Amperometric Biosensor for Hydrogen Peroxide Based on Immobilization of Horseradish Peroxidase on Methylene Blue Modified Graphite Electrode

Comparative understanding of peroxide quantitation assays: a case study with peptide drug product degradation

Peroxide-mediated oxidation of drug molecules is a known challenge faced throughout the pharmaceutical development pathway-from early-stage stability studies to manufacturing processes. During the initial development stage, the major source of peroxide is the formulation excipients, whether they are pre-loaded or generated in situ due to slow degradation, and in the late phase, peroxides can be introduced during sanitization processes or generated via cavitation. In essence, a control strategy for peroxide mitigation often becomes a critical quality attribute for successful drug development. To this end, quantitation of peroxide is essential to monitor the peroxide level to ensure product quality and proposed shelf-life. However, methods for reliable and robust quantitation to detect trace levels of peroxide in a complex drug product matrix become increasingly challenging. This article discusses three high-throughput assays based on absorbance, fluorescence and chemiluminescence measurements to detect peroxide at a low level and compares the methods through validation studies in water. Selected methods have also been tested to understand the forced degradation of model peptide drug products with spiked hydrogen peroxide. Peptide degradation profiles and residual peroxide levels are presented to provide an understanding of the suitability of the quantitation methods and their performance.

Bacterial Peroxidase on Electrochemically Reduced Graphene Oxide for Highly Sensitive H2O2 Detection

Peroxidase enzymes enable the construction of electrochemical sensors for highly sensitive and selective quantitative detection of various molecules, pathogens and diseases. Herein, we describe the immobilization of a peroxidase from Bacillus s. (BsDyP) on electrochemically reduced graphene oxide (ERGO) deposited on indium tin oxide (ITO) and polyethylene terephthalate (PET) layers. XRD, SEM, AFM, FT‐IR and Raman characterization of the sensor confirmed its structural integrity and a higher enzyme surface occupancy. The BsDyP‐ERGO/ITO/PET electrode performed better than other horseradish peroxidase‐based electrodes, as evinced by an improved electrochemical response in the nanomolar range (linearity 0.05–280 μM of H₂O₂, LOD 32 nM). The bioelectrode was mechanically robust, active in the 3.5–6 pH range and exhibited no loss of activity upon storage for 8 weeks at 4 °C.

Hemoglobin–metal2+ phosphate nanoflowers with enhanced peroxidase-like activities and their performance in the visual detection of hydrogen peroxide

Hemoglobin (Hgb)–metal²⁺ phosphate nanoflowers (Hgb–X²⁺-Nfs) were synthesized using Co²⁺, Zn²⁺, Ca²⁺, and Fe²⁺ separately as inorganic components, to generate a visual hydrogen peroxide (H₂O₂) biosensor for the first time.

Binding Kinetics of Methylene Blue on Monolayer Graphene Investigated by Multiparameter Surface Plasmon Resonance

In this paper, we study the interaction of a small dye molecule, namely, methylene blue (MB) with graphene surfaces using surface plasmon resonance (SPR). We show that by utilizing all of the parameters of the SPR angular dip and exploiting the fact that MB absorbs light at the operating wavelength, it is possible to detect the binding of small molecules that would otherwise not give a significant signal. The binding of MB to unmodified graphene is found to be stronger than that for gold. By studying the interaction at modified surfaces, we demonstrate that electrostatic effects play a dominant role in the binding of MB on to graphene. Furthermore, following the binding kinetics at various concentrations allows us to estimate apparent equilibrium binding and rate constants for the interaction of MB with graphene.

Electrospun Chitosan-Gelatin Biopolymer Composite Nanofibers for Horseradish Peroxidase Immobilization in a Hydrogen Peroxide Biosensor

A biosensor based on chitosan-gelatin composite biopolymers nanofibers is found to be effective for the immobilization of horseradish peroxidase to detect hydrogen peroxide. The biopolymer nanofibers were fabricated by an electrospining technique. Upon optimization of synthesis parameters, biopolymers nanofibers, an average of 80 nm in diameter, were obtained and were then modified on the working electrode surface. The effects of the concentration of enzyme, pH, and concentration of the buffer and the working potential on the current response of the nanofibers-modified electrode toward hydrogen peroxide were optimized to obtain the maximal current response. The results found that horseradish peroxidase immobilization on chitosan-gelatin composite biopolymer nanofibers had advantages of fast response, excellent reproducibility, high stability, and showed a linear response to hydrogen peroxide in the concentration range from 0.1 to 1.7 mM with a detection limit of 0.05 mM and exhibited high sensitivity of 44 µA∙mM-1∙cm-2. The developed system was evaluated for analysis of disinfectant samples and showed good agreement between the results obtained by the titration method without significant differences at the 0.05 significance level. The proposed strategy based on chitosan-gelatin composite biopolymer nanofibers for the immobilization of enzymes can be extended for the development of other enzyme-based biosensors.

Application of iridium(III) complex in label-free and non-enzymatic electrochemical detection of hydrogen peroxide based on a novel "on-off-on" switch platform

We herein report a label-free and non-enzymatic electrochemical sensor for the highly sensitive detection of hydrogen peroxide (H2O2) based on a novel "on-off-on" switch system. In our design, MB was used as an electron mediator to accelerate the electron transfer while AuNPs was used to amplify the electrochemical signal due to its excellent biocompatibility and good conductivity. The "switch-off" state was achieved by introducing the guanine-rich capture probe (CP) and an iridium complex onto the electrode surface to form a hydrophobic layer, which then hinders electron transfer. Upon addition of H2O2, fenton reaction occurs and produces OH• in the presence of Fe(2+). The OH• cleaves the CP into DNA fragments, thus resulting in the release of CP and iridium complex from the sensing interface, recovering the electrochemical signal to generate a "switch-on" state. Based on this novel switch system, a detection limit as low as 3.2 pM can be achieved for H2O2 detection. Moreover, satisfactory results were obtained by using this method for the detection of H2O2 in sterilized milk. To the best of our knowledge, this is the first G-quadruplex-based electrochemical sensor using an iridium(III) complex.

Carbon Felt-Based Bioelectrocatalytic Flow-Through Detectors: 2,6-Dichlorophenol Indophenol and Peroxidase Coadsorbed Carbon-Felt for Flow-Amperometric Determination of Hydrogen Peroxide

2,6-dichlorophenol indophenol (DCIP) and horseradish peroxidase (HRP) were coadsorbed on a porous carbon felt (CF) from their mixed aqueous solution under ultrasound irradiation for 5 min. The resulting DCIP and HRP-coadsorbed CF (DCIP/HRP-CF) showed an excellent bioelectrocatalytic activity for the reduction of H₂O₂. The coadsorption of DCIP together with HRP was essential to obtain larger bioelectrocatalytic current to H₂O₂. The DCIP/HRP-CF was successfully used as a working electrode unit of a bioelectrocatalytic flow-through detector for highly sensitive and continuous amperometric determination of H₂O₂. Under the optimized operational conditions (i.e., applied potential, +0.2 V versus Ag/AgCl; carrier pH 5.0, and carrier flow rate, 1.9 mL/min), the cathodic peak current of H₂O₂ linearly increased over the concentration range from 0.1 to 30 μM (the sensitivity, 0.88 μA/μM (slope of linear part); the limit of detection, 0.1 μM (S/N = 3) current noise level, 30 nA) with a sample through-put of ca. 40–90 samples/h.

Amperometric enzyme electrode for organic peroxides determination prepared from horseradish peroxidase immobilized in poly(vinylferrocenium) film

Organic peroxides, t-butyl hydroperoxide, 2-butanone peroxide, cumene hydroperoxide and t-butyl peracetate, were determined by an amperometric enzyme electrode. The enzyme electrode was prepared through electrostatic immobilization of horseradish peroxidase (HRP) in a polyvinylferrocenium (PVF) film. A PVF(+)ClO(4)(-) film was coated on a Pt foil at +0.70 V by electrooxidation of polyvinylferrocene in methylene chloride with 0.1 M tetrabutylammonium perchlorate (TBAP). The enzyme modified electrode PVF(+)HRP(-) was prepared by anion-exchange in a solution of HRP(-) in 0.05 M phosphate buffer at pH 8.5. FTIR spectroscopy was used to identify PVF, PVF(+)ClO(4)(-), and PVF(+)HRP(-). The immobilized amount of the enzyme in the film was determined by UV spectroscopy. The effects of the polymeric film thickness, bulk enzyme concentration used in the immobilization treatment and the temperature on the performance of enzyme electrode were investigated. The inhibitory effect of oxygen was also examined. Linearities, lower detection limits, active life times and sensitivities of the electrode were determined for each peroxide.