A minireview of recent developments in ozone detection using optical chemodosimeters

The development of optical chemodosimeters for ozone detection has been an important research subject in recent years because of the environmental and biological relevance of ozone. The design and development of ozone chemodosimeters, as well as their numerous applications from 2009 to 2022, have all been thoroughly covered in this minireview. In this review, chemodosimeters are categorised according to their distinctive reaction mechanism with ozone. The comparative data for each of these chemodosimeters have also been provided here. We have also discussed the difficulties and potential prospects of this fast-evolving discipline. To the best of our knowledge, this is the first review that has comprehensively analysed the progress made in the development of ozone chemodosimeters.

Constructing firefly luciferin bioluminescence probes for in vivo imaging

Bioluminescence imaging (BLI) is a widely applied visual approach for real-time detecting many physiological and pathological processes in a variety of biological systems. Based on the caging strategy, lots of bioluminescent probes have been well developed. While the targets react with recognizable groups, caged luciferins liberate luciferase substrates, which react with luciferase generating a bioluminescent response. Among the various bioluminescent systems, the most widely utilized bioluminescent system is the firefly luciferin system. The H and carboxylic acid of luciferin are critically caged sites. The introduced self-immolative linker extends the applications of probes. Firefly luciferin system probes have been successfully applied for analyzing physiological processes, monitoring the environment, diagnosing diseases, screening candidate drugs, and evaluating the therapeutic effect. Here, we systematically review the general design strategies of firefly luciferin bioluminescence probes and their applications. Bioluminescence probes provide a new approach for facilitating investigation in a diverse range of fields. It inspires us to explore more robust light emission luciferin and novel design strategies to develop bioluminescent probes.

A highly sensitive fluorescent probe for ozone based on coumarin-benzothiazole derivative

Ozone is widely used in daily life, but studies have shown that O3 can damage human trachea and lungs, leading to diseases such as asthma, emphysema, and bronchitis. Therefore, it is of great significance to develop a simple and efficient detection method for monitoring O3 in living cells. In this study, 3-(but-3-en-1-yl)-2-(7-(but-3-en-1-yloxy)-2-oxo-2H-chromen-3-yl)benzo[d]thiazol-3-ium (BCT) as a new type of water-soluble fluorescent probe was synthesized by substitution reaction of 4-bromo-1-butene and hydroxycoumarin-benzothiazole derivatives, which can specifically detect ozone in aqueous solution. The interaction of ozone on the probe can be completed within 20 min, the fluorescence intensity is significantly enhanced, and it has the advantages of high sensitivity (detection limit LOD = 43 nM). The influence of pH on the fluorescent performance of BCT shows that the probe with super stability under weak alkali and acidic environment, which provides the necessary conditions for its detection of ozone in physiological system detection. Therefore, BCT is expected to become an effective tool for detecting ozone in cellular organisms.

A novel DCM-based NIR fluorescent probe for detecting ozone and its bioimaging in live cells

Nowadays, ozone has been widely applied in industry and medical therapies. However, excessive exposure to ozone can lead to lung dysfunction and many respiratory symptoms. As a member of reactive oxygen species (ROS), ozone was also involved in various physiology and pathology process. Given the fact of this, the effective detection of ozone in the atmosphere and biological system is of vital significance. Herein, we reported a novel dicyanomethylene-4H-pyran (DCM)-based fluorescent probe DCM-O₃ with butenyl being the recognition moiety for monitoring ozone. The probe displayed high selectivity towards ozone, and its response towards ozone could be completed within 5 min under the optimal condition. Besides, a good linear correlation was obtained between the ozone concentrations (0-50 μM) and the corresponding fluorescent intensity at 560 nm, and the limit of detection (LOD) was calculated to be 6.2 × 10^-7 M. Moreover, the probe DCM-O₃ showed low cytotoxicity and was successfully applied to detect ozone in live cells. Given all the merits, the probe DCM-O₃ could function as a robust tool for researchers to investigate ozone-related diseases in the complex biological environment.

Activatable Off-on Near-Infrared QCy7-based Fluorogenic Probes for Bioimaging

The activatable off-on near-infrared QCy7-based fluorogenic probes have emerged as powerful modalities for detecting and monitoring biological analytes and understanding their biological processes in cells and organisms. The use of biomarker-activated QCy7-based probes enables simple synthesis, minimum photo-damage to biological samples, and minimum background interference from biological systems. In this minireview, we aim to provide a rigorous but concise overview of activatable QCy7-based fluorogenic probes by reporting the significant progress made in recent years. The design strategies and the main applications of accurate detection and imaging of disease-related biomarkers (including ROS/RSS, enzymes, metal ions, and other related species) were reasonably analyzed and discussed. The potential challenges and prospects of activatable QCy7-based fluorogenic probes are also emphasized to further advance the development of new methods for biomarker detection and bioimaging.

Postmodified Dual Functional UiO Sensor for Selective Detection of Ozone and Tandemly Derived Sensing of Al3

Development of highly sensitive and selective fluorescent sensors toward hazardous analytes represents great progress in fabricating sensing devices for practical applications. In this work, a highly selective sensor with dual functions has been fabricated via facile postmodification of the UiO-MOF. Butene modified salicylaldehyde is covalently linked to the UiO-66 scaffold via an efficient Schiff-base reaction, resulting in a highly fluorescent ozone sensor of UiO-66-butene. Ozonolysis of the terminal olefin followed by β-elimination could significantly quench the bright blue fluorescence of UiO-66-butene, and linear turn-off detection of ozone in the range of 0-100 μM is well established. The detection is highly sensitive and selective, and a detection limit of 73 nM was calculated. Remarkably, the ozonolysis afforded product could further act as a selective sensor for Al³⁺ via turn-on fluorescence with a detection limit of 142 nM, representing a second potential sensing function. The chemically selective sequential ozonolysis/β-elimination and remarkable dual functions offer the exclusive detection of ozone over other oxidative species as well as Al³⁺ over other cations following a tandem process, representing the first example of a direct MOF sensor for dual sensing of ozone and Al³⁺. This work demonstrates the potential of employing combinatorial principles for fabricating highly selective sensors, and postmodification of MOFs represents a promising facile strategy for developing various functional sensors.

Noncovalently Caged Firefly Luciferins Enable Amplifiable Bioluminescence Sensing of Hyaluronidase-1 Activity in Vivo

Hyaluronidase 1 (Hyal-1) is an important enzyme involved in intracellular hyaluronic acid (HA) catabolism for performing various physiological functions, and its aberrant level is closely associated with many malignant diseases. Bioluminescence imaging is advantageous for monitoring Hyal-1 activity in vivo, but it remains challenging to design an available probe for differentiating Hyal-1 from other isoforms by a traditional strategy that covalently masks the firefly luciferase substrate. Herein, we, for the first time, present a noncovalently caging approach to construct a Hyal-1-specific bioluminogenic nanosensor by entrapping d-luciferin (d-Luc) inside the cholesterylamine-modified HA (CHA) nanoassembly to inhibit the bioluminescence production. When encountered with intracellular Hyal-1, CHA could be fully dissembled to liberate multiple copies of the loaded d-Luc, thereby emitting light by the luciferase-catalyzed bioluminescence reaction. Because of its cascade signal amplification feature, d-Luc@CHA displayed a remarkable "turn-on" response (248-fold) to 5 μg/mL Hyal-1 with a detection limit of 0.07 ng/mL. Importantly, bioluminescence imaging results validated that d-Luc@CHA could be competent for dynamically visualizing endogenous Hyal-1 changes in living cells and animals and possessed the capability of discriminating between normal and cancer cells, thus offering a promising toolbox to evaluate Hyal-1 roles in biological processes as well as to diagnose Hyal-1-related diseases.

A bioluminescent probe for imaging endogenous hydrogen polysulfides in live cells and a murine model of bacterial infection

In this work, we report the first bioluminescent probe BP-PS for detecting H2Sn with high specificity and sensitivity. Owing to the bioluminescence imaging without requiring an excitation light source, tissue autofluorescence is eliminated and BP-PS shows a high signal-to-noise ratio. Moreover, BP-PS was successfully utilized to visualize endogenous H2Sn in live cells and a murine model of bacterial infection.

In situ visualization of ozone in the brains of mice with depression phenotypes by using a new near-infrared fluorescence probe

Ozone (O₃), one of the reactive oxygen species (ROS), is deeply involved in diseases including depression. However, the lack of appropriate in situ detection methods suitable for the complex biological context of brain impedes uncovering the exact relationship between depression and changes in the O₃ level. Therefore, we developed a near-infrared (NIR) fluorescent probe (ACy7) for the direct visualization of O₃ in mice brains. The specific cycloaddition reaction between O₃ and the terminal double bond of the butenyl group extends the conjugation of the "pre-" heptamethine cyanine system, which emits NIR fluorescence of heptamethine cyanine. This makes the ACy7 specific, highly sensitive and able to deeply penetrate tissue. Using ACy7, we found that under glutamate stimulation, the O₃ content in PC12 cells was significantly higher than that in control cells. By imaging analysis on the brains of mice, we revealed for the first time that the levels of O₃ in mice with depression phenotypes were markedly higher than that in control mice. Intriguingly, experimental results unravelled that excess O₃ promoted high expression of the pro-inflammatory cytokine interleukin-8 (IL-8), which ultimately induced depression phenotypes. Our work demonstrates the pivotal role of elevated O₃ in depression and provides a fresh entry point for exploring oxidative stress contributing to depression.

A Bioluminogenic Probe for Monitoring Tyrosinase Activity

A bioluminogenic probe based on luciferin was designed and synthesized to monitor tyrosinase activity. This probe was efficient in assessing tyrosinase activity in a buffered aqueous solution and in measuring endogenous tyrosinase activity in melanoma cells.