Ratiometric two-photon fluorescent probe for detection of hypochlorite in living cells

A ratiometric fluorescent probe for rapid and specific detection of hypochlorite

Hypochlorite (ClO- ), as a kind of essential reactive oxygen species, plays a crucial role in vitro and in vivo. Here, a ratiometric fluorescent probe (TPAM) was designed and constructed for sensing ClO- based on substituted triphenylamine and malononitrile, which exhibited obvious colour transfer from orange to colourless under daylight accompanied by noticeable fluorescence change from red to green in response to ClO- . TPAM could effectively monitor ClO- with the merits of fast response, excellent selectivity, high sensitivity and a low detection limit of 0.1014 μM. 1 H NMR, mass spectra and theoretical calculations proved that ClO- caused the oxidation of the carbon-carbon double bond in TPAM, resulting in compound 1 and marked changes in colour and fluorescence. In addition, TPAM was utilized for imaging ClO- in living cells successfully with good photostability and biocompatibility.

A small-molecule fluorogenic probe for the detection of hypochlorite and its application in the bio-imaging of human breast cancer cells

A certain amount of hypochlorite can help to regulate the body's defense system while excessive hypochlorite has some complex influence on health. Herein, a thiophene-derived biocompatible turn-on fluorescent probe (TPHZ) was synthesized and characterized for the detection of hypochlorite (ClO^-). The fluorescence and colorimetric sensing of the probe followed an ICT OFF strategy. The experimental results showed a remarkable turn on fluorescence enhancement from colorless to bright blue after the addition of ClO^- within 130 s in a solvent system having 80% water with high selectivity and a low detection limit of 53.8 nM. The sensing mechanism was attributed to ClO^- mediated electrophilic addition to the imine bond which was justified by DFT calculations, and ESI-MS and ¹H-NMR titration experiments. The probe was used in an application to visualize ClO^- in human breast cancer cells which can be helpful for investigating the functions of hypochlorite in living cells. Finally, by virtue of fine photophysical properties, good sensing performance, good water solubility and low limit of detection, the probe TPHZ was successfully applied to TLC test strips, and commercial bleach and water samples.

A dual-site fluorescent probe for discriminately detecting low and high concentration of hypochlorite in living cells

Hypochlorite (ClO^-) is an important bioactive molecule of living system which plays essential roles in many physiological and pathological processes. There is no doubt that the biological roles of ClO^- depend highly on the concentration of ClO^-. Unfortunately, the relationship between the concentration of ClO^- and the biological process is unclear. Toward this purpose, in this work we addressed a core challenge for developing a powerful fluorescence tool for monitoring a wide concentration change (0-14 eq.) of ClO^- via two distinct detection manners. The probe displayed fluorescence variation (red to green) upon addition of ClO^- (0-4 eq.) and the color of test medium changed from red to colorless witnessed by the naked eyes. Surprisingly, in the presence of higher concentration of ClO^- (4-14 eq.), the probe displayed another fluorescent signal change from green to blue. After demonstrating the excellent sensing properties of the probe with ClO^- in vitro, it was successfully used to imaging different concentration of ClO^- in living cells. We expected that the probe could act as an exciting chemistry tool for imaging of ClO^- concentration-dependent oxidative stress event in biological system.

Design and Synthesis of Novel Fluorescent Probe Based on Cyanobiphenyl and its Application in Detection of Hypochlorite

Hypochlorite is an important biological reactive oxygen species, which plays a pivotal role in various life activities. Excessive presence in the human body or excessive intake in life causes a series of diseases. To monitor the hypochlorite level in living cells, organisms and environment water samples, we herein designed and synthesized three organic small molecule fluorescent probes with different recognition sites based on nitrile biphenyl. Through performance comparison, it was found that probe A-HM exhibited the best detection performance for hypochlorite with a low detection limit of 2.47 × 10^-6 M. The introduction of hypochlorite will induce probe fluorescence A-HM to turn on, and the fluorescence colour will change from colourless to green. The application of A-HM in biological systems has been demonstrated by the imaging monitoring of hypochlorite in MCF-7, L929 cells and zebrafish. Furthermore, A-HM was also used for the accurate determination of the hypochlorite level in real water samples with high sensitivity and good recoveries.

A super large Stokes shift ratiometric fluorescent probe for highly selective sensing of ClO- in bio-imaging and real water samples

Based on the fluorescence resonance energy transfer (FRET), a ratiometric fluorescent probe (NQ) was successfully designed and synthesized, in which quinolinone moiety was selected as the energy donor and naphthalimide block as the energy acceptor. NQ has a super large Stokes shift (231 nm) and a big quantum yield (0.463). Compared with previously reported probes with similar recognition sites, NQ can high sensitively and selectively recognize ClO^- with a much low limit of detection (LOD = 21 nM) and extremely rapid response time (20 s). NQ has a strong anti-interference effect and a color change in the solution which can be seen by the "naked eye". Moreover, NQ can be applied to detect ClO^- in real water samples and living cells imaging.

A novel and fast-responsive two-photon fluorescent probe with modified group for monitoring endogenous HClO accompanied by a large turn-on signal and its application in zebrafish imaging

Hypochlorous acid (HClO) plays a critical role in physiological activities of maintaining the stable oxidation balance of organisms, which was proved to relate to some serious diseases. In this work, 4-nitrobenzenesulfonylhydrazide based fast-responsive two-photon fluorescent probe CoPh-ClO was designed and synthesized reasonably, which possessed low cytotoxicity, good anti-interference characteristics, a large Stokes shift (85 nm), and good two-photon performance. In addition, probe CoPh-ClO was successfully applied to detect exogenous HClO in living HeLa cells and endogenous HClO in living RAW264.7 cells respectively. Moreover, we successfully achieved tissues imaging with a deep penetration depth of 65 µm and zebrafish imaging accompanied with a high contrast (about 45-fold). Interestingly, the introduce of benzene ring between fluorophore and reaction site made probe CoPh-ClO more sensitive (only 20 s) with a large turn-on signal. The probe CoPh-ClO was modified and possessed better stability (more than 10 mins) even in excessive HClO. All of mentioned above merits demonstrated that CoPh-ClO could be a promising imaging tool for monitoring HClO in various physiological processes, and the introduction of benzene ring would provide a new perspective for the development of multi-function probes.

Engineering of Portable Smartphone Integrated with Liposome-Encapsulated Curcumin for Onsite Visual Ratiometric Fluorescence Imaging of Hypochlorite

Precisely onsite monitoring of hypochlorite (ClO^- ) is of great significance to guide its rational use, reducing/avoiding its potential threat toward food safety and human health. Considering ClO^- could quench fluorescence of curcumin (CCM) by oxidizing the o-methoxyphenol of CCM into benzoquinone, a portable ratiometric fluorescence sensor integrated with smartphone was designed for realizing the visual point-of-care testing (POCT) of ClO^- . The amphiphilic phospholipid polymer was used as carrier to wrap curcumin, forming a novel liposome-encapsulated CCM, which provided a scaffold to bind with [Ru(bpy)₃ ]²⁺ through electrostatic interaction, thus assembling [Ru(bpy)₃ ]²⁺ -functionalized liposome-encapsulated CCM ([Ru(bpy)₃ ]²⁺ @CCM-NPs). Further integrated with smartphone, visual imaging of [Ru(bpy)₃ ]²⁺ @CCM-NPs could be achieved and the accurate onsite detection of ClO^- could be realized with a detection limit of 66.31 nM and a linear range of 0.2210 to 80.0 μM. In addition, the sensor could monitor ClO^- in real samples with an onsite detection time of ∼154.0 s.

Two-photon ratiometric fluorescent probe for imaging of hypochlorous acid in acute lung injury and its remediation effect

Acute lung injury (ALI) is a pulmonary inflammatory disease with high morbidity and mortality rates. However, owing to the unknown etiology and rapid progression of the disease, the diagnosis of ALI is full of challenges with no effective treatment. Since the inflammatory response and oxidative stress played vital roles in the development of ALI, we herein developed the largest emission cross-shift (△λ = 145 nm) two-photon ratiometric fluorescent probe of TPRS-HOCl with high selectivity and short response time toward hypochlorous acid (HOCl) for exploring the relevance between the degree of ALI and HOCl concentration in the development process of the disease. In addition, the inhibition effect of HOCl during different treatment periods was also evaluated. Moreover, the tendency of imaging results was basically in accordance with that of hematoxylin and eosin (H&E) staining and the treatment effect became better in the early stage when using N-acetylcysteine (NAC), demonstrating the sensitivity of TPRS-HOCl toward ALI response. Thus, TPRS-HOCl has great potential to diagnose ALI in the early stage and guide for effective treatment.

A simple strategy for constructing PET fluorescent probe and its application in hypochlorite detection

It is great meaningful to develop a fast and efficient method for detecting hypochlorite (ClO^-) owing to its importance in the immune system. In this work, we proposed a strategy to construct fluorescent probes for ClO^- based on photoinduced electron transfer (PET) mechanism. According to the strategy, we developed four fluorescent probes named TPA-NO₂, TPA-2NO₂, TPB-NO₂ and TPB-2NO₂, and studied their detecting performances for hypochlorite. Among them, TPB-NO₂ displayed the most obvious fluorescence changes towards ClO^- with a rapid response (<90 s). The detection limit was calculated to be 0.36 μM. Moreover, probe TPB-NO₂ was successfully used to detect ClO^- in living cells and zebrafish. These results demonstrated the feasibility of our strategy and provided a guidance for developing more excellent probes in the future.

A TICT + AIE based fluorescent probe for ultrafast response of hypochlorite in living cells and mouse

Hypochlorite (HClO/ClO^-), an important reactive oxygen species (ROS), plays a significant role in the human immune system. Thus, developing a fast and efficient method for detecting ClO^- is quite necessary. Herein, we designed and synthesized a fluorescent probe TPB-CN based on twisted intramolecular charge transfer (TICT) and aggregation-induced emission (AIE) characteristics. The probe could respond to ClO^- with an ultrafast response velocity (<2 s). The detection limit was calculated to be 6.198 nM. In addition, probe TPB-CN was successfully applied for detecting ClO^- in living cells and mouse.

Rational Design of Meso-Phosphino-Substituted BODIPY Probes for Imaging Hypochlorite in Living Cells and Mice

Meso-phosphino-substituted BODIPY probes were developed for concise and rapid detection of hypochlorite (ClO^-). Interestingly, the probe BP gave a turn-on fluorescence response by shutting the photoinduced electron transfer (PET) effect and extending the coplanar conjugated π-system. In contrast, the probe TMBP showed a colorimetric response toward ClO^-. The key role of the steric repulsions was revealed to be for altering the electronic distribution of the BODIPY core, resulting in these obviously different responses. Finally, the probe BP, with high selectivity and sensitivity toward ClO^- (LOD = 1.9 nM; response time, <15 s), was further employed in imaging the variations of exogenous and endogenous hypochlorite (ClO^-) in living RAW 264.7 cells and mouse inflammation models. If wisely utilized, this strategy with meso-phosphino BODIPY dyes may serve as a powerful platform for the preparation of novel chemosensors.

ICT-based fluorescent ratiometric probe for monitoring mitochondrial peroxynitrite in living cells

Mitochondria-targeted near-infrared fluorescent probe for the detection of peroxynitrite and the bioimaging of peroxynitrite in cells.