Quantitative analysis of CL-20 explosive by smartphone-based chemiluminescence method

A new smartphone-based chemiluminescence method has been introduced for the quantitative analysis of CL-20 (Hexanitroazaisowuertzitan) explosive. The solvent mixture, oxidizer agent, and concentration of the reactants were optimized using statistical procedures. CL-20 explosive showed a quenching effect on the chemiluminescence intensity of the luminol-NaClO reaction in the solvent mixture of DMSO/H2O. A smartphone was used as a detector to record the light intensity of chemiluminescence reaction as a video file. The recorded video file was converted to an analytical signal as intensity luminescence-time curve by a written code in MATLAB software. Dynamic range and limit of detection of the proposed method were obtained 2.0-240.0 and 1.1 mg⋅L-1, respectively, in optimized concentrations 1.5 × 10-3 mol⋅L-1 luminol and 1.0 × 10-2 mol⋅L-1 NaClO. Precursors TADB, HBIW, and TADNIW in CL-20 explosive synthesis did not show interference in measurement the CL-20 purity. The analysis of CL-20 spiked samples of soil and water indicated the satisfactory ability of the method in the analysis of real samples. The interaction of CL-20 molecules and OCl- ions is due to quench of chemiluminescence reaction of the luminol-NaClO.

Efficient chemiluminescence of luminol in the presence of hemin without added hydrogen peroxide†

The results reported herein demonstrate for the first time that typical reducing agents in an alkaline medium initiate chemiluminescence of luminol in the presence of hemin, and the efficiency of their action is comparable to that of hydrogen peroxide and exceeds it in the case of the superoxide anion. The pertinent implications of these findings refer to new possibilities for developing chemiluminescence assays and biosensors and to precautions for determining hydrogen peroxide using luminol and hemin in samples of unknown composition, most prominently, of biological origin.

Evaluation of Forensic Luminol in Detection of Blood Stains in Instruments Following Dental Treatment

Background Saliva and blood, being biological materials with a high potential for infectious transmission in dental environments, pose significant risks to dental professionals, assistants, and patients alike. Therefore, practitioners must adopt stringent security measures to ensure patient care, considering all parties as potential carriers of microorganisms capable of causing infectious diseases. Currently, various methods of disinfection and sterilization are employed to maintain the aseptic chain effectively. Having reliable methods for detecting substances in liquids, particularly body fluids, is crucial and highly convenient. Luminol, a chemiluminescent agent widely used in forensic science for detecting minute traces of blood that are invisible to the naked eye, presents itself as a valuable tool. Blood, a major bodily fluid often present in instruments following dental procedures, underscores the importance of its detection. Hence, in this study, luminol was utilized to detect blood traces in dental instruments following dental treatment, both before and after sterilization or disinfection. Objective Blood and saliva splashes, together with highly contagious aerosols, are always a part of dental procedures. The objective of the current study is to detect traces of blood stains on face shields, surgical instruments, and endodontic files using luminol before and after sterilization. Materials and methods Sample size calculation was done with G*Power software (Version 3.1.9.4, Düsseldorf, Germany), and a total of 30 instruments were selected for the study. In the present study, a total of 30 items were collected and utilized, including 14 instruments used after implant placement, 12 endodontic files employed after root canal treatment, and four face shields utilized during these procedures. Meanwhile, a freshly prepared luminol solution was applied to these instruments, and they were viewed in a dark environment both before and after sterilization procedures. Luminescence generated by luminol was observed in the instruments, indicative of the presence of blood not visible to the naked eye. Statistical analysis for both groups was done with IBM SPSS Statistics for Windows, Version 16.0 (Released 2007; SPSS Inc., Chicago, IL, USA). Intragroup comparison was done using the Friedman test, and intergroup comparison was done using the Wilcoxon signed-rank test. Results Blood stains and chemiluminescence were visualized in two out of 10 endodontic files (one #15 K-file and #20 K-files) and two out of four face shields. The intragroup comparison was done using the Friedman test, and it was found to be statistically significant (p < 0.05). Intergroup comparison was done using the Wilcoxon signed-rank test and was found to be statistically insignificant (p > 0.05). Conclusion Following sterilization and disinfection, there were no visual blood stains or chemiluminescence. Therefore, luminol was found to be effective in detecting blood stains in endodontic files, surgical instruments, and face shields, as well as in validating the sterilization and disinfection processes. Hence, sterilization in dentistry stands as a critical measure to guarantee patient safety, halt the dissemination of infections, and uphold exemplary clinical care standards.

Off-Grid Electrogenerated Chemiluminescence with Customized p-i-n Photodiodes

Electrochemiluminescence (ECL) is the generation of light induced by an electrochemical reaction, driven by electricity. Here, an all-optical ECL (AO-ECL) system is developped, which triggers ECL by the illumination of electrically autonomous "integrated" photoelectrochemical devices immersed in the electrolyte. Because these systems are made using small and cheap devices, they can be easily prepared and readily used by any laboratories. They are based on commercially available p-i-n Si photodiodes (≈1 € unit-1), coupled with well-established ECL-active and catalytic materials, directly coated onto the component leads by simple and fast wet processes. Here, a Pt coating (known for its high activity for reduction reactions) and carbon paint (known for its optimal ECL emission properties) are deposited at cathode and anode leads, respectively. In addition to its optimized light absorption properties, using the commercial p-i-n Si photodiode eliminates the need for a complicated manufacturing process. It is shown that the device can emit AO-ECL by illumination with polychromatic (simulated sunlight) or monochromatic (near IR) light sources to produce visible photons (425 nm) that can be easily observed by the naked eye or recorded with a smartphone camera. These low-cost off-grid AO-ECL devices open broad opportunities for remote photodetection and portable bioanalytical tools.

NiCo-LDH Hollow Nanocage Oxygen Evolution Reaction Promotes Luminol Electrochemiluminescence

Conventional luminol co-reactant electrochemiluminescence (ECL) systems suffer from low stability and accuracy due to factors such as the ease of decomposition of hydrogen peroxide and inefficient generation of reactive oxygen species (ROS) from dissolved oxygen. Inspired by the luminol ECL mechanism mediated by oxygen evolution reaction (OER), the nickel-cobalt layered double hydroxide (NiCo-LDH) hollow nanocages with hollow structure and defect state are used as co-reaction promoters to enhance the ECL emission from the luminol-H2 O system. Thanks to the hollow structure and defect state, NiCo-LDH hollow nanocages show excellent OER catalytic activity, which can stabilize and efficiently produce ROS and enhance the ECL emission. Additionally, mechanistic exploration suggests that the ROS involved in the co-reaction of the luminol-H2 O system are derived from the OER reaction process, and there is a positive correlation between ECL intensity and the OER catalytic activity of the co-reaction promoter. The selection of catalysts with excellent OER catalytic activity is a key factor in improving ECL emission. Finally, a dual-mode immunosensor is constructed for the detection and analysis of alpha-fetoprotein (AFP) based on the promoting effect of NiCo-LDH hollow nanocages on the luminol-H2 O ECL system.

Antiradical capacity assay for hydrophobic substances using hemin-catalyzed luminol chemiluminescence in cationic micelles

Antioxidant substances which can diminish the steady-state concentration of free radicals in vivo are important in the human dietary to diminish the deleterious effects of oxidative stress. As the potential of certain substances as antioxidants is difficult to be verified in vivo, simple chemical in vitro assays which test the potential of substances as antioxidants are of great importance for the screening of new antioxidants. These assays measure the capacity of a substance to suppress free radicals. We describe here an antiradical capacity assay, based on luminol chemiluminescence, in cationic micellar medium, allowing the capacity determination of hydrophobic compounds. The antiradical capacity of antioxidants is determined using the Trolox standard by the measurement of the light emission inhibition area caused by the addition of different antiradical concentrations. The obtained results are compared to the values determined using the scavenging of stable free radicals be the substances and shown to be similar for compounds like uric acid, rutin, and quercetin. However, for vitamin E, the luminol assay results in a considerably higher antiradical capacity than the assay with a stable free radical, which is rationalized by the higher reactivity of the radical generated in the luminol assay and a specific localization of vitamin E in the micellar medium.

Detection of Visually Imperceptible Blood Contamination in the Surgical Area Using Luminol Among Different Oral Surgical Procedures: An Observational Study

Introduction Oral surgeons often encounter a significant occupational risk of exposure to potentially harmful infectious diseases during minor oral surgical procedures. These diseases can be transmitted through direct contact with body fluids and aerosolized splatters that may not be visibly detectable. The likelihood of transmission is heightened for clinicians, healthcare workers, and patients alike. The reported prevalence of exposure to blood-borne infections in this field is as high as 90%, with half of these exposures being visually imperceptible. Aim The aim was to detect visually imperceptible blood contamination on personal protective equipment (PPE) and clinical surfaces using the chemiluminescence agent luminol during oral surgical procedures. Materials and methods Thirty minor oral surgical procedures were performed in the Oral and Maxillofacial Surgery Department after obtaining approval from the Institutional Ethics Committee (IEC), Vinayaka Mission's Sankarachariyar Dental College, Vinayaka Mission's Research Foundation, Salem, India. The surgeon, assistant, patient, and clinical surfaces (comprising 15 subsites within the surgical field) wore PPE. The PPE was scrutinized for traces of visually imperceptible blood contamination using luminol. The results of blood splatter on PPE and clinical surfaces in different oral surgical procedures between the non-aerosol and aerosol groups of different durations were analyzed statistically using the chi-square test with p < 0.05 considered significant. Results We observed that visually imperceptible blood contamination in non-aerosol procedures was detected on the assistant PPE kit (46.7%, n = 14), assistant face shield (40%, n = 12), suction apparatus (50%, n = 15), wall (30%, n = 9), and floor (56.7%, n = 17), in both aerosol and non-aerosol procedures. The p-value has been considered statistically significant at p < 0.05 between both the groups (aerosol and non-aerosol). Conclusion Our study results confirmed the presence of undetected blood spillage during aerosol procedures of 30 minutes and non-aerosol surgical procedures of more than 30 minutes over an area of 3.1 feet horizontally and 4.8 feet vertically. So, we strongly emphasize that PPE kits and face shields are mandatory for both surgeon and assistant while performing oral surgical procedures in order to prevent the risk of cross infections, proper infection prevention control protocol for the clinical surfaces also needs to be followed as a standard protocol in all operations.

Fe3 O4 and bimetal-organic framework Zn/Mg composite peroxide-like catalyze luminol chemiluminescence for specific measurement of atropine in Datura plant

Atropine (AT) is an anticholinergic drug. AT is abundantly in Datura plant seeds. Fe3 O4 @Zn/Mg MOF (Fe3 O4 @MOF) composite was synthesized. The compound had a high peroxidase-like activity in a chemiluminescence (CL) reaction. Addition of AT quenched CL. The linear range and limit of detection were 5-600 μg L-1 and 2 × 10-2  μg L-1 . This method is fast, reversible, and selective, without biodegradability effects, high accuracy, and precision for measuring AT in the Datura plant.

Sensitive Detection of Nitrite and Nitrate in Seawater by 222 nm UV-Irradiated Photochemical Conversion to Peroxynitrite and Ion Chromatography-Luminol Chemiluminescence System

Sensitive detection methods for nitrite (NO₂^-) and nitrate (NO₃^-) ions are essential to understand the nitrogen cycle and for environmental protection and public health. Herein, we report a detection method that combines ion-chromatographic separation of NO₂^- and NO₃^-, on-line photochemical conversion of these ions to peroxynitrite (ONOO^-) by irradiation with a 222 nm excimer lamp, and chemiluminescence from the reaction between luminol and ONOO^-. The detection limits for NO₂^- and NO₃^- were 0.01 and 0.03 μM, respectively, with linear ranges of 0.010-2.0 and 0.10-3.0 μM, respectively, at an injection volume of 1 μL. The results obtained by the proposed method for seawater analysis corresponded with those of a reference method (AutoAnalyzer based on the Griess reaction). As luminol chemiluminescence can measure ONOO^- at picomolar concentrations, our method is expected to be able to detect NO₂^- and NO₃^- at picomolar concentrations owing to the high conversion ratio to ONOO^- (>60%), assuming that contamination and background chemiluminescence issues can be resolved. This method has the potential to emerge as an innovative technology for NO₂^- and NO₃^- detection in various samples.

Chemiluminescence Biosensor for the Determination of Cardiac Troponin I (cTnI)

Cardiac vascular diseases, especially acute myocardial infarction (AMI), are one of the leading causes of death worldwide. Therefore cardio-specific biomarkers such as cardiac troponin I (cTnI) play an essential role in the field of diagnostics. In order to enable rapid and accurate measurement of cTnI with the potential of online measurements, a chemiluminescence-based immunosensor is presented as a proof of concept. A flow cell was designed and combined with a sensitive CMOS camera allowing sensitive optical readout. In addition, a microfluidic setup was established, which achieved selective and quasi-online cTnI determination within ten minutes. The sensor was tested with recombinant cTnI in phosphate buffer and demonstrated cTnI measurements in the concentration range of 2-25 µg/L. With the optimized system, a limit of detection (LoD) of 0.6 µg/L (23 pmol/L) was achieved. Furthermore, the selectivity of the immunosensor was investigated with other recombinant proteins, such as cTnT, and cTnC, at a level of 16 µg/L. No cross-reactivity could be observed. Measurements with diluted blood plasma and serum resulted in an LoD of 60 µg/L (2.4 nmol/L) and 70 µg/L (2.9 nmol/L), respectively.

Flow injection assays for NADH and ethanol using photosensitized rose bengal and luminol-copper (II) chemiluminescence system

The on-line photoreaction of rose bengal photosensitized luminol-copper (II) chemiluminescence (CL) system was used for the determination of β-nicotinamide adenine dinucleotide (NADH) and ethanol (EtOH) in pharmaceutical formulations combined with flow injection (FI) technique. NADH can significantly enhance the CL emission of the reaction. For EtOH, alcohol dehydrogenase (ADH) in soluble form was utilized in the presence of nicotinamide adenine dinucleotide (NAD⁺ ) resulting in NADH production. The limit of detection (3σ blank, 𝑛 = 3) of 4.0 × 10^-8 and 2.17 × 10^-5 M, and linear range of 1.3 × 10^-7 -2.5 × 10^-5 M (R² = 0.9998, n = 6) and 0.11-2.17 × 10^-3 M (R² = 0.9996, n = 6) were obtained for NADH and EtOH respectively. The injection rate was 100 h^-1 with relative standard deviation (RSD; n = 3) of 1.5%-4.8% in the range studied for both analytes. The procedure was satisfactorily applied to pharmaceutical formulations with recoveries in the range of 91.6 ± 3.0%-110 ± 2.0% for NADH and 88 ± 3.0%-95.4 ± 4.0% for EtOH. The results obtained were very consistent and did not differ considerably from the reported approaches at 95% confidence limit. The possible mechanism of CL reaction is also explained briefly.

Water Activation for Boosting Electrochemiluminescence

In conventional luminol electrochemiluminescence (ECL) systems, hydrogen peroxide and dissolved oxygen are employed as typical co-reactants to produce reactive oxygen species (ROS) for efficient ECL emission. However, the self-decomposition of hydrogen peroxide and limited solubility of oxygen in water inevitably restrict the detection accuracy and luminous efficiency of luminol ECL system. Inspired by ROS-mediated ECL mechanism, for the first time, we used cobalt-iron layered double hydroxide as co-reaction accelerator to efficiently activate water to generate ROS for enhancing luminol emission. Experimental investigations verify the formation of hydroxyl and superoxide radicals in the process of electrochemical water oxidation, which subsequently react with luminol anion radicals to trigger strong ECL signals. Finally, the detection of alkaline phosphatase has been successfully achieved with impressive sensitivity and reproducibility for practical sample analysis.

Laccase-luminol chemiluminescence system: an investigation of substrate inhibition

Chemiluminescence (CL) reactions are widely used for the detection and quantification of many types of analytes. Laccase has previously been proposed in CL reactions; however, its light emission behaviour has not been characterized. This study was conducted to characterize the laccase-luminol system, determine its kinetic parameters, and analyze the effects of protein and OH- concentration on the CL signal. Laccase from Coriolopsis gallica was combined with different concentrations of luminol (125 nM to 4 mM), and the enzyme kinetics were evaluated using diverse kinetic models. The laccase-luminol system was able to produce CL without an intermediate molecule, but it exhibited substrate-inhibition behaviour. A two-site random model was used and suggested that when the first luminol molecule was bound to the active site, laccase affinity for the second luminol molecule was increased. This inhibition effect could be avoided using a low luminol concentration. At 5 μM luminol concentration, 1 mg/ml (0.13 U) laccase is needed to achieve nearly 90% of the maximum CL signal, suggesting that the available luminol could not bind to all active sites. Furthermore, the concentration of NaOH negatively affected the CL signal. The laccase-luminol system represents an alternative to existing CL systems, with potential uses in molecular detection and quantification.

Cellulose-Based Fluorescent Material for Extreme pH Sensing and Smart Printing Applications

Environment-responsive fluorescence materials are being widely investigated for instrument-free determination of various environmental factors. However, developing an eco-friendly cellulose-based fluorescent pH sensor for sensing extreme acidity and alkalinity is still challenging. Herein, a highly fluorescent and multifunctional material is developed from biopolymer-based cellulose acetate. A biopolymer-based structure containing responsive functional groups such as -C═O and -NH is constructed by chemically bonding 5-amino-2,3-dihydrophthalazine-1,4-dione (luminol) onto cellulose acetate using 4,4'-diphenylmethane diisocyanate (MDI) as a cross-linking agent. The prepared material (Lum-MDI-CA) is characterized by UV-vis, Fourier transform infrared, ¹H NMR, ¹³C NMR spectroscopies, and fluorescence techniques. The material exhibits excellent aqua blue fluorescence and demonstrates extreme pH sensing applications. Interesting results are further revealed after adding a pH-unresponsive dye such as MTPP as the reference to develop the ratiometric method. The ratiometric system clearly differentiates the extreme acidic pH 1 from pH 2 and extreme alkaline pH 12, 13, and 14 by visual and fluorescence color change response under a narrow pH range. In addition, the material is fabricated into transparent flexible fluorescent films which demonstrate an outstanding UV shielding, security printing, and haze properties for smart food packaging and printing applications.

Synthesis and Characterization of a Luminol Based Chemiluminescent Trimeric System

A luminol based chemiluminescent trimeric system, namely 2,3-dihydro-5,8-di(thiophen-2-yl)phthalazine-1,4-dione (T₂B-Lum), bearing thiophene rings as donor units and 2,3-dihydrophthalazine-1,4-dione as an acceptor unit was synthesized in two steps via donor-acceptor-donor approach using two different methods. It was found that T₂B-Lum emits chemiluminescent light when exposed to H₂O₂ in a basic medium, and the presence of substituents and the type of aromatic ring bearing chemiluminescent active group have a direct effect on the compound's sensitivity. Among the members of a large family of metal ions, fluorescent and chemiluminescent T₂B-Lum exhibited high sensitivity to Cu²⁺ and Fe³⁺ ions. Except for other metal cations (silver(I), cadmium(II), cobalt(II), iron(III), lithium(I), magnesium(II), manganese(II), nickel(II), zinc(II)), it has been observed that T₂B-Lum is mostly sensitive to copper(II) ions with a detection limit value of 2.2 × 10^- 3 M. On the other hand, T₂B-Lum was also found to exhibit a high sensitivity to extremely dilute aqueous solutions (e.g., 1:50.000 dilution) of blood samples, making it a promising candidate for use in forensic applications.

Chemiluminescent polymeric nanoprobes for tumor diagnosis: A mini review

Chemiluminescence (CL), a distinct luminescent process by taking advantage of chemical reactions rather than external light source, has recently attracted considerable research interests due to its high sensitivity and low background signal. The sensitivity and specificity of chemiluminescent signals in complex tumor microenvironment provide a sound basis for accurate detection of tumors. Various chemiluminescent nanoprobes with superior performance have been obtained by structural modification of chemiluminescent units or introduction of fluorescent dyes. In this review, we focused on the recent progress of chemiluminescent polymeric systems based on various chromophore substrates, including luminol, peroxyoxalates, 1, 2-dioxetanes and their derivatives for tumor detecting. And we also emphasized the design strategies, mechanisms and diagnostic applications of representative chemiluminescent polymeric nanoprobes. Finally, the critical challenges and perspectives of chemiluminescent systems usage in tumor diagnosis were also discussed.

Decreased plasma H2O2 levels are associated with the pathogenesis leading to COVID-19 worsening and mortality

Oxidative Stress (OS) is involved in the pathogenesis of COVID-19 and in the mechanisms by which SARS-CoV-2 causes injuries to tissues, leading to cytopathic hypoxia and ultimately multiple organ failure. The measurement of blood glutathione (GSH), H₂O₂, and catalase activity may help clarify the pathophysiology pathways of this disease. We developed and standardized a sensitive and specific chemiluminescence technique for H₂O₂ and GSH measurement in plasma and red blood cells of COVID-19 patients admitted to the intensive care unit (ICU). Contrary to what was expected, the plasma concentration of H₂O₂ was substantially reduced (10-fold) in COVID-19 patients compared to the healthy control group. From the cohort of patients discharged from the hospital and those who were deceased, the former showed a 3.6-fold and the later 16-fold H₂O₂ reduction compared to the healthy control. There was a 4.4 reduction of H₂O₂ concentration in the deceased group compared to the discharged group. Interestingly, there was no variation in GSH levels between groups, and reduced catalase activity was found in discharged and deceased patients compared to control. These data represent strong evidence that H₂O₂ is converted into highly reactive oxygen species (ROS), leading to the worst prognosis and death outcome in COVID-19 patients admitted to ICU. Considering the difference in the levels of H₂O₂ between the control group and the deceased patients, it is proposed the quantification of plasma H₂O₂ as a marker of disease progression and the induction of the synthesis of antioxidant enzymes as a strategy to reduce the production of oxidative stress during severe COVID-19.HighlightsH₂O₂ plasma levels is dramatically reduced in patients who deceased compared to those discharged and to the control group.Plasmatic quantification of H₂O₂ can be possibly used as a predictor of disease progression.Catalase activity is reduced in COVID-19.GSH levels remain unchanged in COVID-19 compared to the control group.

Sonochemically synthesized mesoporous cobalt oxide nanoparticles for luminol-enhanced chemiluminescence sensing

In recent years, mesoporous cobalt oxides have attracted more attention due to their exceptional physical and chemical properties and their important applications in various fields. The synthesis of cobalt oxides of various sizes, morphologies, and porosity is still a challenging process. In this report, mesoporous Co₃O₄NPs with different porosity were synthesized through facile, one-step, and cost-effective routes, without using any complicated materials or instruments, via the sonochemical process. X-ray powder diffraction (XRD), BET, and transmission electron microscopy (TEM) were used to characterize the as-synthesized NPs. XRD technique was used to determine the crystal structure and phase of the NPs, BET to describe the porous nature of the NPs, and TEM to investigate the structure and morphology of the NPs. Next, the effect of as-synthesized Co₃O₄NPs as a catalyst for the luminol-H₂O₂chemiluminescence system was studied. Co₃O₄NPs were chosen since they have nanoscale size, high specific surface area, and mesoporous nature. Therefore, these NPs can form more active sites and thus show unique catalytic activity than common ionic catalysts such as Co²⁺, Fe³⁺, Cu²⁺used in the luminol-H₂O₂CL system. Finally, this system was used to detect and measure H₂O₂and glucose under optimal conditions. A good linear relationship was observed between the chemiluminescence intensity of the designed system and the concentration of H₂O₂and glucose. A linear range like 0.25-10 pM for H₂O₂and 1-30 nM for glucose was obtained. The excellent LOD of the proposed method for measuring H₂O₂was about 0.07 pM, and for measuring glucose was about 0.14 nM.

Highly Sensitive Fingerprint Detection under UV Light on Non-Porous Surface Using Starch-Powder Based Luminol-Doped Carbon Dots (N-CDs) from Tender Coconut Water as a Green Carbon Source

This study aims to synthesize carbon dots from a natural resource and will be used to detect a latent fingerprint on a non-porous surface. The carbon dots (CDs) were prepared by adding luminol to coconut water and ethanol via a hydrothermal method. Luminol enhances the chemiluminescence of the CDs, which show more distinct blue light under a UV lamp compared with bare CDs. To detect the latent fingerprint, luminol carbon dots (N-CDs) were combined with commercial starch and stirred at room temperature for 24 h. Their characteristics and optical properties were measured using EDX-SEM, HR-TEM, FTIR, XPS, UV-visible absorption, and fluorescence. In this research, it was found that the N-CDs had a d-spacing of 0.5 nm and a size of 12.9 nm. The N-CDs had a fluorescence intensity 551% higher than the standard normally used. N-CDs can be used to detect latent fingerprints on a non-porous surface and are easy to detect under a UV lamp at 395 nm. Therefore, luminol has a high potential to increase sensitive and stable traces of chemiluminescence from the green CDs for forensic latent fingerprint detection.

A Luminol-Based Self-Illuminating Nanocage as a Reactive Oxygen Species Amplifier to Enhance Deep Tumor Penetration and Synergistic Therapy

The dense extracellular matrix (ECM) in tumor tissues resists drug diffusion into tumors and leads to a poor prognosis. To address this problem, glucose oxidase (GOx)-modified ferritin loaded with luminol-curcumin was fabricated. Once delivered to the tumor, this luminol-based self-illuminating nanocage could actively convert glucose to reactive oxygen species (ROS) to achieve starvation therapy. Then, excessive ROS were transmitted to luminol, thereby emitting 425 nm blue-violet light. Momentarily, light was further absorbed by curcumin and ROS production was amplified. Abundant ROS helps break down the ECM network to penetrate deep into tumors. In addition, ROS produced after cell internalization can induce apoptosis of tumor cells by decreasing the mitochondrial membrane potential and can promote ferroptosis by consuming reduced glutathione. Effective penetration and multiple pathways inducing tumor cell death contributed to the efficient antitumor effect (tumor inhibition rate of GOx-modified ferritin loaded with luminol-curcumin: 71.73%). This study developed a glucose-driven self-illuminating nanocage for active tumor penetration via ROS-mediated destruction of the ECM and provided the synergetic mechanism of apoptosis and ferroptosis.

Biocleaning in operating theatres: validation of cleaning techniques by revealing residual traces of blood

BACKGROUND

In the operating theatre the biocleaning process is essential after each passage to guarantee the non-transmission of potentially pathogenic microbial agents from patients to patient.

AIM

To evaluate the quality of this biocleaning, the Operational Hygiene Team used a very sensitive method to detect residual traces of blood : luminol (3-aminophthalhydrazide) on the basis of methods used by the police.

METHOS

Luminol was used after conventional one-step biocleaning with the usual detergent/disinfectant ; after bleach disinfection before biocleaning ; and after biocleaning with a steam cleaner.

FINDINGS

Lunimol revealed extended traces of blood corresponding to the passage of the strip on the floor, in the corners of the room and on certain pieces of furniture which are difficult to clean. However, no luminescence was detected on the surfaces cleaned by a single passage of the steam cleaner.

CONCLUSION

In all cases, the rooms appeared visually clean and traces of blood only became visible when revealed by luminol. We also showed that usual detergents or disinfectants do not remove blood and instead actually spread it over surfaces that may seem visually clean. These results led us to modify our procedure and also confirmed our wish to generalize the use of the steam cleaning technique for immediate cleaning. Much more our tests show the relevance of luminol as a validation tool for the quality and method of biocleaning.

Determination of organophosphate flame retardant tris(2-chloroethyl)phosphine based on the luminol-H2 O2 chemiluminescence system

Organophosphorus flame retardants (OPFRs) are new types of environmental pollutants, therefore the rapid and sensitive detection of OPFRs is a very important objective. A new experimental phenomenon was found in which tris(2-chloroethyl)phosphine (TCEP), a type of OPFR, could effectively enhance the signal of the luminol-H₂ O₂ chemiluminescence (CL) system. Combined with the controllability of flow injection analysis, a rapid, stable, and sensitive CL method was established. The CL intensity responded linearly to the concentration of TCEP in the range 0.5-100 μg/L (R²  = 0.999) with a low detection limit of 33 ng/L. Relative standard deviation (RSD) was 2.2% (n = 7, c = 100 μg/L). Water samples were labelled and recycled with RSDs of 1.1-5.7% and recoveries of 88.7-116.1%. Based on these results, this study established a new CL detection method for the environmental pollutant TCEP.

Long-Lasting Luminol Chemiluminescence Emission with 1,10-Phenanthroline-2,9-dicarboxylic Acid Copper(II) Complex on Paper

As most of the known systems are flashtype, long-lasting chemiluminescence (CL) emissions are extremely needed for the application of cold light sources, accurate CL quantitative analysis, and biological mapping. In this work, the flashtype system of luminol was altered to a long lasting CL system just because of the paper substrate. The Cu(II)-based organic complex was loaded on the paper surface, which can trigger luminol-H₂O₂ to produce a long lasting CL emission for over 30 min. By using 1,10-phenanthroline-2,9-dicarboxylic acid (PDA) as the ligand, a hexacoordinated Cu(II)-based organic complex was synthesized by the simple freeze-drying method. It is interesting that the complex morphology can be controlled by adding different amounts of water in the synthesizing procedure. The complex with a certain size can be definitely trapped in the pores of the cellulose. Then, slow diffusion, which can be attributed to the long lasting CL emission, was produced. With the high catalytic activity of the complex, reactive oxygen species from H₂O₂ was generated and was responsible for the high CL intensity. By using the paper substrate, the flash-type luminol system can be easily transferred to the long-duration CL system without any extra reagent. This long-lasting emission system was used for hydrogen sulfide detection by the CL imaging method. This paper-based sensor has great potential for CL imaging in the clinical field in the future.

Paper-based Chemiluminescence Device with Co-Fe Nanocubes for Sensitive Detection of Caffeic Acid

In this work, a new chemiluminescence (CL) system of Co-Fe prussian blue analogs nanocubes (Co-Fe PBA NCs) that can catalyze luminol to produce strong CL in the absence of H₂O₂ was established. Co-Fe PBA NCs have the property of oxidase-like activity, and it can catalyze the generation of active oxygen radicals in a dissolved oxygen system. Since caffeic acid (CA) can remove reactive oxygen species in the system, a sensitive detection method for CA on a paper-based chip was developed. Under the optimal conditions, this method showed a good linear response to CA in the range of 10 - 800 ng mL^-1 with a limit of 3 ng mL^-1. The proposed method had been used for the determination of CA in tea samples. The results may open a new avenue for the catalytic property on luminol CL system without extra oxidants.

Gold Nanocluster-catalyzed Luminol Chemiluminescent Sensing Method for Sensitive and Selective Detection of Alkaline Phosphatase

A sensitive sensing method was developed for the determination of alkaline phosphatase (ALP) activity based on gold nanocluster (Au NC)-catalyzed luminol-H2O2 chemiluminescent (CL) reaction. The CL signal of luminol-H2O2-Au NCs can be quenched by ascorbic acid, which was the product of magnesium ascorbyl phosphate (MAP) hydrolysis reaction catalyzed by ALP. The proposed sensing platform showed convenient, sensitive and selective detection of ALP in the range of 0.0027 - 1.3890 U L-1, with the detection limit of 0.0026 U L-1. The broad detection linear range and ultra-high sensitivity were inherited from the efficient free radical scavenging capability of ascorbic acid on the luminol-H2O2-Au NCs CL reaction. The CL sensing platform was applied to the detection of ALP activity in serum samples. We believe that this sensing platform is a universal CL strategy for ALP detection because ascorbic acid is an efficient CL quencher for many CL reactions.

Use of an Artificial Miniaturized Enzyme in Hydrogen Peroxide Detection by Chemiluminescence

Advanced oxidation processes represent a viable alternative in water reclamation for potable reuse. Sensing methods of hydrogen peroxide are, therefore, needed to test both process progress and final quality of the produced water. Several bio-based assays have been developed so far, mainly relying on peroxidase enzymes, which have the advantage of being fast, efficient, reusable, and environmentally safe. However, their production/purification and, most of all, batch-to-batch consistency may inherently prevent their standardization. Here, we provide evidence that a synthetic de novo miniaturized designed heme-enzyme, namely Mimochrome VI*a, can be proficiently used in hydrogen peroxide assays. Furthermore, a fast and automated assay has been developed by using a lab-bench microplate reader. Under the best working conditions, the assay showed a linear response in the 10.0-120 μM range, together with a second linearity range between 120 and 500 μM for higher hydrogen peroxide concentrations. The detection limit was 4.6 μM and quantitation limits for the two datasets were 15.5 and 186 μM, respectively. In perspective, Mimochrome VI*a could be used as an active biological sensing unit in different sensor configurations.

Selective Synthesis and Photoluminescence Study of Pyrazolopyridopyridazine Diones and N-Aminopyrazolopyrrolopyridine Diones

The newly designed luminol structures of pyrazolopyridopyridazine diones and N-aminopyrazolopyrrolopyridine diones were synthesized from versatile 1,3-diaryfuropyrazolopyridine-6,8-diones, 1,3-diarylpyrazolopyrrolopyridine-6,8-diones, or 1,3-diaryl-7-methylpyrazolopyrrolopyridine-6,8-diones with hydrazine monohydrate. Photoluminescent and solvatofluorism properties containing UV–Vis absorption, emission spectra, and quantum yield (Φ_f) study of pyrazolopyridopyridazine diones and N-aminopyrazolopyrrolopyridine diones were also studied. Generally, most of pyrazolopyrrolopyridine-6,8-diones 6 exhibited the significant fluorescence intensity and the substituent effect when compared with N-aminopyrazolopyrrolopyridine diones, particularly for 6c and 6j with a m-chloro group. Additionally, the fluorescence intensity of 6j was significantly promoted due to the suitable conjugation conformation. Based on the quantum yield (Φ_f) study, the value of compound 6j (0.140) with planar structural skeletal was similar to that of standard luminol (1, 0.175).

Preparation, Characterization and Diagnostic Valuation of Two Novel Anti-HPV16 E7 Oncoprotein Monoclonal Antibodies

At present, the clinical detection method of human papillomavirus (HPV) is mainly based on the PCR method. However, this method can only be used to detect HPV DNA and HPV types, and cannot be used to accurately predict cervical cancer. HPV16 E7 is an oncoprotein selectively expressed in cervical cancers. In this study, we prepared an HPV16 E7-histidine (HIS) fusion oncoprotein by using a prokaryotic expression and gained several mouse anti-HPV16 E7-HIS fusion oncoprotein monoclonal antibodies (mAbs) by using hybridoma technology. Two mAbs, 69E2 (IgG2a) and 79A11 (IgM), were identified. Immunocytochemistry, immunofluorescence, immunohistochemistry, and Western blot were used to characterize the specificity of these mAbs. The sequences of the nucleotide bases and predicted amino acids of the 69E2 and 79A11 antibodies showed that they were novel antibodies. Indirect enzyme-linked immunosorbent assay (ELISA) with overlapping peptides, indirect competitive ELISA, and 3D structural modeling showed that mAbs 69E2 and 79A11 specifically bound to the three exposed peptides of the HPV16 E7 (HPV16 E7_49–66, HPV16 E7_73–85, and HPV16 E7_91–97). We used these two antibodies (79A11 as a capture antibody and 69E2 as a detection antibody) to establish a double-antibody sandwich ELISA based on a horseradish peroxidase (HRP)-labeled mAb and tetramethylbenzidine (TMB) detection system for quantitative detection of the HPV16 E7-HIS fusion oncoprotein, however, it was not ideal. Then we established a chemiluminescence immunoassay based on a labeled streptavidin-biotin (LSAB)-ELISA method and luminol detection system—this was sufficient for quantitative detection of the HPV16 E7-HIS fusion oncogenic protein in ng levels and was suitable for the detection of HPV16-positive cervical carcinoma tissues. Collectively, we obtained two novel mouse anti-HPV16 E7 oncoprotein mAbs and established an LSAB-lumino-dual-antibody sandwich ELISA method for the detection of the HPV16 E7-HIS fusion oncogenic protein, which might be a promising method for the diagnosis of HPV16-type cervical cancers in the early stage.

Sensitive Detection of Caffeic Acid and Rutin via the Enhanced Anodic Electrochemiluminescence Signal of Luminol

The electrooxidation of phenolic groups of caffeic acid and rutin promote anodic electrochemiluminescence (ECL) luminol substantially. A sensitive, and cost-effective ECL method has thus been developed to detect caffeic acid, ranging from 0.1 to 5.0 μM, with a detection limit of 0.1 μM and rutin ranging from 0.2 to 25 μM with a detection limit of 0.12 μM. Contrarily, phenolic compounds quench the weak cathodic ECL of luminol. Both of anodic and cathodic ECL mechanisms of luminol in the presence of phenolic compounds are analyzed. The method based on the boomed anodic ECL of luminol is comparable to those based on Ru(bpy)₃²⁺ and S₂O₈^2-/O₂ systems. A lower onset potential and price than the other ECL reagents would realize its widely applications in the detection of phenolic compounds in food and medicine.

Core-shell Au@Pt Nanoparticles Catalyzed Luminol Chemiluminescence for Sensitive Detection of Thiocyanate

In this study, core-shell Au@Pt nanoparticles (Au@Pt NPs) with peroxidase catalytic activity were synthesized by the seed-mediated method, and were used to catalyze the reaction of luminol-H₂O₂ to enhance the chemiluminescence (CL) intensity. It was found that thiocyanate (SCN^-) can effectively inhibit the catalytic activity of Au@Pt NPs. Based on this phenomenon, a method to detect SCN^- by using the Au@Pt NPs-catalytic luminol-H₂O₂ CL system was established, which has an ultra-low detection limit and an ultra-wide linear range, as well as the advantages of being simple and having low-cost and convenient operation. The research mechanism indicated that SCN^- could be adsorbed on the surface of Au@Pt NPs and occupies the active sites of Pt nanostructures, which led to a decrease in the amount of Pt⁰ and a loss of the excellent catalytic activity of Au@Pt NPs. After optimizing the experimental conditions, this assay for detecting SCN^- exhibited a good linear range from 5 to 180 nM, and the low detection limit was 2.9 nM. In addition, this approach has been successfully applied to the detection of SCN^- in tap-water samples, which has practical application value and embodies good development prospects.

Single-Atom Iron Boosts Electrochemiluminescence

The traditional luminol-H₂ O₂ electrochemiluminescence (ECL) sensing platform suffers from self-decomposition of H₂ O₂ at room temperature, hampering its application for quantitative analysis. In this work, for the first time we employ iron single-atom catalysts (Fe-N-C SACs) as an advanced co-reactant accelerator to directly reduce the dissolved oxygen (O₂ ) to reactive oxygen species (ROS). Owing to the unique electronic structure and catalytic activity of Fe-N-C SACs, large amounts of ROS are efficiently produced, which then react with the luminol anion radical and significantly amplify the luminol ECL emission. Under the optimum conditions, a Fe-N-C SACs-luminol ECL sensor for antioxidant capacity measurement was developed with a good linear range from 0.8 μm to 1.0 mm of Trolox.

The horseradish smile: Demonstrating characteristic reactions of peroxidase in a visually appealing way

Easy and visually appealing demonstrations are precious tools for introducing students to the study of enzymes. However, they most often involve purified enzymes and dedicated techniques. Here, we propose a set of demonstrations, which require only fresh horseradish root and consumer chemicals, to help support biochemistry and enzymology courses from high school to the undergraduate level. Horseradish root is a naturally rich source of horseradish peroxidase, an enzyme with many relevant practical applications. Slices of horseradish root are used to demonstrate the characteristic reaction of horseradish peroxidase with hydrogen peroxide, the selective inhibition of this enzyme by dilute hydrochloric acid, its chromogenic reaction with N,N'-diethyl-p-phenylenediamine, and its ability to trigger the chemiluminescent reaction of luminol. © 2019 International Union of Biochemistry and Molecular Biology, 48(1):38-43, 2020.

From Past to Present: The Link Between Reactive Oxygen Species in Sperm and Male Infertility

Reactive oxygen species (ROS) can be generated in mammalian cells via both enzymatic and non-enzymatic mechanisms. In sperm cells, while ROS may function as signalling molecules for some physiological pathways, the oxidative stress arising from the ubiquitous production of these compounds has been implicated in the pathogenesis of male infertility. In vitro studies have undoubtedly shown that spermatozoa are indeed susceptible to free radicals. However, many reports correlating ROS with sperm function impairment are based on an oxidative stress scenario created in vitro, lacking a more concrete observation of the real capacity of sperm in the production of ROS. Furthermore, sample contamination by leukocytes and the drawbacks of many dyes and techniques used to measure ROS also greatly impact the reliability of most studies in this field. Therefore, in addition to a careful scrutiny of the data already available, many aspects of the relationship between ROS and sperm physiopathology are still in need of further controlled and solid experiments before any definitive conclusions are drawn.

Synthesis and Chemiluminescent Properties of Amino-Acylated luminol Derivatives Bearing Phosphonium Cations

The monitoring of reactive oxygen species in living cells provides valuable information on cell function and performance. Lately, the development of chemiluminescence-based reactive oxygen species monitoring has gained increased attention due to the advantages posed by chemiluminescence, including its rapid measurement and high sensitivity. In this respect, specific organelle-targeting trackers with strong chemiluminescence performance are of high importance. We herein report the synthesis and chemiluminescence properties of eight novel phosphonium-functionalized amino-acylated luminol and isoluminol derivatives, designed as mitochondriotropic chemiluminescence reactive oxygen species trackers. Three different phosphonium cationic moieties were employed (phenyl, p-tolyl, and cyclohexyl), as well as two alkanoyl chains (hexanoyl and undecanoyl) as bridges/linkers. Synthesis is accomplished via the acylation of the corresponding phthalimides, as phthalhydrazide precursors, followed by hydrazinolysis. This method was chosen because the direct acylation of (iso)luminol was discouraging. The new derivatives' chemiluminescence was evaluated and compared with that of the parent molecules. A relatively poor chemiluminescence performance was observed for all derivatives, with the isoluminol-based ones being the poorest. This result is mainly attributed to the low yield of the fluorescence species formation during the chemiluminescence oxidation reaction.

Perylene Diimide and Luminol as Potential-Resolved Electrochemiluminescence Nanoprobes for Dual Targets Immunoassay at Low Potential

In the field of clinical diagnosis, it is important to construct a potential-resolved multiplex electrochemiluminescence (ECL) biosensor for decreasing the false-positive rate and improving the diagnostic accuracy. However, the shortage of low-potential cathodic luminophores between -1 and 0 V (vs Ag/AgCl) severely limited the development of the biosensor. Herein, we synthesized a novel luminophore N,N-bis-(3-dimethyl aminopropyl)-3,4,9,10-perylene tetracarboxylic acid diimide (PDI), which gave dual emissions at -0.25/-0.26 V with K₂S₂O₈ as a co-reactant in aqueous solution. The ECL was assigned to excited J-type PDI dimers. Then, PDI and luminol were used as luminophores to respectively combine with graphite oxide and gold nanoparticles and form potential-resolved ECL nanoprobes. Also, this potential-resolved ECL nanoprobes were respectively functionalized by secondary antibodies (Ab₂) to construct a low-potential sandwiched ECL immunosensor for tumor markers carcinoembryonic antigen (CEA) and α-fetoprotein (AFP) simultaneous determination during linear scanning potential range from -0.6 to 0.6 V. The prepared multiplex immunosensor exhibited sensitive ECL response for CEA at -0.6 V due to PDI and that for AFP at 0.6 V due to luminol, and both linear semilogarithmical ranges were from 0.1 pg to 1 ng mL^-1. In addition, PDI with dual ECL peaks showed enticing prospect of built-in self-calibration for a precise quantitative and bioimaging analysis.

Clinical Chemistry Route for Investigation of Alzheimer's Disease: A Label-Free Electrochemiluminescent Biosensor for Glycogen Synthase Kinase-3 Beta

Herein, we report a novel label-free electrochemiluminescent (ECL) biosensor for the detection of glycogen synthase kinase-3 beta (GSK-3β). A simple and feasible sensor was prepared by a two-step process. A polymeric coordination layer of phosphorylated poly vinyl with Zr⁴⁺ was used as the sensory hosting matrix because it efficiently formed a complex. The exterior Zr⁴⁺ can further combine with another phosphate through coordination, and GSK-3β catalyzes the phosphorylation of protein molecules. Thus, the biosensor can detect GSK-3β using luminol as an ECL probe. The ECL intensity of the proposed sensor responded proportionally to the concentration of GSK-3β under direct immersion mode with a linear response in a logarithmic scale over the wide range from 0.5 to 91.5 ng L^-1 and a detection limit of 0.055 ng L^-1. Excellent selectivity, stability, and reproducibility were achieved using the prepared biosensor, which has a simple preparation, low cost, and disposable suitability. This work aims to provide a novel tool for early diagnosis and pathological mechanism exploration about AD by detecting inchoate change of GSK-3β content in body fluid, thus to precaution the risk of Alzheimer's disease. It is of great importance for clinical chemistry for the investigation of Alzheimer's disease.

Water-soluble Hemin-mPEG-enhanced Luminol Chemiluminescence for Sensitive Detection of Hydrogen Peroxide and Glucose

In the present study, we synthesized a water-soluble substance (Hemin-mPEG) at room temperature by using hemin and poly(ethylene glycol) methyl ether (mPEG). It was found that the Hemin-mPEG maintained the excellent catalytic activity inherited from hemin, and was first used to catalyze a luminol-H₂O₂ chemiluminescence (CL) system to generate an intense and slow CL signal. The results of a mechanism research showed that the presence of Hemin-mPEG could promote the production of oxygen-relative radicals from H₂O₂ and dissolved oxygen in solution. Based on this mechanism, an ultra-sensitive, cheap and simply practical sensor for detecting glucose and H₂O₂ was developed. Under the most optimal experimental conditions, H₂O₂ and glucose detection results exhibited a good linear range from 0.002 to 3 μM and from 0.02 to 4 μM, respectively, and the detection limits were 1.8 and 10 nM, respectively. This approach has been successfully used to detect glucose in actual biological samples, and achieved good results.

Bioluminescence Imaging of Inflammation in Vivo Based on Bioluminescence and Fluorescence Resonance Energy Transfer Using Nanobubble Ultrasound Contrast Agent

Inflammation is an immunological response involved in various inflammatory disorders ranging from neurodegenerative diseases to cancers. Luminol has been reported to detect myeloperoxidase (MPO) activity in an inflamed area through a light-emitting reaction. However, this method is limited by low tissue penetration and poor spatial resolution. Here, we fabricated a nanobubble (NB) doped with two tandem lipophilic dyes, red-shifting luminol-emitted blue light to near-infrared region through a process integrating bioluminescence resonance energy transfer (BRET) and fluorescence resonance energy transfer (FRET). This BRET-FRET process caused a 24-fold increase in detectable luminescence emission over luminol alone in an inflammation model induced by lipopolysaccharide. In addition, the echogenicity of the BRET-FRET NBs also enables perfused tissue microvasculature to be delineated by contrast-enhanced ultrasound imaging with high spatial resolution. Compared with commercially available ultrasound contrast agent, the BRET-FRET NBs exhibited comparable contrast-enhancing capability but much smaller size and higher concentration. This bioluminescence/ultrasound dual-modal contrast agent was then successfully applied for imaging of an animal model of breast cancer. Furthermore, biosafety experiments revealed that multi-injection of luminol and NBs did not induce any observable abnormality. By integrating the advantages of bioluminescence imaging and ultrasound imaging, this BRET-FRET system may have the potential to address a critical need of inflammation imaging.

[The comparison of two chemiluminescent models for assessing anti-oxidative activity of blood serum of patients with liver pathology]

The comparative assessment was carried out concerning anti-oxidation activity of blood serum of patients with liver pathology using two chemiluminescent techniques with different models of free radical oxidation: «Hb-Н2О2-luminol» и «ABAP-luminol». The reliable but low correlation of results was established (r=0,798) related mainly to difference in mechanisms of initiation of free radicals and effect of blood serum on initiation process. This effect is stronger manifested in model «Hb-Н2О2-luminol». The discrepancy of results of measurement is more expressed in patients with anomalous higher content of bilirubin in blood. Thereupon, oxidation model «ABAP-luminol» is to be considered as a more preferable for clinical practice.

Evaluation of Bluestar® Forensic Magnum and Other Traditional Blood Detection Methods on Bloodstained Wood Subjected to a Variety of Burn Conditions

Accurate blood detection is a primary concern for forensic scientists, especially in highly compromised situations. In this study, blood was added to wood blocks and subjected to a variety of fire treatments: the absence or presence of accelerant, burn time (1, 3, or 5 min), and extinguishment method (smothering or dousing with water). Burned blocks were given a qualitative burn score, followed by removal of half of the char from each block and subsequent testing of each half for blood using luminol (13% positive; n = 96), Bluestar^® Forensic Magnum (5.2% positive; n = 96), and combined phenolphthalein tetramethylbenzidine test (0% positive; n = 192). Luminol and Bluestar® Forensic Magnum performed similarly, both outperforming PTMB. Additionally, positive results were more likely from samples that were smothered, had a low burn score, and had more concentrated blood solutions (neat or 1:2). Overall, it is extremely unlikely that blood would be detected on combustible substrates exposed to direct fire.

DNA Origami and G-Quadruplex Hybrid Complexes Induce Size Control of Single-Walled Carbon Nanotubes via Biological Activation

DNA self-assembly has enabled the programmable fabrication of nanoarchitectures, and these nanoarchitectures combined with nanomaterials have provided several applications. Here, we develop an approach for cutting single-walled carbon nanotubes (SWNTs) of predetermined lengths, using DNA origami and G-quadruplex hybrid complexes. This approach is based on features of DNA: (1) wrapping SWNTs with DNA to improve the dispersibility of SWNTs in water; (2) using G-quadruplex DNA to confine hemin in close proximity to SWNTs and enhance the biological activation of hydrogen peroxide by hemin; and (3) forming DNA origami platforms to allow for the precise placement of G-quadruplexes, enabling size control. These integrated features of DNA allow for temporally efficient cutting of SWNTs into desired lengths, thus expanding the availability of SWNTs for applications in the fields of nanoelectronics, nanomedicine, nanomaterials, and quantum physics, as well as in fundamental studies.

Detection of Visually Imperceptible Blood Contamination in the Oral Surgical Clinic using Forensic Luminol Blood Detection Agent

Aim and Objectives:

Oral surgical procedures can cause spread of infections in the clinics through visually imperceptible, splattered, and aerosolized blood. The aim of this study was to evaluate visually imperceptible blood contamination of clinical surfaces and personal protective equipment (PPE) in an oral surgery clinic using luminol.

Materials and Methods:

Following ethical approval, oral surgical procedures were performed under local anesthesia in a disinfected clinic, and PPE was used by the oral surgeon, dental assistant, and patients. After the procedure, clinical surfaces and PPE were evaluated for traces of visually imperceptible blood contamination using luminol. Data regarding blood contamination and the duration of the procedure were collected. Nonparametric tests, with 95% significance level (Epi Info, Stat Calc 7, CDC, Atlanta, USA), were used to identify statistical interactions between the duration of the procedure and the frequency of blood contamination.

Results:

Blood contamination was detected in flooring below surgical field (86.67%), instrument tray, operating light, dental chair, and suction unit (100%). Except head caps and shoe covers, blood contamination was detected in all the PPE used by the clinical personnel, and the eyewear and chest drapes used by patients. An increase in the surgical time beyond 40 min significantly increased the risk of blood contamination in the handcuffs of the clinical personnel (P < 0.01).

Discussion and Conclusion:

Visually imperceptible blood contamination of the clinical surfaces and PPE is associated with minor oral surgical procedures. This mandates the cleaning and disinfection of all clinical surfaces before and after minor oral surgical procedures and PPE for clinicians and patients during every procedure.

Flow-Injection Chemiluminescence Method for Sensitive Determination of Ascorbic Acid in Fruit Juices and Pharmaceutical Samples Using a Luminol-Cetyltrimethylammonium Chloride Reversed Micelle System

A highly sensitive flow-injection (FI) method was developed for the determination of ascorbic acid using chemiluminescence (CL) based detection. This method involved the following processes: (1) reduction of tetrachloroaurate(III) in hydrochloric acid with ascorbic acid; (2) on-line extraction of the residual Au(III) with rhodamine B from the aqueous hydrochloric acid solution into toluene, followed by the separation of the Au(III)-containing organic phase from the aqueous phase through a microporous Teflon membrane in the flow system; and (3) the measurement of CL produced in a flow cell upon mixing of the extract stream of Au(III) in toluene with luminol in the reversed micellar medium of cetyltrimethylammonium chloride-water in 1-hexanol-cyclohexane, which was injected into a CL reagent stream. In this procedure, a reduction in the CL intensity occurred due to the addition of ascorbic acid to the Au(III) solution. The CL signal of Au(III) decreased with increasing concentration of ascorbic acid in the aqueous sample solution. The proposed procedure allowed the indirect quantitative determination of ascorbic acid in the range of 1.0 × 10^-12 to 1.0 × 10^-7 M with a correlation coefficient of 0.987 and relative standard deviation of 2.1% (n = 6) at 1.0 × 10^-9 M. The proposed FI-CL methodology was successfully applied for quantitative determination of ascorbic acid in fruit juices and pharmaceutical samples.

[Development and Application of Catalytic Tyrosine Modification]

 The chemical labeling of proteins with synthetic probes is a key technique used in chemical biology, protein-based therapy, and material science. Much of the chemical labeling of native proteins, however, depends on the labeling of lysine and cysteine residues. While those methods have significantly contributed to native protein labeling, alternative methods that can modify different amino acid residues are still required. Herein we report the development of a novel methodology of tyrosine labeling, inspired by the luminol chemiluminescence reaction. Tyrosine residues are often exposed on a protein's surface and are thus expected to be good targets for protein functionalization. In our studies so far, we have found that 1) hemin oxidatively activates luminol derivatives as a catalyst, 2) N-methyl luminol derivative specifically forms a covalent bond with a tyrosine residue among the 20 kinds of natural amino acid residues, and 3) the efficiency of tyrosine labeling with N-methyl luminol derivative is markedly improved by using horseradish peroxidase (HRP) as a catalyst. We were able to use molecular oxygen as an oxidant under HRP/NADH conditions. By using these methods, the functionalization of purified proteins was carried out. Because N-methyl luminol derivative is an excellent protein labeling reagent that responds to the activation of peroxidase, this new method is expected to open doors to such biological applications as the signal amplification of HRP-conjugated antibodies and the detection of protein association in combination with peroxidase-tag technology.

Role of Transient Receptor Potential Ankyrin 1 Ion Channel and Somatostatin sst4 Receptor in the Antinociceptive and Anti-inflammatory Effects of Sodium Polysulfide and Dimethyl Trisulfide

Transient receptor potential ankyrin 1 (TRPA1) non-selective ligand-gated cation channels are mostly expressed in primary sensory neurons. Polysulfides (POLYs) are Janus-faced substances interacting with numerous target proteins and associated with both protective and detrimental processes. Activation of TRPA1 in sensory neurons, consequent somatostatin (SOM) liberation and action on sst4 receptors have recently emerged as mediators of the antinociceptive effect of organic trisulfide dimethyl trisulfide (DMTS). In the frame of the present study, we set out to compare the participation of this mechanism in antinociceptive and anti-inflammatory effects of inorganic sodium POLY and DMTS in carrageenan-evoked hind-paw inflammation. Inflammation of murine hind paws was induced by intraplantar injection of carrageenan (3% in 30 µL saline). Animals were treated intraperitoneally with POLY (17 µmol/kg) or DMTS (250 µmol/kg) or their respective vehicles 30 min prior paw challenge and six times afterward every 60 min. Mechanical pain threshold and swelling of the paws were measured by dynamic plantar aesthesiometry and plethysmometry at 2, 4, and 6 h after initiation of inflammation. Myeloperoxidase (MPO) activity in the hind paws were detected 6 h after challenge by luminescent imaging. Mice genetically lacking TRPA1 ion channels, sst4 receptors and their wild-type counterparts were used to examine the participation of these proteins in POLY and DMTS effects. POLY counteracted carrageenan-evoked mechanical hyperalgesia in a TRPA1 and sst4 receptor-dependent manner. POLY did not influence paw swelling and MPO activity. DMTS ameliorated all examined inflammatory parameters. Mitigation of mechanical hyperalgesia and paw swelling by DMTS were mediated through sst4 receptors. These effects were present in TRPA1 knockout animals, too. DMTS inhibited MPO activity with no participation of the sensory neuron-SOM axis. While antinociceptive effects of POLY are transmitted by activation of peptidergic nerves via TRPA1, release of SOM and its effect on sst4 receptors, those of DMTS partially rely on SOM release triggered by other routes. SOM is responsible for the inhibition of paw swelling by DMTS, but TRPA1 does not contribute to its release. Modulation of MPO activity by DMTS is independent of TRPA1 and sst4.

Novel Iron(III)-Based Metal-Organic Gels with Superior Catalytic Performance toward Luminol Chemiluminescence

Novel metal-organic gels (MOGs) consisting of iron (Fe³⁺) as the central ion and 1,10-phenanthroline-2,9-dicarboxylic acid (PDA) as the ligand were synthesized by a mild facile strategy. The Fe(III)-containing metal-organic xerogels (Fe-MOXs), obtained after removing the solvents in MOGs, were found to exhibit outstanding performance in the catalysis of luminol chemiluminescence (CL) for the first time even in the absence of extra oxidants such as hydrogen peroxide. The possible CL mechanism was discussed according to the electro/optical measurements, including electron paramagnetic resonance (EPR), UV-vis absorption, and CL spectra, as well as the effects of radical scavengers on Fe-MOXs-catalyzed luminol CL system, suggesting that the CL emission of luminol might originate from the intrinsic oxidase-like catalytic activity of Fe-MOXs on the decomposition of dissolved oxygen. Additionally, the potential practical application of the resulting luminol-Fe-MOXs system was evaluated by the quantitative analysis of dopamine. Good linearity over the range from 0.05 to 0.6 μM was obtained with the limit of detection (LOD, 3σ) of 20.4 nM and acceptable recoveries ranging from 98.6 to 105.4% in human urine. These results may open up the promising application of novel metal-organic gels as highly effective catalysts in the field of chemiluminescence.

Ultrasound-mediated drug delivery by gas bubbles generated from a chemical reaction

Highly echogenic and ultrasound-responsive microbubbles such as nitrogen and perfluorocarbons have been exploited as ultrasound-mediated drug carriers. Here, we propose an innovative method for drug delivery using microbubbles generated from a chemical reaction. In a novel drug delivery system, luminol encapsulated in folate-conjugated bovine serum albumin nanoparticles (Fol-BSAN) can generate nitrogen gas (N₂) by chemical reaction when it reacts with hydrogen peroxide (H₂O₂), one of reactive oxygen species (ROS). ROS plays an important role in the initiation and progression of cancer and elevated ROS have been observed in cancer cells both in vitro and in vivo. High-intensity focussed ultrasound (HIFU) is used to burst the N₂ microbubbles, causing site-specific delivery of anticancer drugs such as methotrexate. In this research, the drug delivery system was optimised by using water-soluble luminol and Mobil Composition of Matter-41 (MCM-41), a mesoporous material, so that the delivery system was sensitive to micromolar concentrations of H₂O₂. HIFU increased the drug release from Fol-BSAN by 52.9 ± 2.9% in 10 minutes. The cytotoxicity of methotrexate was enhanced when methotrexate is delivered to MDA-MB-231, a metastatic human breast cancer cell line, using Fol-BSAN with HIFU. We anticipate numerous applications of chemically generated microbubbles for ultrasound-mediated drug delivery.

Development of an Evaluation Method for Hydroxyl Radical Scavenging Activities Using Sequential Injection Analysis with Chemiluminescence Detection

A method for evaluating hydroxyl radical (·OH) scavenging activities using sequential injection analysis (SIA) with chemiluminescence (CL) detection was developed. In this system, CL was produced by the reaction of luminol with ·OH generated from the Fenton reaction. The scavenging activity was expressed as a diminution rate of the CL due to the scavenging of ·OH by a sample. The SIA system allows the automation of a series of experimental procedures including Fenton's reaction, scavenging of ·OH, and luminol CL reaction. The evaluation of scavenging activities in one sample (n = 3) was completed within 3.0 min. Relative standard deviations (n = 3) of scavenging activity with 700 μM L-ascorbic acid were 2.6% (intraday) and 3.7% (interday). The SIA-CL system was applied to measure ·OH scavenging activities of several antioxidants and pharmaceuticals.

A review of electrogenerated chemiluminescent biosensors for assays in biological matrices

Electrogenerated chemiluminescence (ECL) is the production of light via electron transfer reactions between electrochemically produced reagents. ECL-based biosensors use specific biological interactions to recognize an analyte and produce a luminescent signal. Biosensors fabricated with novel biorecognition species have increased the number of analytes detected. Some of these analytes include peptides, cells, enzymes and nucleic acids. ECL biosensors are selective, simple, sensitive and have low detection limits. Traditional methods use ruthenium complexes or luminol to generate ECL. Nanomaterials can be incorporated into ECL biosensors to improve efficiency, but also represent a new class of ECL emitters. This article reviews the application of ruthenium complex, luminol and nanomaterial-based ECL biosensors to making measurements in biological matrices over the past 4 years.

Improving Luminol Blood Detection in Forensics

The aim of this study was to develop chemical improvements to the original Weber protocol, in order to increase the intensity and time length of light emission and to eliminate false-positive reactions. The intensity and duration of light were measured on serial blood dilutions using a plate reader chemiluminometer. Blood stains of various concentrations were impregnated in pure cellulose, dried, and luminol solution was added with/without the potential enhancers. An in silico study was also conducted, aiming to demonstrate the enhancing mechanism of hemoglobin denaturation using 8 M urea. The luminol blood detection test revealed important improvements after urea pretreatment or in the presence of monochloro-triazinyl-β-cyclodextrin. This approach also eliminated the false-positive reaction from sodium hypochlorite. These improvements could provide a higher sensitivity under particular circumstances such as old or washed blood stains, leading to a better localization for further DNA typing and higher quality photographic analysis.