Direct electrochemistry of hemoglobin in cetylpyridinium bromide film: Redox thermodynamics and electrocatalysis to nitric oxide

3D Interconnected Mesoporous Alumina with Loaded Hemoglobin as a Highly Active Electrochemical Biosensor for H2 O2

Alumina is one of the most common and stable metal oxides in nature, which has been developed as a novel adsorbent in enrichment of biomolecules due to its excellent affinity to phosphor or amino groups. In this study, ordered mesoporous alumina (OMA) with interconnected mesopores and surface acidic property is synthesized through a solvent evaporation induced co-assembly process using poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymer as a template and aluminium acetylacetonate (Al(acac)₃ ) as the aluminium source. The pore size (12.1-19.7 nm), pore window size (3.5-9.0 nm) and surface acidity (0.092-0.165 mmol g^-1 ) can be precisely adjusted. The highly porous structure endows the OMA materials with high hemoglobin (Hb) immobilization capacity (170 mg g^-1 ). The obtained Hb@OMA composite is used as an electrocatalyst of biosensor for convienet and fast detection of hydrogen peroxide (H₂ O₂ ) with a low H₂ O₂ detection limit of 1.7 × 10^-8 m and a wide linear range of 2.5 × 10^-8 to 5.0 × 10^-5 m. Moreover, the Hb@OMA sensors show a good performance in real time detection of H₂ O₂ released from Homo sapiens bone osteosarcoma, indicating their potential application in complex biological processes.

Intellectual modifying a bare glassy carbon electrode to fabricate a novel and ultrasensitive electrochemical biosensor: Application to determination of acrylamide in food samples

Acrylamide (AA) is a neurotoxin and carcinogen which is mainly formed in foods containing large quantities of starch processed at high temperatures and its determination is very important to control the quality of foods. In this work, a novel electrochemical biosensor based on hemoglobin-dimethyldioctadecylammonium bromide (HG-DDAB)/platinum-gold-palladium three metallic alloy nanoparticles (PtAuPd NPs)/chitosan-1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (Ch-IL)/multiwalled carbon nanotubes-IL (MWCNTs-IL)/glassy carbon electrode (GCE) is proposed for ultrasensitive determination of AA in food samples. Development of the biosensor is based on forming an adduct by the reaction of AA with α-NH₂ group of N-terminal valine of HG which decreases the peak current of HG-Fe⁺³ reduction. The modifications were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), energy dispersive X-ray spectroscopic (EDS) and scanning electron microscopy (SEM). Under optimized conditions, the biosensor detected AA by square wave voltammetry (SWV) in two linear concentration ranges of 0.03-39.0nM and 39.0-150.0nM with a limit of detection (LOD) of 0.01nM. The biosensor was able to selective detection of AA even in the presence of high concentrations of common interferents which confirmed that the biosensor is highly selective. Also, the results obtained from further studies confirmed that the proposed biosensor has a short response time (less than 8s), good sensitivity, long term stability, repeatability, and reproducibility. Finally, the proposed biosensor was successfully applied to determine AA in potato chips and its results were comparable to those obtained by gas chromatography-mass spectrometry (GC-MS) as reference method.

Electrochemical properties of silver nanoparticle-supported reduced graphene oxide in nitric oxide oxidation and detection

Influence of different concentrations of ascorbic acid in the formation of rGO–Ag nanocomposites using an in situ synthesis method, and the electrocatalytic oxidation and in situ detection of NO were studied.

Direct electrochemistry of hemoglobin immobilized on a functionalized multi-walled carbon nanotubes and gold nanoparticles nanocomplex-modified glassy carbon electrode

Direct electron transfer of hemoglobin (Hb) was realized by immobilizing Hb on a carboxyl functionalized multi-walled carbon nanotubes (FMWCNTs) and gold nanoparticles (AuNPs) nanocomplex-modified glassy carbon electrode. The ultraviolet-visible absorption spectrometry (UV-Vis), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) methods were utilized for additional characterization of the AuNPs and FMWCNTs. The cyclic voltammogram of the modified electrode has a pair of well-defined quasi-reversible redox peaks with a formal potential of −0.270 ± 0.002 V (vs. Ag/AgCl) at a scan rate of 0.05 V/s. The heterogeneous electron transfer constant (ks) was evaluated to be 4.0 ± 0.2 s⁻¹. The average surface concentration of electro-active Hb on the surface of the modified glassy carbon electrode was calculated to be 6.8 ± 0.3 × 10⁻¹⁰ mol cm⁻². The cathodic peak current of the modified electrode increased linearly with increasing concentration of hydrogen peroxide (from 0.05 nM to 1 nM) with a detection limit of 0.05 ± 0.01 nM. The apparent Michaelis-Menten constant (K_m^app) was calculated to be 0.85 ± 0.1 nM. Thus, the modified electrode could be applied as a third generation biosensor with high sensitivity, long-term stability and low detection limit.

Direct electron transfer and electrochemical study of hemoglobin immobilized in ZnO hollow spheres

ZnO hollow spheres were firstly prepared. A new type of amperometric hydrogen peroxide biosensor was fabricated by entrapping Hemoglobin (Hb) through the ZnO hollow spheres (ZHS) nanoparticles. The composition morphology and size were studied by transmission electron microscopy. The surface topography of the prepared films was imaged by atomic force microscope (AFM). Several techniques, including UV-vis absorption spectroscopy, cyclic voltammetry, chronoamperometry were employed to characterize the performance of the biosensor. The results indicated that the ZHS nanoparticles had enhanced the performance of the hydrogen peroxide sensors. The electrochemical parameters of Hb in the ZHS were calculated by the results of the electron-transfer coefficient (α) and the apparent heterogeneous electron-transfer rate constant K (s) as 0.5 and 3.1 s(-1), respectively. The resulting biosensors showed a wide linear range from 2.1 × 10(-6) to 5.18 × 10(-3) M, with a low detection limit of 7.0 × 10(-7) M (S/N = 3) under optimized experimental conditions. The results demonstrated that the ZHS matrix may improve the protein loading with the retention of bioactivity and greatly promote the direct electron transfer, which can be attributed to its unique morphology, high specific surface area, and biocompatibility. The biosensor obtained from this study possesses high sensitivity, good reproducibility, and long-term stability.

Immobilization of hemoglobin on electrodeposited cobalt-oxide nanoparticles: Direct voltammetry and electrocatalytic activity

Cyclic voltammetry at potential range -1.1 to 0.5 V from aqueous buffer solution (pH 7) containing CoCl(2) produced a well defined cobalt oxide (CoOx) nanoparticles deposited on the surface of glassy carbon electrode. The morphology of the modified surface and cobalt oxide formation was examined with SEM and cyclic voltammetry techniques. Hemoglobin (Hb) was successfully immobilized in cobalt-oxide nanoparticles modified glassy carbon electrode. Immobilization of hemoglobin onto cobalt oxide nanoparticles have been investigated by cyclic voltammetry and UV-visible spectroscopy. The entrapped protein can take direct electron transfer in cobalt-oxide film. A pair of well defined, quasi-reversible cyclic voltammetric peaks at about -0.08 V vs. SCE (pH 7), characteristic of heme redox couple (Fe(III)/Fe(II)) of hemoglobin, and the response showed surface controlled electrode process. The dependence of formal potential (E(0')) on the solution pH (56 mV pH(-1)) indicated that the direct electron transfer reaction of hemoglobin was a one-electron transfer coupled with a one proton transfer reaction process. The average surface coverage of Hb immobilized on the cobalt oxide nanoparticles was about 5.2536x10(-11) mol cm(-2), indicating high loading ability of nanoparticles for hemoglobin entrapment. The heterogeneous electron transfer rate constant (k(s)) was 1.43 s(-1), indicating great of facilitation of the electron transfer between Hb and electrodeposited cobalt oxide nanoparticles. Modified electrode exhibits a remarkable electrocatalytic activity for the reduction of hydrogen peroxide and oxygen. The Michaels-Menten constant K(m) of 0.38 mM, indicating that the Hb immobilized onto cobalt oxide film retained its peroxidases activity. The biosensor exhibited a fast amperometric response <5 s, a linear response over a wide concentration range 5 microM to 700 microM and a low detection limit 0.5 microM. According to the direct electron transfer property and enhanced activity of Hb in cobalt oxide film, a third generation reagentless biosensor without using any electron transfer mediator or specific reagent can be constructed for determination of hydrogen peroxide in anaerobic solutions.