Electrochemical Enzyme Sensor Research Articles

Electrochemical Characterization of a Novel Organoelectrocatalyst, 7-Azabicyclo[2.2.1]heptan-7-ol (ABHOL), and Its Application to Electrochemical Sensors.

Electrochemical enzyme sensors are suitable for simple monitoring methods, for example, as glucose sensors for diabetic patients; however, they have several disadvantages arising from the properties of the enzyme. Therefore, non-enzymatic electrochemical sensors using functional molecules are being developed. In this paper, we report the electrochemical characterization of a new hydroxylamine compound, 7-azabicyclo[2.2.1]heptan-7-ol (ABHOL), and its application to glucose sensing. Although the cyclic voltammogram for the first cycle was unstable, it was reproducible after the second cycle, enabling electrochemical analysis of ethanol and glucose. In the first cycle, ABHOL caused complex reactions, including electrochemical oxidation and comproportionation with the generated oxoammonium ions. The electrochemical probe performance of ABHOL was more efficient than the typical nitroxyl radical compound, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), and had similar efficiency to 9-azabicyclo[3.3.1]nonane N-oxyl (ABNO), which is activated by the bicyclic structure. The results demonstrated the advantages of ABHOL, which can be synthesized from inexpensive materials via simple methods.

Electrochemical enzyme sensor based on gold-biomass carbon composite modified electrode

In this paper a three-dimensional biomass porous carbon material (WSBPC) was prepared via carbonization combining with KOH activation method by using waste walnut shells as raw materials. Then WSBPC was adopted as a modifier to construct an electrochemical sensing platform based on carbon ionic liquid electrode for sensitive detection of trichloroacetic acid (TCA) and potassium bromate (KBrO3), in which horseradish peroxidase (HRP) was used as the catalyst and Au nanoparticle was employed as signal amplifier. The detection ranges of the supposed sensing platform for testing TCA and KBrO3 were 10.0–1000.0 mM and 0.10–1.10 mM with the lower detection limits as 3.33 mM and 0.03 mM. Beside, this method was used to determine the KBrO3 content in tap water samples with satisfactory results.

Electrochemical Biosensor Based on Horseradish Peroxidase and Black Phosphorene Quantum Dot Modified Electrode.

Black phosphorene quantum dots (BPQDs) were prepared by ultrasonic-assisted liquid-phase exfoliation and centrifugation with morphologies proved by TEM results. Furthermore, an electrochemical enzyme sensor was prepared by co-modification of BPQDs with horseradish peroxidase (HRP) on the surface of a carbon ionic liquid electrode (CILE) for the first time. The direct electrochemical behavior of HRP was studied with a pair of well-shaped voltammetric peaks that appeared, indicating that the existence of BPQDs was beneficial to accelerate the electron transfer rate between HRP and the electrode surface. This was due to the excellent properties of BPQDs, such as small particle size, high interfacial reaction activity, fast conductivity, and good biocompatibility. The presence of BPQDs on the electrode surface provided a fast channel for direct electron transfer of HRP. Therefore, the constructed electrochemical HRP biosensor was firstly used to investigate the electrocatalytic behavior of trichloroacetic acid (TCA) and potassium bromate (KBrO3), and the wide linear detection ranges of TCA and KBrO3 were 4.0-600.0 mmol/L and 2.0-57.0 mmol/L, respectively. The modified electrode was applied to the actual samples detection with satisfactory results.

The Composite Material of (PEDOT-Polystyrene Sulfonate)/Chitosan-AuNPS-Glutaraldehyde/as the Base to a Sensor with Laccase for the Determination of Polyphenols.

The described research aimed to develop the properties of the conductive composite /poly(3,4-ethylenedioxy-thiophene-poly(4-lithium styrenesulfonic acid)/chitosan-AuNPs-glutaraldehyde/ (/PEDOT-PSSLi/chit-AuNPs-GA/) and to develop an electrochemical enzyme sensor based on this composite material and glassy carbon electrodes (GCEs). The composite was created via electrochemical production of an /EDOT-PSSLi/ layer on a glassy carbon electrode (GCE). This layer was covered with a glutaraldehyde cross-linked chitosan and doped with AuNPs. The influence of AuNPs on the increase in the electrical conductivity of the chitosan layers and on facilitating the oxidation of polyphenols in these layers was demonstrated. The enzymatic sensor was obtained via immobilization of the laccase on the surface of the composite, with glutaraldehyde as the linker. The investigation of the surface morphology of the GCE/PEDOT-PSSLi/chit-AuNPs-GA/Laccase sensor was carried out using SEM and AFM microscopy. Using EDS and Raman spectroscopy, AuNPs were detected in the chitosan layer and in the laccase on the surface of the sensor. Polyphenols were determined using differential pulse voltammetry. The biosensor exhibited catalytic activity toward the oxidation of polyphenols. It has been shown that laccase is regenerated through direct electron transfer between the sensor and the enzyme. The results of the DPV tests showed that the developed sensor can be used for the determination of polyphenols. The peak current was linearly proportional to the concentrations of catechol in the range of 2-90 μM, with a limit of detection (LOD) of 1.7 μM; to those of caffeic acid in the range of 2-90 μM, LOD = 1.9 μM; and to those of gallic acid in the range 2-18 μM, LOD = 1.7 μM. Finally, the research conducted in order to determine gallic acid in a natural sample, for which white wine was used, was described.

Development of interdigitated electrode based enzyme sensor for triglyceride monitoring using engineered oxygen insensitive glycerol 3-phosphate oxidase

Triglycerides (TG) are an important biomarker of various diseases including hyper-lipidemia. Current emergent requirements for TG sensing include the development of electrochemical sensors for easy, cost-effective, disposable and single use triglyceride sensors. We propose a TG sensor using an engineered glycerol 3-phosphate oxidase (GlpO) and electrochemical detection. In this study, we aimed to develop an electrochemical TG sensor based on engineering the oxidative half reaction of GlpO to be oxygen insensitive, with the employment of an interdigitated electrode (IDE). To construct an oxygen insensitive mutant GlpO, we constructed a double mutant, Met104Phe/Asp169Glu, which revealed an engineered GlpO exhibiting repressed oxidase activity, while its dye-mediated dehydrogenase activity enhanced. The electrochemical enzyme sensor was constructed for the measurement of TG based on engineered GlpO using disposable screen-printed carbon electrode (SPCE) or disposable IDE using Ru complex as the electron mediator. By using the disposable IDE sensor, a highly sensitive electrochemical sensor for Glp was achieved, with the sensitivity of 0.4 µA/mM. The improved sensitivity was 2.4 times higher than that of SPCE (0.17 µA/mM), with LOD of 0.022 mM. Furthermore, the dry sensor strip, where the double mutant GlpO and Ru complex were dropcasted and dried on the IDE, was prepared and the Glp concentration was successfully measured in the delipidized serum solution. Therefore, by the employment of the established pretreatment method for TG to release Glp, a highly sensitive, accurate, easy and rapid electrochemical measurement method for TG will be developed using constructed M104F/D169E mutant GlpO with the combination of IDE.

Development of a Versatile Method to Construct Direct Electron Transfer-Type Enzyme Complexes Employing SpyCatcher/SpyTag System.

The electrochemical enzyme sensors based on direct electron transfer (DET)-type oxidoreductase-based enzymes are ideal for continuous and in vivo monitoring. However, the number and types of DET-type oxidoreductases are limited. The aim of this research is the development of a versatile method to create a DET-type oxidoreductase complex based on the SpyCatcher/SpyTag technique by preparing SpyCatcher-fused heme c and SpyTag-fused non-DET-type oxidoreductases, and by the in vitro formation of DET-type oxidoreductase complexes. A heme c containing an electron transfer protein derived from Rhizobium radiobacter (CYTc) was selected to prepare SpyCatcher-fused heme c. Three non-DET-type oxidoreductases were selected as candidates for the SpyTag-fused enzyme: fungi-derived flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase (GDH), an engineered FAD-dependent d-amino acid oxidase (DAAOx), and an engineered FMN-dependent l-lactate oxidase (LOx). CYTc-SpyCatcher (CYTc-SC) and SpyTag-Enzymes (ST-GDH, ST-DAAOx, ST-LOx) were prepared as soluble molecules while maintaining their redox properties and catalytic activities, respectively. CYTc-SC/ST-Enzyme complexes were formed by mixing CYTc-SpyCatcher and SpyTag-Enzymes, and the complexes retained their original enzymatic activity. Remarkably, the heme domain served as an electron acceptor from complexed enzymes by intramolecular electron transfer; consequently, all constructed CYTc-SC/ST-Enzyme complexes showed DET ability to the electrode, demonstrating the versatility of this method.

Electrochemical Enzyme Sensor Based on the Two-Dimensional Metal–Organic Layers Supported Horseradish Peroxidase

Metal-organic frames (MOFs) have recently been used to support redox enzymes for highly sensitive and selective chemical sensors for small biomolecules such as oxygen (O2), hydrogen peroxide (H2O2), etc. However, most MOFs are insulative and their three-dimensional (3D) porous structures hinder the electron transfer pathway between the current collector and the redox enzyme molecules. In order to facilitate electron transfer, here we adopt two-dimensional (2D) metal-organic layers (MOLs) to support the HRP molecules in the detection of H2O2. The correlation between the current response and the H2O2 concentration presents a linear range from 7.5 μM to 1500 μM with a detection limit of 0.87 μM (S/N = 3). The sensitivity, reproducibility, and stability of the enzyme sensor are promoted due to the facilitated electron transfer.

Bioinspired superwettability: From interfacial materials to chemistry

<p indent="0mm">Interfacial wettability is one of the fundamental problems in material science. The research on wettability regulation is of great significance in exploring new knowledge and creating new applications. Learning from nature, Prof. Jiang has summarized three basic principles of superwettability: (1) The static wetting is determined by the cooperative effect of nanostructure and surface energy; (2) the transition point of the superlyophilicity and superlyophobicity on the nanostructure is the lyophilicity-lyophobicity limitation; (3) the direction of liquid transport is regulated by chemical composition gradient, rough gradient, curvature gradient, etc. Based on these principles, he further extended the superwettability interfacial material systems to interfacial chemistry. He established a superwetting interfacial material system including 64 combinations, and expanded to various liquid systems with different pressure and temperature ranges, leading and promoting the global development of this field. In this paper, we will introduce the design of superwetting interface and the new law of liquid/gas/solid three-phase interfacial wettability. Based upon the new law of three-phase interfacial wettability, we state the application of water-oil separation, pesticide spraying, electrochemical sensors, and photoelectric material patterning. And the recent research and application prospect in the field of quantum-confined superfluid are discussed. In the part of water-oil separation, focusing on the key issue of constructing membrane materials with both fine pore structure and super-wetting properties, without changing the traditional separation membrane preparation process, the micro-nano multi-level structure of the membrane surface is constructed through structure-induced tuning, and the surface is chemically modified. Synergistic action is used to realize the regulation of membrane transport behavior of water droplets or oil droplets, and a series of novel structural membrane separation materials have been successfully prepared, realizing high-precision and high-throughput separation of oil-water emulsions under low driving pressure. In-depth research on the relationship between the molecular structure of surfactants and the kinetic behavior and thermodynamic state of droplets on specially wetted surfaces has led to the discovery of a very cheap anionic surfactant (sulfosuccinic acid) capable of forming vesicles. Sodium dioctyl ester (AOT) can inhibit the ejection and sputtering of pesticide droplets on the surface of superhydrophobic plants at a very low concentration (3/1000 mass concentration). Aiming at the historical problem of “deficient oxygen” during the use of electrochemical enzyme sensors, we proposed and constructed an oxygen-enriched enzyme electrode with solid/liquid/gas three-phase coexistence. The three-phase electrode will greatly improve the detection performance of existing sensors, has extremely broad application prospects in future disease monitoring, and provides a new design idea for the development of high-efficiency enzyme sensors. We exploit the principle of “liquid bridge confinement assembly” by inducing site-specific condensation and crystallization of small organic molecules by exploiting asymmetric wettability interfaces, fabricating one-dimensional arrays of organic polymer semiconductors by exploiting highly adhesive three-phase interfaces, and exploiting superwetting The micro-nano interface controls the three-dimensional dewetting process and realizes the preparation of highly oriented one-dimensional single-crystal nanowires. These three methods are the key issues to realize one-dimensional micro-nano materials from material preparation to device application. Since 2008, we have successfully achieved the fabrication of smart nanopores that mimic ion channels in biomembranes. This channel has properties similar to biological ion channel switching, selection and rectification. Furthermore, by imitating the mechanism of energy conversion in living systems, the design of energy conversion systems driven by chemical potential gradients based on biomimetic nanopores and the design of nanopore-based sensing devices are realized. Since 2018, we focused on dynamic superwetting. The concept of ionic/molecular superfluid is proposed, which promotes the understanding of the realization of ultra-low energy conversion and information transmission in biological systems and provides new ideas for the study of ultra-low energy chemical synthesis in biological systems. It is believed that future research on ionic/molecular superfluidity will promote the development of neuroscience and brain science, develop quantum ion technology, develop future chemical and chemical reactors with high flux, high selectivity and low energy consumption, and will produce a series of disruptive technologies.

Nanohybrid electrochemical enzyme sensor for xanthine determination in fish samples.

An amperometric biosensor for xanthine was designed, based on covalent immobilization of xanthine oxidase (XO) of Bacillus pumilus RL-2d onto a screen-printed multi-walled carbon nanotubes gold nanoparticle-based electrodes (Nano-Au/c-MWCNT). The carboxyl groups at the electrode surface were activated by the use of 1-Ethyl-3-(3-dimethylaminopropyl carbodiimide) (EDC) and N-hydroxysuccinimide (NHS). The working electrode was then coated with 6 μL of xanthine oxidase (0.273 U/mg protein). The cyclic voltammetry (CV) study was done for the characterization of the sensor using [K3Fe(CN)6] as an artificial electron donor. The sensitivity (S) and the limit of detection (LOD) of the biosensor were 2388.88 µA/cm2/nM (2.388 µA/cm2/µM) and 1.14nM, respectively. The developed biosensor was used for determination of fish meat freshness.

Carbon Nitride Nanosheet and Myoglobin Modified Electrode for Electrochemical Sensing Investigations

Background: Carbon-based nanomaterials, especially carbon nitride (C3N4) has attracted tremendous interest in biosensor applications. Meanwhile, the mechanism of redox protein sensing and related electrocatalytic reactions can provide a valid basis for understanding the process of biological redox reaction. Objective: The aim of this paper is to construct a new electrochemical enzyme sensor to achieve direct electron transfer of myoglobin (Mb) on CILE surface and display electrocatalytic reduction activity to catalyze trichloroacetic acid (TCA) and H2O2. Methods: The working electrode was fabricated based on ionic liquid modified Carbon Paste Electrode (CILE) and C3N4 nanosheets were modified on the CILE surface, then Mb solution was fixed on C3N4/CILE surface and immobilized by using Nafion film. The as-prepared biosensor displayed satisfactory electrocatalytic ability towards the reduction of TCA and H2O2 in an optimum pH 7.0 buffer solution. Results: The results indicated that C3N4 modified electrode retained the activity of the enzyme and displayed quasi-reversible redox behavior in an optimum pH 7.0 buffer solution. The electrochemical parameters of the immobilized Mb on the electrode surface were further calculated with the results of the electron transfer number (n) as 1.27, the charge transfer coefficient (α) as 0.53 and the electrontransfer rate constant (ks) as 3.32 s-1, respectively. The Nafion/Mb/C3N4/CILE displayed outstanding electrocatalytic reduction activity to catalyze trichloroacetic acid and H2O2. Conclusion: The Nafion/Mb/C3N4/CILE displayed outstanding electrocatalytic reduction, which demonstrated the promising applications of C3N4 nanosheet in the field electrochemical biosensing.

High-performance electrochemical enzyme sensor for organophosphate pesticide detection using modified metal-organic framework sensing platforms

A practical electrochemical biosensor with high sensitivity was developed for detecting organophosphorus (OP). Initially, Ce metal was introduced into an UiO-66-template to form Ce/UiO-66. Later, graphene oxide (GO), carbon black (CB) and multi-walled carbon nanotubes (MWCNTs) were separately added to Ce/UiO-66 to compare the effect of different carbon-based material types on the performance of the biosensor. Exclusively, Ce/UiO-66/MWCNTs with a Ce (7%) and MWCNT (30%) matrix was found to not only load more acetylcholinesterase (AChE) onto vacant sites but also increase electron transfer and decrease the number of diffusion pathways between the thiocholine and electrode surface. Moreover, the appropriate oxophilicity of Ce coupled with the high surface area and good conductivity of MWCNTs in the UiO-66 structure revealed a high affinity to acetylthiocholine chloride (ATCl) and possible catalysis of the hydrolysis of ATCl with a Michaelis-Menten constant of 0.258 mM. This biosensor, under optimal conditions, demonstrated a rapid and sensitive detection of paraoxon over a wide linear range of 0.01–150 nM, with a low detection limit of 0.004 nM. As a result, the AChE/Ce/UiO-66/MWCNTs/GCE biosensor can be employed in laboratory and field experiments to determine paraoxon levels.

Electrochemical behavior of horseradish peroxidase on WS2 nanosheet‐modified electrode and electrocatalytic investigation

In this paper, a WS2 nanosheet was modified on the surface of a carbon ionic liquid electrode (CILE), and horseradish peroxidase (HRP) was further fixed on the electrode with a Nafion film. Direct electrochemistry and bioelectrocatalysis of HRP incorporated on the modified electrode were investigated in detail. On Nafion/HRP/WS2/CILE, a pair of well‐defined quasi‐reversible redox peaks appeared on the cyclic voltammogram, indicating that the presence of the WS2 nanosheet on the electrode surface could provide a specific interface with large surface area for HRP and its direct electron transfer rate was greatly enhanced. The formal potential (E0) obtained was –0.179 V, which was the typical feature of heme Fe(III)/Fe(II) in HRP. The electron transfer coefficient (α) and the heterogeneous electron transfer rate constant (ks) of HRP were calculated as 0.44 and 1.01 s–1, respectively. This HRP‐modified electrode showed excellent electrocatalytic activity for the reduction of trichloroacetic acid and NaNO2 with a wide linear range and low detection limit. Real samples were detected by this proposed method, indicating the successful fabrication of a new third‐generation electrochemical enzyme sensor utilizing the WS2 nanosheet.

Mediator Preference of Two Different FAD-Dependent Glucose Dehydrogenases Employed in Disposable Enzyme Glucose Sensors.

Most commercially available electrochemical enzyme sensor strips for the measurement of blood glucose use an artificial electron mediator to transfer electrons from the active side of the enzyme to the electrode. One mediator recently gaining attention for commercial sensor strips is hexaammineruthenium(III) chloride. In this study, we investigate and compare the preference of enzyme electrodes with two different FAD-dependent glucose dehydrogenases (FADGDHs) for the mediators hexaammineruthenium(III) chloride, potassium ferricyanide (the most common mediator in commercial sensor strips), and methoxy phenazine methosulfate (mPMS). One FADGDH is a monomeric fungal enzyme, and the other a hetero-trimeric bacterial enzyme. With the latter, which contains a heme-subunit facilitating the electron transfer, similar response currents are obtained with hexaammineruthenium(III), ferricyanide, and mPMS (6.8 µA, 7.5 µA, and 6.4 µA, respectively, for 10 mM glucose). With the fungal FADGDH, similar response currents are obtained with the negatively charged ferricyanide and the uncharged mPMS (5.9 µA and 6.7 µA, respectively, for 10 mM glucose), however, no response current is obtained with hexaammineruthenium(III), which has a strong positive charge. These results show that access of even very small mediators with strong charges to a buried active center can be almost completely blocked by the protein.

Preparation and Characterization of Electrochemical Tyrosinase Biosensor

Tyrosinase enzyme is a binuclear copper cluster containing monooxygenase contains a dicopper core in the active site [1]. This enzyme catalyzes the o-hydroxylation of monophenols and subsequent oxidation of the formed o-diphenols into the o-quinones. Depending on the electrochemical reduction of o-quinone, amperometric detection of phenol which is a high toxic compound can be achieved. For this aim spectrophotometric and chromatographic methods have been commonly used. Due to their lots of disadvantages, electrochemical enzyme sensors become promising alternative [2]. The performance of enzyme sensors strongly depends on the immobilization of the enzyme to the appropriate support. Many significant biological and chemical properties of chitosan attract attention as a potential support for enzyme immobilization [3] In current study, tyrosinase enzyme was immobilized on chitosan support enhanced by magnetite nanoparticles. Electrochemical biosensor was constructed by coating this bionanocomposite film on 5mm diameter of working electrode. All electrochemical measurements were performed with a model PGSTAT 128N (AUTOLAB Instruments) having three electrode system (working electrode: tyrosinase–magnetite-chitosan modified glassy carbon, reference electrode: Ag/AgCl, auxiliary electrode: platinum wire). The interaction between the sensor component and their structure were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Electrochemical characterizations were also performed by cyclic voltammetry (CV) and impedance spectroscopy (EIS). The performance of electrochemical tyrosinase biosensor was tested by amperometric method in magnetically stirred PBS, followed by the addition of catechol solution as a phenolic compound. The binding of tyrosinase enzyme to the bionanocomposite support was confirmed by FTIR and SEM analysis. According to the CV measurements, the reduction peak was observed attributed to the direct reduction of quinone on the electrode surface. EIS results showed decrease in mass transfer resistance indicate conducting properties of magnetite nanoparticles. Electrochemical sensing characteristics and analytical performance of developed sensor was also evaluated by amperometric detection of catechol. The designed sensor depicted wide linear range of catechol concentration with high correlation coefficient, high sensitivity, low detection limit and Kmvalue. Acknowledgements This study was supported financially by the Scientific and Technological Research Council of Turkey (TUBITAK Grant Number 114Z417).

Disposable poly (o-aminophenol)-carbon nanotubes modified screen print electrode-based enzyme sensor for electrochemical detection of marine toxin okadaic acid

Based on the inhibition of okadaic acid (OA) on protein phosphatase 2A (PP2A), we developed disposable poly-o-aminophenol-carbon nanotubes (PoAP-CNTs) modified screen print electrode (SPE)-based electrochemical enzyme sensor for OA detection. Electropolymerized PoAP-CNTs composite film was coated on electrode for the immobilization of PP2A. Owing to the excellent physicochemical characteristic of PoAP-CNTs film, the performance of enzyme sensor was enhanced. Under the optimal conditions, the biosensor provides a larger linear range, and lower detection limit for the analysis of OA compared with colorimetric PP2A inhibition assay and PP2A/SPE. The spiked OA shellfish samples were applied to verify the efficiency of method for OA detection. The results shows acceptable recovery rate and low RSD, demonstrating the applicability of this method for in suit OA assessment in the quality and toxicity monitoring of seafood.

Electrochemical enzyme sensor arrays for the detection of the biogenic amines histamine, putrescine and cadaverine using magnetic beads as immobilisation supports

Electrochemical biosensors based on diamine oxidase (DAO) conjugated to magnetic beads (MBs) were developed for the detection of histamine (Hist), putrescine (Put) and cadaverine (Cad), the most relevant biogenic amines (BAs) related to food safety and quality. DAO-MBs were immobilised on Co(II)-phthalocyanine/carbon and Prussian Blue/carbon electrodes to obtain mono-enzymatic biosensors, and on Os-wired HRP-modified carbon electrodes to obtain bi-enzymatic biosensors. The three sensor have low working potentials (+0.4 V, −0.1 V and −0.05 V vs Ag/AgCl, respectively), a linear range of two orders of magnitude (from 0.01 to 1 mM BA), good reproducibility (variability lower than 10 %), high repeatability (up to 8 consecutive measurements), limits of detection in the µM concentration range for Hist and in the sub-µM concentration range for Put and Cad, and no response from possible interfering compounds. The DAO-MB conjugates display excellent long-term stability (at least 3 months). The biosensor has been applied to the determination of BAs in spiked and naturally-spoiled fish, demonstrating its suitability both as screening tool and for BAs quantification. The use of MBs as supports for enzyme immobilisation is advantageous because the resulting biosensors are simple, fast, stable, affordable, and can be integrated into array platforms. This makes them suitable for high-throughput analysis of BAs in the food industry.

Glucose oxidase enzyme inhibition sensors for heavy metals at carbon film electrodes modified with cobalt or copper hexacyanoferrate

Electrochemical enzyme sensors prepared from cobalt or copper hexacyanoferrate modified carbon film electrodes plus glucose oxidase (GOx) immobilised by crosslinking with glutaraldehyde were successfully applied to the determination of heavy metal cations using fixed potential amperometry. Sensor performance was optimised with respect to the applied potential and influence of pH of the electrolyte solution. Cadmium, cobalt, copper and nickel ions were detected in the presence of fixed amounts of glucose, and the response to glucose was tested in the absence and presence of a fixed concentration of inhibitor. Electrochemical impedance spectroscopy was used for the first time to characterise the response of glucose biosensors in the presence of the inhibitors. The enzyme inhibition mechanism is reversible and competitive and 10% enzyme inhibition was achieved with submicromolar or micromolar concentrations of the metal cations.

Enzyme functionalized nanoparticles for electrochemical biosensors: A comparative study with applications for the detection of bisphenol A

We developed electrochemical biosensors based on enzyme functionalized nanoparticles of different compositions for the detection of bisphenol A. We utilized for the first time magnetic nickel nanoparticles as an enzyme immobilization platform and electrode material to construct screen-printing enzyme biosensors for bisphenol A. We compared the analytical performance of these sensors with those based on iron oxide (Fe 3O 4) and gold nanoparticles. The proposed biosensor format exhibited fast and sensitive amperometric responses to bisphenol A with a response time of less then 30 s. Among the three configurations, nickel provided comparable or better characteristics in terms of detection limit and sensitivity than Fe 3O 4 and gold nanoparticles. The biosensors were characterized by good reproducibility, stability of more than 100 assays (residual activity for nickel was 98%) and a wide linear range which spanned from 9.1 × 10 −7 to 4.8 × 10 −5 M for nickel, 2.2 × 10 −8 to 4.0 × 10 −5 M for Fe 3O 4 and 4.2 × 10 −8 to 3.6 × 10 −5 M for gold. The highest sensitivity was obtained with nickel. The detection limits for the three types of biosensors were: 7.1 × 10 −9, 8.3 × 10 −9 and 1 × 10 −8 M for nickel, Fe 3O 4 and gold nanoparticles in that order, respectively. These results demonstrate that nickel nanoparticles can be successfully used in the construction of electrochemical enzyme sensors for the detection of phenolic compounds.

Development of Electrochemical Enzyme Sensor for Phenylalanine as a Biomaker of Phenylketonuria

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Rapid fabrication of electrochemical enzyme sensor chip using polydimethylsiloxane microfluidic channel

Applicability of polydimethylsiloxane (PDMS) for easy and rapid fabrication of enzyme sensor chips, based on electrochemical detection, is examined. The sensor chip consists of PDMS substrate with a microfluidic channel fabricated in it, and a glass substrate with enzyme-modified microelectrodes. The two substrates are clamped together between plastic plates. The sensor chip has shown no leakage around the microelectrodes under continuous solution flow (34 μl/min). Amperometric response of the sensor chips developed in this work suggest that various types of enzyme sensors can be designed by using PDMS microfluidic channels.