Reactive oxygen species and their chemiluminescence-detection methods

Production and transport of plasma-generated hydrogen peroxide from gas to liquid

In this work, the transport of hydroxyl radicals and hydrogen peroxide from a humid atmospheric pressure plasma jet into plasma-treated liquids is analysed. The concentration of H2O2 was measured by a spectrophotometric approach using the reagent ammonium metavanadate. OH was measured by the terephthalic acid dosimeter and the chemiluminescence of luminol. The plasma jet used is based on the design of the well-investigated COST reference jet and is extended by a capillary between the two electrodes. In addition to the experiments, the 0-dimensional plasma-chemical kinetics code GlobalKin was used to analyse the plasma chemistry in the gas phase in more detail. After 5 min plasma treatment, a maximum H2O2 concentration of 1 mM was found in the liquid, while the OH concentration was a factor 50 lower. The concentrations of both species in the liquid increased with plasma power, and the H2O2 concentration also increased with the humidity concentration of the feed gas, while the OH concentration first increased with humidity admixture and then decreased. The transport of both species could be controlled by the treatment distance, the gas flow rate and low frequency pulsing of the RF jet in such a way that the selectivity towards the long-lived species H2O2 was increased. Qualitative trends in the simulated number densities of gas phase H2O2 and OH at the location of the gas-liquid interface fit relatively well to the experimental measurements in the liquid.

A Novel Chemiluminescent Method for Efficient Evaluation of Heterogeneous Fenton Catalysts Using Cigarette Tar

The evaluation of the catalytic capacity of catalysts is indispensable research, as catalytic capacity is a crucial factor to dictate the efficiency of heterogeneous Fenton catalysis. Herein, we obtained cigarette tar-methanol extracts (CTME) by applying methanol to cigarette tar and found that CTME could cause CL reactions with Fe²⁺/H₂O₂ systems in acidic, neutral, and alkaline media. The CL spectrum experiment indicated that the emission wavelengths of the CTME CL reaction with Fe²⁺/H₂O₂ systems were about 490 nm, 535 nm, and 590 nm. Quenching experiments confirmed that hydroxyl radicals (•OH) were responsible for the CL reaction for CTME. Then the CL property of CTME was applied in-situ to rapidly determine the amounts of •OH in tetrachloro-1,4-benzoquinone (TCBQ)/H₂O₂ system in acidic, neutral and alkaline media, and the CL intensities correlated the best (R² = 0.99) with TCBQ concentrations. To demonstrate the utility of the CTME CL method, the catalytic capacity of different types and concentrations of catalysts in heterogeneous Fenton catalysis were examined. It was found that the order of CL intensities was consistent with the order of degradation efficiencies of Rhodamine B, indicating that this method could distinguish the catalytic capacity of catalysts. The CTME CL method could provide a convenient tool for the efficient evaluation of the catalytic capacity of catalysts in heterogeneous Fenton catalysis.

Oxidation potential and coupling effects of the fractionated components in airborne fine particulate matter

Fine particulate matter (PM_2.5) can induce the generation of reactive oxygen species (ROS) and damage human tissues. Fully understanding the generation mechanism of oxidative toxicity of PM is challenging due to the extremely complex composition. Classification methods may be helpful in understanding the ROS production mechanisms of complex PM. This study used a solvent extraction and solid phase extraction methods to separate five different components from PM_2.5 includes non-extractable components that have rarely been studied before, and discussed the coupling effect and heterogeneous characteristics of oxidation activity they produced. It is found that the water-soluble component contribute about half of the PM oxidation activity, and metal ions probably contribute most of the oxidation activity. Experimental results show that oxygen molecules is the main precursor of ROS production, which depends on whether the aerosol component has catalytic conversion ability. After mixing humic-like substance (HULIS) and hydrophilic water-soluble (HP-WSM) PM, the oxidation activity increased, it is most likely to be a synergistic effect between HULIS and metal ions is dominant, but limited contribution to oxidation activity. It turns out that the non-extractable and water-insoluble components have higher oxidation activity than the water-soluble components, and the two components exhibited a more durable ability to produce ¹O₂. The reaction of soluble components to produce ROS is homogeneous, but it is obviously heterogeneous for these insoluble components. This study suggests that future attention should be paid to the oxidative toxicity of the non-extractable component, and that single PM component or compound cannot simply be studied independently.

Research on the on-line determination of formaldehyde gas by the gas-liquid phase chemiluminescence method

Based on the gas-liquid phase chemiluminescence tester independently developed by our laboratory, a highly sensitive, fast and accurate on-line detection method of formaldehyde gas in ambient atmosphere is established. The chemiluminescence system and the trace formaldehyde gas in the air directly undergo an interface heterogeneous chemiluminescence reaction to obtain a strong chemiluminescence signal. Through the measurement of the chemiluminescence signal intensity, a highly sensitive, real-time and on-line method for the determination of formaldehyde in the air was established. Factors influencing the experimental results such as gallic acid, potassium dichromate, reaction medium concentration, surfactant type and concentration, pump speed, tube length, and interfering gas were discussed based on the single factor and orthogonal analysis results. Finally, the optimal detection conditions were collected, and the detection results were compared with the national standard phenol reagent method. The results show that when the concentration of the standard formaldehyde gas is in the range of 0-0.582 μg L-1, the linear equation of this method is y = 208x + 29.667, the linear coefficient is R 2 = 0.997, and the minimum detection concentration of formaldehyde is 2.327 × 10-3 μg L-1. Under the same external conditions, the comparison and analysis using the national standard phenol reagent method proved that this method has the advantages of fast detection speed, low detection limit, good sensitivity, and accurate results, which can be used for real-time and online determination of trace formaldehyde in ambient air.

Electrochemical Sensors for the Detection of Reactive Oxygen Species in Biological Systems: A Critical Review

Reactive oxygen species (ROS) involving superoxide anion, hydrogen peroxide and hydroxyl radical play important role in human health. ROS are known to be the markers of oxidative stress associated with different pathologies including neurodegenerative and cardiovascular diseases, as well as cancer. Accordingly, ROS level detection in biological systems is an essential problem for biomedical and analytical research. Electrochemical methods seem to have promising prospects in ROS determination due to their high sensitivity, rapidity, and simple equipment. This review demonstrates application of modern electrochemical sensors for ROS detection in biological objects (e.g., cell lines and body fluids) over a decade between 2011 and 2021. Particular attention is paid to sensors materials and various types of modifiers for ROS selective detection. Moreover, the sensors comparative characteristics, their main advantages, disadvantages and their possibilities and limitations are discussed.

A new NiS nanoparticles-enhanced chemiluminescence method for determination of cephalexin in the pharmaceuticals and spiked human serum

It is reported that NiS nanoparticles (NPs) can enhance the light emission from chemiluminescence (CL) reaction of luminol-O₂ (λ_max = 425 nm), remarkably. Additionally, it was shown that cephalexin (CEF) could further increase the intensity of light emitted from NiS NPs-luminol-O₂ CL reaction. Inspired in these findings, we intended to develop a new and straightforward CL method for the determination of CEF. A calibration graph over the range of 1.00 × 10^-6 - 4.00 × 10^-5 mol L^-1 was established. The limit of detection (LOD) of the CL method was 8.00 × 10^-7 mol L^-1 . The coefficient of variation (CV) of the CL methods was 2.20% (n = 6) for the measurement of 6.00 × 10^-6 mol L^-1 CEF. NiS NPs were produced by exploiting the precipitation method and identified by employing several spectroscopic approaches. The proposed CL method was successfully used to measure CEF in some pharmaceutical and spiked human serum. The chemical mechanism governing the CL reaction was briefly explained.

Methods of PARP-1 Determination and its Importance in Living Organisms

Abstract:

PARP-1 is one of the 18 PARP enzymes that are involved in important processes at the cellular level. The most important tasks of PARP-1 are to detect and repair DNA damage and to prevent processes of apoptosis. By finding and using new strategies for marking and detecting the activity of this protein, it is possible to identify more and more tasks in which it participates. In pathological states, PARP-1 activity increases significantly. Since the 1980s, scientists have been searching for and discussing substances that may inhibit PARP-1 activity and disrupt DNA damage response pathways. In this way, unwanted cells could be destroyed. The paper presents a short description of the methods used in the determination of PARP-1 by various research groups. A critical approach to each of them was also made by pointing to the advantages and disadvantages of the described analytical methods. The literature review contains information on methods useful for PARP-1 determination, such as SPR, QCM, CL and FL, DPV, SDS-PAGE with MS, MALDI MS, Western Blot, ELISA and ATR-FTIR spectroscopy. It also includes analysis of the results of research on inhibitors that may be effective in the diagnosis and treatment of cancer and other diseases.

Synthesis of rod-like CeO2 nanoparticles and their application to catalyze the luminal-O2 chemiluminescence reaction used in the determination of oxcarbazepine and ascorbic acid

Rod-like CeO₂ nanoparticles (NPs) were produced by the quick precipitation approach and employed as a catalyzer to increase the chemiluminescence (CL) intensity of the luminol-O₂ reaction. The transmission electron microscopy (TEM) images of the CeO₂ NPs showed that rod-like particles with the length and diameter about 15 nm and 5 nm, respectively, were produced. Furthermore, pharmaceuticals including oxcarbazepine (OXP) and ascorbic acid (AA) showed an inhibitory effect against the CL intensity such that the more concentration of the pharmaceuticals, the less was the CL intensity. Therefore, the new CeO₂ NPs-luminol-O₂ CL reaction was developed to determine OXP and AA in the pharmaceutical formulations. It is the first CL method established for the quantification of OXP. The linear dynamic range of this method for OXP was from 6.0 × 10^-7 to 6.0 × 10^-5 mol L^-1 and for AA from 1.0 × 10^-6 to 1.0 × 10^-4 mol L^-1.

Next generation luminol derivative as powerful benchmark probe for chemiluminescence assays

Chemiluminescence (CL) provides outstanding analytical performance due to its independence from external light sources, background-free nature and exceptional sensitivity and selectivity. Yet, ultra-sensitive (bio)analysis is impeded by low hydrophilicity, poor quantum yields, fast kinetics or instability of most CL reagents such as luminol, acridinium esters, dioxetanes or peroxyoxalic derivatives. Photophysical studies show that m-carboxy luminol overcomes these limitations as its hydrophilic design provides a 5-fold increase in relative quantum yield resulting in superior performance in H₂O₂-dependent bioassays with 18-fold higher sensitivity for the quantification of its co-reactant H₂O₂, and 5-times lower detection limits for the luminophore. Studies with CL enhancers suggest its significance for mechanistic investigations in tandem with peroxidases. Finally, its integration into enzymatic and immunoassay applications demonstrates that m-carboxy luminol will provide signal enhancement, lower detection limits, and increased dynamic ranges for any other luminol-based CL assay, thus comprising the potential to replace luminol as benchmark probe.

BODIPY and 2,3-Dihydrophthalazine-1,4-Dione Conjugates As Heavy Atom-Free Chemiluminogenic Photosensitizers

We disclose an interesting concept for developing heavy atom-free chemiluminogenic photosensitizers. To accomplish this, conjugates 2 and 3, which are composed of boron-dipyrromethene (BODIPY) and 2,3-dihydrophthalazine-1,4-dione units, are investigated. 2 and 3 are compared in terms of their photophysical properties, chemiluminescence responses, and singlet oxygen production. Strikingly, the results indicate that decoration of BODIPY with the 2,3-dihydrophthalazine-1,4-dione scaffold boosts the singlet oxygen generation. Furthermore, treatment of epidermoid laryngeal carcinoma Hep-2 (Hep-2) cells with conjugates 2 and 3 results in efficient cellular internalization which ensures live- cell imaging of Hep-2 cells. Finally, it is noteworthy that in vitro cytotoxicity assays reveal that both 2 and 3 induce cytotoxicity when illuminated with red light. Thus, 2 and 3 represent heavy atom-free chemiluminogenic photosensitizers.

A nitrogen doped carbon dots-enhanced peroxynitrous acid chemiluminescence method for 2-naphthol detection

A weak CL emission was initiated by peroxynitrous acid (PA) produced by the interaction of nitrite with hydrogen peroxide in sulphuric acid solution. In the presence of nitrogen doped carbon dots (NCDs), the CL intensity was enhanced significantly. The CL mechanism of the NCDs-PA system was studied using the CL spectrum, FL spectrum and the effect of radical scavengers. The NCDs-PA CL system was developed for the determination of 2-naphthol (2-NAP) based on its inhibition effect. The reduced CL intensity was proportional to the concentration of 2-NAP in the range from 0.3 to 20.0 μM and the detection limit was 48.0 nM. This method had been successfully applied to determine 2-NAP in environmental water samples with recoveries of 99.5-102.8%.

Synthesis and activity of a coumarin-based fluorescent probe for hydroxyl radical detection

As a type of reactive oxygen species (ROS), hydroxyl radical (·OH) is closely associated with many kinds of diseases. The present study aimed to develo p a novel OH fluorescent probe based on coumarin, a new compound that has not been previously reported. This probe exhibited good linear range and selectivity for ·OHl, and is able to avoid interference from some metal ions and other kinds of ROS (H₂ O₂ , O₂ ^.- , ¹ O₂ , and HClO). Meanwhile, this probe has been used to evaluate the ·OH-scavenging efficiency of different compounds, such as isopropyl alcohol, cytosine, uracil, Tempo, Glutathione (GSH), and dimethyl sulfoxide (DMSO). Therefore, the present study shows that this probe not only can effectively measure the level of ·OH, but also can assess the ·OH-scavenging efficiency of different compounds. Furthermore this current study suggested that following further optimization, this probe may be potentially applied in the diagnosis of oxidative stress in human body.

A rapid and economical method for the quantification of hydrogen peroxide (H2O2) using a modified HPLC apparatus

H₂O₂ is one of the most commonly used oxidants for the degradation of recalcitrant organic contaminants in advanced oxidation processes (AOPs). However, most research aiming to optimize AOPs is missing the monitoring of the remaining H₂O₂, an important parameter to assess the efficiency of the process. In this work, a novel method for [H₂O₂] quantification was developed using simple modifications of an HPLC-DAD setup that is available in most analytical chemistry laboratories. The modifications include the use of acidified potassium iodide solution as mobile phase and replacing the reverse phase column with a series of capillary columns. This instrument configuration allowed also the quantification of organic contaminants using the same H₂O₂ containing sample. The method's LOD and LOQ were calculated to be as low as 8.29 × 10^-4 mM and 2.76 × 10^-3 mM, respectively with an LDR range of 0.01-150 mM. The cost per analysis ranged between 0.8 and 1.8 USD cents depending on the concentration tested. This analytical method was validated by a statistical comparison to a well-known titrimetric method that is commonly used for H₂O₂ quantification. It was also tested using standards prepared in natural matrices such as spring and seawater, and in media containing high concentration of several spectator species such as chlorides, bicarbonates, humic acids, fumaric acids and micro pollutants. The method showed excellent robustness by maintaining high regression coefficient and excellent sensitivity in all calibration curves regardless of the matrix content.

Fast-Response Fluorogenic Probe for Visualizing Hypochlorite in Living Cells and in Zebrafish

A fast-response fluorogenic probe-compound D1-for monitoring hypochlorite (ClO^- ), based on specific ClO^- cleavage of a C=N bond and producing results observable to the naked eye, has been developed. The response of the probe to ClO^- increases linearly, and the fluorescence intensity was heightened by a factor of about 25. D1 responses to ClO^- , with high selectivity and sensitivity, were observable by naked eye within 10 s. D1 can not only detect levels of hypochlorite in vitro, such as in urine, but is also capable of monitoring hypochlorite content under extremely cold conditions, as low as -78 °C. Meanwhile, its good biocompatibility permitted the use of D1 to detect intracellular ClO^- by confocal microscopy. Moreover, D1 was successfully applied to monitor exogenous and endogenous ClO^- in zebrafish through fluorescence imaging.

Towards sustainable diagnostics: replacing unstable H2O2 by photoactive TiO2 in testing systems for visible and tangible diagnostics for use by blind people

Blind and color blind people cannot use colorimetric diagnostics; the problem is especially severe in rural areas where high temperatures and the absence of electricity challenge modern diagnostics. Here we propose to replace the unstable component of a diagnostic test, H2O2, with stable TiO2. Under UV irradiation, TiO2 forms reactive oxygen species that initiate polymerization of acrylamide causing liquid-to-gel transition in an analyte-dependent manner. We demonstrate that specific DNA sequences can be detected using this approach. This development may enable the detection of biological molecules by users with limited resources, for example in developing countries or for travelers in remote areas.

A new method for hydroxyl radical detection by chemiluminescence of flue-cured tobacco extracts

Chemiluminescence (CL) reactions usually take place in a severely restricted pH regime, thereby confining their application in media at different pH. In this paper, the CL behavior of tobacco-methanol extract (TME) was explored. Surprisingly, TME exhibited CL behavior upon mixing with Fe2+/H2O2, HRP/H2O2 and gold nanoparticles/H2O2 oxidation systems, i.e., in acidic, neutral and alkaline solution respectively. Addition of different reactive oxygen species scavengers verified that the hydroxyl radical (OH) triggers TME CL reactions. Then, the CL behavior of TME was applied to determine OH in tetrachloro-1,4-benzoquinone (TCBQ)/H2O2 system in acidic, neutral and alkaline solutions. CL intensity correlated most strongly (R2 = 0.99) with TCBQ concentration, which was used as a means to indirectly denote OH concentration. This implies that OH could be determined by a TME CL method in a semi-quantitative way regardless of pH value. Therefore, the TME CL method may be a promising method for OH determination in various OH-generating systems.

Development of an experimental set-up for low-temperature spectroscopic studies of matrix-isolated molecules and molecular ices using synchrotron radiation

An experimental set-up for studying photophysics and photochemistry of molecules in an inert gas medium (matrix-isolated) and in the ice phase at low temperatures has been developed and commissioned at the Photophysics beamline, Indus-1 synchrotron radiation source. This end-station uses an in-house-developed closed-cycle cryostat for achieving cryo-temperatures (∼10 K). Synchrotron radiation from the Photophysics beamline is used as the source of UV-VUV photons and the system is equipped with a Fourier transform infrared spectrometer for characterization of the molecular species formed at low temperature. Various individual components of the end-station like closed-cycle cryostat, experimental chamber, gas mixing and deposition systems are tested to ascertain that the desired performance criteria are satisfied. The performance of the composite system after integration with the Photophysics beamline is evaluated by recording IR and UV-VUV photoabsorption spectra of sulfur dioxide at low temperatures (10 K), both in the ice phase as well as isolated in argon matrices. Results obtained are in good agreement with earlier literature, thus validating the satisfactory performance of the system. As an off-shoot of the study, the VUV absorption spectrum of matrix-isolated SO₂ in argon matrix up to 10.2 eV is reported here for the first time. This experimental end-station will provide new opportunities to study photon-induced reactions in molecules of environmental, astrochemical and industrial importance. Details of the design, development and initial experimental results obtained are presented.

Generation of hydroxyl radicals by Fe-polyphenol-activated CaO2 as a potential treatment for soil-borne diseases

An Fe-polyphenol catalyst was recently developed using anhydrous iron (III) chloride and coffee grounds as raw materials. The present study aims to test the application of this Fe-polyphenol catalyst with two hydrogen peroxide (H2O2) sources in soil as a new method for controlling the soil-borne disease caused by Ralstonia solanacearum and to test the hypothesis that hydroxyl radicals are involved in the catalytic process. Tomato cv. Momotaro was used as the test species. The results showed that powdered CaO2 (16% W/W) is a more effective H2O2 source for controlling bacterial wilt disease than liquid H2O2 (35% W/W) when applied with an Fe-polyphenol catalyst. An electron paramagnetic resonance spin trapping method using a 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) assay and Fe-caffeic acid and Fe-chlorogenic acid complexes as models showed that these organometallic complexes react with the H2O2 released by CaO2, producing hydroxyl radicals in a manner that is consistent with the proposed catalytic process. The application of Fe-polyphenol with powdered CaO2 to soil could be a new environmentally friendly method for controlling soil-borne diseases.

Synergistic Bacterial Stress Results from Exposure to Nano-Ag and Nano-TiO2 Mixtures under Light in Environmental Media

Due to their widespread use and subsequent release, engineered nanomaterials (ENMs) will create complex mixtures and emergent systems in the natural environment where their chemical interactions may cause toxic stress to microorganisms. We previously showed that under dark conditions n-TiO₂ attenuated bacterial stress caused by low concentrations of n-Ag (<20 μg L^-1) due to Ag⁺ adsorption, yet, since both n-Ag and n-TiO₂ are photoactive, their photochemistries may play a key role in their interactions. In this work, we study the chemical interactions of n-Ag and n-TiO₂ mixtures in a natural aqueous medium under simulated solar irradiation to investigate photoinduced stress. Using ATP levels and cell membrane integrity as probes, we observe that n-Ag and n-TiO₂ together exert synergistic toxic stress in Escherichia coli. We find increased production of hydrogen peroxide by the n-Ag/n-TiO₂ mixture, revealing that the enhanced photocatalytic activity and production of ROS likely contribute to the stress response observed. Based on STEM-EDS evidence, we propose that a new composite Ag/TiO₂ nanomaterial forms under these conditions and explains the synergistic effects of the ENM mixture. Overall, this work reveals that environmental transformations of ENM mixtures under irradiation can enhance biological stress beyond that of individual components.

Recent advances and developments on integrating nanotechnology with chemiluminescence assays

Chemiluminescence (CL) techniques are extensively utilized for detection of analytes due to their high sensitivity, rapidity and selectivity. With the advent of nanotechnology and incorporation of the nanoparticles in the CL system has revolutionized the assays due to their unique optical and mechanical properties. Several CL-based reactions have been developed where these nanoparticle based CL sensors have evolved as excellent prospects for sensing in various analytical applications. This review article addresses the nanoparticles based CL detection system that are recently developed, the mechanisms has been summarized and the role of luminophors have been discussed. This article critically analyzes the optimal conditions for the CL detection along with quantitative assessment of the analytes. We have included the use of semiconductor nanoparticles, metal nanoparticles, graphene based nanostructures, mesoporous nanospheres, layered double hydroxides, clays for CL detection. The scope and application of these nanoscale material based CL system in various branches of science and technology including chemistry, biomedical applications, pharmaceutics, food, environmental and toxicological applications has been critically summarized.

Layered double hydroxide-enhanced luminescence in a Fenton-like system for selective sensing of cobalt in Hela cells

This work presented a facile and eco-friendly method for the determination of cobalt ions (Co(II)) in living cells based on layered double hydroxides (Mg-Al CO₃-LDHs) enhanced chemiluminescence (CL) emission of a Co(II)-hydrogen peroxide-sodium hydroxide system. The enhanced CL emission was attributed to the large specific surface area of Mg-Al CO₃-LDHs, which facilitates the generation of an excited-stated intermediate. The proposed method displayed high selectivity toward Co(II) over other metal ions. Under the optimal conditions, the increased CL intensity showed a linear response versus Co(II) concentration in the range of 5.0-1000 nM with a detection limit of 3.7 nM (S/N = 3). The relative standard deviation for nine repeated measurements of 100 nM Co(II) was 3.2%. Furthermore, the proposed method was successfully applied to detect Co(II) in living cell samples, and the results were agreed with those obtained by the standard ICP-MS method.

Singlet Oxygen Detection on a Nanostructured Porous Silicon Thin Film via Photonic Luminescence Enhancements

Because reactive oxygen species are involved in a range of pathologies, developing analytical tools for this group of molecules opens new vistas for biomedical diagnostics. Herein, we fabricate a porous silicon microcavity (pSiMC) functionalized with luminescent singlet oxygen (¹O₂) probe EuA ((Eu(III)-2,2',2″-(10-(2-((4-(2-((4-(2-((anthracen-9-ylmethyl)amino)ethyl)-1H-1,2,3-triazol-1-yl)amino)-2-oxoethyl)-2-oxo-1,2-dihydroquinolin-7-yl)amino)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid) as proof of concept of an optical sensor for reactive oxygen species. We characterize each surface modification step of the pSiMC by means of FTIR and X-ray photoelectron spectroscopy as well as by determining the optical shifts of the resonance wavelength of the pSiMC. The luminescence signal upon detection of ¹O₂ on the EuA-modified pSiMC is enhanced ∼2-fold compared to that of a single layer and a detuned microcavity. The sensing performance of the EuA probe is improved significantly on the pSiMC compared to that in aqueous solution, giving a limit of ¹O₂ detection of 3.7 × 10^-8 M.

Co-metal-organic-frameworks with pure uniform crystal morphology prepared via Co2+ exchange-mediated transformation from Zn-metallogels for luminol catalysed chemiluminescence

Cation exchange-mediated transformation from Zn-metallogels (MOGs), which was a mild facile strategy relative to the demanding hydrothermal method, was employed to develop Co²⁺ metal-organic frameworks (Co-MOFs) at room temperature. The obtained Co-MOFs was of uniform octahedral morphology and possessed high activity to catalyze luminol chemiluminescence without extra oxidants. By adding cysteine, the CL emission of luminol-Co-MOFs system was further enhanced. Based on this phenomenon, Co-MOFs was utilized to build a practical sensing platform for cysteine determination. Under the optimized conditions, the relative CL intensity (ΔI) was proportional to the concentration of cysteine in the range of 2-10μM, and the detection limit was 0.49μM (3S/N). Moreover, the established method was applied to the determination of cysteine in commercially available pharmaceutical injections.

Recent advances in chemiluminescence based on carbonaceous dots

Herein, a broad overview concerning the most recent progress of carbon dots (CDs) in chemiluminescence (CL) as well as the mechanisms and applications are presented. CDs have excellent optical and electronic properties and are very important advancement in the fast growing domain of nanotechnology. CDs enhance the ultraweak CL of different systems. The mechanisms and applications of these enhanced CL reactions are discussed. It is worthy to note that CDs participate in CL reactions as catalysts, energy acceptors or are directly involved in redox reactions with radicals in CL systems. Sometimes, these processes taking place simultaneously to enhance CL intensity. In this report, recent advances in CD based CL are comprehensively summarized and their applications in detection of various reagents and biological molecules are reviewed. The challenges and future prospects of this field are also discussed.

Recent Advances on Luminescent Enhancement-Based Porous Silicon Biosensors

Luminescence-based detection paradigms have key advantages over other optical platforms such as absorbance, reflectance or interferometric based detection. However, autofluorescence, low quantum yield and lack of photostability of the fluorophore or emitting molecule are still performance-limiting factors. Recent research has shown the need for enhanced luminescence-based detection to overcome these drawbacks while at the same time improving the sensitivity, selectivity and reducing the detection limits of optical sensors and biosensors. Nanostructures have been reported to significantly improve the spectral properties of the emitting molecules. These structures offer unique electrical, optic and magnetic properties which may be used to tailor the surrounding electrical field of the emitter. Here, the main principles behind luminescence and luminescence enhancement-based detections are reviewed, with an emphasis on europium complexes as the emitting molecule. An overview of the optical porous silicon microcavity (pSiMC) as a biosensing platform and recent proof-of-concept examples on enhanced luminescence-based detection using pSiMCs are provided and discussed.

Superoxide Ion: Generation and Chemical Implications

Superoxide ion (O2(•-)) is of great significance as a radical species implicated in diverse chemical and biological systems. However, the chemistry knowledge of O2(•-) is rather scarce. In addition, numerous studies on O2(•-) were conducted within the latter half of the 20th century. Therefore, the current advancement in technology and instrumentation will certainly provide better insights into mechanisms and products of O2(•-) reactions and thus will result in new findings. This review emphasizes the state-of-the-art research on O2(•-) so as to enable researchers to venture into future research. It comprises the main characteristics of O2(•-) followed by generation methods. The reaction types of O2(•-) are reviewed, and its potential applications including the destruction of hazardous chemicals, synthesis of organic compounds, and many other applications are highlighted. The O2(•-) environmental chemistry is also discussed. The detection methods of O2(•-) are categorized and elaborated. Special attention is given to the feasibility of using ionic liquids as media for O2(•-), addressing the latest progress of generation and applications. The effect of electrodes on the O2(•-) electrochemical generation is reviewed. Finally, some remarks and future perspectives are concluded.

Antioxidant Activity/Capacity Measurement. 3. Reactive Oxygen and Nitrogen Species (ROS/RNS) Scavenging Assays, Oxidative Stress Biomarkers, and Chromatographic/Chemometric Assays

There are many studies in which the antioxidant potential of different foods have been analyzed. However, there are still conflicting results and lack of information as a result of unstandardized assay techniques and differences between the principles of the methods applied. The measurement of antioxidant activity, especially in the case of mixtures, multifunctional or complex multiphase systems, cannot be evaluated satisfactorily using a simple antioxidant test due to the many variables influencing the results. In the literature, there are many antioxidant assays that are used to measure the total antioxidant activity/capacity of food materials. In this review, reactive oxygen and nitrogen species (ROS/RNS) scavenging assays are evaluated with respect to their mechanism, advantages, disadvantages, and potential use in food systems. On the other hand, in vivo antioxidant activity (AOA) assays including oxidative stress biomarkers and cellular-based assays are covered within the scope of this review. Finally, chromatographic and chemometric assays are reviewed, focusing on their benefits especially with respect to their time saving, cost-effective, and sensitive nature.

Synthesis and physicochemical properties of novel lophine derivatives as chemiluminescent in vitro activators for detection of free radicals

The overproduction of free radicals and reactive oxygen species (ROS) has been proved as a basic damage mechanism and cause for oxidative stress. Their measurement is often hindered by the low signal. This could be resolved with the application of luminescent probes (lophines, luminol, lucigenin, etc.). The focus of this study is to synthesize and describe the spectral properties and physicochemical characteristics of lophine and its derivatives as new chemiluminescent in vitro activators. The prepared luminophores are analogues of lophine. Their absorption maxima are in the range 329-340 nm, with good-to-high extinction coefficients. Their spectral properties are measured in methanol and buffer solutions with pH 3.5, 7.4 and 8.5. Same conditions were applied in the systems for chemiluminescent assay in vitro: (1) Fenton's (Fe(2+)+H2O2) for the generation of ·OH and -OH species, (2) Hydrogen peroxide (H2O2), (3) Iron (II) sulfate (FeSO4), (4) Glutathione-peroxidase, monitoring the deactivation of H2O2, (5) Ascorbic acid-Fenton's reagent: Vit.C appears a strong oxidant, generating free-radical products when applied in higher than physiological concentrations, (6) Reduced α-nicotinamide adenine dinucleotide (NADH)-phenazine methosulfate-for the generation of superoxide radicals (O2 (·-)). Lophine and all novel compounds do not alter the kinetics, except of the dimethyl amino substituted derivative (4-(3a,11b-dihydro-1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-N,N-dimethylaniline) in the glutathione-peroxidase system, at pH 8.5. Same derivative showed a comparable or higher activity than Lucigenin and Rhodamine 6G. In neutral and acidic medium, in the Fenton's system, Rhodamine 6G was the most appropriate probe. In alkaline pH and oxidant H2O2, Lucigenin induced a signal twice as strong as the signal compared to all other activators.