Sensing mechanism of reactive oxygen species optical detection

Novel NIR fluorescent probe based on BODIPY for diagnosis and treatment evaluation of alcoholic liver disease via visualizing HClO fluctuation

Alcoholic liver disease (ALD) is gradually becoming common due to the increasing number of drinkers worldwide, which is a serious threat to human physical and mental health. In the process of ALD, it is often accompanied by the occurrence of inflammation, which induce high expression of reactive oxygen species including HClO. In this work, we successfully fabricated a NIR fluorescent probe BDP-ENE-Fur-HClO for real-time imaging alcoholic liver disease via tracing HClO. The probe displayed good sensitivity and specificity, rapid recognition speed and NIR emitting (700 nm) for detection of HClO in vitro. Based on the remarkable performances, probe was capable of tracing endogenous/exogenous HClO in living cells without interference from other ROS as well as in ALD cell model. Additionally, probe could monitor the exogenous HClO in normal mice and high expression of HClO in the peritonitis mice, that accomplishing the diagnosis of inflammation. What's more, one simulated hazardous drinking ALD mice model and simulated excessive drinking (a type of alcohol use disorder) ALD mice model were developed, probe could image the alcoholic liver injury of mice by monitoring the HClO fluctuation in ALD mice, which affording a valid instrument for the diagnosis of ALD. Ultimately, after hepatoprotective drug administrating to the models, probe could triumphantly evaluate the treatment effect of drug on ALD.

Photothermal/photodynamic synergistic antibacterial Nanocellulose film modified with antioxidant MXene-PANI Nanosheets

TEMPO-CNF film modified by two-dimension transition metal MXene has certain antibacterial properties. However, the problem of long-lasting stability greatly restricts the feasibility of long-term use of the composite film. Here, we introduced polyaniline (PANI) as a modifying molecule, which was electrostatically adsorbed on the surface of the MXene nanosheets to prevent its self-stacking and delay its oxidation. The modified MXene could still maintain >85 % stability after 30 days of room temperature storage. The MXene-PANI nanocellulose (MXP/CNF) film was further prepared by combining electrostatic attraction and hydrogen bonding interactions. Thanks to the synergistic effects of the photothermal conversion and photodynamic of MXene and PANI themselves, as well as the high light-trapping properties of the heterostructures, the photothermal and photodynamic efficiencies of the MXP/CNF film were greatly improved. Under the irradiation of 808 nm near-infrared light at 1.5 W/cm2, the MXP/CNF film reached a temperature of 132.9 °C within 20 s. Meanwhile, reactive oxygen species are generated to degrade 55 % of crystalline violet by modified MXene composite film under light irradiation. Compared to 15 % bacterial survival on cellulose film not modified with PANI, S. aureus and E. coli were completely killed on MXP/CNF film under light conditions. The prepared thin film materials exhibit low cytotoxicity, highlighting their potential applications in biomedicine and desalination.

Sensitive and quick electrochemiluminescence biosensor for the detection of reactive oxygen species in seminal plasma based on the valence regulation of gold nanoclusters

BACKGROUND

Gold nanoclusters (AuNCs) obtained by electroreduction have excellent electrochemiluminescence (ECL) properties, and its ECL intensity is regulated by the valence state. In addition, their ECL signals can be rapidly quenched by reactive oxygen species (ROS). Based on this observation, a sensitive ROS biosensor was designed based on valence regulation of AuNCs. Excessive ROS in seminal plasma can lead to male infertility, and the short half-life and instability of ROS pose a challenge for their detection. Since valence regulation can be done quickly and is very sensitive, this ECL biosensor holds promise to address this issue.

RESULTS

The ECL mechanism of AuNCs and the quenching mechanism of AuNCs by ROS were explored, mainly because ROS change the valence state of AuNCs. The ECL signals of the biosensor have a linear relationship with logarithm of the target concentration in the range of 1.0 × 10-8 to 1.0 × 10-3 M and 1.0 × 10-3 to 1.0 × 10-1 M, with a detection limit of 0.75 × 10-10 M (S/N = 3). The biosensor enables rapid one-step detection of ROS and has the advantage of being stable and reusable. More notably, the results of 57 real samples showed that the biosensor can be used to accurately assess the concentration of seminal plasma ROS, guiding the monitoring of sperm quality and the diagnosis of male infertility.

SIGNIFICANCE

Compared with the traditional strategy of applying AuNCs only as a luminescent body, this strategy of regulating the valence state of AuNCs to achieve sensitive and rapid detection broadens the application of AuNCs in the field of analysis. Compared with other ROS detection strategies, the one-step immediate detection method effectively avoids the inaccuracy caused by the short half-life and natural dissipation of ROS, and is expected to improve the accuracy and efficiency of clinical diagnosis.

Advances in small-molecule fluorescent probes for the study of apoptosis

Apoptosis, as type I cell death, is an active death process strictly controlled by multiple genes, and plays a significant role in regulating various activities. Mounting research indicates that the unique modality of cell apoptosis is directly or indirectly related to different diseases including cancer, autoimmune diseases, viral diseases, neurodegenerative diseases, etc. However, the underlying mechanisms of cell apoptosis are complicated and not fully clarified yet, possibly due to the lack of effective chemical tools for the nondestructive and real-time visualization of apoptosis in complex biological systems. In the past 15 years, various small-molecule fluorescent probes (SMFPs) for imaging apoptosis in vitro and in vivo have attracted broad interest in related disease diagnostics and therapeutics. In this review, we aim to highlight the recent developments of SMFPs based on enzyme activity, plasma membranes, reactive oxygen species, reactive sulfur species, microenvironments and others during cell apoptosis. In particular, we generalize the mechanisms commonly used to design SMFPs for studying apoptosis. In addition, we discuss the limitations of reported probes, and emphasize the potential challenges and prospects in the future. We believe that this review will provide a comprehensive summary and challenging direction for the development of SMFPs in apoptosis related fields.

Recent development in dual function fluorescence probes for HOCl and interaction with different bioactive molecules

Reactive oxygen species (ROS), reactive sulfur species (RSS), metal ions, and nitrogen species (RNS) play important roles in a variety of biological processes, such as a signal transduction, inflammation, and neurodegenerative damage. These species, while essential for certain functions, can also induce stress-related diseases. The interrelation between ROS, RSS, Metal ions and RNS underscores the importance of quantifying their concentrations in live cells, tissues, and organisms. The review emphasizes the use of small-molecule-based fluorescent/chemodosimeter probes to effectively measure and map the species' distribution with high temporal and spatial precision, paying particular attention to in vitro and in vivo environments. These probes are recognized as valuable tools contributing to breakthroughs in modern redox biology. The review specifically addresses the relationship of HOCl/ClO‾ (hypochlorous acid/Hypochlorite) with other reactive species. (Dual sensing probes).

A fluorescent probe based on cyclochalcone for detecting peroxynitrite

A novel cyclic chalcone fluorescent probe C-PN was synthesized to detect ONOO-. After reaction with peroxynitrite, the double bond of C-PN in the cyclic chalcone structure was disconnected, which caused the change of intramolecular charge transfer (ICT) effect, emitting blue fluorescence and quenching orange red fluorescence. Visible to the naked eye, the color of the probe solution changed. The probe showed low sensitivity (detection limit = 20.2 nm), short response time (less than 60 s) at low concentration of ONOO-, good visibility, and good selectivity and stability for ONOO-.

High-Z elements dominated bismuth-based heterojunction nano-semiconductor for radiotherapy-enhanced sonodynamic breast cancer therapy

Ultrasound and X-rays possess remarkable tissue penetration capabilities, making them promising candidates for cancer therapy. Sonodynamic therapy, which utilizes ultrasound excitation, offers a safer alternative to radiotherapy and can be combined with X-rays to mitigate the adverse effects on normal tissues. In this study, we developed a bismuth-based heterostructure semiconductor (BFIP) to enhance the efficacy of radiotherapy and sonodynamic therapy in treating breast cancer. The semiconductor is fabricated through a two-step process involving the synthesis of porous spherical bismuth fluoride and partially reduced to bismuth oxyiodide. Then, followed by surface modification with amphiphilic polyethylene glycol, BFIP is fabricated. Incorporating heavy atoms in the BFIP enhances radiosensitivity. The BFIP exhibits superior carrier separation efficiency compared to bismuth fluoride, generating a substantial quantity of reactive oxygen species upon ultrasound stimulation. Moreover, the BFIP effectively depletes glutathione through coordination and hole-mediated oxidation pathways, disrupting the tumor microenvironment and inducing oxidative stress. Encouraging results are acquired in both in vitro cell and in vivo tumor models. Our study provides a de-risking strategy by utilizing ultrasound as a partial substitute for X-rays in treating deep-seated tumors, offering a viable research direction for constructing a unified nanoplatform.

A highly selective probe engineered to detect polarity and distinguish normal cells and tumor cells in tissue sections

Early diagnostics and therapies for diseases such as cancer are limited by the fact that the inducing factors for the development of cytopathies are not clear. The stable polarity of lipid droplets is a potential biomarker for tumor cells; however, the complex intracellular biological environment poses great difficulties for specific detection of the polarity. Therefore, to meet this pressing challenge, we designed a highly selective fluorescent probe, DCI-Cou-polar, which used the ICT mechanism to differentiate normal cells and tumor cells in tissue sections by detecting changes in the polarities of intracellular lipid droplets. The introduction of a cyclic amine at the 7-position of coumarin (benzoquinolizine coumarin) reduced its ability to donate electrons compared with the diethylamino group, which increased the probe selectivity while retaining the sensitivity to polarity. With NIR emission and large Stokes shifts, DCI-Cou-polar has high sensitivity to polarity, excellent photostability, and biocompatibility, and it tracks lipid droplets with high fidelity. Therefore, we believe that this polarity-sensitive probe provides information on the connection between the polarity of lipid droplets and tumors while improving the development of highly selective polarity probes.

Taming Janus-Faced Quinoline-Derived Fluorescent Probes for Dual-Channel Distinguishable Visualization of HSO3- and HClO in Dried Foods and Living Cells

With the booming development of food manufacturing, developing ideal analytical tools to precisely quantify food additives is highly sought after in the food science field. Herein, a new series of quinoline-derived multifunctional fluorescent probes has been synthesized. Bearing double reactive sites, these compounds display fluorescence response toward both bisulfite (HSO3-) and hypochlorous acid (HClO). Among these compact structures, compound ethyl-2-cyano-3-(6-(methylthio)quinolin-2-yl)acrylate (QTE) was screened out. Probe QTE not only shows ratiometric variation toward HSO3- with little cross talk but also performs turn-off signal toward HClO. In addition, probe QTE has been utilized for bioimaging of HClO in living cells. Furthermore, the HSO3- content in dried food samples has been appraised by QTE with satisfactory results. Meanwhile, relying on the apparent chromaticity change, a flexible dark-box device has been elaborated for chromatic analysis, promoting visualization of HSO3- in the field.

Localized electron-accepted yellow-emission carbon dots encapsulated in UiO-66 for efficient visible-light driven photocatalytic activity

Metal organic frameworks (MOFs) possess a large surface area, inherent porosity and high crystallinity. Nevertheless, they lack electron acceptors, which limit the exploitation of their photocatalytic properties. Carbon dots (CDs) known for excellent optical properties can serve as localized electron acceptors. As a novel hybrid nanomaterial, the structure of CDs@MOFs effectively facilitates charge separation and carrier transfer, bring about a marked improvement of photocatalytic activity. In this study, yellow-emission carbon dots (YCDs) were encapsulated within zirconium-based metal organic framework (UiO-66) via a dynamic adsorption method. Compared with blue carbon dots (BCDs), the YCDs@UiO-66 exhibited superior degradation performance. It demonstrates that incorporation of YCDs broadens the UV absorption range of UiO-66, thereby enhancing light utilization. The degradation efficiency of YCDs@UiO-66 was 92.6%, whereas UiO-66 alone achieved only 63.1%. Notably, the results of the radical quenching experiment and electron paramagnetic resonance (EPR) revealed that h+ and •O2- played a prominent role in the photodegradation of tetracycline hydrochloride (TCH). This study highlights that the introducing YCDs in MOFs-mediated photocatalytic reactions is a viable strategy to improve catalytic efficiency.

Visualization of the elevated levels of hypochlorous acid in Alzheimer's disease with a ruthenium(II) complex-based luminescence probe

Alzheimer's disease (AD) is an age-related neurodegenerative disorder that devastatingly affects people's lives. Accumulating evidence indicates that the pathological progression of AD is inseparably connected with hypochlorous acid (HClO). However, further exploring the biological function remains an open challenging due to a lack of effective tools to image HClO in AD brains. To this end, a ruthenium(II) luminescence probe, Ru-HClO, is developed for quantitative detection and visualization of HClO in nerve cells and AD brains. Ru-HClO shows quenched luminescence due to the PET process (excited electron transfer from Ru(II) center to diaminomaleonitrile) and the CN bond isomerization in the excited state. The HClO-triggered specific cleavage reaction with Ru-HClO cleaves the CN bond to form highly luminescent Ru-COOH. Ru-HClO shows rapid response speed, high sensitivity and selectivity, excellent biocompatibility, which makes the probe to be applied to semi-quantitative analysis of HClO in nerve cells and high-throughput screening of anti-AD drugs in the AD cell model. Moreover, using Ru-HClO as a probe, present work further validated that the elevated levels of HClO secretion were accompanied by the AD progressed. These findings may provide valuable results for figuring out the biological roles that HClO played in AD but also for accelerating anti-AD therapeutic discovery.

An Anthracene Carboxamide-Based Fluorescent Probe for Rapid and Sensitive Detection of Mitochondrial Hypochlorite in Living Cells

Mitochondrial hypochlorite (ClO-) plays important and often contradictory roles in maintaining the redox balance of mitochondria. Abnormal ClO- levels can induce mitochondrial inactivation and further cause cell apoptosis. Herein, we have developed an anthracene carboxyimide-based fluorescent probe mito-ACS for imaging mitochondrial ClO- in living cells. This probe exhibits some distinctive features as excellent resistance to photobleaching, high selectivity and sensitivity, as well as good water solubility. Mito-ACS showed a noticeable fluorescence response toward ClO- with a fast response (within 6 s) and a low detection limit (23 nM). Moreover, the introduction of triphenylphosphonium makes the probe soluble in water and selectively localizes to mitochondria. Furthermore, mito-ACS was successfully applied to image mitochondria ClO- in living cells with low toxicity. Remarkably. the less used fluorophore anthracene carboxyimide exhibiting excellent photostability and desirable optical properties provides a promising application prospect in biological systems.

A Chitosan-Based Fluorescent Probe Combined with Smartphone Technology for the Detection of Hypochlorite in Pure Water

Using chitosan as a raw material, 1,8-naphthimide as the fluorescent chromophore, and sulfur-containing compounds as the recognition groups, a novel naphthimide-functionalized chitosan probe, CS-BNS, for the detection of ClO- was successfully synthesized. The modification of chitosan was verified by SEM, XRD, FTIR, mapping, 13C-NMR, TG and the structure of the probe molecule was characterized. The identification performance of the probes was studied using UV and fluorescence spectrophotometers. The results show that CS-BNS exhibits a specific response to ClO- based on the oxidative reaction of ClO- to the recognition motifs, as well as a good resistance to interference. And the probe has high sensitivity and fast response time, and can complete the detection of ClO- in a pure water system within 60 s. The probe can also quantify ClO- (y = 30.698x + 532.37, R2 = 0.9833) with a detection limit as low as 0.27 μM. In addition, the combination of the probe with smartphone technology enables the visualization and real-time monitoring of ClO-. Moreover, an identification system for ClO- was established by combining the probe with smartphone technology, which realized the visualization and real-time monitoring of ClO-.

A Simple ICT-Based Fluorescent Probe for HOCl and Bioimaging Applications

Over the past few decades, drug-induced liver damage (DILI) has become a serious public health problem due to drug abuse. Among multifarious reactive oxygen species, mounting evidence attests that ClO^- has been used as a potential biomarker in DILI. In this work, a new "turn-on" fluorescent probe 1 was designed and synthesized by modifying 4'-hydroxybiphenyl-4-carbonitrile (dye 2) with N, N-dimethylthiocarbamate as a response site for detecting ClO^-. Probe 1 displayed a low detection limit (72 nM), fast response time (30 s), wide pH operating range (6-8), great tissue penetration, large Stokes shift (125 nm) and 291-fold fluorescence enhancement at 475 nm in the mapping of ClO^-. Probe 1 could trace amounts of exogenous and endogenous ClO^- with high sensitivity in MCF-7 cells and HeLa cells. Expectantly, the fluoxetine-induced liver injury model is successfully established, and probe 1 has been used for detecting the fluctuation of ClO^- levels in the mouse model of fluoxetine-induced liver injury. All in all, probe 1 with its high specificity, good biological compatibility and liver tissue penetration ability is expected to assist with the early diagnosis of DILI and the clinical screening of various new drugs. We expect that probe 1 could be efficiently used as a powerful molecular tool to predict clinical DILI and explore molecular mechanisms between molecules and disease.

A naphthalimide-based and Golgi-targetable fluorescence probe for quantifying hypochlorous acid

The Golgi apparatus (GA) is a vital organelle in biological systems and excess reactive oxygen species (ROS) is produced during stress in the Golgi apparatus. Hypochlorous acid (HOCl) is a significant reactive oxygen species and has strong oxidative and antibacterial activity, but excessive secretion of hypochlorous acid can affect Golgi structure or function abnormally, it will lead to a series of diseases including Alzheimer's disease, neurodegenerative diseases, autoimmune diseases, and Parkinson's disease. In present work, a novel fluorescent probe for Golgi localization utilizing naphthalimide derivatives was constructed to detect hypochlorous acid. The fluorescent probe used a derivatived 1,8-naphthalimide as the emitting fluorescence group, phenylsulfonamide as the localization group and dimethylthiocarbamate as the sensing unit. When HOCl was absent, the intramolecular charge transfer (ICT) process of the developed probe was hindered and the probe exhibited a weak fluorescence. When HOCl was present, the ICT process occurred and the probe showed strong green fluorescence. When the HOCl concentration was altered from 5.0 × 10^-7 to 1.0 × 10^-5 mol·L^-1, the fluorescence intensity of the probe well linearly correlated with the HOCl concentration. The detection limit of 5.7 × 10^-8 mol·L^-1 was obtained for HOCl. The HOCl fluorescent probe possessed a rapid reaction time, a high selectivity and a broad working pH scope. In addition, the probe possessed good biocompatibility and had been magnificently employed to image Golgi HOCl in Hela cells. These characteristics of the probe demonstrated its ability to be used for sensing endogenous and exogenous hypochlorous acids within the Golgi apparatus of living cells.

Nitrogen-doped carbon quantum dots as fluorescent nanosensor for selective determination and cellular imaging of ClO. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022;271:120941. [PMID: 35114635 DOI: 10.1016/j.saa.2022.120941]

The carbon nanomaterial based fluorescent probes have been widely applied in biological imaging. In the current research, we propose an interesting strategy for selective sensing of hypochlorite (ClO^-) by a water-soluble and highly fluorescent nanosensor based on the N-doped carbon quantum dots (CDs) which was fabricated by a facile and environmental friendly hydrothermal approach from polyvinyl pyrrolidone, L-arginine and tryptophan. The structural characteristics of the probe were measured by multitudinous methods which proved the nanometer spherical structure of the probe and the successfully N-doping. Fluorescent investigation demonstrated that the probe is not only highly stable under interferences of pH, ionic strength, and irradiation, but also significantly selective toward ClO^- amongst a variety of attractive bioactive species through the fluorescent quenching process which was correlative with the concentration of ClO^- and linearly in the range of 0.1-50 μmol·L^-1 with the sensitivity of 0.03 μmol·L^-1. The probe can also be further illustrated in a prospective application for determination of ClO^- in environmental water through both solution response and filer paper sensing. Moreover, the positive biocompatibility and ignorable cytotoxicity made the probe a promising effective agent for detection and visualizing ClO^- in living cells which can facilitate the understanding the oxidative stress from the overexpressing ClO^-.

Fluorescent Probes for Selective Recognition of Hypobromous Acid: Achievements and Future Perspectives

Reactive oxygen species (ROS) have been implicated in numerous pathological processes and their homeostasis facilitates the dynamic balance of intracellular redox states. Among ROS, hypobromous acid (HOBr) has a high similarity to hypochlorous acid (HOCl) in both chemical and physical properties, whereas it has received relatively little attention. Meanwhile, selective recognition of endogenous HOBr suffers great challenges due to the fact that the concentration of this molecule is much lower than that of HOCl. Fluorescence-based detection systems have emerged as very important tools to monitor biomolecules in living cells and organisms owing to distinct advantages, particularly the temporal and spatial sampling for in vivo imaging applications. To date, the development of HOBr-specific fluorescent probes is still proceeding quite slowly, and the research related to this area has not been systematically summarized. In this review, we are the first to review the progress made so far in fluorescent probes for selective recognition and detection of HOBr. The molecular structures, sensing mechanisms, and their successful applications of these probes as bioimaging agents are discussed here in detail. Importantly, we hope this review will call for more attention to this rising field, and that this could stimulate new future achievements.