A hydrogen peroxide sensor based on a horseradish peroxidase/polyaniline/carboxy-functionalized multiwalled carbon nanotube modified gold electrode

Carbon-Related Materials: Graphene and Carbon Nanotubes in Semiconductor Applications and Design

As the scaling technology in the silicon-based semiconductor industry is approaching physical limits, it is necessary to search for proper materials to be utilized as alternatives for nanoscale devices and technologies. On the other hand, carbon-related nanomaterials have attracted so much attention from a vast variety of research and industry groups due to the outstanding electrical, optical, mechanical and thermal characteristics. Such materials have been used in a variety of devices in microelectronics. In particular, graphene and carbon nanotubes are extraordinarily favorable substances in the literature. Hence, investigation of carbon-related nanomaterials and nanostructures in different ranges of applications in science, technology and engineering is mandatory. This paper reviews the basics, advantages, drawbacks and investigates the recent progress and advances of such materials in micro and nanoelectronics, optoelectronics and biotechnology.

Electrochemical Biosensors Employing Natural and Artificial Heme Peroxidases on Semiconductors

Heme peroxidases are widely used as biological recognition elements in electrochemical biosensors for hydrogen peroxide and phenolic compounds. Various nature-derived and fully synthetic heme peroxidase mimics have been designed and their potential for replacing the natural enzymes in biosensors has been investigated. The use of semiconducting materials as transducers can thereby offer new opportunities with respect to catalyst immobilization, reaction stimulation, or read-out. This review focuses on approaches for the construction of electrochemical biosensors employing natural heme peroxidases as well as various mimics immobilized on semiconducting electrode surfaces. It will outline important advances made so far as well as the novel applications resulting thereof.

Immobilized dye-decolorizing peroxidase (DyP) and directed evolution variants for hydrogen peroxide biosensing

Immobilized dye-decolorizing peroxidase from Pseudomonas putida MET94 (PpDyP) and three variants generated by directed evolution (DE) are studied aiming at the design of a biosensor for H₂O₂ detection. Structural properties of the enzymes in solution and immobilized state are addressed by resonance Raman (RR) and surface enhanced RR (SERR) spectroscopy, and the electrocatalytic properties are analyzed by electrochemistry. The wild-type (wt) and 29E4 variant (with E188K and H125Y mutations) represent excellent candidates for development of H₂O₂ biosensors, since they exhibit a good dynamic response range (1-200 μM H₂O₂), short response times (2 s) and a superior sensitivity (1.3-1.4 A⋅M^-1⋅cm^-2) for H₂O₂, as well as selectivity and long term stability. In contrast to the solution state, 6E10 (with E188K, A142V and H125Y mutations) and 25F6 (with E188K, A142V, H125Y and G129D mutations) variants display much lower activity and are inhibited by high concentrations of H₂O₂ upon adsorption on an electrode. In terms of sensitivity, the bioelectrodes employing wt PpDyP and 29E4 variant outperform HRP based counterparts reported in the literature by 1-4 orders of magnitude. We propose the development of wt or 29E4 PpDyP based biosensor as a valuable alternative to devices that rely on peroxidases.

An Enzyme-Induced Novel Biosensor for the Sensitive Electrochemical Determination of Isoniazid

In this present work, a glassy carbon electrode (GCE) was modified primarily with multiwalled carbon nanotubes (MWCNTs) and a composite of MWCNTs and titanium oxide nanoparticles (TiO₂NPs). The enzyme horseradish peroxidase (HRP) was immobilized to enhance the sensing ability of GCE. The proposed biosensor was used for the sensitive determination of isoniazid (INZ) in various pharmaceutical samples. The electrochemical behaviour of the developed MWCNT-TiO₂NPs-HRP-GCE biosensor was studied by using cyclic voltammetry (CV) and differential pulse voltammetric (DPV) techniques. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetry (TGA) and transmission electron microscopy (TEM) techniques were used to characterize the developed sensor. Phosphate buffer solution (PBS) with pH 7 was used as supporting electrolyte in the present investigation. The cyclic voltammetric results revealed that the increment of anodic peak currents for the enzyme-induced sensor was almost 8-fold greater than that of a bare GCE. The DPV technique exhibited good limit of detection and limit of quantification values, viz., 0.0335 μM and 0.1118 μM, respectively. Moreover, the developed sensor showed long-lasting stability and repeatability without any interferents. This strongly indicates that the fabricated sensor shows outstanding electrochemical performance towards INZ, with excellent selectivity and sensitivity. The developed sensor was successfully applied to pharmaceutical samples and gave good percentages of recoveries.

Gold Nanocluster-Assisted Fluorescent Detection for Hydrogen Peroxide and Cholesterol Based on the Inner Filter Effect of Gold Nanoparticles

We developed a simple, sensitive inner filter effect (IFE)-based fluorescent assay for sensing H2O2 and cholesterol. In the process, poly(vinylpyrrolidone)-protected gold nanoparticles (PVP-AuNPs) and fluorescent BSA-protected gold nanoclusters (BSA-AuNCs) were used as an IFE absorber/fluorophore pair. PVP-AuNPs can be a powerful absorber to influence the emission of the fluorophore, BSA-AuNCs, in the IFE-based fluorescent assays. That is due to the high extinction coefficient of AuNPs and the complementary overlap between the surface plasmon resonance (SPR) absorption of PVP-AuNPs and the excitation of BSA-AuNCs. The PVP-Au seeds, produced by directly mixing PVP with HAuCl4, were able to catalyze H2O2 to enlarge AuNPs. The SPR absorption of PVP-AuNPs was enhanced with an increased concentration of H2O2 and, subsequently, induced significant fluorescence quenching of BSA-AuNCs. The IFE-based fluorescent assay enabled the detection of H2O2 and generation of H2O2 in the presence of O2/cholesterol and cholesterol oxidase (ChOx) by the fluorescence response of BSA-AuNCs. The present IFE-based approach can detect H2O2 ranging from 1 to 100 μM with a detection limit of 0.8 μM and cholesterol ranging from 1 to 100 μM with a detection limit of 1.4 μM.

A new bifunctional electrochemical sensor for hydrogen peroxide and nitrite based on a bimetallic metalloporphyrinic framework

The bimetallic electrocatalytic ability of a new metallic porphyrin, Cu-CoTCPP, toward redox of H₂O₂ and oxidation of NaNO₂.

Amperometric determination of cadmium, lead, and mercury metal ions using a novel polymer immobilised horseradish peroxidase biosensor system

This work was undertaken to develop a novel Pt/PANI-co-PDTDA/HRP biosensor system for environmental applications to investigate the inhibition studies by specific heavy metals, to provide data suitable for kinetic studies and further application of the biosensor to environmental samples. The newly constructed biosensor was compared to the data of the well-researched Pt/PANI/HRP biosensor. Optimised experimental conditions, such as the working pH for the biosensor was evaluated. The functionality of the amperometric enzyme sensor system was demonstrated by measuring the oxidation current of hydrogen peroxide followed by the development of an assay for determination of metal concentration in the presence of selected metal ions of Cd(2+), Pb(2+) and Hg(2+). The detection limits were found to be 8 × 10(-4) μg L(-1) for cadmium, 9.38 × 10(-4) μg L(-1) for lead and 7.89 × 10(-4) μg L(-1) for mercury. The World Health Organisation recommended that the maximum safety level of these metals should not exceed 0.005 mg L(-1) of Cd(2+), 0.01 mg L(-1) of Pb(2+) and 0.001 mg L(-1) of Hg(2+.), respectively. The analytical and detection data for the metals investigated were observed to be lower than concentrations recommended by several bodies including World Health Organisation and Environmental Protection Agencies. Therefore the biosensors developed in this study can be used to screen the presence of these metals in water samples because of its low detection limit. The modes of inhibition of horseradish peroxidase by Pb(2+), Cd(2+) and Hg(2+) as analysed using the double reciprocal plots of the Michaelis-Menten equation was found to be reversible and uncompetitive inhibition. Based on the Km(app) and Imax values for both biosensors the results have shown smaller values. These results also proved that the enzyme modified electrode is valuable and can be deployed for the determination or screening of heavy metals.

Ferrocene-functionalized polydopamine as a novel redox matrix for H2O2 oxidation

Simple synthesis of a ferrocene-functionalized polydopamine [poly(DA-Fc)] is described. This redox film displays excellent electrocatalytic oxidation of H₂O₂ in neutral buffer solutions in a Fenton-type reaction, and is found to be selective to H₂O₂ with negligible interference from other small molecules.

Enhancing the insulation of wide-range spectrum in the PVA/N thin film by doping ZnO nanowires

PVA/N doped ZnO hybrid thin films provide protection against harmful UV and IR rays.

Microwave-assisted synthesis of hemin–graphene/poly(3,4-ethylenedioxythiophene) nanocomposite for a biomimetic hydrogen peroxide biosensor

The ternary nanocomposite hemin–graphene sheets/poly(3,4-ethylenedioxythiophene) (H–GNs/PEDOT) synthesized by a microwave-assisted method exhibits good electrocatalytic activity towards the reduction of hydrogen peroxide.

Modern micro and nanoparticle-based imaging techniques

The requirements for early diagnostics as well as effective treatment of insidious diseases such as cancer constantly increase the pressure on development of efficient and reliable methods for targeted drug/gene delivery as well as imaging of the treatment success/failure. One of the most recent approaches covering both the drug delivery as well as the imaging aspects is benefitting from the unique properties of nanomaterials. Therefore a new field called nanomedicine is attracting continuously growing attention. Nanoparticles, including fluorescent semiconductor nanocrystals (quantum dots) and magnetic nanoparticles, have proven their excellent properties for in vivo imaging techniques in a number of modalities such as magnetic resonance and fluorescence imaging, respectively. In this article, we review the main properties and applications of nanoparticles in various in vitro imaging techniques, including microscopy and/or laser breakdown spectroscopy and in vivo methods such as magnetic resonance imaging and/or fluorescence-based imaging. Moreover the advantages of the drug delivery performed by nanocarriers such as iron oxides, gold, biodegradable polymers, dendrimers, lipid based carriers such as liposomes or micelles are also highlighted.

Recent advances in electrochemical sensing for hydrogen peroxide: a review

Due to the significance of hydrogen peroxide (H(2)O(2)) in biological systems and its practical applications, the development of efficient electrochemical H(2)O(2) sensors holds a special attraction for researchers. Various materials such as Prussian blue (PB), heme proteins, carbon nanotubes (CNTs) and transition metals have been applied to the construction of H(2)O(2) sensors. In this article, the electrocatalytic H(2)O(2) determinations are mainly focused on because they can provide a superior sensing performance over non-electrocatalytic ones. The synergetic effect between nanotechnology and electrochemical H(2)O(2) determination is also highlighted in various aspects. In addition, some recent progress for in vivo H(2)O(2) measurements is also presented. Finally, the future prospects for more efficient H(2)O(2) sensing are discussed.