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The first difunctional probe H-1 for detecting ONOO− and Zn2+ at the same time showed high selectivity, good anti-interference capability, lower detect limit and short response time to them. [Display omitted] • · A new difuctional probe H-1 for ONOO− and Zn2+ detection at the same time was obtained firstly. • ·H-1 showed good selectivity and strong anti-interference ability for detecting ONOO− and Zn2+. • ·H-1 could fast response to ONOO− and Zn2+ in 15 s. • ·H-1 was used to monitor the ONOO− and Zn2+ level in living cells. Peroxynitrite (ONOO−) is one of the most significant reactive oxygen species (ROS) in living cells. Zn2+ in living cells plays an essential part in different physiological processes. The abnormal concentration of ONOO− and Zn2+ in living cells are related to many kinds of diseases, such as anemia, epilepsy, diarrhea, Alzheimer's disease, and so on. The relationship of ONOO− and Zn2+ in living cells when the relative disease occurs remains unknown. So we develop the first probe H-1 for detecting ONOO− and Zn2+ at the same time. The probe H-1 shows high selectivity, good anti-interference capability, low detection limit and short response time to ONOO− and Zn2+. When the probe was applied to detect ONOO− and Zn2+ in HeLa cells, we could observe the fluorescence changing in the green and blue channels separately without interference in real time. It has the potential to employ the relation of ONOO− and Zn2+ in some disease mechanism research. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel biotin-tagged fluorescent probe Nap-biotin-glu for in situ imaging of GGT on cell surface was developed. • The construction of the Nap-biotin-glu probe required only three steps with a simple and convenient method. • The probe shows obvious fluorescence change with high sensitivity and selectivity toward GGT. • The probe was applied to distinguish tumor tissues from normal tissues. γ-Glutamyl transpeptidase (GGT), a cell-surface enzyme, is strongly implicated in mammalian malignancy growth and migration processes including human hepatocarcinogens. However, simply and conveniently detect of GGT on the cell membrane remains highly challenging. In this study, a biotin-tagged fluorescent probe Nap-biotin-glu was developed using glutamic acid, naphthalimide, and biotin as the reaction site, fluorescent reporter, and membrane-targeting group, which required only three steps. Colocalization fluorescence imaging and immunofluorescence analysis indicated that probe Nap-biotin-glu was successfully realized in situ visualizing of GGT on the cell membrane.Owing to the significant over-expressed GGT level in tumor, the probe was successfully applied to distinguish cancer tissues from adjacent normal tissues. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ratiometric peptide-based fluorescent probe DKA with large Stokes shift (230 nm) was developed. • DKA demonstrated absorbance ratiometric and fluorescent "off-on" sensing for Hg2+ with low LOD of 13.4 nM. • DKA -Hg2+ complex was applied to sequential detect S2− with good selectivity and excellent sensitivity.. • DKA performed well in sequential detecting the distribution of Hg2+ and S2− in living cells. • DKA was used to visually and semi-quantitatively recognize Hg2+ and S2− by smartphone-assisted detection platform. In this work, a new ratiometric fluorescent probe DKA was synthesized based on the double sides of lysine backbone conjugated with alanine and dansyl groups. DKA exhibited fluorescence ratiometric response for Hg2+ with high sensitivity (13.4 nM), specific selectivity (only Hg2+), strong anti-interference ability (no interference), fast recognition (within 60 s) and wide pH range (5–10). The stoichiometry of binding of DKA and Hg2+ was determined to be 1:1 via Job's plot, ESI-HRMS and 1HNMR titration analysis. Subsequently, the in situ formation of DKA -Hg2+ complex was used for highly selective detection of S2− as a novel fluorescence "on–off" probe, and the lowest detection limit for S2− was 12.9 nM. In addition, DKA possessed excellent cells permeation and low toxicity, and fluorescence imaging of Hg2+ and S2− was performed in living Hacat cells. Most importantly, the digital imaging using a smartphone color recognition APP indicated that DKA could semi-quantitatively and visually detected Hg2+ and S2− without expensive equipment. [ABSTRACT FROM AUTHOR]

[Display omitted] • A first dual-response probe for norepinephrine and viscosity is synthesized. • The crosstalk between the two channels is negligible. • Reducing viscosity accelerates the release of norepinephrine in depression cells. Depression is a serious mental disease that causes grievous harm to human health and quality of life. The vesicular exocytosis of noradrenaline (NE), rather than its intrinsic intracellular concentration, is more associated with depression. Based on the reports on exocytosis of NE, it is reasonable to assume that the viscosity of cells has an important effect on the release of NE. Herein, a dual-response fluorescent probe (RHO-DCO-NE) for detecting NE and viscosity was designed and synthesized. The probe can simultaneously detect NE concentration and viscosity level with negligible crosstalk between the two channels. We utilized the probe to study the effect of viscosity changes on the NE release of PC12 and the corticosterone-induced PC12 cells. The experiment data revealed that the decrease in viscosity level can accelerate the release of NE of depression cell models. The finding provides new insight into the study of the pathological mechanisms of depression. [ABSTRACT FROM AUTHOR]

[Display omitted] • We have developed a novel quercetin (a SARS-CoV-2 inhibitor) coupled benzyl ethers (QBE) chemosensor for selective detection of Hg2+. • To date, there are very few reports where quercetin itself have been used in sensing field (table 1) but the use of quercetin derivative in sensing field is almost nil. • To the best of our knowledge our chemosensor QBE is the first chemosensor based on quercetin derivative for the selective detection of Hg2+. • The binding phenomenon of QBE with Hg2+ has been proved by UV–vis, fluorescence, DFT and cyclic voltammograms study. • Lower LOD (Limit of Detection) at 8.47 µM and high binding constant value as 2 × 104 M−1 showed the strong binding affinity of Hg2+ towards QBE. • The intracellular activity of QBE with Hg2+ binding has been examined by using living plant tissue by using green gram seeds. Quercetin is an important antioxidant with high bioactivity and it has been used as SARS-CoV-2 inhibitor significantly. Quercetin, one of the most abundant flavonoids in nature, has been in the spot of numerous experimental and theoretical studies in the past decade due to its great biological and medicinal importance. But there have been limited instances of employing quercetin and its derivatives as a fluorescent framework for specific detection of various cations and anions in the chemosensing field. Therefore, we have developed a novel chemosensor based on q uercetin coupled b enzyl e thers (QBE) for selective detection of Hg2+ with "naked-eye" colorimetric and "turn-on" fluorometric response. Initially QBE itself exhibited very weak fluorescence with low quantum yield (Φ = 0.009) due to operating photoinduced electron transfer (PET) and inhibition of excited state intramolecular proton transfer (ESIPT) as well as intramolecular charge transfer (ICT) within the molecule. But in presence of Hg2+, QBE showed a sharp increase in fluorescence intensity by 18-fold at wavelength 444 nm with high quantum yield (Φ = 0.159) for the chelation-enhanced fluorescence (CHEF) with coordination of Hg2+, which hampers PET within the molecule. The strong binding affinity of QBE towards Hg2+ has been proved by lower detection limit at 8.47 µM and high binding constant value as 2 × 104 M−1. The binding mechanism has been verified by DFT study, Cyclic voltammograms and Jobs plot analysis. For the practical application, the binding selectivity of QBE with Hg2+ has been capitalized in physiological medium to detect intracellular Hg2+ levels in living plant tissue by using green gram seeds. Thus, employing QBE as a fluorescent chemosensor for the specific identification of Hg2+ will pave the way for a novel approach to simplifying the creation of various chemosensors based on quercetin backbone for the precise detection of various biologically significant analytes. [ABSTRACT FROM AUTHOR]

A phenolato-thiazole based small molecule is synthesized and structurally characterized for the naked-eye detection of carbonate anion (LOD, 0.18 µM) in physiological conditions. The new colorimetric probe shows selective reversible chemosensory activity through the formation of a stable adduct (L∙CO 3 2). The cell uptake of the probe is mainly in the cytoplasm. [Display omitted] • A novel "turn-on" chemosensor fluorescent probe (L) for aqueous CO 3 2– anion is reported with crystal structure. • The 1:1 adduct L∙CO 3 2– (Binding constant, K = 1.6 x 10–7 M−1) in the quinonoid form is established by DFT/TDDFT. • The goodness of sensor activity concerns the selectivity, reversibility, and regeneration. • Selectivity with LOD (0.18 µM) in the pH range of 4 to 8. • MTT assay and cell uptakes and degradation of the probe through image study. A new phenolate-thiazole derivative (L) has been synthesized and structurally characterized. The chemo-sensing activity of L is detected by the naked eye for the aqueous carbonate anion in the pH range of 4 to 8. The selective 'turn-on' fluorescence occurs through the formation of a stable intermediate L∙CO 3 2–(1) following the PET mechanism. The limit of detection (LOD) is found 0.18 µM based on the absorbance-based assay. The quinonoid form of bromophenol unit binds strongly with CO 3 2– through thiazole nitrogen and hydrazinic nitrogen. Further, the selective holding of CO 3 2– anion over other planar tetranuclear anions (e.g., SO 3 2–, NO 3 –) happens with several intra and intermolecular hydrogen bonds as envisaged by the DFT/TDFT study. The formation mechanism of L∙CO 3 2– is proposed based on experimental and theoretical studies. The biological experiments (MTT and cell imaging) reveal the non-cytotoxicity nature of L and the biocompatible uptake of L mostly in the cytoplasm at physiological pH. [ABSTRACT FROM AUTHOR]

[Display omitted] • A dual-locked fluorescence probe (TPA-DNP) for LDs and HClO was designed. • TPA-DNP could detect LDs and HClO simultaneously by "turn-on" fluorescence singal. • TPA-DNP had successfully been applied in imaging HClO within LDs accumulation environments. • The real-time dynamic imaging of LDs and HClO by TPA-DNP under the LPS-induced inflammatory system. Inflammation is a key factor leading to the occurrence and development of many diseases, both lipid droplets (LDs) and hypochlorous acid (HClO/ClO-) are regarded as the important biomarkers of inflammation. Therefore, it is of great significance to develop an efficient single chemical sensor that can simultaneously detect these two biomarkers. To achieve the goal, we developed a dual-locked fluorescence probe (TPA-DNP) by fusing two targets activated reporting system, its implementation was achieved by turning-on the fluorescence of TPA-DNP through LDs and HClO/ClO- simultaneously. In simulated LDs environment, TPA-DNP displayed excellent selectivity to HClO/ClO-, high sensitivity (LOD = 0.527 μM) and strong anti-interference ability. In addition, cell and zebrafish imaging experiments showed that TPA-DNP could be utilized to visualize exogenous/endogenous HClO/ClO- in LDs environment, and could also be used to observe the impact of LDs changes on the HClO/ClO- detection. On the basis, TPA-DNP served as a favorable tool to achieve visualization of inflammatory dynamic changes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A convenient approach to construct excimer emissive luminogens was established. • A double-bond linker between π-moiety and side-moiety is essential for AIE. • The structure-luminescence relationship was elucidated. • The high-resolution image of living Hela cells was observed. The excimer emission based on discrete π-stacked dimers of polycyclic π-systems has generated significant interest in the structure-luminescence relationship of excimers owing to their ultra-large Stokes shift. Herein, a series of excimer emissive luminogens were obtained by conjugating different polycyclic aromatic aldehydes (anthraldehyde, pyrenealdehyde and perylenealdehyde) with triphenylmethylamine. In crystalline states, all the molecules were arranged in the form of π-stacked arene dimers which were spatially isolated from each other by the bulky triphenylmethyl groups, and thus emitted bright excimer emission. The anthracene and pyrene derivatives showed fluorescence enhancement responses to grinding and the enhanced fluorescence could recover to the original state upon heating. The aggregation-induced emission (AIE) properties of them were dependent on the shapes and sizes of the polycyclic aromatic groups. The pyrene derivative showed the most excellent excimer-based AIE behavior among them. All of them were more apt to exhibit the excimer emission when formed nanoparticles with pluronic F-127 than that without pluronic F-127. Furthermore, PETP was utilized for bioimaging of living Hela cells and the high-resolution image was observed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel NIR chemosensor BDDH based on isophorone was synthesized and characterized. • BDDH showed selectivity and sensitivity responses to Al3+ with fluorescence enhancement and color change. • The limit of detection (LOD) for Al3+ was reached the level of 10−8 M. • BDDH was applicated in identification of Al3+ in the different water samples. • BDDH was applicated in cell imaging in alive MCF-7 cells and plant imaging in soybean roots. In this paper, an isophorone-based NIR fluorescent and colormetric probe BDDH for Al3+ was synthesized and characterized, it showed highly selectivity and sensitivity through significant fluorescence enhancement and visible color change towards Al3+. The job plot confirmed that the binding ratio of BDDH with Al3+ was 1:1. Furthermore, the limit of detection (LOD) of Al3+ was determined to be 4.01 × 10−8 M. Moreover, BDDH was successfully applicated in identification of Al3+ in the different water samples, cell imaging in alive MCF-7 cells and plant imaging in soybean roots. [ABSTRACT FROM AUTHOR]

A novel series of pentacyclic-fused pyranoquinoliziniums bearing diverse substituents synthesized by one-pot and stepwise rhodium(III)-catalyzed C–H annulation reactions in a modular approach were disclosed. Excellent photophysical properties were obtained via tuning of donor and acceptor moieties allowing the selective bioimaging of mitochondria and lysosome. [Display omitted] • Modular synthetic strategies were rationally designed based on Rh(III) catalysis to build a new series of pentacyclic-fused pyranoquinoliziniums (4a-4i) with novel N and O atom arragnement. • In an one-pot reaction approach, reaction of 2-aryl-4-quinolones (1) with 1,2-diarylalkynes (2) generated two novel products including quinolinone-fused isoquinolines (3) and pyranoquinoliziniums (4). • The isolation of 3 allows the preparation of pyranoquinoliziniums (4) bearing diverse substituents through stepwise synthesis. • By installation of different substituents, these novel pyranoquinoliziniums (4) exhibited tunable absorption and emission properties, and fluorescence quamtum yields. • The newly synthesized pyranoquinoliziniums (4a-4g and 4i) were successfully applied to target mitochondria of living cells while 4h was specific to lysosome. On basis of their unique chemical and photophysical properties, and excellent biological activities, quinoliziniums have been widely used in various research fields. Herein, modular synthetic strategies for efficient synthesis of novel fluorescent quinoliziniums by using one-pot and stepwise rhodium(III)-catalyzed C–H annulations were developed. In the one-pot synthesis, the reaction between 2-aryl-4-quinolones (1) and 1,2-diarylalkynes (2) proceeded in a chemo- and regioselective manner to give quinolinone-fused isoquinolines (3) and pentacyclic-fused pyranoquinoliziniums (4). The structural diversity of pentacyclic-fused pyranoquinoliziniums (4) was expanded by the stepwise synthesis from 3 and 2 , allowing the strategic incorporation of electron-donating (OMe and OH) and electron-withdrawing (Cl) substituents on the top and bottom parts of the pyranoquinoliziniums (4). These newly synthesized pyranoquinoliziniums (4) exhibited tunable absorptions (455–532 nm), emissions (520–610 nm), fluorescence lifetime (0.3–5.6 ns), large Stokes shifts (up to 120 nm), and excellent fluorescence quantum yields (up to 0.73) upon adjusting the different substituents. The the unique arrangement of N and O atoms and extended π-conjugation of 4 could cause the relocation of HOMO comparing with our previous quinoliziniums. Importantly, pyranoquinoliziniums (4a-4g and 4i) targeted the mitochondria, while 4h was localized in lysosome. Due to the remarkable photophysical properties and the potential for organelle targeting of the novel class of quinoliziniums, they could be further applied for biological, chemical and material applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A NIR fluorescent probe was synthesized with fluorescent emission at 695 nm and Stoke's shift as large as 260 nm. • 1,3,4-Thiadiazole is a wonderful unit for ESIPT and ICT process and a good identify group for mental ions. • Probe could identify Cu2+ over other analytes with high sensitivity, fast response within 30 s and low detection limit (0.026 μM). • Probe was suitable to assay the Cu2+ level in wine, fruits and herbs. Fluorescent probe L-I was synthesized to demonstrate that 1,3,4-thiadiazole is an attractive moiety and could be utilized as positive hydrogen bond acceptor for excited state intramolecular proton transfer (ESIPT) processes, guider of electrons movement for intramolecular charge transfer (ICT) process and identify group for mental ions. Furthermore, dicyanoisophorone framework was employed to improve the fluorescence characteristics and near-infrared (NIR) fluorescent emission at 695 nm accompanied by a Stoke's shift as large as 260 nm was obtained. L-I could selectively detect Cu2+ over other analytes taking advantages of high sensitivity, fast response within 30 s and low detection limit (0.026 μM). More important, L-I exhibited good performance for detection of Cu2+ in actual water samples, food products, traditional Chinese medicine and for cell imaging which demonstrates practical significance in the fields of environmental monitor, food safety and biotechnology. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel peptide-based fluorescent probe DNC for sequential detection of Hg2+ and S2− was synthesized. • The detection limits of Hg2+ (8.4 nM) and S2− (5.5 nM) were significantly low. • DNC were successfully applied for sequential detection of Hg2+ and S2− in living cells and zebrafish. • DNC achieved selective and sensitive sensing toward Hg2+ and S2− on test strips. • Smartphone with RGB Color Picker was employed to analyze the different Hg2+ and S2− concentrations. Mercury ions (Hg2+) and sulfur ions (S2−), have caused serious harm to the ecological environment and human health as two kinds of highly toxic pollutants widely used. Therefore, the visual quantitative determination of Hg2+ and S2− is of great significance in the field of environmental monitoring and medical therapy. In this study, a novel fluorescent "on–off-on" peptide-based probe DNC was designed and synthesized using dipeptide (Asn-Cys-NH 2) as the raw material via solid phase peptide synthesis (SPPS) technology with Fmoc chemistry. DNC displayed high selectivity in the recognition of Hg2+, and formed non-fluorescence complex (DNC- Hg2+) through 2:1 binding mode. Notably, DNC- Hg2+ complex generated in situ was used as relay response probe for highly selective sequential detection of S2− through reversible formation-separation. DNC achieved highly sensitive detection of Hg2+ and S2− with the detection limits (LODs) of 8.4 nM and 5.5 nM, respectively. Meanwhile, DNC demonstrated feasibility for Hg2+ and S2− detections in two water samples, and the considerable recovery rate was obtained. More importantly, DNC showed excellent water solubility and low toxicity, and was successfully used for consecutive discerning Hg2+ and S2− in test strips, living cells and zebrafish larvae. As an effective visual analysis method in the field, smartphone RGB Color Picker APP realized semi-quantitative detections of Hg2+ and S2− without the need for complicated device. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel rhodamine-based chemosensor RB-Gly-4-NAP (RGN) was prepared for multi-ion detection. • The sensor enables highly selective detection of Hg2+ and trivalent cations (Fe3+, Al3+, Cr3+) across different channels. • Theoretical calculations confirmed the efficacy of the sensor in coordinating with Fe3+, Al3+, Cr3+, and Hg2+. • The sensor shows excellent sensitivity to Fe3+, Al3+, Cr3+, and Hg2+, with LODs of 10.20, 14.66, 58.78, and 73.33 nM. • The sensor has been successfully applied to actual water samples and bioimaging (cell imaging and zebrafish imaging). A novel rhodamine-based multi-ion fluorescent sensor, RGN, was designed and synthesized for the highly selective detection of mercury ions (Hg2+) in ethanol and water systems, as well as trivalent cations (Fe3+, Al3+, and Cr3+) in acetonitrile and water systems using a two-step Schiff base reaction method. Nuclear magnetic titration experiments and theoretical calculations demonstrated that the sensor achieved the detection of the aforementioned metal ions through the fluorescence turn-on phenomenon induced by lactam ring-opening. Density functional theory (DFT) calculation results showed decreased HOMO-LUMO energy gaps and increased dipole moments, indicating the effective coordination of the sensor with the corresponding metal ions to form more stable complexes, thereby achieving detection objectives. Furthermore, the fluorescence turn-on sensor RGN exhibited relatively low detection limits, with limits of detection (LOD) for Fe3+, Al3+, Cr3+, and Hg2+ being 10.20 nM, 14.66 nM, 58.78 nM, and 73.33 nM, respectively. Finally, practical applications of sensor RGN in environmental water samples, L929 cells, and zebrafish were demonstrated, indicating its potential for detecting and tracking Fe3+, Al3+, Cr3+, and Hg2+ in environmental samples and biological systems, with prospects for biomedical applications in the diagnosis and treatment of heavy metal ion-induced diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bifunctional fluorescent probe NT was developed to detect pH and viscosity. • The first ratiometric probe to detect pH and viscosity in NIR. • NT could respond to pH immediately, reversibly and accurately. • NT realized the accurate detection of pH in real water samples, human serum, and meat. • NT could be used to monitor pH and viscosity changes in cells. In this work, we developed a ratiometric fluorescent probe (NT) based on ICT framework in near-infrared (NIR) which could detect pH and viscosity simultaneously. Long emission wavelength in NIR could protect the probe from interference of background fluorescence and improve the accuracy of the test. Due to the presence of thiazole-salt, the probe possessed good water solubility and could respond immediately to pH in water system. The pH values measured by NT in the actual samples were not much different from that measured by the pH meter, therefore, NT could give excellent accuracy. NT realized the reversible detection of pH by protonation and deprotonation. NT was used successfully to detect the pH of actual water samples, human serum and meat, as well as the viscosity variation caused by thickeners. Additionally, NT could monitor the changes of pH and viscosity in living cells. Therefore, the novel probe exhibited potential application in the fields of the environment, human health and food safety evaluation. [ABSTRACT FROM AUTHOR]

A triphenylamine-benzofuran-derived fluorescent probe TBSF was developed for monitoring the sulfite level in Chinese medicinal materials and imaging in living cells. In the testing system, under 445 nm excitation, TBSF responded to sulfite steadily with a 540 nm fluorescence reporting signal. The testing system showed advantages including high sensitivity, rapid response, and high selectivity. In particular, TBSF achieved the sulfite detection in the water decoction of Chinese medicinal materials from both addition and excessive fumigation. It also realized the intracellular imaging of both exogenous and endogenous sulfite in living HepG2 cells. The imaging in water decoction-treated cells inferred the potential for the interdisciplinary detection. [Display omitted] • A triphenylamine-benzofuran-derived fluorescent probe developed for monitoring sulfite. • Sulfite level determined in Chinese medicinal materials and imaged in living cells. • Advantages including high sensitivity, rapid response, and high selectivity. • Testing water decoction of Chinese medicinal materials from both addition and excessive fumigation. In this work, a triphenylamine-benzofuran-derived fluorescent probe TBSF was developed for monitoring the sulfite level in Chinese medicinal materials and imaging in living cells. In the testing system, under 445 nm excitation, TBSF responded to sulfite steadily with a 540 nm fluorescence reporting signal. The testing system showed advantages including high sensitivity, rapid response, and high selectivity. In particular, TBSF achieved the sulfite detection in the water decoction of Chinese medicinal materials from both addition and excessive fumigation. It also realized the intracellular imaging of both exogenous and endogenous sulfite in living HepG2 cells. The imaging in water decoction-treated cells inferred the potential for the interdisciplinary detection. [ABSTRACT FROM AUTHOR]

A sort of new triphenylphosphine-bonded fluorescence probes have been prepared, which enable dual-color fluorescence imaging of mitochondria and nucleoli in living cells. [Display omitted] • 3-Coumaranone offers excellent opportunities for fluorescence probe design. • The first example to use triphenylphosphonium (TPP)-bonded dyes for RNA imaging. • The proposed probes can discriminate mitochondria and nucleoli via dual-color emissions. • The morphological changes of nucleoli upon drug stress have been evaluated by the synthetic probes. Probing intracellular organelles with fluorescent dyes offers opportunities to understand the structures and functions of these cellular compartments, which is attracting increasing interests. Normally, the design principle varies for different organelle targets as they possess distinct structural and functional profiles against each other. Therefore, developing a probe with dual intracellular targets is of great challenge. In this work, a new sort of donor–π–bridge–acceptor (D-π-A) type coumaranone dyes (CMO-1/2/3/4) have been prepared. Four fluorescent probes (TPP@CMO-1/2/3/4) were then synthesized by linking these coumaranone dyes with an amphiphilic cation triphenylphosphonium (TPP). Interestingly, both TPP@CMO-1 and TPP@CMO-2 exhibited dual color emission upon targeting to two different organelles, respectively. The green emission is well localized in mitochondria, while, the red emission realizes nucleoli imaging. RNA is the target of TPP@CMOs, which was confirmed by spectroscopic analysis and computational calculation. More importantly, the number and morphology changes of nucleoli under drug stress have been successfully evaluated using TPP@CMO-1. [ABSTRACT FROM AUTHOR]

[Display omitted] • More efficient, PF8BT-A for histamine detection with high selectivity. • Narrow average recovery in real sample detection with LOD of 0.38 μmol/L. • FRET was characterized between aptamers and PF8BT-Pdots during detection. • PF8BT-A with high biosafety and reliable cell staining was reported. Histamine has been known as a momentous cause of biogenic amine poisoning. Therefore, the content of histamine in foods is strictly required to be controlled within a certain range. Here, an aptamer fluorescent sensor was developed for detection of histamine. Poly [(9, 9-di-n-octylfluorenyl-2, 7-diyl)-alt-(benzo [2,1,3] thiadia-zol-4, 8-diyl)] (PF8BT) and the styrene maleic anhydride copolymer (PSMA) were used for the preparation of PF8BT-Polymer dots (PF8BT-Pdots). PF8BT-Pdots and the cyanine3-phosphoramidite (Cy3) were linked through aptamer to achieve the ratiometric detection for histamine. PF8BT-Pdots were partly quenched by Cy3 due to the fluorescence resonance energy transfer (FRET), when the histamine molecule was recognized by aptamer on the surface of PF8BT-Pdots. A linear range (3–21 μmol/L) was obtained for histamine detection with a low limit of detection (LOD = 0.38 μmol/L). PF8BT aptamer Pdots (PF8BT-A) were used to detect histamine in simply treated aquaculture water and tuna. The cell imaging of HeLa cells presented a good biosecurity and outstanding fluorescent imaging capability of PF8BT-A. The aptamer fluorescent sensors provided a new platform for rapid and accurate detection of histamine in aquatic products and had great potential for the application in food safety and quality control. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three novel fluorescence chemosensors were developed for Hg2+ determination based on dethioacetalization reaction. • Sensors displayed highly sensitive and selective to Hg2+ in aqueous system with low detection limit. • Sensor was successfully applied to detect Hg2+ in real water samples and herb extract samples. • Sensor is capable of monitoring Hg2+ in living cell. Mercury ion is one of the most harmful metal ions with significant hazards to the environment and human health. Thus, the development of innovative, sensitive, and selective sensors to help address the detrimental impacts of heavy metal contamination is necessary. In this work, we present three new chemosensors based on the deprotection reaction of the thioacetal group for distinguishing Hg2+ in environmental samples. These chemosensors show good photophysical properties with high quantum yield in aqueous medium. These prepared chemosensors were employed as fluorometric sensors for the determination of Hg2+ through the quenching of fluorescence emission due to the Hg2+-induced hydrolysis of the thioacetal to the aldehyde group. In the presence of Hg2+, chemosensors showed an emissive color transformation from blue fluorescence to non-fluorescence under UV light, which was readily seen by the visual eye. These chemosensors also exhibited highly distinctive selectivity toward Hg2+ over other interfering metal ions, with detection limits of 1.1 ppb, 13.4 ppb, and 12.7 ppb. Moreover, the practical applicability of chemosensor was successfully demonstrated in real water samples and herb extract samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel peptide-based fluorescent probe DMDH was developed for sequential recognitions of Cu2+ and glyphosate. • Low detection limits for Cu2+ (40.6 nM) and glyphosate (10.6 nM) were obtained. • DMDH has potential prospect in real sample and living cells analysis. • Test strips of DMDH were made and used for naked eye detection of Cu2+ and glyphosate. • Smartphone with RGB Color Picker were employed to analyze the concentration of Cu2+ and glyphosate. A new peptide-based fluorescent probe named DMDH with easy-to-synthesize, excellent stability, good water solubility and large Stokes shift (225 nm) was synthesized for highly selective sequential detections of copper ions (Cu2+) and glyphosate (Glyp). DMDH demonstrated great detection performance towards Cu2+ via strong fluorescence quenching, and forming non-fluorescence DMDH -Cu2+ ensemble. As a new promising cascade probe, the fluorescence of DMDH -Cu2+ ensemble was significantly recovered based on displacement approach after glyphosate was added. Interestingly, the limit of detections (LODs) for Cu2+ and glyphosate were 40.6 nM and 10.6 nM, respectively, which were far lower than those recommended by the WHO guidelines for drinking water. More importantly, DMDH was utilized to evaluate Cu2+ and glyphosate content in three real water samples, demonstrating that its effectiveness in water quality monitoring. Additionally, it is worth noting that DMDH was also applied to analyze Cu2+ and glyphosate in living cells in view of significant cells permeability and low cytotoxicity. Moreover, DMDH soaked in filter paper was used to create qualitative test strips and visually identify Cu2+ and glyphosate through significant color changes. Furthermore, smartphone RGB color recognition provided a new method for semi-quantitative testing of Cu2+ and glyphosate in the absence of expensive instruments. [ABSTRACT FROM AUTHOR]

[Display omitted] • We present a simplified fluorescent microscopy-surface plasmon resonance (FM-SPR) system. • Real-time simultaneous observation and acquisition of fluorescent carbon dots labeled silk fibroin kinetic processes using FM-SPR system. • The fluorescence image changes fitted well with the SPR signal changes. • The linear detection range was 2.5 μg/mL–100 μg/mL, and the real lowest detection limit reached 0.5 μg/mL. • The association rate and dissociation rate of N-CDs to SF which were 2.65 × 10−5/s and 1.52 × 10 −5/s, respectively. The use of fluorescent carbon dots (CDs) as highly precise biolabeling probes has been widespread in the fields of live cell imaging and protein labeling due to their small size and excellent photoluminescence ability to accurately target specific molecules with surface chemical properties. However, there was a lack of research on the interaction between CDs and labeled molecules. In this work, we presented a novel investigation strategy, the fluorescence microscopy-surface plasmon resonance (FM-SPR) system, which combined the use of fluorescence microscopy and wavelength modulation surface plasmon resonance to study the interaction between CDs and labeled molecules in real-time. Using this system, simultaneously recorded the SPR signals and the fluorescence images on the surface of the FM-SPR sensor chip. We observed the dynamic curve and fluorescence images of the interaction between green emissive nitrogen-doped carbon dots (N-CDs) and silk fibroin (SF) in real-time. The kinetic parameters, the quantitative analysis, and the investigation of the binding could be achieved. The results showed a strong linear relationship between the change in SPR signals and the concentration of N-CDs, with a linear coefficient of 0.99913. The linear detection range was 2.5 μg/mL–100 μg/mL, and the real lowest detection limit reached 0.5 μg/mL. Additionally, the green fluorescence points in the imaging region on the FM-SPR sensor chip increased with the concentration of N-CDs, which was consistent with the change in SPR signals. Using this system we also acquired the association rate and dissociation rate of N-CDs to SF which were 2.65 × 10−5/s and 1.52 × 10−5/s, respectively. This demonstrated the effectiveness of our method in quantitatively analyzing SF labeled with N-CDs. [ABSTRACT FROM AUTHOR]

According to DFT calculations, the coordination ratio (1:1) and mechanism of action (PET) of NRh6G-FA with Cu2+ were further investigated and elucidated. NRh6G-FA has been successfully applied to the detection of Cu2+ in CHM samples, "naked eye" identification and bioimaging of Cu2+ in living MCF-7 cells. [Display omitted] • A near-infrared rhodamine-like probe NRh6G-FA responsive to Copper (II) ions was designed and synthesized. • The responses of NRh6G-FA to Cu2+ were thoroughly confirmed by Job's plot, ESI-HRMS and DFT calculations. • NRh6G-FA can be successfully applied to recovery experiments and "naked eye" detection of Cu2+ in Chinese herbal medicine. • NRh6G-FA has low cytotoxicity and can be used for the detection of Cu2+ in living cells. Copper is one of the common among the heavy metal pollution in Chinese herbal medicine (CHM). So, it is essential to develop rapid and accurate testing method to quantify the Cu2+ content in CHM. Herein, we prepared a coordination-based near-infrared fluorescent probe (NRh6G-FA) by introducing a hemicyanine dye in rhodamine 6G scaffold. NRh6G-FA had a high sensitivity, anti-interference performance, fast response (within 60 s), visualization (from light yellow to green) for Cu2+ and excellent sensing performance for the detection of Cu2+ at low concentrations (LOD = 0.225 μM). The most likely mechanism was verified on the basis of Job's plot, ESI-HRMS and DFT calculations. NRh6G-FA could be successfully applied for the detection and "naked eye" recognition of Cu2+ in CHM samples. Moreover, NRh6G-FA was used to visualize Cu2+ in living MCF-7 cells by confocal fluorescence imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two BODIPY-based NIR fluorescent probes were developed. • These fluorescent probes showed turn-on fluorescence upon viscosity change. • BSZ-Ph and BSZ-R exhibited organelle-targeting properties. • BSZ-R was utilized for cellular-level imaging of lipid droplets and lysosomes. Microenvironmental viscosity is a crucial parameter for biological systems, and its abnormal fluctuations are closely associated with various functional disorders and diseases. However, it is still important and urgent to develop improved near-infrared fluorescent probes for micro-viscosity with dual-organelle targeting properties, low background noise, and high sensitivity. Herein, two BODIPY-based small-molecule fluorescent probes were designed and synthesized, which were explored for their viscosity- and polarity-responsive properties, and were further applied to imaging sub-cellular viscosity in living cells. Interestingly, BSZ-Ph and BSZ-R displayed near-infrared fluorescence (more than 650 nm) and were sensitive to environmental viscosity and polarity due to the introduction of a benzothiazole at the 2-position and electron-rich aniline groups at the 5-position of the BODIPY core, respectively. The fluorescence intensity increased exponentially with the viscosity changes. Furthermore, the probe BSZ-Ph could successfully target lipid droplets and image cellular viscosity changes by treating lipopolysaccharides (LPS) and nystatin. Comparatively, the probe BSZ-R could successfully target the dual organelles of lipid droplets and lysosomes and image cellular viscosity changes by treating LPS and monensin. Therefore, in this work, we reported two new BODIPY-based near-infrared fluorescent probes, BSZ-Ph and BSZ-R, for cellular viscosity imaging, which could target lipid droplets and the dual organelles of lysosomes and lipid droplets, respectively. The study could provide a reference for the future development of fluorescent probes for viscosity in lipid droplets and lysosomes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two spirobifluene-based turn-on fluorescent probes for Cysteine were synthesized. • The probes shows highly selectivity for Cysteine. • The probes had been applied to imaging Cysteine under two-photon excitation. • One probe displayed excellent detection limit for Cysteine. Two spirobifluene-based fluorescent probes SPF1 and SPF2 , were designed and synthesized. The probes displayed "turn-on" fluorescence response for Cysteine. One of the challenges in developing a Cysteine probe is to secure high selectivity. SPF1/SPF2 can discriminate Cysteine from GSH as well as Hcy, and showed high substrate selectivity. The detection limit of SPF1 is 36 nM, which is excellent comparing with other optical sensors for Cysteine. The sensing mechanism of SPF1/SPF2 was verified by experimental data and theoretical calculations. There was a good linear relationship between the fluorescence intensity of SPF1/SPF2 and the concentration of Cysteine. The MTT tests indicated that SPF1/SPF2 had low cytotoxicity and good biocompatibility. Theoretical calculations demonstrated that SPF1 , SPF2 , and their related reaction products with Cysteine exhibited good two-photon absorption properties. Finally, SPF1/SPF2 had been successfully applied to the imaging of Cysteine in living cells under two-photon excitation. [ABSTRACT FROM AUTHOR]

Under physiological conditions, K(TPE)EFYp is converted to K(TPE)EFY containing hydroxyl by dephosphorylation of ALP and fluorescence is turned on. [Display omitted] • An enzyme-responsive biosensor with AIE properties. • A peptide-based Fluorescent supramolecular hydrogel (FSH) material. • Sol-gel phases transformation to determine alkaline phosphatase (ALP) activity. • "Turn-on" strategy due to the AIE effect has a higher sensitivity and a lower LOD. Alkaline phosphatase is an important biomarker for medical diagnosis. An enzymatic fluorescence supramolecular hydrogel with AIE properties was developed and used for sensing alkaline phosphatase in vitro and in living cells. In the presence of ALP, K(TPE)EFYp was partially converted to the hydrogelator K(TPE)EFY and self-assembled into nanofibers to form Hydrogel. With the sol–gel transition and the AIE effect, the fluorescence emission was turned on. The linear concentration range of ALP activity in vitro quantified by this method was determined as 0–3 U/L with a LOD at 0.02 U/L. In addition, cell imaging and serum experiment showed that K(TPE)EFYp could also be used to detect ALP activity in living cells and biological samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two organic fluorescent dyes DCM-1 and DCM-2 with near-infrared fluorescence were designed and synthesized. • DCM-1 and DCM-2 have a specific fluorescence response to viscosity. • DCM-1 and DCM-2 can be successfully applied to the imaging of dynamic changes in viscosity in living cells. The development of near-infrared organic fluorescent dyes with tunable emission profiles is highly required in the field of biological sensing and imaging. In this paper, we designed and synthesized two organic fluorescent dyes, DCM-1 and DCM-2, through the hybridization of indolizine and dicyanomethylene-4H-pyran skeleton. These two compounds show near-infrared fluorescence with emission maximum approximately at 640 and 680 nm, respectively. Notably, both DCM-1 and DCM-2 have specific responses to viscosity without being interfered by biological relevant species. Cell experiments demonstrate that DCM-1 and DCM-2 can detect dynamic changes in viscosity within living cells, suggesting their potential applications in chemical biology research. [ABSTRACT FROM AUTHOR]

[Display omitted] • The first coumarin-based HNO donor (CD1) was developed. • HNO-releasing has a t 1/2 ∼90 min under physiological conditions. • The fluorescence intensity increased by about 4.9-fold. • HNO release can be visualized by cellar images. Nitroxyl (HNO), the single-electron reduction product of nitric oxide (NO), has attracted great interest in the treatment of congestive heart failure in clinical trials. In this paper, we describe the first coumarin-based compound N -hydroxy-2-oxo-2H-chromene-6-sulfonamide (CD1) as a dualfunctional HNO donor, which can release both an HNO signaling molecule and a fluorescent reporter. Under physiological conditions (pH 7.4 and 37 °C), the CD1 HNO donor can readily decompose with a half-life of ∼90 min. The corresponding stoichiometry HNO from the CD1 donor was confirmed using both Vitamin B 12 and phosphine compound traps. In addition to HNO releasing, specifically, the degradation product 2-oxo-2H-chromene-6-sulfinate (CS1) was generated as a fluorescent marker during the decomposition. Therefore, the HNO amount released in situ can be accurately monitored through fluorescence generation. As compared to the CD1 donor, the fluorescence intensity increased by about 4.9-fold. The concentration limit of detection of HNO releasing was determined to be ∼0.13 μM according to the fluorescence generation of CS1 at physiological conditions. Moreover, the bioimaging of the CD1 donor was demonstrated in the cell culture of HeLa cells, where the intracellular fluorescence signals were observed, inferring the site of HNO release. Finally, we anticipate that this novel coumarin-based CD1 donor opens a new platform for exploring the biology of HNO. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new lysosome-targeted fluorescent probe for HOCl has been designed and developed. • The probe has excellent sensitivity to HOCl. • The probe was applied to the fluorescence imaging of HOCl in HeLa cells and zebrafish. Lysosomes, as crucial acidic organelles in cells, play a significant role in cellular functions. The levels and distribution of hypochlorous acid (HOCl) within lysosomes can profoundly impact their biological functionality. Hence, real-time monitoring of the concentration of HOCl in lysosomes holds paramount importance for further understanding various physiological and pathological processes associated with lysosomes. In this study, we developed a bodipy-based fluorescent probe derived from pyridine and phenyl selenide for the specific detection of HOCl in aqueous solutions. Leveraging the probe's sensitive photoinduced electron transfer effect from phenyl selenide to the fluorophore, the probe exhibited satisfactory high sensitivity (with a limit of detection of 5.2 nM and a response time of 15 s) to hypochlorous acid. Further biological experiments confirmed that the introduction of the pyridine moiety enabled the probe molecule to selectively target lysosomes. Moreover, the probe successfully facilitated real-time monitoring of HOCl in cell models stimulated by N -acetylcysteine (NAC) and lipopolysaccharide (LPS), as well as in a normal zebrafish model. This provides a universal method for dynamically sensing HOCl in lysosomes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple single step multicomponent ugi type reaction was carried out to yield N-(tert-butyl)-2-(furan-2-yl)imidazo[1,2- a ]pyridine-3-amine (TBFIPA). • The synthesized TBFIPA was characterized using 1H NMR, 13C NMR and HRMS spectroscopic methods. • The selective & sensitive detection was identified using hypsochromic shift (lab : 335nm → 285nm) & fluorescence quenching. • The proposed mechanism is evident from Job plot, 1H NMR titration, ESI-MS data and theoretical DFT calculation. • The Cr3+ ion-selective TBFIPA was successfully applied in the design of a user-friendly silica-based portable test kits. • Also, the fluorescence quenching ability of TBFIPA in presence of Cr3+ ions are validated by imaging onion epidermal cells. • Real samples contaminated with Cr3+ ions were identified using TBFIPA with an appropriated relative error percentage. A simple single step one pot multicomponent reaction was performed to synthesize N-(tert -butyl)-2-(furan-2-yl)imidazo[1,2- a ]pyridine-3-amine (TBFIPA). The synthesized TBFIPA was subjected to library of cations to study its ability for selective and sensitive detection of specific metal ions. Selective detection of chromium ions by TBFIPA were found from the significant hypsochromic shift (335 nm → 285 nm) in the UV–Visible spectra. The fluorescent TBFIPA displays complete quenching of fluorescence under UV lamp (365 nm) only in the presence of chromium without the interference of common metal ions. Binding constant (k a) obtained from Benesi-Hildebrand plot is 0.21 × 105 M−1, limit of detection (LOD) and limit of quantification (LOQ) of TBFIPA toward Cr3+ ions are 4.70 × 10−7 M and 1.56 × 10−7 M, respectively. The mechanism proposed during complex formation were supported by stoichiometric Job continuous variation plot, 1H NMR titration and ESI-MS spectroscopic data. All the experimental confirmation for complex formation were corroborated with theoretical DFT studies optimized using RB3LYP/6-31G(d) basis set. The selectivity and sensitivity of TBFIPA toward Cr3+ ions are found suitable to design a user-friendly silica based portable test kit. Alongside, TBFIPA was successfully utilized for imaging onion epidermal cells. Furthermore, the results obtained for biological, environmental, and industrial samples provided solid evidence to estimate chromium ions using TBFIPA in these real samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • Based on dicyanoisophorone skeleton a near-infrared fluorescent probe was prepared and used to detect CO with high selectivity. • Two emission channels ratiometric fluorescence changes can be observed through adjusting the ICT effect of probe by CO. • The design of the probe enables it to be used for detecting CO in lysosomal subcellular organelles and further validated through cell co-localization imaging experiments. • The probe can be used to detect the endogenous and exogenous CO in Hela cells and could be used in living mice. • The probe is capable of detecting endogenous and exogenous CO through cell imaging experiments and has been successfully used in living mice. Carbon monoxide (CO) as an endogenous gas signaling molecule possesses important physiological functions and is of great significance in the treatment of various diseases. Real-time tracking of CO in living organisms has become a research hotspot in recent years. This article presents a lysosomal targeted near-infrared ratio fluorescence probe (TBM-CO) for selective detection of CO based on the dicyanoisophorone skeleton and morpholine fragment. The probe TBM-CO with weak ICT effect can be transformed to precursor TBM-NH 2 with strong ICT effect by the traditional Tsuji-Trost reaction procession in the presence of Pd2+ ions. The mechanism was proved by DFT calculation or the MS and HPLC results respectively. In the near-infrared region an obvious ratio fluorescence intensity change (F 686 / F 616) is observed in vitro spectral experiments. The concentration titration experiments indicate that there is a good liner relationship between the ratio fluorescence intensity and the concentration in the range of 0 to 50 μM (R2 = 0.996) and the detection limit is calculated as 0.38 μM. The cell fluorescence imaging and co-localization experiments further demonstrate that TBM-CO is able to detect the exogenous and endogenous CO in lysosomal subcellular organelle. Finally, it was used to detect the changes of CO concentration in living mice successfully. In short, a probe with three advantages of near-infrared emission, ratiometric fluorescence and organelle targeting was reported and used to detect CO successfully in cells and in living mice. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel turn-on near-infrared fluorescent probe TQ-AChE was developed to detect endogenous AChE. • The probe had high selectivity and sensitivity to AChE (LOD = 0.02 U/mL) and a fast response time (30 min). • In vivo studies in mouse models validate the potential of the probe in real-time monitoring of AChE expression in liver injury. Acetylcholinesterase (AChE) is a key enzyme in the cholinergic pathway of the nervous systems, with its aberrant expression linked to various diseases. In this study, we have developed a novel Turn-On near-infrared fluorescent probe, TQ-AChE, for the sensitive and selective detection of AChE activity. Characterized by its near-infrared emission at 740 nm, TQ-AChE effectively overcomes the limitations of traditional fluorescent probes, such as short excitation wavelengths and limited tissue penetration, crucial for both in vitro and in vivo applications. The probe's low limit of detection (LOD) of 0.02 U/mL for AChE makes it highly sensitive, enabling rapid quantification of AChE activity in serum effectively. Cell imaging studies demonstrate that TQ-AChE can confirm higher AChE activity expression in normal liver cells compared to liver cancer cells. TQ-AChE can also monitor AChE fluctuations in APAP-induced acute effectively, facilitating the evaluation of the efficacy of liver detoxifying agents. Additionally, in vivo studies in mouse models validate the potential of the probe in real-time monitoring of AChE expression in liver injury. The ability of TQ-AChE to visualize AChE expression signifies its potential as a promising tool for early liver disease diagnosis and therapeutic monitoring, opening new possibilities in hepatological research and clinical diagnostics. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new fluorescent probe CSH based on carbazole-thiophene was synthesized for the detection of ClO−. • CSH exhibits specific recognition of ClO− in the UV and fluorescence spectra, with detection limits as low as 3.61 × 10−6 mol/L and 1.16 × 10−6 mol/L. • Probe CSH can not only realize the detection of real water samples, but also can be applied to the detection of exogenous ClO− in HeLa cells. A carbazole thiophene-aldehyde and 4-methylbenzenesulfonhydrazide conjugate CSH was synthesized by introducing 5-thiophene aldehyde at the 3-position of the carbazole group as the precursor and then condensing it with 4-methylbenzenesulfonhydrazide. CSH has high selectivity and sensitivity towards ClO−, which can specifically identify ClO− by UV–Vis and fluorescence spectroscopy. CSH can rapidly respond to ClO− in the physiological pH range through a fluorescence quenching pattern, accompanied by the color of CSH changing markedly from turquoise to yellowish green under the 365 nm UV light. Probe CSH exhibits a quantitative response to ClO− (0–11 μM) with a low detection limit (1.16 × 10−6 M). Cell imaging experiments have shown that CSH can capture fluorescent signals in the cyan and yellow channels of HeLa cells through fluorescence confocal microscopy, and can successfully identify exogenous ClO− in HeLa cells. In addition, probe CSH can also be used to detect ClO− in environmental water samples. These results indicate that CSH has potential application prospects in the environmental analysis and biological aspects. [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe YX is a near-infrared fluorescent probe. • The probe YX can complete continuous detection Zn2+ and PPi. • The probe YX has a good application prospect in biology. • The probe can detect Zn2+ and PPi in actual samples. As the second most abundant transition metal element in the human body, zinc ions play an important role in the normal growth and development of the human body. We have successfully synthesized a near-infrared fluorescent probe with FRET effect for the detection of Zn2+. Probe DR6G has good selectivity and anti-interference ability for Zn2+. When Zn2+ is added to the probe DR6G solution, it responds completely within seconds, releasing red fluorescence with a detection limit of 2.02 × 10−8 M. As the main product of ATP hydrolysis, PPi is indispensable in various metabolic activities in cells and the human body. Due to the strong binding ability of Zn2+ and PPi, it is easy to form ZnPPi precipitation, so we added PPi to the solution to complete the Zn2+ detection, and realized the continuous detection of PPi, and the detection limit was 2.06 × 10−8 M. Since Zn2+ and PPi play an important role in vivo, it is of great practical significance to design and synthesize a fluorescent probe that can continuously detect Zn2+ and PPi. Biological experiments have shown that the probe DR6G has low cytotoxicity and can complete the detection of exogenous Zn2+ and PPi in cells and living mice in vitro. Bacterial experiments have shown that the DR6G probe also has certain research value in the field of environmental monitoring and microbiology. Due to the constant variation of the fluorescence signals of Zn2+ and PPi during detection, we designed the logic gate program. In practical applications, the probe DR6G can quantitatively detect Zn2+ in zinc-containing oral liquids and qualitatively detect PPi in toothpaste. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel ratiometric peptide-based fluorescent probe DWPH was developed. • DWPH showed highly selective ratiometric response to Hg2+ and S2− in 100 % aqueous solutions. • Low detection limits for Hg2+ (24.6 nM) and S2− (23.3 nM) were obtained. • DWPH were successfully used to determine Hg2+ and S2− in living cells and zebrafish. • Smartphone-assisted detection platform could achieve visual assay of different Hg2+ and S2− concentrations. A new ratiometric peptide-based fluorescent probe DWPH was designed and synthesized, comprising dansyl fluorophore as a fluorescent dye, and tripeptide backbone (Trp-Pro-His-NH 2) as a recognition group. The addition of Hg2+ caused the maximum emission peak of DWPH to blue shift from 560 nm to 510 nm. DWPH exhibited large Stokes shift (230 nm), satisfactory water solubility (100 % aqueous medium), good selectivity (only Hg2+), high sensitivity (24.6 nM), rapid response (within 50 s) and strong anti-interference ability for Hg2+ detection over a wide pH range (7–11). Additionally, the complex DWPH -Hg2+ as a relay response probe could also be applied to S2− according to displacement approach. Notably, the detection limit for S2− was calculated as 23.3 nM, exhibiting that DWPH showed great potential for environmental monitoring and bioimaging. In addition, DWPH were successfully used to determine Hg2+ and S2− in living cells and zebrafish based on excellent permeability and low cytotoxicity. What's more, the gradient concentration color changes of Hg2+ and S2− were combined with the smartphone APP to obtain red–green–blue (RGB) values, thus enabling rapid semi-quantitative detection of Hg2+ and S2− without expensive instruments. [ABSTRACT FROM AUTHOR]

[Display omitted] • G-CQDs as a probe had high stability, great sensitivity and excellent specificity. • An optical dual-mode sensor indicated wide linear range and low detection limit. • Smartphone-based sensor detected ClO- in drinking water with high recovery rate. • G-CQDs was used for real-time detection of intracellular ClO- due to low toxicity. Hypochlorite (ClO-) is an important redox regulator in reactive oxygen species, which play a considerable role in oxidative stress and related diseases. Hence, accurate and sensitive monitoring of ClO- concentration was urgently needed in the fields of life sciences, food and environment. Bright green fluorescent carbon quantum dots (G-CQDs) were synthesized utilizing one-step hydrothermal method with citric acid and acriflavine precursors. Through TEM, FTIR, XPS and zeta potential characterization procedures, G-CQDs illustrated uniformly dispersed and significant number of –NH 2 and –OH on the surface. Meanwhile, the fluorescence and colorimetric analysis exhibited wide linear range and low detection limit response to ClO-. The fluorescence changes of G-CQDs were identified via smartphone to realize mobile sensing of ClO-. Subsequently, G-CQDs was applied for visualization and quantitative detection of ClO- in drinking water samples with satisfactory recovery rate. More importantly, G-CQDs demonstrated good water solubility, optical stability and excellent biocompatibility, which offered a promising analysis approach in cell imaging and exogenous ClO- detection in living cells. G-CQDs illustrated bright prospect and great potential in practical application of ClO- associated disease prevention and early clinical diagnosis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Developed FDCM-BChE, a near-infrared probe, for accurate BChE quantification in serum. • The probe features rapid response and high selectivity, enhancing fluorescence-based BChE assays. • Employed FDCM-BChE in cellular imaging to reveal BChE downregulation in liver cancer and hepatic injury. • Demonstrated the probe's utility in identifying elevated BChE levels in diabetic subjects. Butyrylcholinesterase (BChE) is a crucial hydrolytic enzyme predominantly synthesized in the liver, playing a significant role in conditions like liver disorders, diabetes, Alzheimer's disease, and fat metabolism regulation. This study aims to address the current limitations in visualizing BChE activity in diseases at various states by introducing an ultra-sensitive near-infrared fluorescent probe, FDCM-BChE. The probe was engineered to have several properties, such as a large Stokes shift, rapid response time, high stability, excellent selectivity, and low detection limits. We validated the efficacy of FDCM-BChE in quantifying BChE activity in human serum and leveraged its low cytotoxicity for cellular imaging. The study revealed the downregulation of BChE activity in liver cancer and hepatic injury and the upregulation in diabetes. Thus, FDCM-BChE shows promise as a tool for specific applications, providing insights into diseases associated with BChE activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel fluorescence (DHP-CT1) enhancing selectively with Hg2+ was discovered. • DHP-CT1 could sensitively sense Hg2+ with the extremely low LOD in aqueous media. • The presence of Hg2+ results in the hydrolysis of a thiocarbamate unit to 1,4-DHP. • DHP-CT1 was developed on a paper-based sensing strip for Hg2+ detection. • DHP-CT1 has been used for determination of Hg2+ in water samples and living cells. In this study, two fluorescent sensing probes, dihydropyridine (DHP) derivatives (DHP-CT1 and DHP-CT2) bearing phenoxy thiocarbonyl group, have been developed for Hg2+ detection. The tandem trimerization-cyclization of methylpropiolate with ammonium acetate gave 1.4-DHP and 1,2-DHP derivatives, which were reacted with O -phenylcarbonochloridothioate to produce DHP-CT1 and DHP-CT2 , respectively. DHP-CT1 exhibits superior sensitivity and selectivity of fluorescence enhancement towards Hg2+ in aqueous media. The fluorescence intensity shows a good linear relationship with the concentration of Hg2+ in the range of 0–10 µM providing the extremely low LOD of 346 nM (69.4 ppb). The fluorescence enhancement is caused by the Hg 2+ promoted hydrolysis of the thioamide bond releasing the fluorescent 1,4-DHP that was confirmed by NMR and HRMS. The quantitative analysis of Hg2+ in water samples using DHP-CT1 probe was demonstrated in aqueous solution and paper-based sensing strips. Furthermore, DHP-CT1 was also applied for monitoring intracellular Hg2+ in living RAW264.7 macrophages through fluorescence cell imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new family of tetraphenylethylene-based N,O-chelated boranil complexes (TPE-BAs) with AIE properties were synthesized. • The stability, photophysical properties, and crystal stacking of TPE-BAs are closely related to the substituents on the aniline portion. • Electron-donor-substituted TPE-BA-OMe exhibits the best stability and high quantum yield. • TPE-BA-OMe can serve as excellent fluorescent probes for specific imaging of lipid droplets in living cells. A new family of tetraphenylethylene-based N,O-chelated boranil complexes (TPE-BAs) with aggregation-induced emission (AIE) characteristics were developed. X-ray crystallographic analysis indicated that the terminal substituents on the aniline moiety significantly affected the intermolecular stacking mode, thereby influencing the photophysical properties. The stabilities of these compounds are closely related to the substituents on the aniline moiety. Electron-donor-substituted TPE-BA-OMe exhibited the best stability, whereas the electron-acceptor-substituted compounds exhibited poor stability. Benefitting from its AIE properties and suitable lipophilicity, TPE-BA-OMe served as an excellent fluorescent probe for the specific bioimaging of lipid droplets in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • Successful synthesis and characterization of a new fluorescent probe, NR-ClO, for ClO– detection in biological systems. • NR-ClO demonstrated low cytotoxicity, high selectivity, and sensitivity to ClO–. • Confirmed applicability of NR-ClO in both in vitro HepG2 cell studies and in vivo mouse model of rheumatoid arthritis. This study presents the synthesis and application of a novel fluorescent probe, NR-ClO, for the detection of hypochlorite ion (ClO–) in biological systems. The probe was synthesized through a nucleophilic substitution reaction between Nile red and dimethylcarbamothioic chloride. The synthesized probe had high sensitivity and selectivity towards ClO–, with a detection limit of 75 nM and a linear range of 0.1–200 μM. The probe's efficacy was validated through in vitro studies using HepG2 cells and in vivo experiments using a mouse model of rheumatoid arthritis. The findings demonstrate that the NR-ClO probe is a promisingly reliable tool for real-time monitoring of ClO– in complex biological environments. [ABSTRACT FROM AUTHOR]

Herein, we synthesized green luminescent nitrogen (N) and sulfur (S) co-doped carbon dots (N, S-CDs) which could realize the monitor of 4-nitrophenol (4-NP) and pH. The N, S-CDs can be designed as a fluorescent probe for sensitive detection of 4-NP in water samples with linear ranges of 0–85 µM and a detection limit of 0.037 µM. Moreover, the fluorescence intensity of N, S-CDs is sensitive to pH and shows a linear relationship with pH values ranging from 3.50 to 7.25 and 7.25–12.00, accompanied with a significant color variation of the N, S-CDs solution from colorless to brown. Finally, the proposed N, S-CDs have also been applied to monitor the 4-NP in oocysts due to its low cytotoxicity. Scheme 1. Schematic diagram of the synthesis and application of the N, S-CDs. [Display omitted] • N, S-doped carbon dots (N, S-CDs) with green emission were synthesized by one-step hydrothermal method. • N, S-CDs can be used as a bifunctional sensing platform for the detection of pH and 4-nitrophenol (4-NP). • The detection of 4-nitrophenol (4-NP) in water samples were successfully realized by using N, S-CDs. • N, S-CDs can also be used for cell imaging. Using p-aminophenol and dithioacetamide as precursors, green luminescent nitrogen (N) and sulfur (S) co-doped carbon dots (N, S-CDs) are prepared by hydrothermal method with the quantum yield (QY) of 7.1 %. Superior properties of the N, S-CDs including high photostability, outstanding biocompatibility, and desirable biological penetration were found, which could realize the monitor of 4-nitrophenol (4-NP) and pH. The N, S-CDs can be designed as a fluorescent probe for sensitive detection of 4-NP in water samples with linear ranges of 0–85 µM and a detection limit of 0.037 µM. Moreover, the fluorescence intensity of N, S-CDs is sensitive to pH and shows a linear relationship with pH values ranging from 3.50 to 7.25 and 7.25–12.00, accompanied with a significant color variation of the N, S-CDs solution from colorless to brown. Finally, the proposed N, S-CDs have also been applied to monitor the 4-NP in oocysts due to its low cytotoxicity, providing a great capacity for various targets molecules detection. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Al3+ Schiff base probe JHK was designed and synthesized. • JHK has high selectivity, high fluorescence quantum yield and low detection limit for Al3+. • JHK was successfully applied to living cells and zebrafish. A novel fluorescent probe N'-(2-hydroxybenzylidene)-indole-3-formylhydrazine (JHK) was designed and synthesized based on the condensation reaction of indole-3-formylhydrazine and salicylaldehyde. The probe JHK solution could highly selectively recognize Al3+ by the obvious fluorescence enhancement (288-fold) after adding Al3+. And the probe solution with Al3+ had a very high fluorescence quantum yield (89.29 %). The detection limit was calculated to be 1.135 nM, which was significantly lower than many reported detection limits, indicating that the probe JHK had pretty good sensitivity. The ratio of JHK to Al3+ (1:1) and the sensing mechanism were determined by Job's plot, 1H NMR spectra, FTIR spectra, ESI-MS and Gaussian calculation. The probe solution and medium-speed filter paper were successfully used to make test papers for more convenient detection of Al3+. Furthermore, the probe JHK had been successfully applied to the detection of Al3+ in real water, zebrafish and living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new asymmetrical photochromic diarylethene (DTE-HQo) exhibiting multicolour photoswitching behaviors have been successfully synthesized. • DTE-HQo can effectively distinguishes between Zn2+ and Cd2+ through visual observation due their distinct binding mode. • DTE-HQo could be applied in cell imaging. A new asymmetrical photochromic diarylethene DTE-HQo composed of a 2-hydrazinoquinoline moiety as the binding unit for ions and dithenylethene as a photoswitching trigger was reported. DTE-HQo displayed favourable photochromism upon irradiation with UV/vis light. Its fluorescent behaviour could be efficiently modulated by light, Zn2+, Cd2+ and HSO 4 −. The binding of Zn2+ induced a strong fluorescence peak at 510 nm in D TE -HQo due to the formation of a 1:2 complex [Zn2+ + 2 D TE -HQo ], resulting in a notable colour change from dark to intense white emission. Triggered by Cd2+, D TE -HQo formed a 1:1 complex [Cd2+ + D TE -HQo ], leading to an enhanced emission intensity by 21-fold with an emission peak red-shifted from 461 nm to 514 nm. Unexpectedly, [Zn2+ + 2 D TE -HQo ] underwent hydrolysis when stimulated with water, generating a yellow-emitting complex [Zn2+ + D TE -HQo ]. This color change easily distinguishes it from Cd2+ complex. Additionally, DTE-HQo showed high selectivity towards HSO 4 − and exhibited distinct "turn-on" fluorescence with a colour change from dark to bright blue upon stimulation. Moreover, the strong emission complexes of DTE-HQo with Zn2+, Cd2+ and HSO 4 − could be effectively quenched during the photocyclization process. Therefore, DTE-HQo can serve as an unimolecular multicolour photoswitching chemosensor, offering potential applications as a multifunctional probe for detecting Zn2+, Cd2+ and HSO 4 −. [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe EDPH specializes in the detection of H 2 S with high selectivity, high sensitivity and good detection limits. • The probe EDPH has been shown to have applications in intracellular fluorescence imaging. • Purine-based fluorescent probes for the detection of H 2 S are a new direction. Hydrogen sulfide (H 2 S) is a gas with a toxic odor that plays an irreplaceable role in physiological activities within the mammalian body. Therefore, it is important to do the distribution and quantitative detection of H 2 S in mammalian cells. In this paper, a fluorescence probe (EDPH) based on purine scaffold was designed and synthesized with high sensitivity and good selectivity. H 2 S induced ether bond breakage in EDPH , resulting in a significant redshift of the absorption band (from 370 nm to 500 nm) with a Stokes shift of 130 nm. After the addition of H 2 S, the fluorescence intensity of EDPH showed a good linear correlation with the concentration of H 2 S, which enabled the quantitative detection of H 2 S with a low limit of detection (41 nM). Finally, the EDPH was applied to the cellular Hele, and the probe has good cellularity imaging capability for the detection of H 2 S in living systems. [ABSTRACT FROM AUTHOR]

In this manuscript, we designed and synthesized a fluorescent probe HBA based on caffeic acid for detecting Al3+ and HPO 4 2− by the mode of "off-on-off". The probe HBA can be utilized as a powerful method for the sequential recognition of Al3+ and HPO 4 2– in biological samples. [Display omitted] • A new dual-functioned fluorescent probe HBA based on caffeic acid was synthesized. • The new fluorescent probe HBA can sequential detect Al3+ and HPO 4 2–− with good selectivity and excellent sensitivity. • The probe HBA has good performance for detection of Al3+/HPO 4 2– in HeLa cells. In this work, we focused on synthesizing a new fluorescent probe HBA based on caffeic acid for detecting Al3+/HPO 4 2− by the mode of "off-on-off". HBA alone exhibited a weak fluorescence emission in aqueous solution. When Al3+ was added into the HBA solution, a significant green fluorescence was found at 498 nm. However, the introduction of HPO 4 2− to the solution of [ HBA -Al3+] complex induced the disappearance of green fluorescence. The detection limit of HBA was calculated as low as 41.7 nM for Al3+ and 62.1 nM for HPO 4 2−, respectively. Probe HBA exhibited good cell-membrane penetrability and had the potential to trace Al3+/HPO 4 2− in biological systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two TPE fluorescence probes with morpholine/pyrrolidone group were synthesized. • TPE-Ma and TPE-Py exhibited AIE character and lysosome targeting capability. • Two-photon fluorescence nanoprobes labels lysosomes in MCF-7 cells. Lysosomes are essential cellular organelles, serving vital functions in cellular metabolism and degradation. The design of specifically targeting lysosomes probes with aggregation-induced emission (AIE) characteristics using two-photon excitation techniques is significance and challenging work. Here we designed and synthesized two tetraphenylethylene (TPE)-based AIE fluorescence probes, naming TPE-Ma and TPE-Py , with TPE as the matrix and morpholine (Ma) or pyrrolidone (Py) as the targeting group. These probes exhibit a significant Stokes shift, low cytotoxicity, two-photo fluorescence imaging and lysosome-specific targeting capability ensuring their suitability for fluorescence imaging applications. To enhance the water solubility and cellular accumulation of TPE-Ma and TPE-Py in tumor cells, we employed a biocompatible polymer 1,2-distearoyl- sn -glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-mPEG 2000) as a nanocarrier. By encapsulating TPE-Ma and TPE-Py within DSPE-mPEG 2000 , we successfully developed two AIE fluorescent nanoprobes known as DSPE@ TPE-Ma and DSPE@ TPE-Py. The results demonstrated that fluorescent nanoprobes DSPE@ TPE-Ma and DSPE@ TPE-Py possess excellent cell permeability, biocompatibility, superior photostability and specific targeting towards lysosomes in MCF-7 cells. Our findings highlight the potential of these fluorescent nanoprobes as effective tools for two-photon fluorescence imaging and targeted detection of lysosomes in cancer cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A mitochondria-targeting fluorescence probe NIR1 for H 2 S visualization. • NIR1 has excellent detection limits as low as 30.2 nM. • NIR1 was successfully applied for H 2 S imaging analysis in living inflammatory mice. The mechanism of the interaction between the signaling molecule hydrogen sulfide (H 2 S) and mitochondria and its related diseases is difficult to elusive. Thus it is urgent to develop effective methods and tools to visualize H 2 S in mitochondria and in vivo. In this work, a robust mitochondrial-targeting NIR fluorescence "turn-on" fluorescent probe, NIR1, was reported, by adopting a Changsha-OH near-infrared (NIR) dye as the NIR fluorophore, a 2,4-dinitrophenyl (DNB) moiety as both the responsive site of the H 2 S and the fluorescence quenching group of the NIR fluorophore, and an oxygen onium ion site as the mitochondria-targeting group, for the detection and analysis of H 2 S in living Raw 264.7 cells and drug-induced inflammatory mice models. NIR1 exhibited a much smaller background fluorescence signal in lack of H 2 S, whereas strong enhanced NIR fluorescence "turn-on" was detected in the presence of H 2 S, these results showed a low detection limit (30.2 nM) for quantitative detection of H 2 S in aqueous solutions with concentrations ranging from 0 to 1 μM H 2 S. These characteristics were beneficial to direct detection and imaging analysis of H 2 S in complicated biosystems. Therefore, first, NIR1 was applied for the NIR detection of mitochondrial H 2 S in living inflammatory cells with satisfactory results. Finally, NIR1 was applied to detect H 2 S in drug-induced inflammatory mice models with agreeable results, demonstrating that NIR1 as a molecular tool has an excellent practical application in the study of the interaction between inflammatory and H 2 S. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lysosome-targeted carbon dots (L-CDs) were synthesized from hematoxylin. • The L-CDs have been used to visually recognize Hg2+ and SO 3 2− by smartphone. • The L-CDs have been employed to differentiate Hg2+ and SO 3 2− in living cells. Smartphone-assisted visual assay not only expands quantitative analysis but also enhance real-time on-site sensing capabilities. Herein, lysosome-targeted dual-emissive carbon dots (L-CDs) can not only recognize Hg2+ and SO 3 2− by ratiometric fluorescence and ratiometric absorption, but also visually quantify Hg2+ and SO 3 2− by smartphone-assisted method. With monitoring of intrinsic ratiometric fluorescent variation (I 580 /I 468), L-CDs are developed as an effective sensing platform for ratiometric fluorescent successive identification of Hg2+ and SO 3 2− accompanying with continuous fluorescence variation of blue, purplish pink, pink, and light yellow. With detecting of inherent ratiometric absorption change (A 538 /A 206), L-CDs are also constructed as an efficacious sensing terrace for ratiometric absorption consecutive discrimination of Hg2+ and SO 3 2−. More crucially, integrating continuous fluorescence color change and color recognizer APP in the smartphone, visual quantification of Hg2+ and SO 3 2− can be accomplished on the basis of the ratio of red value and blue value (R/B) with linear ranges of 0–130 and 0–850 µM, respectively, as well as LOD of 8.4 and 12.9 nM, respectively. More interestingly, confocal fluorescent imaging of HeLa cells further verifies that L-CDs can be regarded as favorable biosensors for on-site, real-time differentiation of Hg2+ and SO 3 2− in vitro and in vivo with ratiometric manners. [ABSTRACT FROM AUTHOR]

[Display omitted] • An efficient dual-function fluorescent probe SN-F for SO 2 derivatives and H 2 S. • SN-F had a swift response (2 min), strong selectivity and anti-interference capability for SO 2 derivatives. • Probe SN-F had a wide linear range for H 2 S. • Probe SN-F had superior endoplasmic reticulum-targeting. As gas signaling molecules in organisms, SO 2 derivatives and H 2 S play crucial regulating roles in a series of physiological processes. Therefore, developing an assay that can accurately monitor the concentration of SO 2 derivatives and H 2 S in cells is extremely important for the research and treatment of related illnesses. A bifunctional probe SN-F based on FRET mechanism for SO 2 derivatives and H 2 S was designed. SN-F had a short response time to SO 2 (2 min), excellent anti-interference capability and selectivity in the non-organic solvent system (pH = 7.4), which was suitable for the determination of SO 2 derivatives in cells. SN-F had a wide linear range for H 2 S. Moreover, SN-F was applied in cell imaging successfully with high targeting ability to endoplasmic reticulum (ER) and could monitor endogenous and exogenous H 2 S in cells. [ABSTRACT FROM AUTHOR]

The fluorescent probe HOS for Hg2+ detection and its application to water sample detection and bioimaging. [Display omitted] • Development of a xanthene-based fluorescent sensor HOS for ratiometric fluorescence detection of Hg2+. • HOS is capable of detecting ultra-trace Hg2+ levels. • Successful determination of Hg2+ levels in shrimp and water samples. • HOS can be used to visualize Hg2+ in living cells, zebrafish and tobacco seedlings. In this paper, an Hg2+ detection probe, HOS , was prepared with a xanthene as the parent fluorophore. Hg2+-initiated thioacetal deprotection reaction is the detection mechanism of this probe. After testing, the probe HOS was able to accurately determine Hg2+ with a detection limit of 36 nM. It was successfully applied to the detection of Hg2+ in different water samples and shrimp samples, meanwhile, the filter paper strips prepared by HOS were obviously changed from light yellow to dark yellow under daylight, and from green to yellow under 365 nm UV light. Furthermore, probe HOS enabled Hg2+ bioimaging experiments on HepG2 cells, zebrafish and tobacco seedlings under laser confocal microscopy. [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe 3-STF is first designed based on 3-thiolflavone. • The probe 3-STF exhibited a specific "turn-on" fluorescence response towards biothiols (Cys, Hcy, and GSH) with a large stokes shift of 140.6 nm. • The detection of biothiols did not suffer from the interference of other amino acids. • The detection mechanism was discussed in detail. • The probe 3-STF can be successfully applied to monitor endogenous and exogenous biothiols in HepG-2 cells. Abnormal levels of intracellular biothiol species, including glutathione (GSH), homocysteine (Hcy), and cysteine (Cys), are closely relevant to a variety of diseases. In this study, we first report the design and synthesis of a 3-thiolflavone-based probe 3-STF with an S–S linkage both as the fluorescence quenching agent and the recognition site. Upon treatment with biothiols, the S–S linkage was cleaved by nucleophilic attack of RS-, and 3 -STF exhibited a specific "turn-on" fluorescence response at 543.8 nm upon 390 nm excitation. Meanwhile, 3 -STF was proved to be highly sensitive and selective for the detection of biothiols over other nucleophiles such as amino acids and H 2 S. The sensing mechanism was further verified by 1H NMR and ESI-MS analysis. In addition, 3-STF with low cytotoxicity can be successfully applied to detect endogenous and exogenous biothiols in HepG-2 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescent probe NBPI, utilizing cyanine phenothiazine and 7-nitro-1,2,3-benzoxadiazole (NBD), was developed for selective detection of Cys-SO 2 components. • The phenothiazine structure increased the bond energy of sulfonamide, thus the probe NBPI achieved a selective response to Cys. • The probe NBPI was successfully employed for the imaging of endogenous and exogenous Cys and SO 2 in HepG2 cells. A fluorescent probe has been designed using cyanine phenothiazine and 7-nitro-1,2,3-benzoxadiazole (NBD) for selective detection of Cys-SO 2 components. The probe utilizes the NBD structure to achieve specificity towards Cys and employs a reaction mechanism between the double bond of cyanine and phenothiazine with SO 3 2− to achieve selectivity towards SO 2. Importantly, the NBPI phenothiazine structure incorporates a large C-O bond energy attached to NBD, effectively eliminating interference from Hcy and ensuring highly selective response to Cys. The optimized design of the probe enables excellent linearity and extremely low detection limits for Cys-SO 2 components in vitro experiments. The probe NBPI allows separate detection of Cys-SO 2 in the presence of both components. Furthermore, the probe NBPI demonstrated successful imaging of endogenous and exogenous Cys and SO 2 in cell studies. [ABSTRACT FROM AUTHOR]