread presence in the environment, considerable attention has been given to the development of methods for the detection of cyanide. Among the most simple, inexpensive and rapid methods to detect cyanide ions are chemosensors that rely on fluorometric and colorimetric responses. This review, which focuses on CN− fluorescence and colorimetric chemosensors that have been developed since 2010, follows a format in which the sensors are classified according to their structural features and reaction mechanisms. Finally, a general overview of the design of fluorometric and colorimetric chemosensors for CN− is provided.

Two dinuclear copper complexes with and without ammonium moieties were synthesized. The complexes exhibited selective binding affinity to pyrophosphate in aqueous solution. The dinuclear copper complex, with ammonium arms, showed a ca. 527-fold enhancement in pyrophosphate binding affinity compared with its analogue without ammonium units.

A novel naphthalimide-based fluorescent probe employing a sulfonamide unit as a thiol-responsive group is reported. It is capable of efficiently distinguishing GSH from cysteine and homocysteine. Bioimaging shows that it has high selectivity in living cells and can visualize the level of GSH in lysosomes. It is worth mentioning that different groups on the imide unit can affect the selectivity and reaction dynamics of the probe towards thiols.

The presence of cyanide ions in surface water is not only caused by industrial waste but also by biological processes. Owing to the extreme toxicity of cyanide in physiological systems and its widespread presence in the environment, considerable attention has been given to the development of methods for the detection of cyanide. Among the most simple, inexpensive and rapid methods to detect cyanide ions are chemosensors that rely on fluorometric and colorimetric responses. This review, which focuses on CN− fluorescence and colorimetric chemosensors that have been developed since 2010, follows a format in which the sensors are classified according to their structural features and reaction mechanisms. Finally, a general overview of the design of fluorometric and colorimetric chemosensors for CN− is provided.

Polydiacetylenes (PDAs) have received increasing attention as smart materials owing to their unique properties. Upon addition of various stimuli, blue PDAs can undergo a colorimetric transition from blue to red along with a change from non-fluorescent to fluorescent. The optical changes can be readily detected by the naked eye and by using absorption and fluorescence spectrometers. These properties make PDAs excellent materials for use in platforms for sensing chemical or biological targets. In recent years, a number of biosensors and chemosensors based on the optical responses of polydiacetylenes have been reported. In this review, recent advances made in this area were discussed following a format based on different cognizing targets, including temperature, metal ions, anions, surfactants, amines, water, gas, sugars, hydrocarbons, neomycin, heparin, virus, enzymes, bacteria, and cancers. Emphasis is given to the methods used to prepare PDA sensing systems as well as their sensing performance.