Hemoglobin-graphene modified carbon fiber microelectrode for direct electrochemistry and electrochemical H2O2 sensing

H.O.S.T.: Hemoglobin microbubble-based Oxidative stress Sensing Technology

In this work, we discuss the development of H.O.S.T., a novel hemoglobin microbubble-based electrochemical biosensor for label-free detection of Hydrogen peroxide (H2O2) towards oxidative stress and cancer diagnostic applications. The novelty of the constructed sensor lies in the use of a sonochemically prepared hemoglobin microbubble capture probe, which allowed for an extended dynamic range, lower detection limit, and enhanced resolution compared to the native hemoglobin based H2O2 biosensors. The size of the prepared particles Hemoglobin microbubbles was characterized using Coulter Counter analysis and was found to be 4.4 microns, and the morphology of these spherical microbubbles was shown using Brightfield microscopy. The binding chemistry of the sensor stack elements of HbMbs' and P.A.N.H.S. crosslinker was characterized using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy and UV-Vis Spectroscopy. The electrochemical biosensor calibration (R2 > 0.95) was done using Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, and Square Wave Voltammetry. The electrochemical biosensor calibration (R2 > 0.95) was done using Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, and Square Wave Voltammetry. The specificity of the sensor for H2O2 was analyzed using cross-reactivity studies using ascorbic acid and glucose as interferents (p < 0.0001 for the highest non-specific dose versus the lowest specific dose). The developed sensor showed good agreement in performance with a commercially available kit for H2O2 detection using Bland Altman Analysis (mean bias = 0.37 for E.I.S. and - 24.26 for CV). The diagnostic potential of the biosensor was further tested in cancerous (N.G.P.) and non-cancerous (H.E.K.) cell lysate for H2O2 detection (p = 0.0064 for E.I.S. and p = 0.0062 for CV). The Michaelis Menten constant calculated from the linear portion of the sensor was found to be [Formula: see text] of 19.44 µM indicating that our biosensor has a higher affinity to Hydrogen peroxide than other available enzymatic sensors, it is attributed to the unique design of the hemoglobin polymers in microbubble.

A graphene-printed paper electrode for determination of H2O2 in municipal wastewater during the COVID-19 pandemic

Graphene prepared through exfoliation process was printed on paper substrate using inkjet-printer and then printed paper electrode was used as an electrochemical sensor for analysis of H2O2 in cyclic voltammetry.

Self-Terminated Electroless Deposition of Surfactant-Free and Monodispersed Pt Nanoparticles on Carbon Fiber Microelectrodes for Sensitive Detection of H2O2 Released from Living Cells

We report a self-terminated electroless deposition method to prepare surfactant-free and monodispersed Pt nanoparticle (NP)-modified carbon fiber microelectrodes (Pt NP/CFEs) for electrochemical detection of hydrogen peroxide (H₂O₂) released from living cells. The surfactant-free and monodispersed Pt NPs with a uniform size of 65 nm are spontaneously deposited on a CFE surface by immersing an exposed carbon fiber (CF) of CFE in the PtCl₄^2- solution, in which an exposed CF can be used as the reducing agent and stabilizer. A self-terminated electroless deposition method is demonstrated, in which the density and size of Pt NPs on a CFE surface do not increase when the reaction time increases from 20 to 60 min. The self-terminated electroless deposition process not only can effectively avoid any manual electrode modification and thus largely minimize person-to-person and electrode-to-electrode deviations but also can avoid the use of any extra reductant or surfactant in the fabrication process. Therefore, Pt NPs/CFEs, with good reproducibility and sensitivity, not only exhibit high electrocatalytic activity toward the oxidation of H₂O₂ but also maintain the spatial resolution of CFEs. Moreover, Pt NPs/CFEs can detect H₂O₂ with a wide linear range of 0.5-80 μM and a low detection limit of 0.17 μM and then can be successfully applied in the monitoring of H₂O₂ released from RAW 264.7 cells. The self-terminated electroless deposition method can also be extended to selectively prepare other metal NP-modified CFEs, such as Au NPs/CFEs or Ag NPs/CFEs, by choosing the metal ions with higher reduction potential as precursors. This work provides a simple, straightforward, and general method for the preparation of small, surfactant-free, and monodispersed metal NP-modified CFEs with high sensitivity, reproducibility, and spatial resolution.

Synthesizing Electrodes Into Electrochemical Sensor Systems

Electrochemical sensors that can determine single/multiple analytes remain a key challenge in miniaturized analytical systems and devices. In this study, we present in situ synthesis and modification of gold nanodendrite electrodes to create an electrochemical system for the analysis of hydrogen peroxide. The sensor system consisted of the reference and counter electrodes as well as the working electrode. Electrochemical reduction of graphene oxide, ErGO, on the thin-film gold and gold nanodendrite working electrodes was used to achieve an efficient sensor interface for the adsorption of a biomimetic electrocatalytic sensor material, Mn(III) meso-tetra(N-methyl-4-pyridyl) porphyrin complex, with as high as 10^-10 mol cm^-2 surface coverage. The sensor system demonstrated a detection limit of 0.3 µM H₂O₂ in the presence of oxygen. Electrochemical determination of hydrogen peroxide in plant material in the concentration range from 0.09 to 0.4 µmol (gFW)^-1 using the electrochemical sensor system was shown as well as in vivo real-time monitoring of the hydrogen peroxide dynamics as a sign of abiotic stress (intense sunlight). Results of the electrochemical determination were in good agreement with the results of biochemical analysis with the spectrophotometric detection. We anticipate that this method can be extended for the synthesis and integration of multisensor arrays in analytical microsystems and devices for the quantification and real-time in vivo monitoring of other analytes and biomarkers.

Immobilization of hemoglobin on MnCO3 sphere-loaded Au nanoparticles as highly efficient sensing platform towards hydrogen peroxide

In this paper, we report the synthesis of MnCO₃-Au hybrid microspheres and their application on the electrochemical biosensing of hydrogen peroxide (H₂O₂) based on the immobilization of hemoglobin (Hb). The characterization of MnCO₃-Au microspheres revealed that an abundance of Au nanoparticles (AuNPs) has been absorbed on the surface of the spherical MnCO₃ by the electrostatic assembly. The combined unique properties of MnCO₃-Au microspheres are beneficial for the realization of the direct electron transfer of Hb. Hb immobilized on the microspheres maintained its biological activity, showing a surface-controlled process with the heterogeneous electron transfer rate constant (k _s) of 2.63 s^-1. The fabricated biosensor displayed an excellent performance for the electrocatalytic reduction of H₂O₂. The linear range for the determination of H₂O₂ was from 0.06-40.0 μM with a detection limit of 0.015 µM (S/N = 3). The biosensor also exhibited high selectivity, good repeatability and long-term stability, which offers great potential for H₂O₂ detection in real sample analysis.

Preyssler-type polyoxometalate-based crystalline materials for the electrochemical detection of H2O2

Four Preyssler-type polyoxometalate-based organic–inorganic hybrid materials were synthesized as non-enzymatic H₂O₂ electrochemical sensors, with high sensitivity and low detection limit.

Bioelectrocatalysis of Hemoglobin on Electrodeposited Ag Nanoflowers toward H2O2 Detection

Hydrogen peroxide (H2O2) is a partially reduced metabolite of oxygen that exerts a diverse array of physiological and pathological activities in living organisms. Therefore, the accurate quantitative determination of H2O2 is crucial in clinical diagnostics, the food industry, and environmental monitoring. Herein we report the electrosynthesis of silver nanoflowers (AgNFs) on indium tin oxide (ITO) electrodes for direct electron transfer of hemoglobin (Hb) toward the selective quantification of H2O2. After well-ordered and fully-grown AgNFs were created on an ITO substrate by electrodeposition, their morphological and optical properties were analyzed with scanning electron microscopy and UV-Vis spectroscopy. Hb was immobilized on 3-mercaptopropionic acid-coated AgNFs through carbodiimide cross-linking to form an Hb/AgNF/ITO biosensor. Electrochemical measurement and analysis demonstrated that Hb retained its direct electron transfer and electrocatalytic properties and acted as a H2O2 sensor with a detection limit of 0.12 µM and a linear detection range of 0.2 to 3.4 mM in phosphate-buffered saline (PBS). The sensitivity, detection limit, and detection range of the Hb/AgNF/ITO biosensor toward detection H2O2 in human serum was also found to be 0.730 mA mM-1 cm-2, 90 µM, and 0.2 to 2.6 mM, indicating the clinical application for the H2O2 detection of the Hb/AgNF/ITO biosensor. Moreover, interference experiments revealed that the Hb/AgNF/ITO sensor displayed excellent selectivity for H2O2.

Intrinsic peroxidase-like activity of Cu2ZnSn(SxSe1-x)4 nanocrystals, and their application to the colorimetric detection of H2O2

Nanocrystals (NCs) of type Cu₂ZnSn(S_xSe_1-x)₄ (CZTSSe) were prepared via a solvothermal approach. They are shown to be highly efficient peroxidase (POx) mimics for colorimetric detection of H₂O₂. By varying the molar ratio of S and Se during preparation, the NCs showed different crystal structures, morphologies, surface properties, and POx-like activities. Among them, the type CZTSSe-0.25 NCs exhibit the strongest POx-like activities towards the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of H₂O₂ to generate a blue product. The enhanced activity is attributed to its more negative potential and larger specific surface of the NCs. Based on these findings, a rapid and ultrasensitive method was developed for the visual and colorimetric determination of H₂O₂. The method is selective, and the NCs are reusable and long-term stable. The detection limit of H₂O₂ is 50 nM. Kinetic and active species trapping experiments were performed to elucidate the POx-like mechanism of the NCs. Graphical abstract Schematic presentation of the process of Cu₂ZnSn(S_xSe_1-x)₄ nanocrystals catalyzing the oxidation of peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂ to induce a typical blue color reaction, which can be applied in colorimetric detection of H₂O₂.

Dimensional confinement of graphene in a polypyrrole microbowl for sensor applications

A novel bowl-shaped polypyrrole/three dimensional graphene sensor shows a good analytical performance towards dopamine.

Graphene composite coated carbon fiber: electrochemical synthesis and application in electrochemical sensing

A universal method for the fabrication of graphene composite modified carbon fiber is reported.