A Volume Miniaturized Hydrogen Peroxide Sensor Based on Peroxidase Activity of Copper(II) Chlorophyllin on Zinc Oxide and Polypyrrole Nanocomposite

Measurement of hydrogen peroxide (H2O2) is essential in human physiology and pathology as it provides valuable information with regard to signaling and prognostic of various diseases viz. oxidative stress and cardiovascular diseases. Therefore, we developed an alternate volume miniaturized electrochemical enzyme mimetic sensor having high stability, reproducibility and fast response time for the determination of H2O2. The enzyme mimetic sensor was constructed using copper (II) chlorophyllin trisodium (CuCP) functionalized on to the zinc oxide (ZnO)-polypyrrole (PPy) nanocomposite modified screen printed carbon electrode (SPCE). Scanning electron microscope (SEM) was used to characterize the surface morphology of nanocomposite PPy and ZnO-CuCP modified electrodes. The electrochemical behavior of enzyme mimetic sensor was examined by cyclic voltammetry exhibiting a characteristic quasi-reversible peak at the potential, +0.06 V versus Ag/AgCl, for the electrodeposited CuCP. It reveals that the combination of ZnO and CuCP could enhance the sensor performance in terms of sensitivity and selectivity. In addition, new reversible redox peaks at +0.15 and -0.15 V were observed accounting for the mechanism of superoxide anion radical (O2•-) formation. The enzyme mimetic sensor exhibited a linear response over the H2O2 concentration ranges from 300 nM to 1 mM with a detection limit of 100 nM and a sensitivity of 78.4 ± 1.5 nA μM-1 cm-2. Further, the sensor was successfully applied for the determination of H2O2 in biological samples such as human blood and plasma

Subcutaneous aspergillosis with coexisting atypical mycobacterial infection

A 60-year-old woman, a known diabetic and asthmatic, was admitted for acute exacerbation of chronic obstructive pulmonary disease. Physical examination revealed two soft nodules in the left infra axillary region. Fine needle aspiration cytology (FNAC) showed fungal granulomatous reaction suggestive of fungal infection. Periodic acid Schiff stain (PAS stain) revealed PAS positive, acutely branching, septate fungal hyphae. Wet mount of the aspirate revealed plenty of pus cells and branching septate hyphae. Ziehl-Neelsen (ZN) stain showed moderate numbers of acid fast bacilli. Culture yielded Aspergillus flavus and Mycobacterium fortuitum

Electrochemical Determination of Hydrogen Peroxide and Bicarbonate Using Peroxidase Activity of Copper, Zinc Superoxide Dismutase on Carbon Nanotube, Polypyrrole Nanocomposite Modified Pt Electrode

Measurement of hydrogen peroxide (H2 O2) and bicarbonate (HCO– 3) are essential in human pathology and pathophysiology as it provides valuable information with regard to signalling and prognostic of various diseases viz. oxidative stress and cardiovascular diseases. Therefore, we have developed here a novel electrochemical method for the determination of H2O2and HCO– 3 based on the peroxidase activity of copper, zinc superoxide dismutase (SOD). By immobilizing SOD onto the single walled carbon nanotubes (SWCNT)-polypyrrole (PPy) nanocomposite modified platinum electrode, the concentrations of H2O2and HCO– 3 were measured. The electrochemical behaviour of the SOD modified electrode was examined by cyclic voltammetry exhibiting characteristic quasi-reversible redox peak at the potential,+ 0.06 V versus Ag/AgCl. The peroxidase activity of SOD observed at –0.45 V was linear from 300 nM to 1 mM with a detection limit of 100 nM and sensitivity of 78.6 ± 1.7 nA μ M–1 cm–2. In the presence of HCO– 3, the peroxidase activity of SOD was enhanced linearly with HCO– 3concentration from 500 M to 50 mM. Based on this, we have measured here the HCO– 3 with a detection limit of 200 M and sensitivity of 1.23 μ A mM–1. Further, the concentrations of H2 O2 and HCO– 3 present in the human plasma samples were measured

Recent trends in electrochemical biosensors of superoxide dismutases

Superoxide dismutases (SODs), a family of ubiquitous enzymes, provide essential protection to biological systems against uncontrolled reactions with oxygen- and nitrogen- based radical species. We review first the role of SODs in oxidative stress and the other biological functions such as peroxidase, nitrite oxidase, thiol oxidase activities etc., implicating its role in neurodegenerative, cardiovascular diseases, and ageing. Also, this review focuses on the development of electrochemical label-free immunosensor for SOD1 and the recent advances in biosensing assay methods based on their catalytic and biological functions with various substrates including reactive oxygen species (superoxide anion radical, hydrogen peroxide), nitric oxide metabolites (nitrite, nitrate) and thiols using thiol oxidase activity. Furthermore, we emphasize the progress made in improving the detection performance through incorporation of the SOD into conducting polymers and nanocomposite matrices. In addition, we address the potential opportunities, challenges, advances in electrochemical-sensing platforms and development of portable analyzer for point-of-care applications

Nanomaterial-based electrochemical biosensors for cytochrome c using cytochrome c reductase

Emerging evidences have pointed out that the release of cytochrome c (cyt c) from mitochondria into cytosol is a critical step in the activation of apoptosis. This article presents a novel approach for the detection of mitochondrial cyt c release for the first time using cytochrome c reductase (CcR) immobilized on nanoparticles decorated electrodes. Two kinds of nanomaterial-based biosensor platforms were used: (a) carbon nanotubes (CNT) incorporated polypyrrole (PPy) matrix on Pt electrode and (b) self-assembled monolayer (SAM) functionalized gold nanoparticles (GNP) in PPy-Pt. Scanning electron microscope was used to characterize the surface morphologies of the nanomaterial modified electrodes. Cyclic voltammograms of both the biosensors showed reversible redox peaks at − 0.45 and − 0.34 V vs Ag/AgCl, characteristic of CcR. In comparison, the CcR-CNT biosensor gave a detection limit of 0.5 ± 0.03 μM cyt c, which was 4-fold better than the CcR-GNP biosensor (2 ± 0.03 μM). Moreover, the CcR-CNT biosensor achieved a much larger linear range (1–1000 μM) over the CcR-GNP biosensor (5–600 μM) with 2-fold better sensitivity. The CcR-CNT-PPy-Pt biosensor was further applied to quantify the mitochondrial cyt c released in cytosol of A549 cells upon induction of apoptosis with doxorubicin, the results agreed well with standard western blot analysis

Virtual Instrumentation for Electrochemical Biosensor Applications

Virtual instrumentation (VI) is defined as an instrument whose general function and capabilities are determined in software. Especially, graphical user interface (GUI) software LabVIEW (Laboratory Virtual Instrumentation Engineering Workbench) is ideal for creating low cost and user friendly virtual instruments. In recent times, development of VI for electroanalytical applications are highly focused since the existing commercial instruments involve high cost and pre-defined hardware components restricting the users for the field study. Meticulously, highly flexible and hand held VI is needed for the detection of clinically important biomarkers using electrochemical biosensor technique. Therefore, in this article, we have attempted to explore the development of VI for the biosensor applications. In this context, a virtual instrument made up of home-made potentiostat connected with data acquisition system (NI MyDAQ) processed by GUI software performing cyclic voltammetry is discussed for the biosensing of nitric oxide and its metabolites and immunosensing of cytochrome c. The electroanalytical parameters viz. detection limit, linearity and sensitivity of the biosensors observed using VI are comparable with the results obtained using standard commercial instrument. But, in terms of cost, size and flexibility, VI is superior to the standard instrument for the biosensor applications and also enhancing the skill of the operator

Nanomaterial-based electrochemical biosensors for cytochrome c using cytochrome c reductase

Emerging evidences have pointed out that the release of cytochrome c (cyt c) from mitochondria into cytosol is a critical step in the activation of apoptosis. This article presents a novel approach for the detection of mitochondrial cyt c release for the first time using cytochrome c reductase (CcR) immobilized on nanoparticles decorated electrodes. Two kinds of nanomaterial-based biosensor platforms were used: (a) carbon nanotubes (CNT) incorporated polypyrrole (PPy) matrix on Pt electrode and (b) self-assembled monolayer (SAM) functionalized gold nanoparticles (GNP) in PPy-Pt. Scanning electron microscope was used to characterize the surface morphologies of the nanomaterial modified electrodes. Cyclic voltammograms of both the biosensors showed reversible redox peaks at − 0.45 and − 0.34 V vs Ag/AgCl, characteristic of CcR. In comparison, the CcR-CNT biosensor gave a detection limit of 0.5 ± 0.03 μM cyt c, which was 4-fold better than the CcR-GNP biosensor (2 ± 0.03 μM). Moreover, the CcR-CNT biosensor achieved a much larger linear range (1–1000 μM) over the CcR-GNP biosensor (5–600 μM) with 2-fold better sensitivity. The CcR-CNT-PPy-Pt biosensor was further applied to quantify the mitochondrial cyt c released in cytosol of A549 cells upon induction of apoptosis with doxorubicin, the results agreed well with standard western blot analysis