A human whole blood chemically modified electrode for the hydrogen peroxide reduction and sensing: Real-time interaction studies of hemoglobin in the red blood cell with hydrogen peroxide

Hemozoin anchored MWCNTs for mediated reduction of hydrogen peroxide and real-time intracellular oxidative stress monitoring in colon cancer cells

Hemozoin (HZ, a malarial pigment) is an insoluble crystalline byproduct formed during the intraerythrocytic breakdown of hemoglobin by some blood-feeding parasites, such as Plasmodium falciparum. It consists of polymerized iron-porphyrin molecular units linked by carboxylic bonds. Due to the rigid molecular structure, studying the electron transfer activity of HZ is challenging. In this work, we report the development of a redox-active HZ-functionalized multi-walled carbon nanotube (MWCNT) modified glassy carbon electrode (GCE/MWCNT@HZ-redox). Here, HZ-redox refers to the redox-active form of hemozoin. This electrode is designed to study the electron transfer activity and mimic the peroxidase enzyme's ability to mediate hydrogen peroxide reduction in a neutral pH solution. The modified electrode exhibited a stable and well-defined redox peak at -0.385 V vs. Ag/AgCl in N2-purged PBS (pH 7.0) with a surface excess value of 1.64 × 10-9 mol cm-2. The MWCNT@HZ-redox was characterized using Raman spectroscopy, FT-IR, and FESEM techniques. This biomimicking electrode showed excellent electrocatalytic reduction of H2O2 using cyclic voltammetry. Batch-injection analysis coupled with a screen-printed electrode demonstrated the electroanalytical performance for H2O2 sensing. The electrode exhibited a linear concentration range of 50-300 μM, with a sensitivity of 21 μA μM-1 and a detection limit of 220 nM. As a bioanalytical application, we successfully demonstrated the in situ monitoring of H2O2 within the reactive oxygen species of HCT-116 colon cancer cells under stimulated conditions.

Tailored electrochemical biosensor with poly-diallydimethylammonium chloride-functionalised multiwalled carbon nanotubes/gold nanoparticles/manganese dioxide, and haemoglobin for sensitive hydrogen peroxide detection

A very sensitive electrochemical biosensor, with haemoglobin (Hb) as its basis, has been created to quantify hydrogen peroxide (H2O2), an essential marker in environmental monitoring, food safety, and medical diagnosis. The sensor uses a simple, eco-friendly preparation method. Hb was immobilised on manganese dioxide nanostructure/gold nanoparticles/poly-diallydimethylammonium chloride-functionalised multiwalled carbon nanotubes (PDDA-MWCNT/AuNP/MnO2), characterised using various techniques: amperometry, voltammetry, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Nafion was used as a binder membrane to preserve the biological and electrochemical properties of the protein on the modified electrode. In comparison to earlier research, the novel biosensor had a lower detection limit (1.83 μM) and a limit of quantification (6.11 μM) (S/N = 3) for H2O2. It also exhibited notable reproducibility, long-term stability, and repeatability. It was effectively used to measure the amount of H2O2 in cow milk and orange juice, yielding recoveries in the order of 98.90-99.53 % with RSDs less than 5.0 %, which makes it a promising biosensor for food control.

Electrical Wiring of Malarial Parasite Intermediate Hematin on a Tailored N-Doped Carbon Nanomaterial Surface and Its Bioelectrocatalytic Hydrogen Peroxide Reduction and Sensing

Hematin, an iron-containing porphyrin compound, plays a crucial role in various biological processes, including oxygen transport, storage, and functionality of the malarial parasite. Specifically, hematin-Fe interacts with the nitrogen atom of antimalarial drugs, forming an intermediate step crucial for their function. The electron transfer functionality of hematin in biological systems has been scarcely investigated. In this study, we developed a biomimicking electrical wiring of hematin-Fe with a model N-drug system, represented as {hematin-Fe---N-drug}. We achieved this by immobilizing hematin on a multiwalled carbon nanotube (MWCNT)/N-graphene quantum dot (N-GQD) modified electrode (MWCNT/N-GQD@Hemat). N-GQD serves as a model molecular drug system containing nitrogen atoms to mimic the {hematin-Fe---N-drug} interaction. The prepared bioelectrode exhibited a distinct redox peak at a measured potential (E1/2) of -0.410 V vs Ag/AgCl, accompanied by a surface excess value of 3.54 × 10-9 mol cm-2. This observation contrasts significantly with the weak or electroinactive electrochemical responses documented in literature-based hematin systems. We performed a comprehensive set of physicochemical and electrochemical characterizations on the MWCNT/N-GQD@Hemat system, employing techniques including FESEM, TEM, Raman spectroscopy, IR spectroscopy, and AFM. To evaluate the biomimetic electrode's electroactivity, we investigated the selective-mediated reduction of H2O2 as a model system. As an important aspect of our research, we demonstrated the use of scanning electrochemical microscopy to visualize the in situ electron transfer reaction of the biomimicking electrode. In an independent study, we showed enzyme-less electrocatalytic reduction and selective electrocatalytic sensing of H2O2 with a detection limit of 319 nM. We achieved this using a batch injection analysis-coupled disposable screen-printed electrode system in physiological solution.

A π-π Bonding-Assisted Molecular-Wiring of Folded-Cytochrome c and Naphthoquinone and Its Electron-Relay-Based Bioelectrocatalytic H2O2 Reduction Reaction Visualized by Redox-Competitive Scanning Electrochemical Microscopy

The electron-transfer (ET) reaction of cytochrome c (Cytc) protein with biomolecules is a cutting-edge research area of interest in understanding the functionalities of natural systems. Several electrochemical biomimicking studies based on Cytc-protein-modified electrodes prepared via electrostatic interaction and covalent bonding approaches have been reported. Indeed, natural enzymes involve multiple types of bonding, such as hydrogen, ionic, covalent, and π-π, etc. In this work, we explore a Cytc-protein chemically modified glassy carbon electrode (GCE/CB@NQ/Cytc) prepared via π-π bonding using graphitic carbon as an underlying surface and an aromatic organic molecule, naphthoquinone (NQ), as a cofactor for an effective ET reaction. A simple drop-casting technique-based preparation of GCE/CB@NQ showed a distinct surface-confined redox peak at a standard electrode potential (E°) = -0.2 V vs Ag/AgCl (surface excess = 21.3 nmol cm-2) in pH 7 phosphate buffer solution. A control experiment of modification of NQ on an unmodified GCE failed to show any such unique feature. For the preparation of GCE/CB@NQ/Cytc, a dilute solution of Cytc-pH 7 phosphate buffer was drop-cast on the GCE/CB@NQ surface, wherein the protein folding and denaturalization-based complication and its associated ET functionalities were avoided. Molecular dynamics simulation studies show the complexation of NQ with Cytc at the protein binding sites. The protein-bound surface shows an efficient and selective bioelectrocatalytic reduction performance of H2O2, as demonstrated using cyclic voltammetry and amperometric i-t techniques. Finally, the redox-competition scanning electrochemical microscopy (RC-SECM) technique was adopted for in situ visualization of the electroactive adsorbed surface. The RC-SECM images clearly show the regions of highly bioelectrocatalytic active sites of Cytc-proteins bound to NQ molecules on a graphitic carbon surface. The binding of Cytc with NQ has significant implications for studying the biological electron transport mechanism, and the proposed method provides the requisite framework for such a study.

Boosting Photo-Electro-Fenton Process Via Atomically Dispersed Iron Sites on Graphdiyne for InVitro Hydrogen Peroxide Detection

Hydrogen peroxide (H2 O2 ) is essential in oxidative stress and signal regulation of organs of animal body. Realizing in vitro quantification of H2 O2 released from organs is significant, but faces challenges due to short lifetime of H2 O2 and complex bio-environment. Herein, rationally designed and constructed a photoelectrochemical (PEC) sensor for in vitro sensing of H2 O2 , in which atomically dispersed iron active sites (Hemin) modified graphdiyne (Fe-GDY) serves as photoelectrode and catalyzes photo-electro-Fenton process. Sensitivity of Fe-GDY electrode is enhanced 8 times under illumination compared with dark condition. The PEC H2 O2 sensor under illumination delivers a wide linear range from 0.1 to 48 160 µm and a low detection limit of 33 nm, while demonstrating excellent selectivity and stability. The high performance of Fe-GDY is attributed to, first, energy levels matching of GDY and Hemin that effectively promotes the injection of photo-generated electrons from GDY to Fe3+ for reduced Fe2+ , which facilitates the Fe3+ /Fe2+ cycle. Second, the Fe2+ actively catalyzes H2 O2 to OH- through the Fenton process, thereby improving the sensitivity. The PEC sensor demonstrates in vitro quantification of H2 O2 released from different organs, providing a promising approach for molecular sensing and disease diagnosis in organ levels.

Design of a label-free aptasensor for electrochemical determination of hemoglobin: investigation of the peroxidase-like activity of hemoglobin for the sensing of different substrates

The unbalanced hemoglobin level in biological fluids can cause several diseases; hence it can be used as a biomarker for diagnosis. We aim, in the present study, to construct a label-free electrochemical aptasensor for the quantification of hemoglobin. For that, a conjugate of L-cysteine and gold nanoparticles was used for the aptamer immobilization on screen printed carbon electrodes. Using square wave voltammetry, the calibration plot was obtained and it was linear in the range of 50 ng ml^-1 to 36 000 ng ml^-1 while the detection limit was 1.2 ng ml^-1. After the binding of Hb on the modified screen-printed carbon electrode surface, the peroxidase-like activity of the bound hemoglobin was explored in the quantification of different substrates. Hydrogen peroxide and nitrite were chosen as model analytes. Amperometric measurements showed wide linear ranges: 0.2 μM-7.7 mM and 3.6 nM-1.3 mM for H₂O₂ and nitrite, respectively, with detection limits of 0.044 μM and 0.55 nM. In the proposed strategy, the aptamer provides excellent orientation and a biocompatible environment for hemoglobin whose catalytic activity plays a key role in H₂O₂ and nitrite analysis.

Synthesis and characterization of MXene (Ti3C2Tx)/Iron oxide composite for ultrasensitive electrochemical detection of hydrogen peroxide

Due to the widespread usage of hydrogen peroxide (H₂O₂) in various consumer and industrial products (Examples: fuel cells and antibacterial agents), it became important to accurately detect H₂O₂ concentration in environmental, medical and food samples. Herein, titanium carbide Ti₃C₂T_x (MXene) was synthesized by using Ti, Al and C powders at high-temperature. Then, nanocrystalline iron oxide (α-Fe₂O₃) was obtained from a single solid-phase method. Using Ti₃C₂T_x and Fe₂O₃ powders, Ti₃C₂T_x-Fe₂O₃ nanocomposite was prepared by ultrasonication. As-synthesized, Ti₃C₂T_x-Fe₂O₃ composite had been characterized by UV-Visible (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and Raman spectroscopy. The Fe₂O₃ nanoparticles (NPs) were decorated on the surface of Ti₃C₂T_x as observed by high resolution scanning electron microscopy (HR-SEM) and high resolution transmission electron microscopy (HR-TEM). The Ti₃C₂T_x nanosheets were formed with the average size of 400-500 nm. HR-SEM images of α-Fe₂O₃ showed that the coral-like particles with the average length ~5 μm were obtained_. The electrochemical properties of the individual (Ti₃C₂T_x and α-Fe₂O₃) and composite materials (Ti₃C₂T_x-Fe₂O₃) were investigated by cyclic voltammetry (CV). Ti₃C₂T_x-Fe₂O₃ nanocomposite modified electrode had exhibited potent electro-catalytic activity for H₂O₂ reduction by reducing the overpotential about 320 mV and a linear response was recorded from 10 nM to 1 μM H₂O₂. The optimization of various parameters such as material composition ratio, amount of catalyst, effects of pH, scan rate and interference effects with other biomolecules were carried out. In addition, the kinetic parameters such as rate constant, diffusion coefficient and the active surface area of the electrodes were calculated. Moreover, the Ti₃C₂T_x-Fe₂O₃ composite modified electrode was used successfully to detect H₂O₂ in food and urine samples. We believe that Ti₃C₂T_x-Fe₂O₃ composite based materials could be used for the fabrication of non-enzymatic H₂O₂ sensors for medical diagnosis, food safety and environmental monitoring applications.

Biocompatible MXene (Ti3C2Tx) Immobilized with Flavin Adenine Dinucleotide as an Electrochemical Transducer for Hydrogen Peroxide Detection in Ovarian Cancer Cell Lines

Flavin adenine dinucleotide (FAD) is a coenzyme and acts as a redox cofactor in metabolic process. Owing to such problems as poor electron transfer properties, unfavorable adsorption, and lack of stability on rigid electrodes, the bio-electrochemical applications of FAD have been limited. Herein, a novel fabrication method was developed for the immobilization process using 2D MXene (Ti₃C₂T_x), which enhanced the redox property of FAD and improved the electro-catalytic reduction of hydrogen peroxide (H₂O₂) in neutral medium. The FAD-immobilized Ti₃C₂T_x electrode (FAD/Ti₃C₂T_x) was studied by UV-Visible and Raman spectroscopies, which confirmed the successful adsorption of FAD on the Ti₃C₂T_x surface. The surface morphology and the elemental composition of Ti₃C₂T_x were investigated by high resolution transmission electron microscopy and the energy dispersive X-ray analysis. The redox property of the FAD/Ti₃C₂T_x modified glassy carbon electrode (FAD/Ti₃C₂T_x/GCE) was highly dependent on pH and exhibited a stable redox peak at −0.455 V in neutral medium. Higher amounts of FAD molecules were loaded onto the 2D MXene (Ti₃C₂T_x)-modified electrode, which was two times higher than the values in the reported work, and the surface coverage (ᴦ_FAD) was 0.8 × 10⁻¹⁰ mol/cm². The FAD/Ti₃C₂T_x modified sensor showed the electrocatalytic reduction of H₂O₂ at −0.47 V, which was 130 mV lower than the bare electrode. The FAD/Ti₃C₂T_x/GCE sensor showed a linear detection of H₂O₂ from 5 nM to 2 µM. The optimization of FAD deposition, amount of Ti₃C₂T_x loading, effect of pH and the interference study with common biochemicals such as glucose, lactose, dopamine (DA), potassium chloride (KCl), ascorbic acid (AA), amino acids, uric acid (UA), oxalic acid (OA), sodium chloride (NaCl) and acetaminophen (PA) have been carried out. The FAD/Ti₃C₂T_x/GCE showed high selectivity and reproducibility. Finally, the FAD/Ti₃C₂T_x modified electrode was successfully applied to detect H₂O₂ in ovarian cancer cell lines.

A prototype device of microliter volume voltammetric pH sensor based on carbazole-quinone redox-probe tethered MWCNT modified three-in-one screen-printed electrode

As an alternate for the conventional glass-based pH sensor which is associated with problems like fragile nature, alkaline error, and potential drift, the development of a new redox-sensitive pH probe-modified electrode that could show potential, current-drift and surface-fouling free voltammetric pH sensing is a demanding research interest, recently. Herein, we report a substituted carbazole-quinone (Car-HQ) based new redox-active pH-sensitive probe that contains benzyl and bromo-substituents, immobilized multiwalled carbon nanotube modified glassy carbon (GCE/MWCNT@Car-HQ) and screen-printed three-in-one (SPE/MWCNT@Car-HQ) electrodes for selective, surface-fouling free pH sensor application. This new system showed a well-defined surface-confined redox peak at an apparent standard electrode potential, Eo' = - 0.160 V versus Ag/AgCl with surface-excess value, Γ = 47 n mol cm-2 in pH 7 phosphate buffer solution. When tested with various electroactive chemicals and biochemicals such as cysteine, hydrazine, NADH, uric acid, and ascorbic acid, MWCNT@Car-HQ showed an unaltered redox-peak potential and current values without mediated oxidation/reduction behavior unlike the conventional hydroquinone, anthraquinone and other redox mediators based voltammetry sensors with serious electrocatalytic effects and in turn potential and current drifts. A strong π-π interaction, nitrogen-atom assisted surface orientation and C-C bond formation on the graphitic structure of MWCNT are the plausible reasons for stable and selective voltammetric pH sensing application of MWCNT@Car-HQ system. Using a programed/in-built three-in-one screen printed compatible potentiostat system, voltammetric pH sensing of 3 μL sample of urine, saliva, and orange juice samples with pH values comparable to that of milliliter volume-based pH-glass electrode measurements has been demonstrated.

Current and emerging methods for treatment of hemoglobin related cutaneous discoloration: A literature review

BACKGROUND

Currently, there is no available medication for immediate correction of bruise discoloration. Instead, makeup, cosmetic powders, concealers, and various traditional herbal remedies are used to mask discoloration. These approaches have no influence on the pathology behind the discoloration. The purpose of this study was to explore existing methods and current trends in correction of hemoglobin related cutaneous discoloration.

METHODS

This paper describes the treatment methodologies available for proposed correction of hemoglobin related cutaneous discoloration. A thorough literature review was conducted to assess current knowledge of available treatments for bruise discoloration.

RESULTS

current cosmetics being marketed under the names "Bleacher bruises," "Bleaching agents" and "Blood bleachers" addressing bruise related discoloration do not offer targeted pathological treatment. Several methods for immediate discoloration of the skin and nail plate in the area of bruising and hematoma were found, yet no method offered sufficient clinical data in support of its efficacy and safety. The intricate mechanisms of discoloration associated with hemoglobin extravascular deterioration are not targeted by any treatment method. Only one paper outlining the clinical application of bleaching agents was found.

CONCLUSION

The primary blood pigments responsible for the discoloration in bruises include methemoglobin, oxyhemoglobin, carbohymoglobin, verdoglobin, biliverdin, and bilirubin. No existing method targets the degradation of hemoglobin in the area of ecchymosis. The efficacy of existing patented methods remains questionable and unsupported clinically. Future research should focus on developing a drug targeting hemoglobin derivatives, preventing discoloration at an early stage.

A magnetic electrode modified with hemoglobin for determination of hydrogen peroxide: distinctly improved response by applying a magnetic field

A facile and highly sensitive biosensor was developed for the determination of hydrogen peroxide (H₂O₂) via electrochemical catalytic reduction of H₂O₂ by hemoglobin (Hb). Hb was enriched and immobilized simply in a chitosan (Chit) membrane on a magnetic electrode to construct an enzyme-like biosensor. The biosensor catalyzes the electrochemical reduction of H₂O₂ under an external magnetic field. The response improved roughly twice as Hb was adsorbed by Chit in an alkaline medium. The response of the biosensor under the magnetic field increased by 16% owing to the paramagnetism of Hb. The effect of pH values on Hb adsorption by Chit, as well as the effect of an external magnetic field on Hb configuration were investigated by UV-vis spectroscopy. The reduction peak current has linear and log-linear relationships with H₂O₂ concentration in the range of 5-250 μmol∙L^-1 and 0.01-1 μmol∙L^-1, respectively. The detection limit was 0.003 μmol∙L^-1, with a good sensitivity of 0.227 μA∙μM^-1∙cm^-2. The biosensor was successfully applied to the determination of H₂O₂ in milk samples and in disinfectant solutions. Recoveries ranged from 96.3 to 105.4%, and from 95.3 to 107.7%, respectively. Graphical abstractConstruction of the biosensor, and principle of H₂O₂ determination based on Hb bioelectrocatalysis.