Enzyme Sensor Research Articles

Fabrication of a dual mimetic enzyme sensor based on gold nanoparticles modified with Cu(II)-coordinated methanobactin for gallic acid detection

Fabrication of a dual mimetic enzyme sensor based on gold nanoparticles modified with Cu(II)-coordinated methanobactin for gallic acid detection

Continuous Ketone Monitoring via Wearable Microneedle Patch Platform.

Ketone bodies (KBs), especially β-hydroxybutyrate (BHB), have gained tremendous attention as potential biomarkers as their presence in bodily fluids is closely associated with health and wellness. While a variety of blood fingerstick test strips are available for self-testing of BHB, there are major needs for wearable devices capable of continuously tracking changing BHB concentrations. To address these needs, we present here the first demonstration of a wearable microneedle-based continuous ketone monitoring (CKM) in human interstitial fluid (ISF) and illustrate its ability to closely follow the intake of ketone drinks. To ensure highly stable and selective continuous detection of ISF BHB, the new enzymatic microneedle BHB sensor relies on a gold-coated platinum working electrode modified with a reagent layer containing toluidine blue O (TBO) redox mediator, β-hydroxybutyrate dehydrogenase (HBD) enzyme, a nicotinamide adenine dinucleotide (NAD+) cofactor, along with carbon nanotubes (CNTs), chitosan (Chit), and a poly(vinyl chloride) (PVC) outer protective layer. The skin-worn microneedle sensing device operates with a miniaturized electrochemical analyzer connected wirelessly to a mobile electronic device for capturing, processing, and displaying the data. Cytotoxicity and skin penetration studies indicate the absence of potential harmful effects. A pilot study involving multiple human subjects evaluated continuous BHB monitoring in human ISF, against gold standard BHB meter measurements, revealing the close correlation between the two methods. Such microneedle-based CKM offers considerable promise for dynamic BHB tracking toward the management of diabetic ketoacidosis and personal nutrition and wellness.

Fluorescent Enzymatic Sensor Based Glucose Oxidase Modified Bovine Serum Albumin-Gold Nanoclusters for Detection of Glucose.

An enzymatic fluorescent probe is developed for the selective detection of glucose. In this work, a Bovine Serum Albumin stabilized gold nanocluster (BSA-AuNCs) was synthesized by microwave assisted method, and it is modified with glucose oxidase, thereby a fluorescent enzymatic sensor (BSA-AuNCs@GoX) was designed for the sensitive detection of glucose with a limit of detection of 0.03 mM. The red fluorescence exhibited by the probe is quenched by the production of H2O2 on addition of glucose via. a static quenching mechanism from UV visible absorption and Fluorescence lifetime results. The developed probe exhibits good selectivity and sensitivity with other coexisting molecular species such as glycine, creatinine, methionine, histidine, uric acid, albumin, and ions such as sodium, potassium, calcium, magnesium, zinc etc. that appear in the body fluid. The practical applicability was studied in paper strip and extended its reproducibility in biological matrixes such as human serum and urine and found a good recovery percentage of 94-101 %. By this way, we have fabricated an effective fluorescent enzymatic "turn-off" sensing probe for the detection of glucose.

Sol-gel synthesized RexBi1-x-O thin films for electrochemical creatinine sensing: A facile fabrication approach

The escalating predominance of renal diseases has obliged vigorous research on developing efficient and cost-effective biosensors for creatinine, an aspirant biomarker reflecting renal health. Herein, we fabricated a highly sensitive and selective Rhenium (Re)-doped Bismuth oxide (Bi2O3) (RexBi1-x-O) based enzymatic electrochemical creatinine biosensor. Various concentrations of Re (5%, 10%, and 20%) were mixed with Bi2O3 solution via facile sol-gel synthesis and deposited on an Indium Tin oxide (ITO) substrate. The detailed physicochemical and electrochemical performance of the thin film was investigated and compared at different annealing temperatures (400 °C, 500 °C, and 600 °C). The optimized RexBi1-x-O thin film (Re0.10Bi0.90-O at 500 °C annealing temperature) depicted a limit of detection (LOD) as low as 28 μM in a concentration range of 0.05 mM–2 mM with excellent selectivity. To ensure the feasibility of the proposed creatinine sensor, its sensing performance was verified in human serum contaminated with altered creatinine concentrations, which manifested a satisfactory recovery rate. Eventually, the outstanding performance of RexBi1-x-O-based enzymatic creatinine sensor indorsed it as an accountable candidate for even more complex markers detection.

Enzymatic Plasmonic Optical Fiber Biosensor for Uric Acid Detection

Uric acid plays important roles in the body, acting as an antioxidant, contributing to the elimination of metabolic waste, and helping to combat some infections. Alterations in uric acid concentration can be important indicators of disease and their real-time and point-of-care monitoring is of extreme importance, for instance in primary care facilities. Optical fibre biosensors are a promising option, allowing real-time detection, quantification, and monitoring of uric acid concentrations in blood plasma or urine. In this work, enzymatic plasmonic sensors were developed for the detection of uric acid using multimode optical fibres composed of a 400 µm silica core and a polymer cladding. To prepare the sensors, the coating and cladding were removed from a section at the fibre tip, and nano film of gold was deposited on their surface, obtaining gold-coated sensors at the fibre tips (Au-tips). Initially, the sensor was characterized to bulk refractive index, exhibiting a sensitivity of 1420.7 ± 59.8 nm/RIU. The Au-tip was biofunctionalized with the enzyme uricase and detection tests were carried out. Uric acid detection tests revealed a response consistent with the Michaelis-Menten function, which was employed to assess the enzymatic kinetics of uricase immobilized on the Au-tips.

An electrochemical sensor based on copper oxide nanoparticles loaded on a mesoporous MCM-41 for non-enzymatic detection of glucose

Numerous researchers are interested in glucose monitoring systems for diabetes mellitus, which is a serious health problem on a global scale. Due to its low detection limit, quick reaction, and good stability, the new generation of electrochemical glucose biosensors has attracted a lot of research attention. However, enzymatic electrochemical sensors are highly susceptible to changes in temperature, humidity, and pH, which can adversely affect their performance. Herein, we developed a non-enzymatic electrochemical sensor for the detection of glucose by using copper oxide (CuO) nanoparticles loaded on mesoporous substrate mobile crystalline material-41 (MCM-41) by the standard solvothermal method and confirmed by standard characterization techniques. The CuO@MCM-41-based electrochemical sensor having redox properties was designed to quantitatively determine glucose, and the relative mechanism was explored. The designed sensor showed a broad linear response in the range of 83 μM - 1.5 mM for glucose with a rapid response time of 4 s, a sensitivity of 17.23 mAcm−2mM−1, and a LOD of 16 nM. The CuO@MCM-41 composite possesses good characteristics that point to the possible commercial applications of mesoporous material-based composites for nonenzymatic electrochemical glucose sensing.

One-Step Method for the Direct Growth of NiO Nanoflowers on Pencil Graphite Electrode for Highly Sensitive Non-Enzymatic Glucose Sensing

Electrochemical glucose sensors, including enzymatic and non-enzymatic sensors, have been considered as quick, accurate, and efficent means for glucose measurement. Recently, non-enzymatic electrochemical glucose sensor based on metal oxides have been paid attention to develop thank to their outstanding behaviours. In most of these studies, metal oxides were synthesized individually and subsequently deposited on the electrode surface using a binder. In this study, we aim at developing a non-enzymatic glucose sensor based on NiO nanoflowers directly grown on a commercial pencil graphite electrode. NiO matetials were deposited on the electrode without a binder via a facile and low-cost chemical procedure. The synthesised materials’ morphologies and components of were characterized by a field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analyses. Electrocatalytic performance was recorded by cyclic voltammetry and chronoamperometry. The resulting NiO nanoflowers, characterized by funnel-shaped structures measuring 500–600 nm in diameter and 20 nm in thickness, were formed on the pencil graphite electrode. The fabricated electrode showed a remarkably high sensitivity of 337 μA mM−1 cm−2, a low limit of detection of 4 μM, and good selectivity. The fabricated electrode can be a potential candidate for clinically medical applications.

Screen-printed electrode designed with MXene/doped-polyindole and MWCNT/doped-polyindole for chronoamperometric enzymatic glucose sensor

The enzymatic glucose sensors as modified by MXene-dPIn and MWCNT-dPIn on a screen-printed carbon electrode (SPCE) were investigated. Herein, MXene was molybdenum carbide (Mo3C2) which has never been utilized and reported for glucose sensors. The biopolymer type to support the enzyme immobilization was examined and compared between chitosan (CHI) and κ-carrageenan (κC). MWCNT-dPIn obviously showed a larger electroactive surface area, lower charge transfer resistance and higher redox current than Mo3C2-dPIn, indicating that MWCNT-dPIn is superior to Mo3C2-dPIn. For the chitosan-based sensors, the sensitivity value of CHI-GOD/Mo3C2-dPIn is 3.53 μA mM−1 cm−2 in the linear range of 2.5–10 mM with the calculated LOD of 1.57 mM. The sensitivity value of CHI-GOD/MWCNT-dPIn is 18.85 μA mM−1 cm−2 in the linear range of 0.5–25 mM with the calculated LOD of 0.115 mM. For the κ-carrageenan based sensors, κC-GOD/MWCNT-dPIn exhibits the sensitivity of 15.80 μA mM−1 cm−2 and the widest linear range from 0.1 to 50 mM with the calculated LOD of 0.03 mM. The presently fabricated sensors exhibit excellent reproducibility, good selectivity, high stability, and disposal use. The fabricated glucose sensors are potential as practical glucose sensors as the detectable glucose ranges well cover the glucose levels found in blood, urine, and sweat for both healthy people and diabetic patients.

Patterned thin film enzyme electrodes via spincoating and glutaraldehyde vapor crosslinking: towards scalable fabrication of integrated sensor-on-CMOS devices.

Effective continuous glucose monitoring solutions require consistent sensor performance over the lifetime of the device, a manageable variance between devices, and the capability of high volume, low cost production. Here we present a novel and microfabrication-compatible method of depositing and stabilizing enzyme layers on top of planar electrodes that can aid in the mass production of sensors while also improving their consistency. This work is focused on the fragile biorecognition layer as that has been a critical difficulty in the development of microfabricated sensors. We test this approach with glucose oxidase (GOx) and evaluate the sensor performance with amperometric measurements of in vitro glucose concentrations. Spincoating was used to deposit a uniform enzyme layer across a wafer, which was subsequently immobilized via glutaraldehyde vapor crosslinking and patterned via liftoff. This yielded an approximately 300 nm thick sensing layer which was applied to arrays of microfabricated platinum electrodes built on blank wafers. Taking advantage of their planar array format, measurements were then performed in high-throughput parallel instrumentation. Due to their thin structure, the coated electrodes exhibited subsecond stabilization times after the bias potential was applied. The deposited enzyme layers were measured to provide a sensitivity of 2.3 ± 0.2 μA mM-1 mm-2 with suitable saturation behavior and minimal performance shift observed over extended use. The same methodology was then demonstrated directly on top of wireless CMOS potentiostats to build a monolithic sensor with similar measured performance. This work demonstrates the effectiveness of the combination of spincoating and vapor stabilization processes for wafer scale enzymatic sensor functionalization and the potential for scalable fabrication of monolithic sensor-on-CMOS devices.

A new plant-esterase inhibition based electrochemical sensor with signal amplification by MoS2@N-CDs for chlorpyrifos detection.

Chlorpyrifos (CPF) is the most common pesticide entering the food chain and posing a threat to human health. This study presents a new electrochemical biosensor based on molybdenum disulfide nanosheets and nitrogen-doped carbon dot nanocomposite (MoS2@N-CDs) and kidney bean esterase (KdBE), and it is shown to achieve accurate detection of CPF. MoS2@N-CDs were prepared by a facile solvothermal method and characterized by electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Electrochemical characterization confirmed that MoS2@N-CDs facilitated electron transfer and increased the electroactive surface area of the electrode, thereby improved the sensing performance of the electrode. The oxidation peak current of 1-naphthol, which was produced by the hydrolysis of 1-naphthyl acetate catalyzed by KdBE, was adopted as the signal of the sensor. CPF can suppress KdBE activity and consequently cause a decrease in the sensing signal. The experimental results show that the variation of sensing signal is a reliable index to evaluate the CPF level. Under the optimized conditions, the developed enzyme sensor showed superior CPF assay performance with a linear detection range as wide as 0.01-500 μg L-1 and LOD as low as 3.5 × 10-3 μg L-1 (S/N = 3). The inter- and intra-batch RSDs for electrode testing were 4.02% and 2.69%, respectively. Moreover, the developed biosensor also showed good stability and anti-interference. The spiked recoveries of CPF in oilseed rape and cabbage ranged from 98.09% to 106.01% with low relative standard deviation (RSD) (<5.23%), suggesting that the sensor is a promising tool to enable simple, low-cost but highly sensitive large-scale screening of CPF residues in food.

Development of Glutamate Sensor Based on Mxene/NiO Modified Screen Printed Carbon Electrode

Glutamate plays a vital role as a neurotransmitter, contributing significantly to both physiological and pathological processes. Although enzymatic electrochemical sensors exhibit the ability to selectively detect glutamate, the presence of enzymes introduce sensor instability. Consequently, there is a pressing need for the advancement of enzyme-free glutamate sensors [1-3]. In this study, we have developed an incredibly sensitive non-enzymatic electrochemical sensor for detecting glutamate.This was achieved by synthesizing nanoparticles of nickel oxide (NiO) and physically combining them with MXene on a Screen-printed carbon electrode (SPCE)[2]. Fig. 1 shows the MXene-NiO nanoparticles (NPs) modification process on SPCE. In this work, cyclic voltammetry and amperometric techniques were carried out in a three-electrode system with an oxygen-saturated environment, where MXene-NiO/SPCE, pt wire, and Ag/AgCl electrode were used as working, counter, and reference electrode respectively. MXene-NiO/SPCE showed significant electro-catalytic activity in catalyzing the oxidation of glutamate in 0.1 M NaOH solution. A linear relationship was established between the current response and Glutamate concentration after the electrochemical experiments were conducted while working parameters were optimized. We conducted an extensive investigation of glutamate-sensing mechanism. The optimized sensor exhibited an irreversible oxidation process for glutamate, involving the transfer of one electron and one proton. It displayed a fast response time of < 5 s and a linear response within the concentration range of 20 to 300 µM at a pH of 7, with a LOD of 17.5 µM, sensitivity of 4500 µA.mM−1.cm−2. The morphology of the MXene-NiO composites was characterized using SEM, EDX, XRD, FT-IR, and UV spectroscopy techniques. The investigation into interference on the MXene-NiO/SPCE revealed a noteworthy current response to glutamate even in the presence of uric acid and ascorbic acid. As a result, the development of a reliable, enzyme-free glutamate sensor could be enabled by this simple sensor based on MXene-NiO composites.Fig. 1. The process of MXene/NiO/SPCE electrode.Reference[1] M. Jamal et al., Microsyst. Technol., 24, 4217–4223, 2018. doi: 10.1007/s00542-018-3724-6.[2] M. Jamal et al., Biosens. Bioelectron., 40, 213–218, 2013. doi: 10.1016/j.bios.2012.07.024.[3] K. M. Razeeb et al., Vertically Aligned Nanowire Array-Based Sensors and Their Catalytic Applications. In: Vestergaard, M., Kerman, K., Hsing, IM., Tamiya, E. (eds) Nanobiosensors and Nanobioanalyses, Springer, Tokyo, 2015. Figure 1

Advances and application of common biosensors

Biosensors are devices that can detect and measure chemical components in organisms through specialized biological properties or reactions. This paper provides an overview of the three main types of biosensors: enzymatic, immunosensors, and microbial sensors. Enzymatic biosensors utilize enzymes to catalyze specific reactions between target molecules and other components of the biosensor, creating measurable signals. Immunosensors rely on immunological reactions between antigens and antibodies to detect and quantify substances in a solution. Microbial sensors use microbial cells to produce signal outputs being tested. Each type of biosensor has unique applications and mechanisms that make them useful in various scientific studies, including clinical medicine, laboratory research, environmental monitoring, and food engineering. Ongoing advancements in technology will undoubtedly continue to expand the scope of biosensors uses, making them increasingly important in many fields. This paper aims to provide researchers with an understanding of the mechanisms behind biosensors and strategies to improve their performance for better measurement, detection, and monitoring capabilities.

Graphene‐Based Enzymatic and Non‐Enzymatic Electrochemical Glucose Sensors: Review of Current Research and Advances in Nanotechnology

AbstractThe determination of the body's glucose level is a difficult job that has served as the foundation for substantial research efforts in biosensing applications. Recent advances in material engineering and synthesis methodologies have had a significant influence on the development of enzymatic and non‐enzymatic sensors for glucose detection that may be used in managing diabetes, food technology, and clinical, and bio‐processing applications. The intricate fabrication, detecting principles and phenomena involved, material alterations, and design to improve sensor performance. There is a great need for high‐efficiency, low‐cost blood glucose sensors that may be used on industrial and domestic scales. This review is primarily intended to shed light on the current state of knowledge about the use of graphene. The performance of non‐enzymatic glucose sensors is comprehensively compared with that of enzymatic electrochemical sensors based on graphene. This study will go over the research efforts that have been conducted to build biosensors employing nanostructures such as carbon nanotubes, graphene, metal nanoparticles, metal oxides, and metal sulfides. The manufacturing of the very sensitive enzyme‐free glucose biosensor will be thoroughly discussed. A thorough examination of the use of graphene as a co‐catalyst to improve the sensitivity of electrochemical sensors for glucose detection is also provided.

A General Review of Methodologies Used in the Determination of Cholesterol (C27H46O) Levels in Foods.

Cholesterol (C27H46O) is a lipid-derived substance found in lipoproteins and cell membranes. It is also one of the main sources for the production of bile acids, vitamin D, and steroid hormones. Today, foods are evaluated by consumers not only according to their taste and nutritional content but also according to their effects on consumer health. For example, many consumers choose foods according to their cholesterol level. The cholesterol in the food can directly affect the blood cholesterol level when consumed, which can lead to cardiovascular diseases. High levels of cholesterol can lead to diet-related human diseases such as cardiac arrest, paralysis, type II diabetes, and cerebral hemorrhage. In societies with high living standards, interest in and consumption of foods that lower or have low cholesterol levels have increased recently. Accordingly, efforts to increase the variety of foods with reduced cholesterol levels are on the rise. This has indirectly led to the accurate measurement of cholesterol levels in blood and food being of great importance. Classical chemical, enzymatic, colorimetric, polarographic, chromatographic, and spectrophotometric methods; enzymatic, nonenzymatic, and electrochemical sensors; and biosensors are used for the determination of cholesterol in foods. The purpose of this review is to reveal and explore current and future trends in cholesterol detection methods in foods. This review will summarize the most appropriate and standard methods for measuring cholesterol in biological components and foods.

Zwitterionic hydrogel for preserving stability and activity of oxidase enzyme for electrochemical biosensor

Enzymatic electrochemical biosensor is the most common analytical platform for medical diagnosis. To mimic the biological environment of the enzyme for maintaining the function of biosensor, zwitterionic hydrogels have been recognized as effective matrices for enzymatic immobilization. Herein, a zwitterionic hydrogel derived from a copolymer, poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-co-N-methacryloyloxyethyl tyrosine methylester (MAT)] (PMM) was firstly applied as versatile coating to preserve stability and activity of oxidase enzymes, glucose oxidase (GOx) and lactate oxidase (LOx) for enzymatic electrochemical sensor. A screen-printed carbon electrode (SPCE) was sequentially coated with nitrogen-doped graphene (NDG), oxidase enzyme, and PMM mixed with Ru(II)bpy32+ and (NH4)2S2O8 followed by visible light irradiation for 3 min to induce PMM gelation. Electrochemical detection of glucose and lactate using the modified SPCE was performed via amperometry in the presence of hydrogen peroxide. The activity of both GOx and LOx immobilized on the modified SPCE was well maintained for 49 days at 87 and 80 %, respectively. Additionally, two different electrodes, a screen-printed graphene electrode (SPGE), and a screen-printed silver electrode (SPAgE), similarly modified gave the same satisfactory detection of spiked glucose and lactate in human plasma and sweat with 93–118 % recovery. This indicates the potential of the PMM hydrogel as a universal platform for preservation of enzymes which can be easily fabricated without the need for specific chemical modification of the electrode.

Modification of substrate specificity of l-arginine oxidase for detection of l-citrulline

Enzymatic detection of citrulline, a potential biomarker for various diseases, is beneficial. However, determining citrulline levels requires expensive instrumental analyses and complicated colorimetric assays. Although l-amino acid oxidase/dehydrogenase is widely used to detect l-amino acids, an l-citrulline-specific oxidase/dehydrogenase has not been reported. Therefore, in this study, we aimed to develop an l-citrulline-specific enzyme by introducing a mutation into l-arginine oxidase (ArgOX) derived from Pseudomonas sp. TPU 7192 to provide a simple enzymatic l-citrulline detection system. The ratio of the oxidase activity against l-arginine to that against l-citrulline (Cit/Arg) was 1.2%, indicating that ArgOX could recognize l-citrulline as a substrate. In the dehydrogenase assay, the specific dehydrogenase activity towards l-arginine was considerably lower than the specific oxidase activity. However, the specific dehydrogenase activity towards l-citrulline was only slightly lower than the oxidase activity, resulting in improved substrate specificity with a Cit/Arg ratio of 49.5%. To enhance the substrate specificity of ArgOX, we performed site-directed mutagenesis using structure-based engineering. The 3D model structure indicated that E486 interacted with the l-arginine side chain. By introducing the E486 mutation, the specific dehydrogenase activity of ArgOX/E486Q for l-citrulline was 3.25 ± 0.50 U/mg, which was 3.8-fold higher than that of ArgOX. The Cit/Arg ratio of ArgOX/E486Q was 150%, which was higher than that of ArgOX. Using ArgOX/E486Q, linear relationships were observed within the range of 10–500 μM l-citrulline, demonstrating its suitability for detecting citrulline in human blood. Consequently, ArgOX/E486Q can be adapted as an enzymatic sensor in the dehydrogenase system.Graphical

Fabrication of conductive Ag/AgCl/Ag nanorods ink on Laser-induced graphene electrodes on flexible substrates for non-enzymatic glucose detection

An unusual strategy was designed to fabricate conductive patterns for flexible surfaces, which were utilized for non-enzymatic amperometric glucose sensors. The Ag/AgCl/Ag quasi-reference ink formulation utilized two reducing agents, NaBH_{4} and ethylene glycol. The parameters of the ink, such as sintering time and temperature, NaBH_{4} concentration, and layer number of coatings on flexible laser-induced graphene (LIG) electrodes were investigated. The conductive Ag/AgCl/Ag ink was characterized using electrochemical and surface analysis techniques. The electrocatalytic activity of Ag/AgCl/Ag NRs can be attributed to their high surface area, which offer numerous active sites for catalytic reactions. The selectivity and sensitivity of the electrodes for glucose detection were investigated. The XRD analysis showed (200) oriented AgCl on covered Ag NRs, and with the addition of NaBH_{4}, the intensity of the peaks of the Ag NRs increased. The wide linear range of non-enzymatic sensors was attained from 0.003 to 0.18 mM and 0.37 to 5.0 mM, with a low limit of detection of 10 upmuM and 20 upmuM, respectively.The linear range of enzymatic sensor in real sample was determined from 0.040 to 0.097 mM with a detection limit of 50 upmuM. Furthermore, results of the interference studies demonstrated excellent selectivity of the Ag/AgCl/Ag NRs/LIG electrode. The Ag/AgCl/Ag NRs on the flexible LIG electrode exhibited excellent sensitivity,long-time stablity,and reproducibility. The efficient electroactivity were deemed suitable for various electrochemical applications and biosensors.

HEXOKINASE1 and glucose-6-phosphate fuel plant growth and development.

As photoautotrophic organisms, plants produce an incredible spectrum of pigments, anti-herbivory compounds, structural materials and energic intermediates. These biosynthetic routes help plants grow, reproduce and mitigate stress. HEXOKINASE1 (HXK1), a metabolic enzyme and glucose sensor, catalyzes the phosphorylation of hexoses, a key introductory step for many of these pathways. However, previous studies have largely focused on the glucose sensing and signaling functions of HXK1, and the importance of the enzyme's catalytic function is only recently being connected to plant development. In this brief Spotlight, we describe the developmental significance of plant HXK1 and its role in plant metabolic pathways, specifically in glucose-6-phosphate production. Furthermore, we describe the emerging connections between metabolism and development and suggest that HXK1 signaling and catalytic activity regulate discrete areas of plant development.

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.

A high–performance non–enzymatic glucose sensor based Au and ZrO2 nanoparticles supported on multi-walled carbon nanotubes

Gold (Au) and zirconia (ZrO2) nanoparticles as the co–catalyst on modified multi–walled carbon nanotubes (Au/ZrO2@MWCNTs) were prepared by simple method. ZrO2 and Au NPs, Au/ZrO2@MWCNTs exhibited excellent electrochemical performances when applied as glucose sensor. The sensor showed a wide linear operating range (10 μM to 13 mM glucose concentration), high sensitivity (162.52 μA cm−2 mM−1 at 10 μM–13 mM), and a low detection limit (0.95 μM) at 0.2 V. After 15 days of consecutive tests, over 90.0 % of the original current was retained, verifying the stability of Au/ZrO2@MWCNTs. Furthermore, the non–enzymatic glucose sensor also exhibited strong catalytic activity for the conversion of glucose to gluconic acid with a large active surface area. It is expected to be applicable in the further development of non–enzymatic glucose sensors.