Electrochemical DNA Sensor Designed Using the Pencil Graphite Electrode to Detect Listeria monocytogenes

In the present work, a novel electrochemical DNA sensor was designed to detect L. monocytogenes. Two different gene fragments were selected for the sensor design. One is a 702 bp long fragment of the hlyA gene, encoding the synthesis of listeriolysin O toxin, which is unique only to pathogenic strains of L. monocytogenes and is essential for pathogenicity. The other is a 209 bp long fragment of the 16 S RNA gene found in all species of the Listeria genus. As the working electrode, the pencil graphite electrode was modified in various ways (activated or covered with polypyrrole), and six different combinations were constituted using three types of the modified working electrode and two different gene fragments. The developed system is based on differential pulse voltammetric transduction of guanine oxidation after hybridization between the selected gene fragment (38 µg/mL) and the selected fragment-specific inosine-modified probe (1.8 µmol/L) immobilized on a pencil graphite electrode surface. The comparison of all combinations demonstrates that the best results are obtained with the combination formed from a polypyrrole-coated pencil graphite electrode (prepared at 2 scans) and 702 bp fragment of the hlyA gene. The analysis time is less than 1 hour, and the necessary DNA concentrations for the analysis have been determined as 8.2 × 10-11 M DNA and 2.7 × 10-10 M DNA respectively, for the hlyA gene and 16 S RNA gene.

Oxidative stress in the brain-lung crosstalk: cellular and molecular perspectives

Oxidative stress is caused by an imbalance between the production of reactive oxygen species (ROS) and the body's ability to counteract their harmful effects, playing a key role in the pathogenesis of brain and lung-related diseases. This review comprehensively examines the intricate mechanisms by which oxidative stress influences cellular and molecular pathways, contributing to neurodegenerative, cardiovascular, and respiratory disorders. Emphasizing the detrimental effects on both brain and lung health, we discuss innovative diagnostic biomarkers, such as 8-hydroxy-2'-deoxyguanosine (8-OHdG), and the potential of antioxidant therapies. For these topics, we provide insights into future research directions in the field of oxidative stress treatment, including the development of personalized treatment approaches, the discovery and validation of novel biomarkers, and the development of new drug delivery systems. This review not only provides a new perspective on understanding the role of oxidative stress in brain and lung-related diseases but also offers new insights for future clinical treatments.

Construction of an electrochemical sensing platform for the sensitive determination of chlorogenic acid in locally consumed bitter coffee known as Mirra

The demand for foods with high antioxidant capacity has increased and research on food analysis continues to increase. Chlorogenic acid is a potent antioxidant molecule and can exhibit various physiological activities. This study aims to analyze Mirra coffee for the determination of chlorogenic acid using an adsorptive voltammetric method. The method is based on the strong synergistic effect between carbon nanotubes and nanoparticles of gadolinium oxide and tungsten, providing sensitive determination of chlorogenic acid. The proposed method yielded a dynamic linear range of 2.5 × 10^-9 ∼ 1.6 × 10^-6 M with a detection limit of 1.08 × 10^-9 M for chlorogenic acid. The amount of chlorogenic acid in Mirra coffee was found to be 46.1 ± 0.69 mg/L by the proposed electrochemical platform.

Luminescent Ruthenium(II) Complexes Used for the Detection of 8-Oxoguanine in the Human Telomeric Sequence

Detecting cancer at the early stage of the disease is crucial to keep the best chance for successful treatment. The recent development of genomic screening, a methodology that is addressed to asymptomatic patients presumably at risk of carcinogenesis, has stimulated the quest for new tools able to signal the level of risk. Carcinogenesis has been associated to chronic oxidative stress exceeding the antioxidant defenses and leading to critical genome alteration levels. The telomeric regions are presumably the most exposed to oxidative stress due to their high concentration of guanine (i.e., the easiest oxidizable nucleic base). Accumulation of 8-oxoguanine in telomeres, thus oxidative lesions, was reportedly associated with telomeric crisis and carcinogenesis. In this study, we report on the capacity of Ru(II) polyazaaromatic complexes to photoprobe 8-oxoguanine into the human telomeric sequence with the view of developing new tools for cancer risk screening.

A sonochemical synthesis of SrTiO3 supported N-doped graphene oxide as a highly efficient electrocatalyst for electrochemical reduction of a chemotherapeutic drug

A sonochemical based green synthesis method playa powerful role in nanomaterials and composite development. In this work, we developed a perovskite type of strontium titanate via sonochemical process. SrTiO₃ particles were incorporated with nitrogen doped graphene oxide through simple ultrasonic irradiation method. The SrTiO₃/NGO was characterized by various analytical methods. The nanocomposite of SrTiO₃/NGO was modified with laser-induced graphene electrode (LIGE). The SrTiO₃/NGO/LIGE was applied for electrochemical sensor towards chemotherapeutic drug detection (nilutamide). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques have been used to examine the electrochemical performance of nilutamide (anti-cancer drug). DPV was found to be more sensitive and found to exhibit a sensitivity 8.627 µA µM^-1 cm^-2 for SrTiO₃/NGO/LIGE with a wide linear range (0.02-892 µM) and low Limit of detection (LOD: 1.16 µM). SrTiO₃/NGO/LIGE has been examined for the detection of nilutamide in blood serum and urine samples and obtained a good recovery in the range of 97.2-99.72 %. The enhanced stability and selectivity and practical application results indicates the suitability of SrTiO₃/NGO/LIGE towards the detection of nilutamide drug in pharmaceutical industries.

Sonochemical construction of hierarchical strontium doped lanthanum trisulfide electrocatalyst: An efficient electrode for highly sensitive detection of ecological pollutant in food and water

Herbicides are used constantly in agriculture to enhance productivity across the globe. This herbicide monitoring requires utmost importance since its high dose leads to ecological imbalance and a negative impact on the environment. Moreover, a quantification of toxic herbicide is one of the important problems in the food analysis. In this work, deals with the development of a simple, and facile one-pot sonochemical synthesis of strontium doped La₂S₃ (Sr@La₂S₃). Morphological and structural characterization confirms the doping of Sr@La₂S₃ to generate a hierarchical layered structure. The electrochemical performance of modified with rotating disk electrode (RDE) using Sr@La₂S₃ composite is high, compared to La₂S₃ and bare electrodes towards the quantitative detection of mesotrione (MTO) in phosphate buffer. Sr@La₂S₃/RDE showed good sensitivity for MTO detection and it exhibit a range of 0.01-307.01 μM and limit of detection of 2.4 nM. Besides, the selectivity of fabricated electrode is high as it can electrochemically reduce MTO particularly, even in the presence of other chemicals, biological molecules and inorganic ions. The repeatability of MTO detection is high even after 30 days with a lower RSD values. Hence, simple fabrication of Sr@La₂S₃/RDE could be a novel electrode for the sensitive, selective, and reproducible determination of herbicides in real-time applications.

An optical and electrochemical sensor based on L-arginine functionalized reduced graphene oxide

The electrochemical and photochemical properties of graphene derivatives could be significantly improved by modifications in the chemical structure. Herein, reduced graphene oxide (RGO) was functionalized with L-arginine (L-Arg) by an amidation reaction between the support and amino acid. Deposition of a powerful ligand, L-Arg, on the optically active support generated an effective optical chemosensor for the determination of Cd(II), Co(II), Pb(II), and Cu(II). In addition, L-Arg-RGO was used as an electrode modifier to fabricate L-Arg-RGO modified glassy-carbon electrode (L-Arg-RGO/GCE) to be employed in the selective detection of Pb(II) ions by differential pulse anodic stripping voltammetry (DP-ASV). L-Arg-RGO/GCE afforded better results than the bare GCE, RGO/GCE, and L-Arg functionalized graphene quantum dot modified GCE. The nanostructure of RGO, modification by L-Arg, and homogeneous immobilization of resultant nanoparticles at the electrode surface are the reasons for outstanding results. The proposed electrochemical sensor has a wide linear range with a limit of detection equal to 0.06 nM, leading to the easy detection of Pb(II) in the presence of other cations. This research highlighted that RGO as a promising support of optical, and electrochemical sensors could be used in the selective, and sensitive determination of transition metals depends on the nature of the modifier. Moreover, L-Arg as an abundant amino acid deserves to perch on the support for optical, and electrochemical determination of transition metals.

Graphene-Based Biosensors for Molecular Chronic Inflammatory Disease Biomarker Detection

Chronic inflammatory diseases, such as cancer, diabetes mellitus, stroke, ischemic heart diseases, neurodegenerative conditions, and COVID-19 have had a high number of deaths worldwide in recent years. The accurate detection of the biomarkers for chronic inflammatory diseases can significantly improve diagnosis, as well as therapy and clinical care in patients. Graphene derivative materials (GDMs), such as pristine graphene (G), graphene oxide (GO), and reduced graphene oxide (rGO), have shown tremendous benefits for biosensing and in the development of novel biosensor devices. GDMs exhibit excellent chemical, electrical and mechanical properties, good biocompatibility, and the facility of surface modification for biomolecular recognition, opening new opportunities for simple, accurate, and sensitive detection of biomarkers. This review shows the recent advances, properties, and potentialities of GDMs for developing robust biosensors. We show the main electrochemical and optical-sensing methods based on GDMs, as well as their design and manufacture in order to integrate them into robust, wearable, remote, and smart biosensors devices. We also describe the current application of such methods and technologies for the biosensing of chronic disease biomarkers. We also describe the current application of such methods and technologies for the biosensing of chronic disease biomarkers with improved sensitivity, reaching limits of detection from the nano to atto range concentration.

Development of a Dy2O3@Eu2O3-carbon nanofiber based electrode for highly sensitive detection of papaverine

A sensitive electrochemical method based on carbon nanofibers (CNFs) and bimetallic nanoparticles of dysprosium oxide (Dy₂O₃) and europium oxide (Eu₂O₃) was developed for the determination of papaverine in pharmaceuticals and human urine. Several electrodes were compared in respect to their electrochemically active surface area calculated as 0.0603, 0.1300, 0.3440, 0.3740 and 0.4990 cm² for bare GCE, CNFs/GCE, Eu₂O₃-CNFs/GCE, Dy₂O₃-CNFs/GCE and Dy₂O₃@Eu₂O₃-CNFs/GCE, respectively. Electrodes were also compared in respect to their performance towards the voltammetric process of papaverine. The peak potential (Epa) of papaverine was 1.094 V, 0.993 V, 0.978 V, 0.969 V and 0.966 V at unmodified GCE, CNFs/GCE, Eu₂O₃-CNFs/GCE, Dy₂O₃-CNFs/GCE and Dy₂O₃@Eu₂O₃-CNFs/GCE, respectively. This indicated that the oxidation peak potential of papaverine shifted gradually towards the negative potentials and the peak current increased gradually from unmodified GCE to CNFs/GCE, Eu₂O₃-CNFs/GCE, Dy₂O₃-CNFs/GCE and Dy₂O₃@Eu₂O₃-CNFs/GCE. The influence of experimental parameters such as scan rate and pH on the voltammetry of papaverine was studied. The Dy₂O₃@Eu₂O₃-CNFs/GCE system presented a dynamic working range between 1.0 × 10^-7 and 2.0 × 10^-6 M with a detection limit of 1.0 × 10^-8 M for papaverine. The platform (Dy₂O₃@Eu₂O₃-CNFs/GCE) exhibited excellent sensitivity and selectivity for papaverine in the presence of uric acid and was successfully applied for determining papaverine in pharmaceuticals and urine samples.

Nanostructured material-based electrochemical sensing of oxidative DNA damage biomarkers 8-oxoguanine and 8-oxodeoxyguanosine: a comprehensive review

Oxidative DNA damage plays an important role in the pathogenesis of various diseases. Among oxidative DNA lesions, 8-oxoguanine (8-oxoG) and its corresponding nucleotide 8-oxo-2'-deoxyguanosine (8-oxodG), the guanine and deoxyguanosine oxidation products, have gained much attention, being considered biomarkers for oxidative DNA damage. Both 8-oxoG and 8-oxodG are used to predict overall body oxidative stress levels, to estimate the risk, to detect, and to make prognosis related to treatment of cancer, degenerative, and other age-related diseases. The need for rapid, easy, and low-cost detection and quantification of 8-oxoG and 8-oxodG biomarkers of oxidative DNA damage in complex samples, urine, blood, and tissue, caused an increasing interest on electrochemical sensors based on modified electrodes, due to their high sensitivity and selectivity, low-cost, and easy miniaturization and automation. This review aims to provide a comprehensive and exhaustive overview of the fundamental principles concerning the electrochemical determination of the biomarkers 8-oxoG and 8-oxodG using nanostructured materials (NsM), such as carbon nanotubes, carbon nanofibers, graphene-related materials, gold nanomaterials, metal nanoparticles, polymers, nanocomposites, dendrimers, antibodies and aptamers, and modified electrochemical sensors.

Sonochemical approach to the synthesis of metal tungstate/nafion composite with electrocatalytic properties and its electrochemical sensing performance

High-intensity ultrasound can be used to produce novel materials, offering an atypical pathway to recognized products without high bulk temperatures, high pressures, or long reaction times. A highly sensitive and selective robust modified sensor was developed using a composition of electrochemically active strontium metal (Sr) based tungstate interconnected with nafion polymer through a facile sonochemical approach. In addition, multiple parameters are important for sonochemical methods and specifically nanomaterial or electrocatalyst development during the ultrasonic irradiation. Moreover, high-intensity ultrasonic probe (Ti-horn) was used to synthesis of nanomaterial at 50 kHz and 200 W. The SrWO₄/nafion was characterized via FESEM, EDX and XRD methods. 8-HD-guanosine (8-hydroxydeoxyguanosine) is one of the major byproduct of deoxyribonucleic acid (DNA) oxidation. The concentrations of 8-HD-guanosine within a cell are a measurement of oxidative stress in body and however its excess level in body causes carcinogenic threats. Therefore, the quantification of 8-HD-guanosine in biological samples with high sensitivity is of great significance. The SrWO₄/nafion modified sensor displayed low detection of 14.36 nM and wide linear range (0.025-398.6 µM), compare to previous reports.

Analytical and Structural Studies for the Investigation of Oxidative Stress in Guanine Oligonucleotides

DNA damage plays a decisive role in epigenetic effects. The detection and analysis of DNA damages, like the most common change of guanine (G) to 8-oxo-7,8-dihydroguanine (OG), is a key factor in cancer research. It is especially true for G quadruplex structure (GQ), which is one of the best-known examples of a non-canonical DNA arrangement. In the present work, we provided an overview on analytical methods in connection with the detection of OG in oligonucleotides with GQ-forming capacity. Focusing on the last five years, novel electrochemical tools, like dedicated electrodes, were overviewed, as well as different optical methods (fluorometric assays, resonance light scattering or UV radiation) along with hyphenated detection and structural analysis methods (CD, NMR, melting temperature analysis and nanopore detection) were also applied for OG detection. Additionally, GQ-related computational simulations were also summarized. All these results emphasize that OG detection and the analysis of the effect of its presence in higher ordered structures like GQ is still a state-of-the-art research line with continuously increasing interest.

Facile synthesis of copper ferrite nanoparticles with chitosan composite for high-performance electrochemical sensor

Herein, the synthesis of copper ferrite nanoparticles (CuFe₂O₄ NPs)/chitosan have been prepared by sonochemical route under ultrasonic irradiation bath at 40 kHz and 50 W. A high sensitive and stable modified electrochemical sensor was developed using a composition of copper ferrite nanoparticles coordinated with biopolymer through a facile ultrasound approach. Besides, power and frequency parameters are highly important for sonochemical synthesis and specifically structure, and size of the nanomaterials development during the ultrasonic irradiation time. In this work, ultrasonic bath was used to synthesis of CuFe₂O₄ nanomaterial at 40 kHz with 1 h. CuFe₂O₄/chitosan was characterized by FESEM, EDX, XRD and electrochemical methods. Furthermore, 8-hydroxyguanine is one of biomarker by oxidative stress. The concentrations of 8-hydroxyguanine within a cell are a measurement of oxidative stress in human body. Consequently, the measurement of 8-hydroxyguanine in blood serum samples with high specificity is of greatest importance. The CuFe₂O₄/chitosan modified electrode is displayed a low detection limit of 8.6 nM and long linear range (0.025-697.175 µM).

Facile sonochemical synthesis of rutile-type titanium dioxide microspheres decorated graphene oxide composite for efficient electrochemical sensor

In this reports the facile and green synthesis of rutile-type titanium dioxide nanoparticles decorated graphene oxide nanocomposite via the ultrasonication process (frequency: 50 kHz, Power: 100 W/cm² and Ultrasonic type: Ti-horn). Because, the sonochemical synthesis method is simple, non-explosive and harmless method than other conventional technique. Furthermore, the synthesized material was characterized by various analytical techniques including FESEM, EDX, XRD, EIS and electrochemical methods. Then, the synthesized TiO₂ MPs@GOS composite was applied for the electrocatalytic detection of theophylline (TPL) using CV and amperometric (current-time) techniques. Captivatingly, the modified sensor has excellent electrocatalytic performance with the wider linear range from 0.02 to 209.6 µM towards the determination of theophylline and the LOD and sensitivity of the modified sensor was calculated as 13.26 nM and 1.183 μA·µM^-1·cm^-2, respectively. In addition, a selectivity, reproducibility and stability of the TiO₂ MPs@GOS modified GCE were analyzed towards the determination of theophylline molecule. Finally, the real time application of TiO₂ MPs@GOS modified theophylline sensor was established in serum and drug samples.

Sonochemical synthesis and fabrication of honeycomb like zirconium dioxide with chitosan modified electrode for sensitive electrochemical determination of anti-tuberculosis (TB) drug

Herein, novel honeycomb like zirconium dioxide with chitosan (ZrO₂@chitosan) nanocomposite have been designed through a facile ultrasound-assisted method and followed by a simple sonication process (bath-type ultrasound washer; Honda Electronics-W-118T; 100 W/cm² and 300 kHz frequency). After then, as-synthesized ZrO₂@chitosan was characterized by FESEM, XRD and EIS. The ZrO₂@chitosan nanocomposite modified glassy carbon electrode shows excellent electrochemical sensing performance towards anti-tuberculosis drug (rifampicin). Furthermore, the ZrO₂@chitosan modified and fabricated electrochemical sensor showed a wide linear range between 0.015 µM and 547.4 µM and nanomolar detection limit (7.5 nM). Moreover, the ZrO₂@chitosan modified electrode showed selectivity towards the detection of anti-tuberculosis drug (rifampicin). The ZrO₂@chitosan nanocomposite film modified non-enzymatic sensor has high stable and good reproducible towards the detection of rifampicin. In addition, the as-synthesized ZrO₂@chitosan nanocomposite modified electrode has been applied to the determination of rifampicin in biological samples such as human serum and urine samples.

A sensitive electrochemical determination of chemotherapy agent using graphitic carbon nitride covered vanadium oxide nanocomposite; sonochemical approach

We have developed a graphitic carbon nitride covered vanadium oxide nanocomposite (V₂O₅@g-C₃N₄) by a simple sonochemical approach (50 kHz and 150 W/cm²). Furthermore, the morphology and chemical composition of the V₂O₅@g-C₃N₄ nanocomposite was carried out by X-rays diffractometry (XRD), transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS). Furthermore, the V₂O₅@g-C₃N₄ nanocomposite modified electrode was investigate electrochemical behavior of the anticancer drug. Compared with bare SPCE, V₂O₅/SPCE and g-C₃N₄/SPCE, V₂O₅@g-C₃N₄ modified SPCE showed highest current response towards anti-cancer drug (methotrexate). Furthermore, the modified sensor exhibits with a sharp peaks and wide linear range (0.025-273.15 μM) by using DPV with the sensitivity of 7.122 μA μM^-1 cm^-2. Notably, we have achieved a nanomolar detection limit (13.26 nM) for the DPV detection of methotrexate. Further, the practicability of the V₂O₅@g-C₃N₄ nanocomposite modified sensor can be used for real time sensing of methotrexate in drug and blood serum samples with good recover ranges. It has potential applications in routine analysis with high specificity, excellent reproducibility and good stability.

A novel electrochemical sensor for determination of DNA damage biomarker (8-hydroxy-2'-deoxyguanosine) in urine using sonochemically derived graphene oxide sheets covered zinc oxide flower modified electrode

To explore a novel and multi-layer based graphene oxide covered zinc oxide nanoflower (ZnO NFs@GOS) as a modified electrode materials by sonochemical technique (40 kHz, 300 W). Herein, novel nanocomposite is successfully characterized by various characterization analysis (FESEM, HRTEM, XRD, XPS and (EIS) electrochemical impedance spectroscopy) and employed as high sensitive modified electrode (ZnO NFs@GOS nanocomposite) for the electrochemical determination of biomarker. 8-hydroxy-2'-deoxyguanosine (8-HDG) is one of the important cancer and oxidative stress biomarker. The results demonstrated that the ZnO NFs@GOS modified SPCE reveal well-defined electro-oxidation peak at 0.36 V (vs. Ag/AgCl). The high sensitive properties of the optimized flower like modified electrode are because of the excellent synergistic effect of the ZnO flower and the graphene oxide nanosheets, as evidenced by a superior bio-sensing performance. The nanocomposite fabricated modified biosensor was facilitating the analysis of 8-HDG in the concentration ranges of 0.05-536.5 µM with a low detection limit is 8.67 nM. The ZnO NFs@GOS modified sensor can also employed for the determination of 8-HDG in human urine samples, promising its application towards the quantification of cancer biomarker in biological samples.

Developing green sonochemical approaches towards the synthesis of highly integrated and interconnected carbon nanofiber decorated with Sm2O3 nanoparticles and their use in the electrochemical detection of toxic 4-nitrophenol

Highly integrated and interconnected carbon nanofiber hybrid nanofibers decorated with samarium(III) oxide (Sm₂O₃ NPs) nanoparticles was synthesized by ultrasound assisted method and characterized using X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), energy dispersive x-rays (EDX), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The electrocatalytic activity (ECA) was monitored by detection of toxic 4-nitrophenol under phosphate buffer (pH 7.0). The sonochemical route employed was efficient to prepare Sm₂O₃ NPs modified electrode and this class of catalysts might be active electrocatalyst for the detection of 4-nitrophenol in drinking water. The screen-printed carbon electrode (SPCE) modified with Sm₂O₃ NPs@f-CNFs was fabricated in a facile way for the sensitively electrochemical determination of 4-nitrophenol. Under optimized preparation conditions, the electrochemical testing (differential pulse voltammetry) of 4-nitrophenol exhibited a reduction peak at -0.64 V. Compared with bare SPCE, Sm₂O₃ NPs, f-CNFs, Sm₂O₃ NPs@f-CNFs modified SPCE showed highest current response. The reduction peaks current vs the concentration of 4-nitrophenol exhibits a linear relation with the concentration range from 0.02 to 387.2 μM and the limit of detection was determined to be M (S/N = 3). In addition, Sm₂O₃ NPs@f-CNFs was contributed to detecting 4-nitrophenol in drinking water and river water samples with the recover ranging from 95.6% to 98.2%.

Biomarkers in Stress Related Diseases/Disorders: Diagnostic, Prognostic, and Therapeutic Values

Various internal and external factors negatively affect the homeostatic equilibrium of organisms at the molecular to the whole-body level, inducing the so-called state of stress. Stress affects an organism's welfare status and induces energy-consuming mechanisms to combat the subsequent ill effects; thus, the individual may be immunocompromised, making them vulnerable to pathogens. The information presented here has been extensively reviewed, compiled, and analyzed from authenticated published resources available on Medline, PubMed, PubMed Central, Science Direct, and other scientific databases. Stress levels can be monitored by the quantitative and qualitative measurement of biomarkers. Potential markers of stress include thermal stress markers, such as heat shock proteins (HSPs), innate immune markers, such as Acute Phase Proteins (APPs), oxidative stress markers, and chemical secretions in the saliva and urine. In addition, stress biomarkers also play critical roles in the prognosis of stress-related diseases and disorders, and therapy guidance. Moreover, different components have been identified as potent mediators of cardiovascular, central nervous system, hepatic, and nephrological disorders, which can also be employed to evaluate these conditions precisely, but with stringent validation and specificity. Considerable scientific advances have been made in the detection, quantitation, and application of these biomarkers. The present review describes the current progress of identifying biomarkers, their prognostic, and therapeutic values.

Biomarkers in Stress Related Diseases/Disorders: Diagnostic, Prognostic, and Therapeutic Values

Various internal and external factors negatively affect the homeostatic equilibrium of organisms at the molecular to the whole-body level, inducing the so-called state of stress. Stress affects an organism's welfare status and induces energy-consuming mechanisms to combat the subsequent ill effects; thus, the individual may be immunocompromised, making them vulnerable to pathogens. The information presented here has been extensively reviewed, compiled, and analyzed from authenticated published resources available on Medline, PubMed, PubMed Central, Science Direct, and other scientific databases. Stress levels can be monitored by the quantitative and qualitative measurement of biomarkers. Potential markers of stress include thermal stress markers, such as heat shock proteins (HSPs), innate immune markers, such as Acute Phase Proteins (APPs), oxidative stress markers, and chemical secretions in the saliva and urine. In addition, stress biomarkers also play critical roles in the prognosis of stress-related diseases and disorders, and therapy guidance. Moreover, different components have been identified as potent mediators of cardiovascular, central nervous system, hepatic, and nephrological disorders, which can also be employed to evaluate these conditions precisely, but with stringent validation and specificity. Considerable scientific advances have been made in the detection, quantitation, and application of these biomarkers. The present review describes the current progress of identifying biomarkers, their prognostic, and therapeutic values.

Detection of 8-Hydroxy-2'-Deoxyguanosine Biomarker with a Screen-Printed Electrode Modified with Graphene

In this work we present the preparation of graphene material by exfoliation of graphite rods via pulses of current in electrolyte, containing a mixture of boric acid (0.05 M) and sodium chloride (0.05 M). The material was morphologically and structurally characterized by SEM/TEM/HR-TEM, XRD and FTIR techniques. TEM investigation of graphene flakes deposited onto carbon-coated grids allowed the visualization of thin and transparent regions, attributed to few-layer graphene (FLG), as well as thick and dark regions attributed to multi-layer graphene (MLG). The mixed composition of the material was additionally confirmed by XRD, which further indicated that the amount of FLG within the sample was around 83%, while MLG was around 17%. The performance of a screen-printed electrode (SPE) modified with graphene (SPE-Gr) was tested for 8-hydroxy-2′-deoxyguanosine detection. The graphene-modified electrode had a higher sensitivity in comparison with that of SPE, both in standard laboratory solutions (phosphate buffered saline—PBS) and in human saliva.

Facile synthesis and characterization of erbium oxide (Er2O3) nanospheres embellished on reduced graphene oxide nanomatrix for trace-level detection of a hazardous pollutant causing Methemoglobinaemia

The nanomaterials have received enormous attention in the catalysis applications. Particularly, we have focused on the fabrication of nanocomposite for an electrochemical sensor with improved electrocatalytic performance. Herein, a rapid and sensitive electrochemical detection of nitrite is essential for assessing the risks facing ecosystems in environment. We report a simple and robust ultrasonic-assisted synthetical route via prepared Er₂O₃ nanoparticles decorated reduced graphene oxide nanocomposite (Er₂O₃ NPs@RGO) modified electrode for nitrite detection. The composition and morphological formation were characterized by XRD, XPS, FESEM, and HRTEM. The amperometric (i-t) and cyclic voltammetry were exhibits tremendous electrocatalytic capability and superior performance toward nitrite oxidation. A sensitive and reproducible amperometric nitrite sensor was fabricated which able to detect trace concentration as 3.69 nM and excellent sensitivity (24.17 µA µM^-1 cm^-2). The method worked well even in cured meat and water samples and the results has indicates the reliability of the method in real-time analysis.

Ultrasound-assisted synthesis of tungsten trioxide entrapped with graphene nanosheets for developing nanomolar electrochemical (hormone) sensor and enhanced sensitivity of the catalytic performance

Herein, we have reported a simple sonochemical synthesis of multi-layer graphene covered tungsten trioxide nanoballs (WO₃ NBs) and the nanocomposite was characterized by FESEM, HRTEM, XRD, XPS, CV and EIS. Furthermore, progesterone (PGT) is a preferred marker for various biological problems like pregnancy problem, mood swings, anxiety, depression, nervousness and body pain. Therefore, its selective and sensitive determination in various biological fluids is beneficial for the evaluation of malformation problems. We describe the fabrication of an amperometric and non-enzymatic biosensor based on WO₃ NBs@GR nanocomposite modified electrode for nanomolar detection of PGT. The results showed that the nanocomposite modified electrode exhibit well-defined electro-oxidation peak compared to bare and control electrodes, demonstrating the superior electrocatalytic ability and performances. The fabricated modified sensor was facilitates the analysis of PGT in the concentration ranges of 0.025-1792.5 µM with a low detection limit of 4.28 nM. Further, the as-prepared WO₃ NBs@GR electrode has been applied to determination of PGT in human blood samples with outstanding recovery results and more importantly, the facile and environment-friendly sonochemical construction strategy extended here, may be open a cost-effective way for setting up the nanocomposites based (bio) sensing platform.

A carbon dot and gold nanoparticle-based fluorometric immunoassay for 8-hydroxy-2'-deoxyguanosine in oxidatively damaged DNA

A method is described for the fluorometric determination of DNA containing oxidatively damaged product 8-hydroxy-2'-deoxyguanosine (DNA-8-OHdG). Carbon dots (CDs) were modified with glutaraldehyde for DNA conjugation, and antibody against 8-OHdG was immobilized on gold nanoparticles (AuNPs). The presence of DNA-8-OHdG can be linked to CDs by reaction of amino groups on DNA with glutaraldehyde. AuNPs were brought closely to CDs by specific immune reaction between 8-OHdG and antibody on AuNPs. Under 350 nm photoexcitation, the emission of CDs with a peak at 440 nm is quenched by the AuNPs and not restored. In the presence of DNA-8-OHdG, the measured fluorescence intensity decreases and quenching efficiency increases. The limit of detection is 700 pM, and the assay works in the 0.01 nM to 25 μM DNA-8-OHdG concentration range. The method is perceived to possess a good potential as a tool for detecting biomarkers for DNA damage due to oxidative stress. Graphical abstract A fluorometric immunoassay for detecting 8-hydroxy-2'-deoxyguanosine (8-OHdG) in oxidatively damaged DNA is reported. It is based on the use of carbon dots (CDs) and gold nanoparticles (AuNPs). Black wavy lines represent DNA. Yellow polygonal sharps represent 8-OHdG. Blue and pink balls represent CDs and AuNPs, respectively.

An electrochemical sensor with a copper oxide/gold nanoparticle-modified electrode for the simultaneous detection of the potential diabetic biomarkers methylglyoxal and its detoxification enzyme glyoxalase

Highly sensitive electro-oxidation of the MGO and GLO biomarkers at the CuO/Au/GCE sensor employing the AdSDPV method.