Electrochemistry and application of a novel monosubstituted squarate electron-transfer mediator in a glucose oxidase-doped poly(phenol) sensor

Electrosynthetic poly(phenol) nanofilms were deposited in situ on platinum electrodes in the presence and absence of glucose oxidase. The synthesis charges and currents of the nonconducting polymer films were recorded at various applied potentials for films grown from 25–100 mM phenol concentrations. Film parameters such as the standard rate constant for film deposition, film thickness, and surface concentration of the poly(phenol) films were evaluated from the cyclic and step voltammograms of the polymerization process. A novel electron-transfer mediator consisting of monosubstituted 4-hydroxycyclobut-3-ene-1,2-dione (squarate) was used as a mediator for Pt/poly(phenol) nano-film/GOx amperometric glucose biosensors. Amperometric responses for 3-diphenylamino-4-hydroxycyclobut-3-ene-1,2- dione (diphenylaminosquarate: E°′ = of +328 mV/Ag-AgCl at pH 7.0)-mediated systems were measured by both steady-state amperometric and cyclic voltammetry. The sensor sensitivity was calculated to be 558 nA cm –2 (µM) –1

Development of an amperometric biosensor for the detection of alcohol: a thesis presented in partial fulfilment of the requirements for the degree of Masters in Science in Biochemistry at Massey University

The aim of the following work was to design a biosensor for the detection of ethanol. A biosensor is an analytical device in which a biological sensing element is connected to or integrated with a physical transducing element. Amperometric enzyme biosensors utilise one or more enzymes to convert a substance which cannot be measured electrochemically to one which can be. In the case of an alcohol biosensor one of two enzymes (alcohol dehydrogenase and alcohol oxidase) can be used to convert electrochemically stable alcohol to either hydrogen peroxide or NADH which can be oxidised. In the design of an alcohol biosensor there are three major variables to consider, these are; enzyme type, electrode material, and immobilisation technique. The goal was to select optimum conditions for the formulation of the desired sensor. In the present work the electrode materials used were platinum, carbon (foil and paste) and the conducting organic salt N-methyl phenazinium.Tetracyanoquinodimethane (NMP.TCNQ). The immobilisation techniques used were; adsorption, cross-linking to a protein matrix and covalent binding. Of the biosensors produced from a selected combination or these variables each was tested by one or more of the following; cyclic voltammetry, enzyme assay, and amperometry. The most promising approach appears to be that of conjugating enzyme to haemin and allowing the conjugate to bind irreversibly to platinum via the haemin group. An electrode made with the organic salt NMP.TCNQ looked promising also but because the salt is readily oxidised it is unstable and therefore not an ideal electrode material

High-Performance Bioinstrumentation for Real-Time Neuroelectrochemical Traumatic Brain Injury Monitoring

Traumatic brain injury (TBI) has been identified as an important cause of death and severe disability in all age groups and particularly in children and young adults. Central to TBIs devastation is a delayed secondary injury that occurs in 30–40% of TBI patients each year, while they are in the hospital Intensive Care Unit (ICU). Secondary injuries reduce survival rate after TBI and usually occur within 7 days post-injury. State-of-art monitoring of secondary brain injuries benefits from the acquisition of high-quality and time-aligned electrical data i.e., ElectroCorticoGraphy (ECoG) recorded by means of strip electrodes placed on the brains surface, and neurochemical data obtained via rapid sampling microdialysis and microfluidics-based biosensors measuring brain tissue levels of glucose, lactate and potassium. This article progresses the field of multi-modal monitoring of the injured human brain by presenting the design and realization of a new, compact, medical-grade amperometry, potentiometry and ECoG recording bioinstrumentation. Our combined TBI instrument enables the high-precision, real-time neuroelectrochemical monitoring of TBI patients, who have undergone craniotomy neurosurgery and are treated sedated in the ICU. Electrical and neurochemical test measurements are presented, confirming the high-performance of the reported TBI bioinstrumentation

Design and construction of a distributed sensor NET for biotelemetric monitoring of brain energetic metabolism using microsensors and biosensors

Neurochemical pathways involved in brain physiology or disease pathogenesis are mostly unknown either in physiological conditions or in neurodegenerative diseases. Nowadays the most frequent usage for biotelemetry is in medicine, in cardiac care units or step-down units in hospitals, even if virtually any physiological signal could be transmitted (FCC, 2000; Leuher, 1983; Zhou et al., 2002). In this chapter we present a wireless device connected with microsensors and biosensors capable to detect real-time variations in concentrations of important compounds present in central nervous system (CNS) and implicated in brain energetic metabolism (Bazzu et al., 2009; Calia et al., 2009)

Fully Integrated Biochip Platforms for Advanced Healthcare

Recent advances in microelectronics and biosensors are enabling developments of innovative biochips for advanced healthcare by providing fully integrated platforms for continuous monitoring of a large set of human disease biomarkers. Continuous monitoring of several human metabolites can be addressed by using fully integrated and minimally invasive devices located in the sub-cutis, typically in the peritoneal region. This extends the techniques of continuous monitoring of glucose currently being pursued with diabetic patients. However, several issues have to be considered in order to succeed in developing fully integrated and minimally invasive implantable devices. These innovative devices require a high-degree of integration, minimal invasive surgery, long-term biocompatibility, security and privacy in data transmission, high reliability, high reproducibility, high specificity, low detection limit and high sensitivity. Recent advances in the field have already proposed possible solutions for several of these issues. The aim of the present paper is to present a broad spectrum of recent results and to propose future directions of development in order to obtain fully implantable systems for the continuous monitoring of the human metabolism in advanced healthcare applications

Amperometric enzyme sensor to check the total antioxidant capacity of several mixed berries. comparison with two other spectrophotometric and fluorimetric methods

The aim of this research was to test the correctness of response of a superoxide dismutase amperometric biosensor used for the purpose of measuring and ranking the total antioxidant capacity of several systematically analysed mixed berries. Several methods are described in the literature for determining antioxidant capacity, each culminating in the construction of an antioxidant capacity scale and each using its own unit of measurement. It was therefore endeavoured to correlate and compare the results obtained using the present amperometric biosensor method with those resulting from two other different methods for determining the total antioxidant capacity selected from among those more frequently cited in the literature. The purpose was to establish a methodological approach consisting in the simultaneous application of different methods that it would be possible to use to obtain an accurate estimation of the total antioxidant capacity of different mixed berries and the food product

Applications of Graphene Quantum Dots in Biomedical Sensors

Due to the proliferative cancer rates, cardiovascular diseases, neurodegenerative disorders, autoimmune diseases and a plethora of infections across the globe, it is essential to introduce strategies that can rapidly and specifically detect the ultralow concentrations of relevant biomarkers, pathogens, toxins and pharmaceuticals in biological matrices. Considering these pathophysiologies, various research works have become necessary to fabricate biosensors for their early diagnosis and treatment, using nanomaterials like quantum dots (QDs). These nanomaterials effectively ameliorate the sensor performance with respect to their reproducibility, selectivity as well as sensitivity. In particular, graphene quantum dots (GQDs), which are ideally graphene fragments of nanometer size, constitute discrete features such as acting as attractive fluorophores and excellent electro-catalysts owing to their photo-stability, water-solubility, biocompatibility, non-toxicity and lucrativeness that make them favorable candidates for a wide range of novel biomedical applications. Herein, we reviewed about 300 biomedical studies reported over the last five years which entail the state of art as well as some pioneering ideas with respect to the prominent role of GQDs, especially in the development of optical, electrochemical and photoelectrochemical biosensors. Additionally, we outline the ideal properties of GQDs, their eclectic methods of synthesis, and the general principle behind several biosensing techniques.DFG, 428780268, Biomimetische Rezeptoren auf NanoMIP-Basis zur Virenerkennung und -entfernung mittels integrierter Ansätz

Printed, Flexible Lactate Sensors: Design Considerations Before Performing On-Body Measurements.

This work reports the process of sensor development, optimization, and characterization before the transition to on-body measurements can be made. Sensors using lactate oxidase as a sensing mechanism and tetrathiafulvalene as a mediator were optimized for sporting applications. Optimized sensors show linear range up to 24 mM lactate and sensitivity of 4.8 μA/mM which normalizes to 68 μA*cm-2/mM when accounting for surface area of the sensor. The optimized sensors were characterized 3 different ways: using commercially available reference and counter electrodes, using printed reference and counter electrodes, and using a printed reference electrode with no counter electrode. Sensors intended for measuring sweat must be selective in the presence of sweat constituents. Thus, in addition to traditional characterization in pH 7.0 buffer, we characterized sensor performance in solutions intended to approximate sweat. Sensor performance in pH 7.0 buffer solution was not reflective of sensor performance in artificial sweat, indicating that further characterization is necessary between sensor measurement in pH 7.0 buffer and on-body measurements. Furthermore, we performed enzyme activity measurements and sensor measurements concurrently in five different salts individually, finding that while NH4Cl and MgCl2 do not affect enzyme activity or sensor performance in physiologically relevant ranges of salt concentration, NaCl concentration or KCl concentration decreases enzyme activity and sensor current. On the other hand, CaCl2 induced a nonlinear change in sensor performance and enzyme activity with increasing salt concentration

Catalase-based modified graphite electrode for hydrogen peroxide detection in different beverages

A catalase-based (NAF/MWCNTs) nanocomposite film modified glassy carbon electrode for hydrogen peroxide (H2O2) detection was developed. The developed biosensor was characterized in terms of its bioelectrochemical properties. Cyclic voltammetry (CV) technique was employed to study the redox features of the enzyme in the absence and in the presence of nanomaterials dispersed in Nafion polymeric solution. The electron transfer coefficient, , and the electron transfer rate constant, , were found to be 0.42 and 1.71 s−1, at pH 7.0, respectively. Subsequently, the same modification steps were applied to mesoporous graphite screenprinted electrodes. Also, these electrodes were characterized in terms of their main electrochemical and kinetic parameters. The biosensor performances improved considerably after modification with nanomaterials. Moreover, the association of Nafion with carbon nanotubes retained the biological activity of the redox protein. The enzyme electrode response was linear in the range 2.5– 1150 mol L−1, with LOD of 0.83 mol L−1. From the experimental data, we can assess the possibility of using the modified biosensor as a useful tool for H2O2 determination in packaged beverages