A colorimetric and far-red fluorescent probe for rapid detection of bisulfite/sulfite in full water-soluble based on biquinolinium and its applications

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.

Near-infrared xanthene fluorescence probe for frequency upconversion fluorescence detection of HSO3- in evaluation of drug-induced hepatotoxicity

Bisulfite (HSO3-) plays an important role in life activities. Abnormal content of HSO3- may cause cardiovascular, cancer and other diseases. Frequency upconverted luminescent (FUCL) probes are a class of anti-Stokes luminescent materials with long-wavelength excitation and short-wavelength emission properties, which offer advantages in a range of applications due to their higher sensitivity and photostability. In addition, FUCL imaging has the advantages of high tissue penetration depth and low photo-damage, thus, it is more suitable for fluorescence imaging. In this work, a FUCL probe based on an xanthene fluorophore was designed and synthesised to detect HSO3-. The Probe PT-1 could respond to HSO3- and had high selectivity and sensitivity. It also exhibited a quenched FUCL signal. The detection limit of FUCL concerning HSO3- was 43 nM (λex = 730 nm), which is half the detection limit achieved under traditional excitation (93 nM, λex = 643 nm). Cell fluorescence imaging showed that PT-1 could effectively target mitochondria and monitor endogenous/exogenous HSO3- in living cells. More importantly, PT-1 was successfully used to monitor the level of HSO3- in mice with drug-induced liver injury through FUCL imaging.

A novel BODIPY-derived colorimetric and ratiometric dual-mode fluorescent probe for highly sensitive and visual detection of sulfite in food and living organisms

Sulfite, widely used as a food additive, performs indispensable functions in the field of food sterilization, bleaching, and antisepsis. However, the overuse of sulfite may destroy food nutrition and pose health risks to people. In this work, an innovative BODIPY-based fluorescent probe (BODIPY-DBC) was constructed for highly sensitive recognition of sulfite. The BODIPY-DBC probe possessed both colorimetric and ratiometric dual mode, a low detection limit (33.12 nM), high sensitivity, a wide pH usage range (5-12), a fast response time (2 min), and superior fluorescence imaging capability for detecting sulfite. The recognition mechanism was certificated by 1H NMR titration, HRMS analysis, and DFT calculation. The BODIPY-DBC probe was not only loaded on test strips for detecting sulfite conveniently with the naked eye, but also employed to detect sulfite content in real food samples to ensure food safety. Furthermore, it also achieved excellent performances for monitoring sulfite in dual-channel fluorescence imaging (HeLa cell and zebrafish).

A sensing label or gel loaded with an NIR emission fluorescence probe for ultra-fast detection of volatile amine and fish freshness

A simple benzopyran-based fluorescence probe DCA-Apa detection of volatile amine has been synthesized. DCA-Apa can recognize volatile amines by dual channel mode (changing from blue to light yellow in sunlight, and from weak pink to orange under 365 nm) in pure water system. DCA-Apa has the advantages of ultra-fast response (∼6 s), NIR emission (655 nm), and a good fluorescence response for many amines. The sensing label or gel loaded with DCA-Apa was prepared by the dipping or mixing method using filter paper or gelatin as solid carriers, which can identify volatile amine vapor and monitor the freshness of salmon by colorimetric and fluorescent dual channels. When the color of the label changes to light yellow-green or the fluorescence of the label becomes orange fluorescence (365 nm UV lamp), it indicates that the fish has rotted. The two-channel method makes up for the deficiency of the single colorimetric method, and establishes a theoretical foundation for more precise assessment of fish freshness.

A colorimetric and NIR fluorescent probe for ultrafast detecting bisulfite and organic amines and its applications in food, imaging, and monitoring fish freshness

Herein, for the first time, we have successfully constructed a novel near-infrared (NIR) emission fluorescent probe Dpyt for ultrafast detecting (within 5 s) bisulfate and organic amines based on a 1,2-dihydrocyclopenta[b]chromene-barbiturate conjugation system. Upon addition of bisulfate or organic amines, Dpyt displayed a distinct color change from blue to colorless or from purple to blue, respectively, suggesting that the Dpyt can be used to detect two analytes by the naked eye. Based on quantum chemistry calculations, the fluorescence quenching of Dpyt after the addition of HSO3- is caused by the photoinduced electron transfer (PET) process of the adduct Dpyt-HSO3-. The fluorescence enhancement of Dpyt caused by most organic amines is due to the enhanced intramolecular charge transfer (ICT) process of deprotonated Dpyt. Notably, Dpyt can be applied for detecting HSO3- in actual food samples such as red wine and sugar, as well as for imaging of HSO3- and representative propylamine in living cells. And more importantly, indicator labels constructed by filter paper loaded with Dpyt can visually monitor the freshness of salmon in real-time by daylight and fluorescence dual-mode. The comparison with national standard method of China manifests that indicator labels are a valid tool to assess the freshness of seafood.

Imaging and detection of sulfite in acute liver injury with a novel quinoxaline-based fluorescent probe

Herein, a novel fluorescent probe HZY was developed for monitoring the sulfite (SO₃^2-) dynamics. For the first time, the SO₃^2- triggered implement was applied in the acute liver injury (ALI) model. The levulinate was selected to achieve the specific and relatively steady recognition reaction. With the addition of SO₃^2-, the fluorescence response of HZY exhibited a large Stokes shift of 110 nm under the 380 nm excitation. The merits included high selectivity under various pH conditions. Compared with the reported fluorescent probes for sulfite, HZY indicated above-moderate performances including remarkable and rapid response (40 folds, within 15 min), and high sensitivity (limit of detection = 0.21 μM). Further, HZY could visualize the exogenous and endogenous SO₃^2- level in living cells. Moreover, HZY could gauge the changing levels of SO₃^2- in three types (induced by CCl₄, APAP, and alcohol) of ALI models. Both in vivo imaging and depth-of-penetration fluorescence imaging demonstrated that HZY could characterize the developmental and therapeutic status during the liver injury process by measuring the dynamic of SO₃^2-. The successful implementation of this project would promote the accurate in-situ detection of SO₃^2- in liver injury, which was expected to guide the pre-clinical diagnosis and clinical practice.

A dual-site multifunctional fluorescent probe for selective detection of endogenous H2O2 and SO2 derivatives based on ICT process and its bioimaging application

In this paper, we reported a coumarin-based fluorescent probe for selective detection of H₂O₂/SO₂ derivatives via ICT process. To the best of our knowledge, it was few reported with the same probe to enable visual detection of H₂O₂/SO₂ derivatives in vivo and in vitro. H₂O₂ and SO₃^2- were selectively sensed over other analytes, and the probe displayed 20-fold and 220-fold relative fluorescence intensity respectively, as well as the good linear relationship and the excellent detection limits of 2.7 * 10³ nM and 19.3 nM. Furthermore, the probe was successfully used for fluorescence imaging of the HeLa cells and the mice to monitor exogenous and endogenous H₂O₂ and SO₃^2-, suggesting its potential biomedical application for investigation and detection the intermediate indicator of oxidative stress in vitro and in vivo.

Dual-response and lysosome-targeted fluorescent probe for viscosity and sulfur dioxide derivatives

Viscosity and sulfur dioxide levels are important factors to evaluate the changes of cell micro-environment because a series of diseases usually occur when they are abnormal. At present, dual-response probes that can detect both viscosity and sulfur dioxide are rare. Therefore, we developed a novel fluorescent probe CBN for simultaneous detection of sulfur dioxide and viscosity. Besides, probe CBN could target lysosome of which normal function will be disrupted by the abnormality of viscosity. Therefore, probe CBN has the potential to be served as an effective biological tool to monitor the intracellular micro-environment.

A mitochondria-targeted near-infrared fluorescent probe for detection and imaging of HSO3- in living cells

Sulfur dioxide, an essential gas signaling molecule mainly produced in mitochondria, plays important roles in many physiological and pathological processes. Herein, a near-infrared fluorescent probe, A1, with good mitochondria targeting ability was developed for colorimetric and fluorescence detection of HSO₃^-. Probe A1 has a conjugated cyanine structure that can selectively react with HSO₃^- through the nucleophilic addition. The reaction with HSO₃^- destroys the conjugated structure of probe A1, resulting in fluorescence quenching, and accompaniedby color change of probe A1 solution from purple-red to colorless. Probe A1 showed high selectivity and good sensitivity to HSO₃^- in PBS. And the limit of detection was calculated to be 1.28 and 0.037 μM for colorimetry and fluorescence spectrophotometry respectively. In addition, probe A1 mainly entered the mitochondria in living cells, and was successfully used for imaging the exogenous/endogenous HSO₃^- in cells. These results suggest the potential applications of probe A1 in biological systems.

Optimizing the framework of indolium hemicyanine to detect sulfur dioxide targeting mitochondria

Endogenous sulfur dioxide (SO₂) is mainly produced by the enzymatic reaction of sulfur-containing amino acids in mitochondria, which has unique biological activity in inflammatory reaction, regulating blood pressure and maintaining the homeostasis of biological sulfur. It is more and more common to detect monitor SO₂ levels by fluorescence probe. In recent years, the indolium hemicyanine skeleton based on the D-π-A structure has been widely used in the development of fluorescent sensors for the detection of SO_2. However, subtle changes in the chemical structure of indolium may cause significant differences in SO₂ sensing behavior. In this article, we designed and synthesized two probes with different lipophilicities to further study the relationship between the structure and optical properties of hemicyanine dyes. On the basis of previous studies, the structure of indolium hemicyanine skeleton was optimized by introducing -OH group, so that MC-1 and MC-2 had the best response to SO₃^2- in pure PBS system. In addition, the lipophilicity of MC-2 was better than that of MC-1, which enabled it to respond quickly to SO₃^2- and better target mitochondria for SO₂ detection. Most importantly, the low detection limits of MC-1 and MC-2 conducive to the detection of endogenous SO₂. This work provided an idea for developing SO₂ fluorescent sensors with excellent water solubility and low detection limit.

An AIRE-active far-red ratiometric fluorescent chemosensor for specifically sensing Zn2+ and resultant Zn2+ complex for subsequent pyrophosphate detection in almost pure aqueous media

A simple Schiff-base fluorescent chemosensor (1) was synthesized by the reaction of 3-amino-pyrazine-2-carbohydrazide and 7-diethylamino-3-formylcoumarin; the sensor 1 displayed a notable green emission at 524 nm in DMSO and an aggregation-induced ratiometric emission (AIRE) at 555 nm in an almost buffered aqueous media (0.5% DMSO content). The AIRE of 1 was quenched following binding to Zn²⁺ ions, while the fluorescence emission in the far-red region was evidently enhanced at 628 nm. Notably, the ratiometric signal output could be utilized to specifically distinguish Zn²⁺ among various metal ions. Moreover, the 1-Zn²⁺ complex was effectively employed as a fluorescent ratiometric chemosensor for pyrophosphate (PPi) detection. The detection limit was 3.52 μM and 2.45 μM for Zn²⁺ and PPi, respectively. The binding mechanism was evaluated by ¹H NMR, ESI-MS, single-crystal X-ray diffraction, TEM, time-resolved fluorescence spectrophotometry, and density functional theory studies. Overall, owing to its sensitive fluorescence behavior, cell imaging studies demonstrated that this sensor is capable of sensing Zn²⁺ and PPi in living cells.

A novel fluorescent probe based on a triphenylamine derivative for the detection of HSO3- with high sensitivity and selectivity

A novel highly active fluorescence chemical sensor (TBQN) for HSO₃^- was synthesized by the Knoevenagel reaction based on triphenylamine-benzothiazole as a new fluorophore. The probe possessed good selectivity toward HSO₃^- and anti-interference ability with common ions. The fluorescence and UV-vis spectra of the TBQN probe were significantly changed after the addition of HSO₃^-. At the same time, the probe solution released obvious green fluorescence. Moreover, the limit of detection for HSO₃^- was calculated to be 3.19 × 10^-8 M. The TBQN probe displayed a rapid response to HSO₃^- and it took about 3 min to complete the recognition. The detection mechanism is the nucleophilic addition reaction between HSO₃^- and -C[double bond, length as m-dash]C- in the probe molecule. The π-conjugation and ICT (intramolecular charge transfer) transition in the TBQN molecule were destroyed by this addition, which resulted in the change of the fluorescence before and after the addition of HSO₃^-. Then, the mechanism was verified by theoretical calculations, ¹H NMR measurements and mass spectroscopy. In addition, the probe showed low cytotoxicity and could be used for biological imaging in RAW264.7 cells.

A near-infrared fluorescent probe targeting mitochondria for sulfite detection and its application in food and biology

Sulfur dioxide (SO2) is the main air pollutant in the environment, causing great harm to human health. Abnormal SO2 levels are usually associated with some respiratory diseases, cardiovascular diseases, and neurological disorders (even brain cancer). Therefore, monitoring SO2 levels is helpful to better understand its special physiological and pathological role. Although many fluorescent probes for SO2 have been reported, many of them were not ideal for in vivo imaging due to the short emission wavelength. In this work, a near-infrared fluorescent probe NIR-BN with emission wavelength of 680 nm was constructed by conjugating the benzopyrylium moiety and 6-hydroxy-2-naphthaldehyde. NIR-BN had high selectivity and rapidity for SO2 detection. In addition, the detection limit of NIR-BN was relatively low, which can be used for the determination of sulfite in different sugar samples with high accuracy. Of course, due to the excellent spectral and structural properties of NIR-BN, we have applied NIR-BN to the detection of SO2 in biological systems.