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Herein, fibroin, polylactide (PLA), and carbon are investigated for their suitability as biocompatible and biodegradable materials for amperometric biosensors. For this purpose, screen‐printed carbon electrodes on the biodegradable substrates fibroin and PLA are modified with a glucose oxidase membrane and then encapsulated with the biocompatible material Ecoflex. The influence of different curing parameters of the carbon electrodes on the resulting biosensor characteristics is studied. The morphology of the electrodes is investigated by scanning electron microscopy, and the biosensor performance is examined by amperometric measurements of glucose (0.5–10 mM) in phosphate buffer solution, pH 7.4, at an applied potential of 1.2 V versus a Ag/AgCl reference electrode. Instead of Ecoflex, fibroin, PLA, and wound adhesive are tested as alternative encapsulation compounds: a series of swelling tests with different fibroin compositions, PLA, and Ecoflex has been performed before characterizing the most promising candidates by chronoamperometry. Therefore, the carbon electrodes are completely covered with the particular encapsulation material. Chronoamperometric measurements with H2O2 concentrations between 0.5 and 10 mM enable studying the leakage current behavior. [ABSTRACT FROM AUTHOR]

This work aimed to develop an easy-to-use smartphone-based electrochemical biosensor to quickly assess a coffee blend's total polyphenols (Phs) content at the industrial and individual levels. The device is based on a commercial carbon-based screen-printed electrode (SPE) modified with multi-walled carbon nanotubes (CNTs) and gold nanoparticles (GNPs). At the same time, the biological recognition element, Laccase from Trametes versicolor, TvLac, was immobilized on the sensor surface by using glutaraldehyde (GA) as a cross-linking agent. The platform was electrochemically characterized to ascertain the influence of the SPE surface modification on its performance. The working electrode (WE) surface morphology characterization was obtained by scanning electron microscopy (SEM) and Fourier-transform infrared (FT-IR) imaging. All the measurements were carried out with a micro-potentiostat, the Sensit Smart by PalmSens, connected to a smartphone. The developed biosensor provided a sensitivity of 0.12 μA/μM, a linear response ranging from 5 to 70 μM, and a lower detection limit (LOD) of 2.99 μM. Afterward, the biosensor was tested for quantifying the total Phs content in coffee blends, evaluating the influence of both the variety and the roasting degree. The smartphone-based electrochemical biosensor's performance was validated through the Folin–Ciocâlteu standard method. [ABSTRACT FROM AUTHOR]

COVID-19, a viral respiratory illness, is caused by Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2), which was first identified in Wuhan, China, in 2019 and rapidly spread worldwide. Testing and isolation were essential to control the virus's transmission due to the severity of the disease. In this context, there is a global interest in the feasibility of employing nano-biosensors, especially those using graphene as a key material, for the real-time detection of the virus. The exceptional properties of graphene and the outstanding performance of nano-biosensors in identifying various viruses prompted a feasibility check on this technology. This paper focuses on the recent advances in using graphene-based electrochemical biosensors for sensing the SARS-CoV-2 virus. Specifically, it reviews various types of electrochemical biosensors, including amperometric, potentiometric, and impedimetric biosensors, and discusses the current challenges associated with biosensors for SARS-CoV-2 detection. The conclusion of this review discusses future directions in the field of electrochemical biosensors for SARS-CoV-2 detection, underscoring the importance of continued research and development in this domain. [ABSTRACT FROM AUTHOR]

In this study, an implantable stereo-electroencephalography (sEEG) depth electrode was functionalised with an enzyme coating for enzyme-based biosensing of glucose and L-glutamate. This was done because personalised medicine could benefit from active real-time neurochemical monitoring on small spatial and temporal scales to further understand and treat neurological disorders. To achieve this, the sEEG depth electrode was characterised using cyclic voltammetry (CV), differential pulse voltammetry (DPV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS) using several electrochemical redox mediators (potassium ferri/ferrocyanide, ruthenium hexamine chloride, and dopamine). To improve performance, the Pt sensors on the sEEG depth electrode were coated with platinum black and a crosslinked gelatin-enzyme film to enable enzymatic biosensing. This characterisation work showed that producing a useable electrode with a good electrochemical response showing the expected behaviour for a platinum electrode was possible. Coating with Pt black improved the sensitivity to H2O2 over unmodified electrodes and approached that of well-defined Pt macro disc electrodes. Measured current showed good dependence on concentration, and the calibration curves report good sensitivity of 29.65 nA/cm2/μM for glucose and 8.05 nA/cm2/μM for L-glutamate with a stable, repeatable, and linear response. These findings demonstrate that existing clinical electrode devices can be adapted for combined electrochemical and electrophysiological measurement in patients and obviate the need to develop new electrodes when existing clinically approved devices and the associated knowledge can be reused. This accelerates the time to use and application of in vivo and wearable biosensing for diagnosis, treatment, and personalised medicine. [ABSTRACT FROM AUTHOR]

Biosensor behaviour is characterised by non-linear differential equations that describe well-defined physical, chemical, and biological processes. Mathematical modelling of these biosensors is highly desirable since they have many applications. These models enable the prediction of a variety of their properties. In this study, the cyclic conversion of the substrate in an amperometric biosensor with an oxidase enzyme membrane electrode is studied using a mathematical model. The governing parameters for the Michaelis–Menten kinetics of enzymatic reactions are the enzyme kinetic and diffusion rates across the enzymatic layer. In this paper, we solved the non-linear equations analytically and numerically for all experimental values of parameters. This problem is simulated in MATLAB® v2016b software using the PDE solver. Our analytical solutions are compared to simulation results to validate the proposed model.

A sensitive biological system and a detector system with appropriate transducers for obtaining the output signals make up a biosensor. These devices have a wide range of uses, including disease screening, the detection of environmental pollutants, agriculture, and routine medical examinations. The product's selectivity, sensitivity, stability, and lower production costs will all be critical factors in its widespread commercialisation. Recently, scientists have tackled the issue of developing a nano biosensor with a high degree of sensitivity and selectivity for the recognition of biomarkers of immune responses and cancer. The fact that electrochemical nano biosensors may successfully be employed for detecting medications in addition to pathogen biomarkers has significantly altered the COVID picture in our favour. During the worldwide epidemic, a number of cutting-edge SARS - CoV-2 biosensors with portable, smartphone-connected instant detection devices were helpful. This article provides a concise summary of the underlying working principle, generations of developments and numerous detection methods employed by electrochemical biosensors. The difficulties, knowledge gaps, and possible solutions in the field of electrochemical biosensors are all discussed in the context of this categorisation. This novel overview also sheds light on the different kinds of electrochemical biosensors and the tasks they perform, as well as recent developments in the “smart biosensor” industry with potential future directions and challenges for this growing subject.

The investigated polymeric matrixes consisted of epoxidized linseed oil (ELO), acrylated epoxidized soybean oil (AESO), trimethylolpropane triglycidyl ether (RD1), vanillin dimethacrylate (VDM), triarylsulfonium hexafluorophosphate salts (PI), and 2,2-dimethoxy-2-phenylacetophenone (DMPA). Linseed oil-based (ELO/PI, ELO/10RD1/PI) and soybean oil-based (AESO/VDM, AESO/VDM/DMPA) polymers were obtained by cationic and radical photopolymerization reactions, respectively. In order to improve the cross-linking density of the resulting polymers, 10 mol.% of RD1 was used as a reactive diluent in the cationic photopolymerization of ELO. In parallel, VDM was used as a plasticizer in AESO radical photopolymerization reactions. Positron annihilation lifetime spectroscopy (PALS) was used to characterize vegetable oil-based UV-cured polymers regarding their structural stability in a wide range of temperatures (120–320 K) and humidity. The polymers were used as laccase immobilization matrixes for the construction of amperometric biosensors. A direct dependence of the main operational parameters of the biosensors and microscopical characteristics of polymer matrixes (mostly on the size of free volumes and water content) was established. The biosensors are intended for the detection of trace water pollution with xenobiotics, carcinogenic substances with a very negative impact on human health. These findings will allow better predictions for novel polymers as immobilization matrixes for biosensing or biotechnology applications. [ABSTRACT FROM AUTHOR]

Clinical assessment based on a single biomarker is in many circumstances not sufficient for adequate diagnosis of a disease or for monitoring its therapy. Multiplexing, the measurement of multiple analytes from one sample and/or of the same target from different samples simultaneously, could enhance the accuracy of the diagnosis of diseases and their therapy success. Thus, there is a great and urgent demand for multiplexed biosensors allowing a low-cost, easy-to-use, and rapid on-site testing. In this work, we present a simple, flexible, and highly scalable strategy for implementing microfluidic multiplexed electrochemical biosensors (BiosensorX). Our technology is able to detect 4, 6, or 8 (different) analytes or samples simultaneously using a sequential design concept: multiple immobilization areas, where the assay components are adsorbed, followed by their individual electrochemical cells, where the amperometric signal readout takes place, within a single microfluidic channel. Here, first we compare vertical and horizontal designs of BiosensorX chips using a model assay. Owing to its easier handling and superior fluidic behavior, the vertical format is chosen as the final multiplexed chip design. Consequently, the feasibility of the BiosensorX for multiplexed on-site testing is successfully demonstrated by measuring meropenem antibiotics via an antibody-free β-lactam assay. The multiplexed biosensor platform introduced can be further extended for the simultaneous detection of other anti-infective agents and/or biomarkers (such as renal or inflammation biomarkers) as well as different (invasive and non-invasive) sample types, which would be a major step towards sepsis management and beyond. [ABSTRACT FROM AUTHOR]

Amperometric biosensors have emerged as a cutting-edge technology in clinical diagnostics, thanks to their high level of sensitivity, rapid analytical results, compact size, and ability to monitor health parameters non-invasively and continuously using flexible and wearable sensors. This review explores the latest developments in the field of amperometric biosensing for medical applications. It discusses the materials used to construct these sensors and pays particular attention to biosensors designed to measure glucose, lactate, cholesterol, urea, and uric acid levels. The review also addresses the technological limitations and drawbacks of these devices. Furthermore, it presents the current status and identifies future trends in the development of flexible, wearable biosensors capable of providing continuous monitoring of a patient's health status., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

This work aimed to develop an easy-to-use smartphone-based electrochemical biosensor to quickly assess a coffee blend’s total polyphenols (Phs) content at the industrial and individual levels. The device is based on a commercial carbon-based screen-printed electrode (SPE) modified with multi-walled carbon nanotubes (CNTs) and gold nanoparticles (GNPs). At the same time, the biological recognition element, Laccase from Trametes versicolor, TvLac, was immobilized on the sensor surface by using glutaraldehyde (GA) as a cross-linking agent. The platform was electrochemically characterized to ascertain the influence of the SPE surface modification on its performance. The working electrode (WE) surface morphology characterization was obtained by scanning electron microscopy (SEM) and Fourier-transform infrared (FT-IR) imaging. All the measurements were carried out with a micro-potentiostat, the Sensit Smart by PalmSens, connected to a smartphone. The developed biosensor provided a sensitivity of 0.12 μA/μM, a linear response ranging from 5 to 70 μM, and a lower detection limit (LOD) of 2.99 μM. Afterward, the biosensor was tested for quantifying the total Phs content in coffee blends, evaluating the influence of both the variety and the roasting degree. The smartphone-based electrochemical biosensor’s performance was validated through the Folin–Ciocâlteu standard method.

Metallic nanoparticles potentially have wide practical applications in various fields of science and industry. In biosensorics, they usually act as catalysts or nanozymes (NZs) and as mediators of electron transfer. We describe here the development of amperometric biosensors (ABSs) based on purified oxidases, synthesized nanoparticles of CuCe (nCuCe), and micro/nanoporous gold (pAu), which were electro-deposited on a graphite electrode (GE). As an effective peroxidase (PO)-like NZ, nCuCe was used here as a hydrogen-peroxide-sensing platform in ABSs that were based on glucose oxidase, alcohol oxidase, methylamine oxidase, and L-arginine oxidase. At the same time, nCuCe is an electroactive mediator and has been used in laccase-based ABSs. As a result, the ABSs we constructed and characterized were based on glucose, methanol, methyl amine, L-arginine, and catechol, respectively. The developed nCuCe-based ABSs exhibited improved analytical characteristics in comparison with the corresponding PO-based ABSs. Additionally, the presence of pAu, with its extremely advanced chemo-sensing surface layer, was shown to significantly increase the sensitivities of all constructed ABSs. As an example, the bioelectrodes containing laccase/GE, laccase/nCuCe/GE, and laccase/nCuCe/pAu/GE exhibited sensitivities to catechol at 2300, 5055, and 9280 A·M−1·m−2, respectively. We demonstrate here that pAu is an effective carrier of electroactive nanomaterials coupled with oxidases, which may be promising in biosensors. [ABSTRACT FROM AUTHOR]

Biosensor behaviour is characterised by non-linear differential equations that describe well-defined physical, chemical, and biological processes. Mathematical modelling of these biosensors is highly desirable since they have many applications. These models enable the prediction of a variety of their properties. In this study, the cyclic conversion of the substrate in an amperometric biosensor with an oxidase enzyme membrane electrode is studied using a mathematical model. The governing parameters for the Michaelis–Menten kinetics of enzymatic reactions are the enzyme kinetic and diffusion rates across the enzymatic layer. In this paper, we solved the non-linear equations analytically and numerically for all experimental values of parameters. This problem is simulated in MATLAB® v2016b software using the PDE solver. Our analytical solutions are compared to simulation results to validate the proposed model. [ABSTRACT FROM AUTHOR]

A compact, low-cost and low-powered device was developed and arranged for multiplexed biodetection of sea water contaminants from continuous flow mode. Electronics, mechanics and fluidics were designed to guarantee identical functional liquid flow through eight parallel sensor microchambers during a predetermined time period providing 8 values at the same time. The accuracy and repeatability of the device was tested in-lab, achieving a deviation of less than 10% when measuring the same analyte in all the chambers. The experimental results obtained with our device were finally compared with those measured in continuous flux by a commercial potentiostat SP150 (Bio-Logic Science Instruments), obtaining identical results, which validated the proposed device.

Although the basic theory for electrochemical measurement is well known, there is still much to be developed in specific instrumental systems for biosensors, especially to achieve fast response times, usefulness, and low-cost equipment. In this regard, continuous flow analysis (CFA) systems with an integrated biosensor are valuable tools for bioanalysis monitoring. These systems are suitable for automation and monitoring in real time with a short response time. Among biosensors, amperometric ones are the most used due to their high selectivity and wide linear range. In this work, we design and develop all parts of an automated CFA system for bioanalysis based on amperometric biosensors. It consists of several inlets for the samples, standards, and carrier solution; a fluidic subsystem; an electronic subsystem in which output voltage will be directly correlated to the analyte concentration in the solution; and a software application to configure and control all the features of the system. The prototype was successfully validated using an amperometric biosensor to analyze the ethanol content of low-alcohol beers. [ABSTRACT FROM AUTHOR]

There are limited data on amperometric biosensors (ABSs) for L-arginine (Arg) determination based on oxidases that produce hydrogen peroxide (H2O2) as a byproduct of enzymatic reaction, and artificial peroxidases (POs) for decomposition of H2O2. The most frequently proposed Arg-sensitive oxidase-based ABSs contain at least two enzymes in the bioselective layer; this complicates the procedure and increases the cost of analysis. Therefore, the construction of a one-enzyme ABS for Arg analysis is a practical problem. In the current work, fabrication, and characterization of three ABS types for the direct measurement of Arg were proposed. L-arginine oxidase (ArgO) isolated from the mushroom Amanita phalloides was co-immobilized with PO-like nanozymes (NZs) on the surface of graphite electrodes. As PO mimetics, chemically synthesized NZs of CeCu (nCeCU) and NiPtPd (nNiPtPd), as well as green-synthesized hexacyanoferrate of copper (gCuHCF), were used. The novel ABSs exhibited high sensitivity and selectivity to Arg, broad linear ranges and good storage stabilities. Two ABSs were tested on real samples of products containing Arg, including the pharmaceutical preparation "Tivortine", juices, and wine. A high correlation (R = 0.995) was demonstrated between the results of testing "Tivortine" and juice using nCeCU/GE and nNiPtPd/GE. It is worth mentioning that only a slight difference (less than 1%) was observed for "Tivortin" between the experimentally determined content of Arg and its value declared by the producer. The proposed ArgO-NZ-based ABSs may be promising for Arg analysis in different branches of science, medicine, and industry. [ABSTRACT FROM AUTHOR]

Metallic nanoparticles potentially have wide practical applications in various fields of science and industry. In biosensorics, they usually act as catalysts or nanozymes (NZs) and as mediators of electron transfer. We describe here the development of amperometric biosensors (ABSs) based on purified oxidases, synthesized nanoparticles of CuCe (nCuCe), and micro/nanoporous gold (pAu), which were electro-deposited on a graphite electrode (GE). As an effective peroxidase (PO)-like NZ, nCuCe was used here as a hydrogen-peroxide-sensing platform in ABSs that were based on glucose oxidase, alcohol oxidase, methylamine oxidase, and L-arginine oxidase. At the same time, nCuCe is an electroactive mediator and has been used in laccase-based ABSs. As a result, the ABSs we constructed and characterized were based on glucose, methanol, methyl amine, L-arginine, and catechol, respectively. The developed nCuCe-based ABSs exhibited improved analytical characteristics in comparison with the corresponding PO-based ABSs. Additionally, the presence of pAu, with its extremely advanced chemo-sensing surface layer, was shown to significantly increase the sensitivities of all constructed ABSs. As an example, the bioelectrodes containing laccase/GE, laccase/nCuCe/GE, and laccase/nCuCe/pAu/GE exhibited sensitivities to catechol at 2300, 5055, and 9280 A·M−1·m−2, respectively. We demonstrate here that pAu is an effective carrier of electroactive nanomaterials coupled with oxidases, which may be promising in biosensors.

There are limited data on amperometric biosensors (ABSs) for L-arginine (Arg) determination based on oxidases that produce hydrogen peroxide (H2O2) as a byproduct of enzymatic reaction, and artificial peroxidases (POs) for decomposition of H2O2. The most frequently proposed Arg-sensitive oxidase-based ABSs contain at least two enzymes in the bioselective layer; this complicates the procedure and increases the cost of analysis. Therefore, the construction of a one-enzyme ABS for Arg analysis is a practical problem. In the current work, fabrication, and characterization of three ABS types for the direct measurement of Arg were proposed. L-arginine oxidase (ArgO) isolated from the mushroom Amanita phalloides was co-immobilized with PO-like nanozymes (NZs) on the surface of graphite electrodes. As PO mimetics, chemically synthesized NZs of CeCu (nCeCU) and NiPtPd (nNiPtPd), as well as green-synthesized hexacyanoferrate of copper (gCuHCF), were used. The novel ABSs exhibited high sensitivity and selectivity to Arg, broad linear ranges and good storage stabilities. Two ABSs were tested on real samples of products containing Arg, including the pharmaceutical preparation “Tivortine”, juices, and wine. A high correlation (R = 0.995) was demonstrated between the results of testing “Tivortine” and juice using nCeCU/GE and nNiPtPd/GE. It is worth mentioning that only a slight difference (less than 1%) was observed for “Tivortin” between the experimentally determined content of Arg and its value declared by the producer. The proposed ArgO-NZ-based ABSs may be promising for Arg analysis in different branches of science, medicine, and industry.

• Modification of electrodes with Polypyrrole prepared through biocatalysis. • Incorporation of enzyme extract within Ppy, proved by chronoamperometric analysis. • Sensitive catechol detection in fruit wines based on white-rot fungi enzyme extract and polypyrrole. Utilization of polyphenol oxidases (laccase, tyrosinase) in biosensor technology is an efficient approach towards phenol detection, which is significant in numerous fields such as environmental monitoring, food industry etc. The use of crude extract instead of pure enzyme eliminates the need for costly and laborious processes of enzyme separation and purification. This study employs polyphenol oxidase extract, biosynthesized by white-rot fungi Trametes pubescens (TP) for the development of amperometric biosensors for catechol detection. The catalytic activity of the crude extract was firstly used to induce the bio-synthesis of conducting polymer - polypyrrole (Ppy), resulting in the self-encapsulation of the enzyme extract within the conducting material. The viability and biological integrity of the enzyme extract was preserved after the synthesis and was able to efficiently detect phenolic compounds such as catechol. Comparative evaluations between the biosynthesized Ppy based biosensor (bio-Ppy) and the biosensor based on bio-PPy with additional enzyme extract (bio-Ppy- TP) were performed. Lastly, the performance of these two biosensors was compared with that of a third one, based on chemically synthesized Ppy with enzyme extract (chem-Ppy- TP). All three types of biosensors proved high efficiency for catechol detection at low concentration (1–60 μM) and were employed for real sample detection in fruit wines showing linear correlation with the spectrophotometric results obtained with the Folin-Ciocalteau standard test. [ABSTRACT FROM AUTHOR]

Novel nanomaterials, including metallic nanoparticles obtained via green synthesis (gNPs), have a great potential for application in biotechnology, industry and medicine. The special role of gNPs is related to antibacterial agents, fluorescent markers and carriers for drug delivery. However, application of gNPs for construction of amperometric biosensors (ABSs) is not well documented. The aim of the current research was to study potential advantages of using gNPs in biosensorics. The extracellular metabolites of the yeast Ogataea polymorpha were used as reducing agents for obtaining gNPs from the corresponding inorganic ions. Several gNPs were synthesized, characterized and tested as enzyme carriers on the surface of graphite electrodes (GEs). The most effective were Pd-based gNPs (gPdNPs), and these were studied further and applied for construction of laccase- and alcohol oxidase (AO)-based ABSs. AO/GE, AO-gPdNPs/GE, laccase/GE and laccase-gPdNPs/GE were obtained, and their analytical characteristics were studied. Both gPdNPs-modified ABSs were found to have broader linear ranges and higher storage stabilities than control electrodes, although they are less sensitive toward corresponding substrates. We thus conclude that gPdNPs may be promising for construction of ABSs for enzymes with very high affinities to their substrates. [ABSTRACT FROM AUTHOR]

Abstract A chemical vapor deposition (CVD) was employed to deposit ZnO thin films on two different substrates, glass (quartz) and silicon. The characterization of structural properties of the comb-like nanostructure ZnO thin films were carried out through X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Nanostructured thin film sensor has been fabricated to detect the Na 2 SO 2 aqueous solution concentrations. The obtained films are strongly c-axis oriented along (100) direction and have other low intensity towards the directions (101), (200) and (211), indicating polycrystalline characteristics. The film exhibits high dense comb-like nanostructured distribution which has been indicated in the SEM images, AFM images depicted the film porosity, the film deposited on the glass substrate has more pinholes and porosity than that deposited on the silicon substrate. A new sensing method has been established depending on the piezoelectrical properties of the ZnO material and the electrochemical interaction with the salt. Furthermore, the Na 2 SO 4 sensing properties of the ZnO thin film were investigated for various salt concentrations (100, 200, 300 and 400) mg/L. The nanostructured ZnO thin film exhibits higher response, very fast rise time and acceptable recovery time upon working at room temperature. The relative response of ZnO film linearly behaves with the salt concentrations biomedical sensor was obtained. In this work, the results of detailed [ABSTRACT FROM AUTHOR]

The last decade has witnessed an intensive research effort in the field of electrochemical sensors, with a particular focus on the design of amperometric biosensors for diverse analytical applications. In this context, nanomaterial integration in the construction of amperometric biosensors may constitute one of the most exciting approaches. The attractive properties of nanomaterials have paved the way for the design of a wide variety of biosensors based on various electrochemical detection methods to enhance the analytical characteristics. However, most of these nanostructured materials are not explored in the design of amperometric biosensors. This review aims to provide insight into the diverse properties of nanomaterials that can be possibly explored in the construction of amperometric biosensors.

Design, optimization and integration of biosensors hold a great potential for the development of cost-effective screening and point-of-care technologies. However, significant progress in this field can still be obtained on condition that sufficiently accurate mathematical models will be developed. Herein, we present a novel approach for the improvement of mechanistic models which do not only combine the fundamental principles but readily incorporate the results of electrochemical and morphological studies. The first generation glucose biosensors were chosen as a case study for model development and to perform cyclic voltammetry (CV) measurements. As initial step in the model development we proposed the interpretation of experimental voltammograms obtained in the absence of substrate (glucose). The model equations describe dynamic diffusion and reaction of the involved species (oxygen, oxidized/reduced forms of the mediator - Prussian Blue/Prussian White). Furthermore, the developed model was applied under various operating conditions as a crucial tool for biosensor design optimization. The obtained qualitative and quantitative dependencies towards amperometric biosensors design optimization were independently supported by results of cyclic voltammetry and multi-analytical studies, such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). Remarkably, a linear response of the optimized biosensors tested at the applied voltage (−0.14 V) in the presence of the glucose was obtained from 10 −3 to 10 −5  M (relative standard deviation (RSD) <7% per electrode). We believe that the presented model can be used to determine the exact mechanism driving the electrochemical reactions and to identify critical system parameters affecting the biosensor response that would significantly contribute to the knowledge on biosensing, device’s design and bioengineering strategies in the future. [ABSTRACT FROM AUTHOR]

Novel nanomaterials, including metallic nanoparticles obtained via green synthesis (gNPs), have a great potential for application in biotechnology, industry and medicine. The special role of gNPs is related to antibacterial agents, fluorescent markers and carriers for drug delivery. However, application of gNPs for construction of amperometric biosensors (ABSs) is not well documented. The aim of the current research was to study potential advantages of using gNPs in biosensorics. The extracellular metabolites of the yeast Ogataea polymorpha were used as reducing agents for obtaining gNPs from the corresponding inorganic ions. Several gNPs were synthesized, characterized and tested as enzyme carriers on the surface of graphite electrodes (GEs). The most effective were Pd-based gNPs (gPdNPs), and these were studied further and applied for construction of laccase- and alcohol oxidase (AO)-based ABSs. AO/GE, AO-gPdNPs/GE, laccase/GE and laccase-gPdNPs/GE were obtained, and their analytical characteristics were studied. Both gPdNPs-modified ABSs were found to have broader linear ranges and higher storage stabilities than control electrodes, although they are less sensitive toward corresponding substrates. We thus conclude that gPdNPs may be promising for construction of ABSs for enzymes with very high affinities to their substrates.

Amperometric biosensors based on glassy carbon electrodes (GCE) modified with graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) were developed. Two types of biosensors were realized employing tyrosinase (Tyr) or laccase (Lac). Before enzyme deposition GO was reduced by electrochemical route performing cyclic voltammetry. The enzyme immobilisation on the modified GC was optimised employing different agents (bovine serum albumin and glutaraldehyde as crosslinking agent, chitosan, and Nafion). The conditions for the fabrication and the storage of the biosensors were established in order to obtain good enzyme retention, high sensitivities and long-life devices. The biosensors were used for the determination of catechol and other polyphenols, i.e. , pyrogallol, epicatechin, gallic acid, 1,2-dihydroxybenzoic acid, caffeic acid, chlorogenic acid, rutin, catechin and dopamine. Eventually, their practical applicability was demonstrated by estimating the total polyphenols concentration in juice samples, expressed as epicatechin equivalents. [ABSTRACT FROM AUTHOR]

Thermal evaporated Sn thin film was deposited followed by atmospheric oxidation annealing at 550°C for 1 h to fabricate nanostructured SnO2thin film sensor. The nanostructures were characterized through X-ray diffraction, scanning electron microscopy (SEM) and electrochemical amperometric glucose (C6H12O6) sensing. The obtained film was strongly c-axis oriented along (100) direction and has other low intensity towards the directions 101, 200 and 211, indicating polycrystalline characteristics. The film exhibited high dense porous nature has been indicated in the SEM images. Furthermore, the glucose sensing properties of the as-prepared SnO2 thin film were investigated for various glucose concentrations (50, 100, 150 and 200) mg/L. The nanostructured SnO2 thin film exhibited a higher response, fast rise time 8s and suitable recovery time 53s upon working at room temperature. Linear relative response with the glucose concentrations for SnO2 thin film biomedical sensor was obtained. [ABSTRACT FROM AUTHOR]

The development and applications of biosensors in the food industry has had a rapid grown due to their sensitivity, specificity and simplicity of use with respect to classical analytical methods. In this study, glucose and ethanol amperometric biosensors integrated with a wireless telemetry system were developed and used for the monitoring of top and bottom fermentations in beer wort samples. The collected data were in good agreement with those obtained by reference methods. The simplicity of construction, the low cost and the short time of analysis, combined with easy interpretation of the results, suggest that these devices could be a valuable alternative to conventional methods for monitoring fermentation processes in the food industry. [ABSTRACT FROM AUTHOR]

Mixed self-assembled monolayers (Mixed SAMs) consisting of 8-Ferrocenyl-1-octanethiol and 6-Mercapto-1-hexanol (FcOT:MCH) with probe PNA on gold electrodes were fabricated by using two-step after the optimization of immobilization temperature of FcOT:MCH SAMs. Using AC voltammetry, a novel nucleic acid detection platform, with mixed SAMs, was proposed. A negative formal potential shift was observed after complementary ssDNA hybridization while there was no significant difference after non-complementary ssDNA hybridization. Compatible results were obtained with the measurement of formal potential differences between mixed SAMs and target DNA (complementary and non-complementary DNA) in different target DNA concentrations. The formal potential difference between mixed SAMs immobilization and complementary ssDNA hybridization was measured in different ionic strength concentrations. [ABSTRACT FROM AUTHOR]

L-glutamate is one the most important excitatory neurotransmitter at the central nervous system level and it is implicated in several pathologies. So, it is very important to monitor its variations, in real time in animal models’ brain. The present study aimed to develop and characterize a new amperometric glutamate biosensor design that exploits the selectivity of Glutamate Oxidase (GluOx) for l-glutamate, and the capability of a small molecule as propylene glycol (PG), never used before, to influence and extend the stability and the activity of enzyme. Different designs were evaluated by modifying the main components in their concentrations to find the most suitable design. Moreover, enzyme concentrations from 100 U/mL up to 200 U/mL were verified and different PG concentrations (1%, 0.1% and 0.05%) were tested. The most suitable selected design was Ptc/PPD/PEI(1%)2/GlutOx5/PG(0.1%) and it was compared to the same already described design loading PEDGE, instead of PG, in terms of over-time performances. The PG has proved to be capable of determining an over-time stability of the glutamate biosensor in particular in terms of linear region slope (LRS) up to 21 days.

The vegetable kingdom is a wide source of a diverse variety of enzymes with broad biotechnological applications. Among the main classes of plant enzymes, the polyphenol oxidases, which convert phenolic compounds to the related quinones, have been successfully used for biosensor development. The oxidation products from such enzymes can be electrochemically reduced, and the sensing is easily achieved by amperometric transducers. In this work, the polyphenoloxidases were extracted from jurubeba (Solanum paniculatum L.) fruits, and the extract was used to construct a carbon paste-based biosensor for pharmaceutical analysis and applications. The assay optimization was performed using a 0.1 mM catechol probe, taking into account the amount of enzymatic extract (50 or 200 μL) and the optimum pH (3.0 to 9.0) as well as some electrochemical differential pulse voltammetric (DPV) parameters (e.g., pulse amplitude, pulse range, pulse width, scan rate). Under optimized conditions, the biosensor was evaluated for the quantitative determination of acetaminophen, acetylsalicylic acid, methyldopa, and ascorbic acid. The best performance was obtained for acetaminophen, which responded linearly in the range between 5 and 245 μM (R = 0.9994), presenting a limit of detection of 3 μM and suitable repeatability ranging between 1.52% and 1.74% relative standard deviation (RSD).

Diabetes is a highly prevalent and chronic metabolic disease, and the continuous monitoring of diabetes is of great importance for diabetes management. Interstitial fluid glucose has an excellent correlation with blood glucose, and therefore transdermal glucose biosensors can provide accurate monitoring of diabetes. The ongoing challenges are the synergetic integration of biosensing principles, device configuration, signal transduction, novel materials, and fabrication methods. In recent years, there have been several attempts for developing new -transdermal glucose biosensors. To successfully construct a transdermal glucose biosensor, there are several interesting questions: What is the sensing principle for diabetes monitoring? What device configuration should be used? What kinds of materials should be chosen and how to integrate them into one device? What are the application and commercial status? This review would attempt to address the above questions, and explore the fundamental aspects and the practical applications of a variety of transdermal glucose biosensors. It is anticipated that this review could open up exciting opportunities for the development of next-generation transdermal devices, as well as providing monitoring methods for diabetes patients. [Display omitted] • The work reviews the sensing mechanisms for subcutaneous glucose biosensors. • The work reviews the sensing materials, device configurations, and fabrication methods comprehensively. • The work reviews the commercial devices and the application status for subcutaneous glucose biosensors. [ABSTRACT FROM AUTHOR]

High mesoporous carbon aerogels (CA) were prepared by a sol-gel method, followed by supercritical drying with liquid CO2 and pyrolysis under inert atmosphere. The morphological and structural characteristics (surface area, pore size distribution and pore volume) of CA were examined by using N2 adsorption/desorption isotherms, TEM, SEM and AFM measurements. CA, dispersed in a chitosan (Chi) solution, was immobilized on the surface of a glassy carbon (GC) electrode aiming to prepare an amperometric transducer able to improve the direct electron transfer (DET) between Phanerochaete chrysosporium cellobiose dehydrogenase ( PcCDH) and the electrode. The resulting GC/CA-Chi/ PcCDH biosensor was optimized with regards to the loading of CA and PcCDH, as well as pH of the buffer solution. The electroanalytical parameters of the optimized biosensor (maximum current responses (Imax), apparent Michaelis-Menten constants (KM)) were estimated from amperometric calibration curves for lactose. The remarkably high sensitivity towards lactose (133.7±0.2 µA cm−2 mM−1) at the GC/CA-Chi/ PcCDH electrode recommends the GC/CA-Chi electrode as an efficient transducer for PcCDH based biosensors, exploiting DET. [ABSTRACT FROM AUTHOR]

Laccase amperometric biosensors were developed to detect the catechol compound. The laccase enzyme (LAC) immobilization was performed on nanostructures of (a) titania (TiO2); (b) titania/Nafion (TiO2/NAF) (both immobilized by the sol-gel method) and a third nanostructure, which consisted of a single biosensor composite of Nafion and laccase enzyme denoted as NAF/LAC. The Nafion was deposited on a graphite electrode and used to avoid “cracking” on the matrix. The TiO2 particle size was an average of 66 nm. FTIR spectroscopy vibration modes of different composites were determined. The electrochemical behavior of the biosensor was studied using electrochemical spectroscopy (EIS) and cyclic voltammetry (CV). The biosensor based on TiO2/NAF/LAC presented the best electro-chemical properties with regard to sensitivity, stability and detection limit after a period of 22 days. [ABSTRACT FROM AUTHOR]

A flow system method for continuous determination of phenolic compounds in environmental matrices was employed using a dialysis membrane sampler and laccase- and tyrosinase-based biosensors as detector. The biosensors response to different phenolic compounds was investigated. The laccase-based biosensor showed high sensitivity to guaiacol and chloroguaiacol, while the tyrosinase-based biosensor was more sensitive to phenol and chlorophenol. Both of the biosensors presented highly selective measurements of micromolar concentration of these compounds. Detection limits around 1.1 x 10-7 mol L-1 for guaiacol and 1.9 x 10-7 mol L-1 for chloroguaiacol could be estimated for the laccase-based biosensor. Using the tyrosinase-based biosensor detection limits of 1.5 x 10-7 mol L-1 for phenol and 9.0 x 10-8 mol L-1 for chlorophenol were observed. The proposed flow method presented a linear response range between 1.0 mumol L-1 and 100.0 mumol L-1, in the optimized operational conditions (laccase-based biosensor: pH 5.0 and 0 mV vs Ag/AgCl as working potential; tyrosinase-based biosensor: pH 5.5 and 50 mV vs Ag/AgCl as working potential). Real paper mill effluent sample was analyzed by this system and by the reference colorimetric method and the results were discussed.

The last decade has witnessed an intensive research effort in the field of electrochemical sensors, with a particular focus on the design of amperometric biosensors for diverse analytical applications. In this context, nanomaterial integration in the construction of amperometric biosensors may constitute one of the most exciting approaches. The attractive properties of nanomaterials have paved the way for the design of a wide variety of biosensors based on various electrochemical detection methods to enhance the analytical characteristics. However, most of these nanostructured materials are not explored in the design of amperometric biosensors. This review aims to provide insight into the diverse properties of nanomaterials that can be possibly explored in the construction of amperometric biosensors. [ABSTRACT FROM AUTHOR]