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Background: Pseudomonas aeruginosa (PA) and Burkholderia cepacia complex (Bcc), commonly found in the lungs of cystic fibrosis (CF) patients, often produce cyanide (CN), which inhibits cellular respiration. CN in sputa is a potential biomarker for lung infection by CF pathogens. However, its actual concentration in the infected lungs is unknown., Methods and Findings: This work reports observation of CN in the lungs of mice infected with cyanogenic PA or Bcc strains using a CN fluorescent chemosensor (4',5'-fluorescein dicarboxaldehyde) with a whole animal imaging system. When the CN chemosensor was injected into the lungs of mice intratracheally infected with either PA or B. cepacia strains embedded in agar beads, CN was detected in the millimolar range (1.8 to 4 mM) in the infected lungs. CN concentration in PA-infected lungs rapidly increased within 24 hours but gradually decreased over the following days, while CN concentration in B. cepacia-infected lungs slowly increased, reaching a maximum at 5 days. CN concentrations correlated with the bacterial loads in the lungs. In vivo efficacy of antimicrobial treatments was tested in live mice by monitoring bacteriogenic CN in the lungs., Conclusions: The in vivo imaging method was also found suitable for minimally invasive testing the efficacy of antibiotic compounds as well as for aiding the understanding of bacterial cyanogenesis in CF lungs.

Intermolecular proton transfer from a flavonol-based probe to the arginine (Arg222) in drug site 1 of human serum albumin triggers an unusual red-shifted ratiometric fluorescence response, which can be applied in the point-to-care diagnosis of hypoalbuminemia. [ABSTRACT FROM AUTHOR]

Bacterial infection is one of the greatest threats to public health. In vivo real‐time monitoring and effective treatment of infected sites through non‐invasive techniques, remain a challenge. Herein, we designed a PtII metallacycle‐based supramolecular photosensitizer through the host‐guest interaction between a pillar[5]arene‐modified metallacycle and 1‐butyl‐4‐[4‐(diphenylamino)styryl]pyridinium. Leveraging the aggregation‐induced emission supramolecular photosensitizer, we improved fluorescence performance and antimicrobial photodynamic inactivation. In vivo studies revealed that it displayed precise fluorescence tracking of S. aureus‐infected sites, and in situ performed image‐guided efficient PDI of S. aureus without noticeable side effects. These results demonstrated that metallacycle combined with host‐guest chemistry could provide a paradigm for the development of powerful photosensitizers for biomedicine. [ABSTRACT FROM AUTHOR]

Sulfadiazine is an environmental pollutant derived from abuse of antibiotics. Its content in environmental water is closely related to human health. Thus, a novel dual‐emission surface molecularly imprinted nanosensor is designed for the specific adsorption and detection of sulfadiazine. In the system, blue emissive carbon quantum dots wrapped with silica served as the internal reference signal for eliminating background interference, while red emissive thioglycolic acid modified CdTe quantum dots (CdTe QDs), which are low dimensional semiconductor materials by the combination of cadmium and tellurium with excellent optical properties, were encapsulated in the imprinted layer to offer recognition signal. The fluorescence of CdTe quantum dots was quenched and the fluorescence quenching degree of carbon quantum dots was inconspicuous with the increase of concentration of sulfadiazine, thereby reflecting the color change. The detection of sulfadiazine was successfully achieved in a concentration range of 0.25–20 μmol/L with detection limit of 0.042 μmol/L and nanosensors had specific recognition for sulfadiazine over its analogues. Compared to single‐emission fluorescence sensors, ratiometric fluorescence nanosensors had wider linear range and higher detection accuracy. Furthermore, the nanosensors were also successfully applied for the determination of sulfadiazine in real water and milk samples with acceptable recoveries. The study provides a feasible method for the detection of sulfadiazine and a reference for the detection of sulfonamides. [ABSTRACT FROM AUTHOR]

Utilizing the colorimetric and fluorogenic changes, a system based on polydiacetylenes (PDAs) is developed for the detection of neomycin. The PDA supramolecules polymerized from the mixed liposome composed of N-(3-hydroxyphenyl)pentacosa-10,12-diynamide (PCDA-AP) and pentacosa-10,12-diynoic acid (PCDA) at an optimized ratio of 1:9 display a unique colorimetric change (blue to red) and fluorescent enhancement in the presence of neomycin. The detection limit for neomycin is estimated to be 2.55 × 10−7 M by the fluorogenic method. The optical changes induced by neomycin can be attributed to the disruption of the hydrogen bonding between phenol and carboxylic acid from PCDA-AP and PCDA. [ABSTRACT FROM AUTHOR]

Abstract: New rhodamine derivatives bearing binaphthyl group were synthesized as selective fluorescent and colorimetric sensors for Cu2+. Highly selective “off–on” type fluorescent changes were observed upon the addition of Cu2+. Selective fluorescent enhancement of two rhodamine derivatives was attributed to ring opening from the spirolactam (nonfluorescent) to ring-opened amide (fluorescent). A chemo-sensing based on rhodamine derivative was further applied to the microfluidic system. [Copyright &y& Elsevier]

A new NIR fluorescent sensor based on an amine-substituted heptamethine cyanine dye displayed a highly selective fluorescence enhancement with cyanide in aqueous solutions, and was applied for the imaging of anthropogenic and biogenic cyanide. [ABSTRACT FROM AUTHOR]

In this study, a new "AND" logic platform based on intramolecular charge transfer (ICT) and Förster resonance energy transfer (FRET) is developed for constructing a near-infrared dual-locked fluorescence probe with high resistance to pH in biological environments. Using esterase and glutathione (GSH) as representative activators, the developed dual-locked probe BBQ650-SS-ClHC-E discriminates cancer cells from normal cells. The esterase substrate in the probe blocks the ICT process, while the GSH substrate acts as a linker to connect the fluorescence part with the quencher part to induce the FRET process. The fluorescence activation at 732 nm operates as an "AND" logic that depends on the "ICT-on" and "FRET-off" states in the presence of both esterase and GSH. BBQ650-SS-ClHC-E can successfully discriminate HeLa, 4T1, and RAW264.7 cancer cells from HFL1 normal cells and 4T1 tumor-bearing cells in living mice. This new platform can be used to develop dual-locked fluorescence probes. [Display omitted] • A novel "AND" logic platform for constructing NIR dual-locked fluorescence probe. • The activation of the fluorescence is based on ICT-on and FRET-off processes. • The quantum yield of the dual-locked BBQ650-SS-ClHC-E (0.25 %) is very small. • The fluorescence signal after activation possesses high resistance to pH at pH > 6.2. • The constructed dual-locked probe distinguished cancer cells from normal cells with high imaging contrast and specificity. [ABSTRACT FROM AUTHOR]

Abstract: An iminofluorescein-Cu2+ ensemble probe was prepared for the detection of thiols in aqueous solution. In HEPES buffer, among various amino acids, only cysteine (Cys) induced fluorescence enhancement of Cu2+ ensemble. The mechanism was proposed that addition of Cys induced decomplexation of Cu2+ from weak-fluorescent ensemble, followed by hydrolytic cleavage of the resulted Schiff base to give a strongly fluorescent fluoresceinaldehyde. By fluorescence titration using 2μM iminofluorescein-Cu2+ ensemble probe, the detection limit for Cys was evaluated to be 9μM with a signal-to-noise ratio of 3. Furthermore, the confocal microscopy experiments demonstrated that this sensor was potential for the imaging of thiols in living cells. [Copyright &y& Elsevier]

Graphical abstract Highlights • A polydiacetylenes-based sensor for the efficient detection of phospholipase D activity has been developed. • The sensor showed clolour and fluorescence changes in the presence of PLD and L-α-phosphatidylcholine. • The paper-based PDAs sensor also demonstrated the ability of monitoring PLD activity. Abstract Phospholipase D (PLD), as an enzyme that catalyses the hydrolysis of L-α-phosphatidylcholine to produce phosphatidic acid, plays an important role in regulating biological processes. In this work, polydiacetylenes (PDAs) bearing imidazolium as head group are reported for the efficient detection of PLD activity. Owing to the strong interaction between negatively charged phosphatidic acid and positively charged imidazolium moieties of PDAs, the PDAs were found to produce a colour transition from blue to red, and an increase in fluorescence. No obvious changes to PDAs were observed when PLD was absent in the reaction, or when the activity of PLD was inhibited by halopemide. The colour and fluorescence changes of PDAs are attributed to the generation of phosphatidic acid in the PLD-catalysed reaction. Furthermore, a paper sensor based on PDAs was constructed and exhibited convenient and sensitive detection of PLD activity. [ABSTRACT FROM AUTHOR]

A fluorescent probe is constructed to quickly and accurately detect bisulfite. The detection mechanism was considered to operate via the bisulfite, causing deprotonation of amido bond of 8-aminoquinoline derivative leading to fluorescence enhancement. The probe has a good selectivity for bisulfite over the other competitive substances such as F − , Cl − , Br − , I − , C 2 O 4 2− , NO 2 − , ClO 4 − , OAc − , PO 4 3− , CO 3 2− , HCO 3 − , HS − , HSO 4 − , SCN − , SO 4 2− , S 2 O 3 2− , Cys, Hcy and GSH. There is a good linear relationship between fluorescence intensity and the concentration of bisulfite in the range of 0–200 μM. The limit of detection was calculated to be 0.61 μM. Furthermore, the probe has also been successfully used for imaging bisulfite in living cells. [ABSTRACT FROM AUTHOR]

l -Arginine ( l -Arg) and l -lysine ( l -Lys) are both essential amino acids and paly significant roles in human beings and other living organisms. Therefore, it is necessary to develop the feasible methods with high selectivity and sensitivity for the detection of l -Arg and l -Lys. Herein, aminopyrene modified diacetylene monomer (PCDA-PY) was prepared and incorporated into diacetylene monomer (PCDA) to form polydiacetylene (PDA) vesicles. With the assist of Mg 2+ , PDAs system underwent colorimetric and fluorescent changes upon the addition of l -Arg or l -Lys. The introduction of Mg 2+ and pyrene moiety makes PDAs system more sensitive toward l -Arg or l -Lys. Furthermore, an “OR AND” logic gate was constructed based on the optical changes of PDAs system with the three elements including Mg 2+ , l -Arg and l -Lys. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: A ratiometric sensor (QA) for detecting Zn2+ with high sensitivity and selectivity was reported. The fluorescence changes of sensor upon the addition of Zn2+ were attributed to the conjugation of internal charge transfer and fluorescence resonance energy transfer mechanisms. There is a good linear relationship between the fluorescence ratio I 497 nm/I 420 nm and the concentrations of Zn2+ ranging from 0 μM to 40 μM, which makes an effective ratiometric detection of Zn2+ ion. The limit of detection (LOD) was evaluated to be 33.6 nM. The imaging experiments indicated that QA is cell-permeable and can be used to detect Zn2+ within living cells with good selectivity over Cd2+. [Copyright &y& Elsevier]

Abstract: A quinoline-based fluorescent chemosensor was reported for the simultaneous detection of Zn2+ and Cd2+ in aqueous solution. In HEPES buffer, among various metal ions, only Zn2+ and Cd2+ exhibited fluorescence enhancement at 497nm accompanied by the red-shift emission wavelength. The mechanism was proposed that internal charge transfer effect induced by binding with Zn2+ or Cd2+ produced the fluorescence changes. With the addition of cysteine, the fluorescent solution containing sensor and Cd2+ show the decreased fluorescence at 497nm and the increased fluorescence at 420nm, which was attributed to the dissociation of the complex formed by sensor and Cd2+. In contrast, the fluorescence of solution containing sensor and Zn2+ is unchanged with the addition of Cys. Furthermore, the confocal microscopy experiments indicated that this sensor can provide real-time detection for intracellular Zn2+ and Cd2+. [Copyright &y& Elsevier]

Abstract: Fluorescent polymeric spheres with uniform sizes are of great interests in the measurement and calibration of the pore sizes and defects of porous media, including separating membranes. We reported the preparation of such nanospheres by dissolving amphiphilic block copolymers of polystyrene-block-poly(2-vinyl pyridine) (PS-b-P2VP) together with chromophores (perylene and pyrene) in acetic acid at elevated temperatures. Micellar nanosphere with the chromophores residing in the cores were formed through the heating-enabled micellization process. Following quaternization of the P2VP coronae gave the spheres a positively charged surface and a good water dispersibility. Scanning and transmission electron microscopy and dynamic light scattering analysis confirmed that the micellar nanospheres were uniform in size both in the dry and wet state. The micelle size and the thickness of coronae can be tuned by altering the molecular weight of the constituent blocks. Encapsulation of chromophores in the micelle cores provided a strong fluorescent emission to the micellar nanospheres, while quaternization of the P2VP coronae gave the nanospheres a greatly variable size according to pHs and salt concentrations in the surroundings. Taking advantages of their uniform size, water dispersibility, and fluorescent emission for accurate detection, we demonstrated that the micellar nanospheres were capable of characterizing pore sizes of separating membranes and detecting their large-pore defects. [Copyright &y& Elsevier]

Abstract: Hydrogen sulfide (H2S) is an important gaseous mediator in cellular physiology and pathology. For understanding the biological action of H2S to both healthy and disease states, it is important to develop H2S-selective sensor. Herein we report a colorimetric and fluorescent probe, which employs an NBD moiety as fluorophore, and is equipped with azide group as H2S-active unit. The probe exhibits selective and sensitive response to H2S in aqueous solution. By employing 1 μM sensor, the detection limit was evaluated to be 680 nM with a signal-to-noise ratio of 3. Confocal microscopy imaging experiments demonstrate the probe has potential as a powerful tool for the imaging of hydrogen sulfide in living cells. [Copyright &y& Elsevier]

Abstract: A fluorescein-based sensor bearing nitroolefin moiety for the detection of thiols was prepared. Upon addition of thiols, such as cysteine (Cys), homocysteine (Hcy) and glutathione, the solution containing sensor showed an increase of absorption intensity at 497 nm with a slight blue-shift as well as the enhancement in fluorescence intensity at 520 nm. The fluorescence enhancement and absorption change are attributed to the Michael addition of thiols to the double bond of nitroolefin moiety in sensor. The probe displays a fast response to Cys with the rate constant (k obs) of 2.3 min−1 and the detection limit to Cys was evaluated to be 0.2 μM. The confocal microscopy experiments demonstrate that this sensor is potential for the imaging of thiols in living cells. [Copyright &y& Elsevier]

Abstract: New BODIPY dyes have been synthesized via the condensation of R–CH2COCl (R=H, Br, Cl and Et2N) with 2,4-dimethylpyrrole and the coordination with BF3 etherate. The acetyl chlorides with electron-withdrawing substituents (R=Br or Cl) are easier to react with the 2,4-dimethylpyrrole to form the related dyes and make a red-shift in absorbance and fluorescence maximum. Dye 4 (R=Et2N), based on PET mechanism, exhibits good properties as a pH fluorescent sensor with a pK a of 8.74 and a 15-fold fluorescence enhancement in the pH range of 9.38–7.60. [Copyright &y& Elsevier]

• The development of Zn2+ fluorescence probe in recent years (2015–2020) is systematically reviewed in this paper. • Zn2+ fluorescence probes are classified based on different fluorophore groups. • The characteristics of fluorescence probes are introduced by the emission wavelength of different groups. Zinc is of great importance to humans and other biological systems. For example, too high or low levels of zinc(II) ions (Zn2+) can result in various human disease states, and poor handling of Zn2+ leads to environmental pollution. Owing to the important roles played by this metal, many convenient, low-cost and easy-to-operate fluorescence probes for Zn2+ detection have been developed. Chief among these are fluorescence-based sensors that have high sensitivities and selectivities. In this review, we describe the fluorescence probes for Zn2+ which have been prepared and assessed in the time period since 2015. The presentation is organized according to different fluorophore families, including quinoline, naphthalene, coumarin, rhodamine, naphthalimide, pyrene, fluorescein, phenol derivatives, as well as several other fluorophores. The discussion of each probe concentrates mainly on its mode of action. [ABSTRACT FROM AUTHOR]