Nanocomposite Bienzymatic Sensor for Monitoring Xanthine in Wound Diagnostics

This work reports a biosensor for monitoring xanthine for potential wound healing assessment. Active substrate of the biosensor has xanthine oxidase (XO) and horseradish peroxidase (HRP) physisorbed on a nanocomposite of multiwalled carbon nanotubes (MWCNT) decorated with gold nanoparticles (AuNP). The presence of HRP provided a two-fold increase in response to xanthine, and a three-fold increase in response to the nanocomposite. With a sensitivity of 155.71 nA μM−1 cm−2 the biosensor offers a detection limit of 1.3 μM, with linear response between 22 μM and 0.4 mM. Clinical sample analyses showed the feasibility of xanthine detection from biofluids in a lesion site due to diffusion of the analyte into surrounding biofluids. Higher concentrations by three-fold were observed from wound proximity, than away from injury, with an average recovery of 110%. Results show the feasibility of monitoring wound severity through longitudinal measurements of xanthine from injured vicinity

A Review on Direct Electrochemistry of Catalase for Electrochemical Sensors

Catalase (CAT) is a heme enzyme with a Fe(III/II) prosthetic group at its redox centre. CAT is present in almost all aerobic living organisms, where it catalyzes the disproportionation of H2O2 into oxygen and water without forming free radicals. In order to study this catalytic mechanism in detail, the direct electrochemistry of CAT has been investigated at various modified electrode surfaces with and without nanomaterials. The results show that CAT immobilized on nanomaterial modified electrodes shows excellent catalytic activity, high sensitivity and the lowest detection limit for H2O2 determination. In the presence of nanomaterials, the direct electron transfer between the heme group of the enzyme and the electrode surface improved significantly. Moreover, the immobilized CAT is highly biocompatible and remains extremely stable within the nanomaterial matrices. This review discusses about the versatile approaches carried out in CAT immobilization for direct electrochemistry and electrochemical sensor development aimed as efficient H2O2 determination. The benefits of immobilizing CAT in nanomaterial matrices have also been highlighted

A Review on the Electrochemical Sensors and Biosensors Composed of Nanowires as Sensing Material

The development and application of nanowires for electrochemical sensors and biosensors are reviewed in this article. Next generation sensor platforms will require significant improvements in sensitivity, specificity and parallelism in order to meet the future needs in variety of fields. Sensors made of nanowires exploit some fundamental nanoscopic effect in order to meet these requirements. Nanowires are new materials, which have the characteristic of low weight with extraordinary mechanical, electrical, thermal and multifunctional properties. The advantages such as size scale, aspect ratio and other properties of nanowires are especially apparent in the use of electrical sensors such as electrochemical sensors and in the use of field-effect transistors. The preparation methods of nanowires and their properties are discussed along with their advantages towards electrochemical sensors and biosensors. Some key results from each article are summarized, relating the concept and mechanism behind each sensor, with experimental conditions as well as their behavior at different conditions

A Review on the Electrochemical Sensors and Biosensors Composed of Nanowires as Sensing Material

The development and application of nanowires for electrochemical sensors and biosensors are reviewed in this article. Next generation sensor platforms will require significant improvements in sensitivity, specificity and parallelism in order to meet the future needs in variety of fields. Sensors made of nanowires exploit some fundamental nanoscopic effect in order to meet these requirements. Nanowires are new materials, which have the characteristic of low weight with extraordinary mechanical, electrical, thermal and multifunctional properties. The advantages such as size scale, aspect ratio and other properties of nanowires are especially apparent in the use of electrical sensors such as electrochemical sensors and in the use of field-effect transistors. The preparation methods of nanowires and their properties are discussed along with their advantages towards electrochemical sensors and biosensors. Some key results from each article are summarized, relating the concept and mechanism behind each sensor, with experimental conditions as well as their behavior at different conditions

Recent Updates of DNA Incorporated in Carbon Nanotubes and Nanoparticles for Electrochemical Sensors and Biosensors

Innovations in the field of electrochemical sensors and biosensors are of much importance nowadays. These devices are designed with probes and micro electrodes. The miniaturized designs of these sensors allow analyses of materials without damaging the samples. Some of these sensors are also useful for real time analysis within the host system, so these sensors are considered to be more advantageous than other types of sensors. The active sensing materials used in these types of sensors can be any material that acts as a catalyst for the oxidation or reduction of particular analyte or set of analytes. Among various kinds of sensing materials, deoxyribonucleic acid (DNA), carbon nanotubes (CNTs) and nanoparticles have received considerable attraction in recent years. DNA is one of the classes of natural polymers, which can interact with CNTs and nanoparticles to form new types of composite materials. These composite materials have also been used as sensing materials for sensor applications. They have advantages in characteristics such as extraordinary low weight and multifunctional properties. In this article, advantages of DNA incorporated in CNT and nanoparticle hybrids for electrochemical sensors and biosensors are presented in detail, along with some key results noted from the literature

Nanomaterials- Acetylcholinesterase Enzyme Matrices for Organophosphorus Pesticides Electrochemical Sensors: A Review

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Methyl salicylate detection via electrochemical transients using nano spinel Co3O4 films

The mixed nano spinel Co3O4 films were fabricated through electrochemical deposition followed by peroxide oxidation and heat treatment. Electrochemical characteristics of the deposition and textural as well as morphological characteristics of the films were analyzed. Both 400 plane for Co3O4 and the 200 plane for CoO were noted. Based on IR studies, hydroxides decomposed into oxides on annealing. Oxide films are having the stoichiometric atomic weight ratio, O:Co as 1:2.7. Chronopotentiometric and chronoamperometric transients were recorded for the anodic oxidation of methyl salicylate using cobalt oxide films. Based on the electrochemical kinetic data, oxidation mechanism scheme is proposed and the net oxidation rate depends on sluggish charge-transfer limitations. Salicylate di-ion to 1, 2 benzoquinone is more favorable than 1, 4 benzoquinone derivative with four-electron transfer, whereas methoxide to formaldehyde involves two-electron transfer

A Model for Safe Transport of Critical Patients in Unmanned Drones with a 'Watch' Style Continuous Anesthesia Sensor

We envision unmanned aerial vehicles (UAV) for rapid evacuation of critically-ill patients from hazardous locations to health care facilities in safe zones. For safety, medical teams accompany patients to monitor vital signs and titrate anesthesia dose during transport. UAV transports would require continuous automated remote monitoring of both vital signs and of sedative dose to be feasible and safe. Volatile anesthetics (isoflurane) are the only anesthetic agents that can be monitored continuously with infrared spectroscopy (IR) devices; but unsuitable for transport. Our objective is to devise a safe UAV transport protocol incorporating novel technology for gas monitoring. Our group has developed and tested a miniaturized wearable fuel cell sensor that can detect isoflurane gas vapors as low as 40 ppm (within therapeutic range) with a sensitivity of 0.0112 nA ppm−1 cm−2. Ambient signal interference was resolved by principal component analysis (PCA). Data variance of 1st and 2nd principal components was 88.68% and 11.31%, respectively. The PCA regression model reported here can determine accurate Isoflurane concentrations. Electronic IoT platform has been built constituting micro-fuel cell, miniaturized electronic components with Bluetooth. This wearable sensor can be incorporated into a comprehensive life support system for casualty evacuation in conjunction with autonomous UAV emergency medical operations

Kinetic and Mechanistic Parameters of Laccase Catalyzed Direct Electrochemical Oxygen Reduction Reaction

This article presents the kinetic studies of oxygen reduction by one of the most important multicopper oxidases (fungal laccase) using the classic tool of electrochemistry: rotating ring-disk electrode (RRDE). Laccase was immobilized on a multiwalled carbon nanotube (MWNT) modified inert disk electrode using 1-pyrenebutanoic acid succinimidyl ester (PBSE), as a tethering agent. The conditions for laccase immobilization on MWNT were optimized to prepare a highly active composite electro-catalyst for O₂ reduction. The mechanistic as well as kinetic parameters such as Tafel slopes, number of electrons transferred, electrochemical rate constants (for heterogeneous charge transfer) and electron transfer rate constant were calculated from the RRDE experiment results. The Tafel slope obtained was close to the value of that of ideal four-electron reduction of O₂ to water indicating a highly active laccase in the tethered composite. The RRDE results also suggested the presence of intermediate steps in the oxygen reduction reaction. A model pathway for O₂ reduction reaction at the laccase composite modified electrode was postulated, and rate constants for individual reactions in the pathway were calculated. The rate constant for four-electron O₂ reduction was determined to be 1.46 × 10^–3 mol s^–1, indicating excellent electro-catalytic activity of the laccase-MWNT composite catalyst