Near-infrared fluorescent probe visual detection of Hg2+ and its application in biological system and ecological system.

Mercury ion (Hg2+), a heavy metal cation with greater toxicity, is widely present in the ecological environment and has become a serious threat to human health and environmental safety. Currently, developing a solution to simultaneously visualize and monitor Hg2+ in environmental samples, including water, soil, and plants, remains a great challenge. In this work, we created and synthesized a near-infrared fluorescent probe, BBN-Hg, and utilized Hg2+ to trigger the partial cleavage of the carbon sulfate ester in BBN-Hg as a sensing mechanism, and the fluorescence intensity of BBN-Hg was significantly enhanced at 650 nm, thus realizing the visualization of Hg2+ with good selectivity (detection limit, 53 nM). In live cells and zebrafish, the probe BBN-Hg enhances the red fluorescence signal in the presence of Hg2+, and successfully performs 3D imaging on zebrafish, making it a powerful tool for detecting Hg2+ in living systems. More importantly, with BBN-Hg, we are able to detect Hg2+ in actual water samples, soil and plant seedling roots. Furthermore, the probe was prepared as a test strip for on-site determination of Hg2+ with the assistance of a smartphone. Therefore, this study offers an easy-to-use and useful method for tracking Hg2+ levels in living organisms and their surroundings.

Fluorescence based metabisulfite sensing: New aspects of ion sensing by a styryl benzothiazolium dye and understanding nitrite interference.

Detection of specific ions using fluorescent probes has relevance in several areas of therapeutics development and environmental science. Here, we provide new perspectives to the sensing of a styryl benzothiazolium-based fluorescent compound 1 and report that sensing properties are for sulfite ions in general with highest preference for metabisulfite ions (S2O52-) adding to its previously determined role as a bisulfite ion sensor. This probe exhibits its sensing action via an addition reaction in which the styryl double bond gets reduced. The interference studies highlighted that the sequence of addition of nitrite and metabisulfite has a bearing on the overall interference outcome. Spectroscopic studies revealed that the order of preferential sensing of sulfites and sulfide ion is S2O52- > HSO3- > SO32- > S2-. Although this probe displays robust sensing on its own through fluorescence quenching, its fluorescence emission can be enhanced at much lower concentrations in the presence of a G-quadruplex DNA without compromising the outcome of the sensing.

A multifunctional near-infrared fluorescent probe based on benzothiazole structure for fluoride-ion detection.

Fluoride ions (F-) are one of the essential trace elements for the human body and are widely existed in nature. In this study, we present a novel fluorescent probe (YF-SZ-F) designed and synthesized for the specific detection of F-. The probe exhibits high sensitivity, excellent selectivity, and low cytotoxicity, making it a promising tool for biomedical applications. Imaging experiments conducted on zebrafish and Arabidopsis roots demonstrate the probe's remarkable cellular permeability and biocompatibility, laying a solid foundation for its potential biomedical utility. Furthermore, the probe holds potential for practical applications in environmental monitoring and public health through its capability to detect fluoride ions in water samples and via mobile phone software. This multifaceted functionality underscores the broad applicability and significance of the fluorescent probe, not only in scientific research but also in real-world scenarios, contributing to the development of more convenient and precise methods for fluoride detection.

A near-infrared ratiometric fluorescent probe for the sensing and imaging of sulfur dioxide derivatives in living systems.

As a reactive sulfur species, sulfur dioxide (SO2) and its derivatives play crucial role in various physiological processes, which can maintain redox homeostasis at normal levels and lead to the occurrence of many diseases at abnormal levels. So, the development of a suitable fluorescent probe is a crucial step in advancing our understanding of the role of SO2 derivatives in living organisms. Herein, we developed a near-infrared fluorescent probe (SP) based on the ICT mechanism to monitor SO2 derivatives in living organisms in a ratiometric manner. The probe SP exhibited excellent selectivity, good sensitivity, fast response rate (within 50 s), and low detection limit (1.79 µM). In addition, the cell experiment results suggested that the SP has been successfully employed for the real-time monitoring of endogenous and exogenous SO2 derivatives with negligible cytotoxicity. Moreover, SP was effective in detecting SO2 derivatives in mice.

Fluorescent probes based on N-CQDs: For direct detection of food additives STPP and Al3.

Sodium tripolyphosphate (STPP), as one of the many food additives, can cause gastrointestinal discomfort and a variety of adverse reactions when ingested by the human body, which is a great potential threat to human health. Therefore, it is necessary to develop a fast, sensitive and simple method to detect STPP in food. In this study, we synthesized a kind of nitrogen-doped carbon quantum dots (N-CQDs), and were surprised to find that the addition of STPP led to the gradual enhancement of the emission peaks of the N-CQDs, with a good linearity in the range of 0.067-1.96 µM and a low detection limit as low as 0.024 µM. Up to now, there is no report on the use of carbon quantum dots for the direct detection of STPP. Meanwhile, we found that the addition of Al3+ effectively bursts the fluorescence intensity of N-CQDs@STPP solution and has a good linear relationship in the range of 0.33-6.25 µM with a lower detection limit of 0.24 µM. To this end, we developed a fluorescent probe to detect STPP and Al3+. In addition, the probe was successfully applied to the detection of bread samples, which has great potential for practical application.

Assessment of Viability of Listeria monocytogenes by Flow Cytometry.

In food industry, Listeria monocytogenes contamination can occur accidentally despite the quality control of raw materials and factory. Decontamination processes or inhibitory effects of ingredients/additives in food products are set up to ensure compliance with hygiene and microbiological criteria. These actions represent stresses for the pathogenic agent, causing fluctuations in its physiological states. Moreover, during these environmental stresses, Listeria monocytogenes can enter in a viable but nonculturable (VBNC) state which is not detected by plate counting but by flow cytometry. This technique coupled with cell staining by fluorescent dyes offers the possibility to assess different physiological states based on different cellular parameters: enzymatic activity, transmembrane integrity, membrane potential, and respiratory activity. In this chapter, we present a method to assess the viability of foodborne pathogens using a double-staining principle based on the assessment of membrane integrity and intracellular esterase activity.

Cysteine triggered cascade reaction forming coumarin: Visualization of cysteine fluctuation in alcoholic liver disease by a NIR fluorescent probe.

Alcoholic liver disease (ALD) is a chronic toxic liver injury caused by long-term heavy drinking. Due to the increasing incidence, ALD is becoming one of important medical tasks. Many studies have shown that the main mechanism of liver damage caused by large amounts of alcohol may be related to antioxidant stress. As an important antioxidant, cysteine (Cys) is involved in maintaining the normal redox balance and detoxifying metabolic function of the liver, which may be closely related to the pathogenesis of ALD. Therefore, it is necessary to develop a simple non-invasive method for rapid monitoring of Cys in liver. Thus, a near-infrared (NIR) fluorescent probe DCI-Ac-Cys which undergoes Cys triggered cascade reaction to form coumarin fluorophore is developed. Using the DCI-Ac-Cys, decreased Cys was observed in the liver of ALD mice. Importantly, different levels of Cys were monitored in the livers of ALD mice taking silybin and curcumin with the antioxidant effects, indicating the excellent therapeutic effect on ALD. This study provides the important references for the accurate diagnosis of ALD and the pharmacodynamic evaluation of silybin and curcumin in the treatment of ALD, and support new ideas for the pathogenesis of ALD.

The first ER-targeting flavone-based fluorescent probe for Cys: Applications in real-time tracking in an epilepsy model and food analysis.

Epilepsy is one of the most commonly-seen neurological disorders, and both endoplasmic reticulum stress (ERS) and oxidative stress (OS) have been demonstrated to be associated with epileptic seizures. As one of the three endogenous thiol-containing amino acids, cysteine (Cys) is recognized not only as an important biomarker of various biological processes but also widely used as a significant additive in the food industry. However, the exact role that Cys plays in ERS has not been well answered up to now. In this paper, we reported the first flavone-based fluorescent probe (namely BFC) with nice endoplasmic reticulum (ER)-targeting ability, which was capable of monitoring Cys in a fast response (3.0 min), large stokes shift (130 nm) and low detection limit (10.4 nM). The recognition mechanism of Cys could be attributed to the addition-cyclization reaction involving a Cys residue and an acrylate group, resulting in the release of the strong excited-state intramolecular proton transfer (ESIPT) emission molecule of benzoflavonol (BF). The low cytotoxicity and good biocompatibility of the probe BFC allowed for monitoring the fluctuation of endogenous Cys levels under both ERS and OS processes, as well as in zebrafish models of epilepsy. Quantitative determination of Cys with the probe BFC was also achieved in three different food samples. Additionally, a probe-immersed test strips integrated with a smartphone device was successfully constructed for on-site colorimetric detection of Cys. Undoubtedly, our work provided a valuable tool for tracking Cys levels in both an epilepsy model and real food samples.

A novel structurally modified isophorone fluorescent probe for H2S detection.

Hydrogen sulfide (H2S) has a comprehensive contribution to the normal operation and stability of organisms and is also present in environmental water samples and food deterioration. Thus, it is exceedingly promising and significant to develop a highly sensitive detection technique for tracing H2S. Inspired by this, we designed and synthesized a new fluorescent probe 2-[3-[2-[3-bromo-4-(2,4- dinitrobenzenesulfonate)] ethenyl]-5,5-dimethyl-2-cyclohexen-1-ylidene]propanedinitrile (SP-Br) for hydrosulfide ion detection by introducing bromine atom. Compared with reported H2S probes based on the same fluorescent parent, SP-Br has longer fluorescence emission (λem = 670 nm), shorter response time (3 min), lower detection limit (149 nM), and wider detection range (0-30 nM). SP-Br can emit weak yellow fluorescence, and the emission intensity at 670 nm is considerably enhanced in the presence of hydrosulfide ions. The identification mechanism of hydrosulfide ion by SP-Br was verified by high-resolution mass spectrometry, fluorescence, and UV-vis absorption spectroscopy. In addition, SP-Br has been successfully applied to the monitoring of actual water samples and beer samples and has certain development prospects and value in the fields of environmental pollution and food quality analysis.

Automated In Vivo Phenotypic Screening Platform for Identifying Factors that Affect Cell Regeneration Kinetics.

Various strategies for replacing retinal neurons lost in degenerative diseases are under investigation, including stimulating the endogenous regenerative capacity of Müller Glia (MG) as injury-inducible retinal stem cells. Inherently regenerative species, such as zebrafish, have provided key insights into mechanisms regulating MG dedifferentiation to a stem-like state and the proliferation of MG and MG-derived progenitor cells (MGPCs). Interestingly, promoting MG/MGPC proliferation is not sufficient for regeneration, yet mechanistic studies are often focused on this measure. To fully account for the regenerative process, and facilitate screens for factors regulating cell regeneration, an assay for quantifying cell replacement is required. Accordingly, we adapted an automated reporter-assisted phenotypic screening platform to quantify the pace of cellular regeneration kinetics following selective cell ablation in larval zebrafish. Here, we detail a method for using this approach to identify chemicals and genes that control the rate of retinal cell regeneration following selective retinal cell ablation.

Dual excitation channel ratiometric fluorescent probes for visual and fluorescent detection of anthrax spore biomarker and tetracycline hydrochloride.

Long-term and excessive use of tetracycline hydrochloride (TC) can lead to its accumulation in the environment, which can cause water contamination, bacterial resistance, and food safety problems. 2,6-Pyridine dicarboxylic acid (DPA) is a major biomarker of Bacillus anthracis spores, and its rapid and sensitive detection is of great significance for disease prevention and counter-terrorism. A bifunctional ratiometric fluorescent nanoprobe has been fabricated to detect DPA and TC. 3,5-dicarboxyphenylboronic acid (BOP) was intercalated into layered europium hydroxide (LEuH) by the ion-exchange method and exfoliated into nanosheets as a fluorescent nanoprobe (PNP). DPA and TC could significantly enhance the red fluorescence of Eu3+ through the antenna effect under different excitation wavelengths, while the fluorescence of BOP can be used as a reference based on the constant emission intensity, realizing ratiometric detection. A low limit of detection (LOD) for the target (DPA: 9.7 nM, TC: 21.9 nM) can be achieved. In addition, visual detection of DPA and TC was realized using color recognition software based on the obvious color changes. This is the first ratiometric fluorescent nanoprobe based on layered rare-earth hydroxide (LRH) for the detection of DPA and TC simultaneously, which opens new ideas in the design of multifunctional probes.

Highly selective and visual detection of vanillin based on fluorescence Cd-MOF sensor in milk powders.

Vanillin is a commonly used synthetic flavoring agent in daily life. However, excessive intake of vanillin may pose risks to human health. Therefore, there is an urgent need for rapid and sensitive detection methods for vanillin. In this study, we developed a fluorescent sensor based on Cd-MOF for the sensitive and selective recognition of vanillin. The presence of vanillin leads to significant fluorescence quenching of Cd-MOF due to competitive absorption and photoinduced electron transfer (PET). The limit of detection was determined to be 39.6 nM, which is the lowest-among the reported fluorescent probes. The sensor was successfully applied for the detection of vanillin in real samples such as powdered milk and milk, with a recovery rate ranging from 96.88 % to 104.83 %. Furthermore, by immobilizing the Cd-MOF probe into a polyvinyl alcohol (PVA) film, we achieved a portable and visual detection composite materials for vanillin.

Diagnostic value for methylation in cervical cancer based on a small-molecule fluorescent probe targeting DNMT1.

BACKGROUND: Value analysis of a small-molecule fluorescent probe for methylation detection in different cervical lesions. MATERIALS AND METHODS: (1) The grayscale values of distinct lesion tissues were remarkably distinct among the four groups (p < 0.05). The comparison of the grayscale value between the two groups showed that the CA group noticeably exceeded the LSIL and cervicitis groups, and the HSIL group was apparently higher than the LSIL and cervicitis groups (p < 0.05); (2) The mean grayscale values of the enrolled subjects were calculated with 55.21 as the midline, with >55.21 as positive and ≤55.21 as negative. RESULTS: The results showed that the positive rate of the cervicitis group was 0.00%, the LSIL group 67.74%, the HSIL group 83.33%, and the CA group 100.00%. The results among the four groups were notably distinct (p < 0.05); (3) The comparison among DAPI, probe, bright, and merged images of cervicitis, LSIL, HSIL, and CA indicated that different cervical lesions were with quite various stains. CONCLUSION: The grayscale value, positive rate, and stained picture of distinct cervical lesions were remarkably different. The small-molecule fluorescent probe has a good value in differentiating cervical lesions and can be considered for popularization and application.

Old innovations and shifted paradigms in cellular neuroscience.

Once upon a time the statistics of quantal release were fashionable: "n" available vesicles (fusion sites), each with probability "p" of releasing a quantum. The story was not so simple, a nice paradigm to be abandoned. Biophysicists, experimenting with "black films," explained the astonishing rapidity of spike-induced release: calcium can trigger the fusion of lipidic vesicles with a lipid bilayer, by masking the negative charges of the membranes. The idea passed away, buried by the discovery of NSF, SNAPs, SNARE proteins and synaptotagmin, Munc, RIM, complexin. Electrophysiology used to be a field for few adepts. Then came patch clamp, and multielectrode arrays and everybody became electrophysiologists. Now, optogenetics have blossomed, and the whole field has changed again. Nice surprise for me, when Alvarez de Toledo demonstrated that release of transmitters could occur through the transient opening of a pore between the vesicle and the plasma-membrane, no collapse of the vesicle in the membrane needed: my mentor Bruno Ceccarelli had cherished this idea ("kiss and run") and tried to prove it for 20 years. The most impressive developments have probably regarded IT, computers and all their applications; machine learning, AI, and the truly spectacular innovations in brain imaging, especially functional ones, have transformed cognitive neurosciences into a new extraordinarily prolific field, and certainly let us imagine that we may finally understand what is going on in our brains. Cellular neuroscience, on the other hand, though the large public has been much less aware of the incredible amount of information the scientific community has acquired on the cellular aspects of neuronal function, may indeed help us to eventually understand the mechanistic detail of how the brain work. But this is no more in the past, this is the future.

Organelle Interactions in Plant Cells.

The sequestration of enzymes and associated processes into sub-cellular domains, called organelles, is considered a defining feature of eukaryotic cells. However, what leads to specific outcomes and allows a eukaryotic cell to function singularly is the interactivity and exchanges between discrete organelles. Our ability to observe and assess sub-cellular interactions in living plant cells has expanded greatly following the creation of fluorescent fusion proteins targeted to different organelles. Notably, organelle interactivity changes quickly in response to stress and reverts to a normal less interactive state as homeostasis is re-established. Using key observations of some of the organelles present in a plant cell, this chapter provides a brief overview of our present understanding of organelle interactions in plant cells.

A fluorescent probe for monitoring carboxylesterases in pulmonary cells under permissive hypercapnia condition.

Herein, by combining the benzofuranone-derived fluorophore and the carbamate recognition group, a fluorescent probe named BFO-CarE was developed for monitoring the carboxylesterase (CarE) level in pulmonary cells under the permissive hypercapnia condition. It showed a notable fluorescence response towards CarE at 570 nm under the excitation of 510 nm. The in-solution tests revealed the advantages of BFO-CarE including high sensitivity, high specificity, relatively rapid response, and high steadiness. It was also low-toxic upon the pulmonary cell lines. During the intracellular imaging in pulmonary cells, BFO-CarE achieved the monitoring of the CarE level in both inhibition and activation status. In particular, BFO-CarE realized the visualization of the affection of the permissive hypercapnia condition on the CarE level, which indicated the hypoxia tolerance of CarE. This work was informative for investigating the impact of hypoxia in pulmonary cells, and the corresponding anaesthesia-related approaches.

Green whitening of polyester fabric using fluorescent brightener OB-1 in a mixture of water and decamethylcyclopentasiloxane media.

Fluorescent brightening agent OB-1 (OB-1) is often used in plastic goods because of its non-toxic nature, chemical stability, remarkable heat resistance, and light stability. Raw OB-1 is challenging to use in textiles using the exhaustion method. This study used a novel method using raw OB-1 powder to whiten polyester fabric in water and decamethylcyclopentasiloxane (D5). The Taguchi approach investigated the interaction between whitening process parameters such as temperature, OB-1 mass, water: D5 ratio, and treatment time with four levels. The study shows that the temperature and water: D5 ratio during the whitening process significantly affect the whiteness of polyester fabric (P < 0.05), with contribution percentages of 74.2 % and 25.2 %. Subsequently, various analytical techniques were employed, including FTIR, SEM, TGA, and XRD, to characterise the whitened fabric. The findings imply that using water: D5 medium was effective in whitening polyester fabric without causing major alterations to the structure of the PET fabric. The study also examined the fastness of washing and crocking to determine their whitening stability. Overall, polyester fabric whitened with water and D5 medium exhibited satisfactory whitening performance and might be a potential scope for use on a larger scale in developing the sustainable textile industry.

Theoretical insights into a turn-on fluorescence probe based on naphthalimide for peroxynitrite detection.

Compared with other reactive oxygen species, peroxynitrite (ONOO-) has diversified reactions and transformations in organisms, and its specific action mechanism is not very clear. The study of reactive oxygen species is of great significance in the field of physiology and pathology. Recently an effective on/off fluorescent probe HCA-OH was designed by Liu et al. through tethering p-aminophenol to 1,8-naphthalimide directly. The probe HCA-OH could release the fluorophore HCA-NH2 with good photostability and high fluorescence quantum yield under oxidation of ONOO- via dearylation process. In this work, the sensing mechanism and spectrum character of probe HCA-OH were studied in detail under quantum chemistry calculation. The electronic structures, reaction sites and fluorescent properties of the probe were theoretically analyzed to benefit us for in-depth understanding the principle of detection on reactive oxygen species (ONOO-) with the fluorescent probe HCA-OH. These theoretical results could inspire the medical research community to design and synthesize highly efficient fluorescent probe for reactive oxygen species detection.

Bioimaging of thiazolidine-4-one-based new probes, fluorimetric detection of Cu2+ "on-off" sensor property, DFT calculation, molecular docking studies, and multiple real samples application.

Thiazolidinones have been the subject of various research areas for their biological activities, thus they were promising scaffolds to develop new drug agents. A novel thiazolidine 4-one-based fluorescent chemosensor probes PS (thiazolidine) and BO (oxazolidine) were designed and synthesized. Both probes showed specific recognition against Cu2+ via a "turn-off" fluorescence response in ACN/H2O (v/v: 50/50) stock solution (10 mM, pH = 7.0) with a detection limit of (for BO: 1.9 nM and PS: 1.03 nM). Finally, the detection of chemosensory PS and BO showed positive potential for the determination of Cu2+ in real food samples, drinking water, and mung beans. The compounds were characterized by diferent chemical and spectroscopic methods. The proposed binding mode for PS and BO with Cu2+ was confirmed by DFT calculation, and also they elucidated by bioimaging studies against MCF-7 live cell lines. Additionally, the docking experiment was performed on XylE and hAChE targets.

Smartphone-assisted fluorescent microfluidic-chip for sensitive detection of sweat glucose via dual-sensing of O2/H2O2.

A novel smartphone-assisted fluorescent microfluidic-chip was designed for detecting sweat glucose. The microfluidic chip contained six microchambers, each of which was equipped with a glucose sensing membrane incorporating glucose oxidase (GOD), fluorescent O2 probe PtTFPP and H2O2 probe G1. Based upon O2 consumption and H2O2 generation during glucose catalysis by GOD, the chip produced two fluorescence signals towards glucose under single-wavelength excitation, i.e. green fluorescence in response to H2O2 and red fluorescence to O2. The limit of detection (LOD) based on H2O2 monitoring was 0.005 mM, while the LOD based on O2 monitoring was 0.04 mM. Furthermore, the obtained chip was integrated with a smartphone-based portable platform to record RGB values for point-of-care testing of sweat glucose. Glucose calibration (Y = -3.45 + 1.81∗R + 0.68∗G) at 6-min time point was performed by combining R and G channels signals. The dual-monitoring analysis provided a more accurate and reliable verification of glucose detection. This smartphone-assistant optical microfluidic-chip device holds significant potential for portable self-management of glucose in personalized healthcare and clinical diagnosis.