Search

The construction of biosensors for specific, sensitive, and rapid detection of tumor biomarkers significantly contributes to biomedical research and early cancer diagnosis. However, conventional assays often involve large sample consumption and poor sensitivity, limiting their further application in real samples. In recent years, single-molecule biosensing has emerged as a robust tool for detecting and characterizing biomarkers due to its unique advantages including simplicity, low sample consumption, ultra-high sensitivity, and rapid assay time. This review summarizes the recent advances in the construction of single-molecule biosensors for the measurement of various tumor biomarkers, including DNAs, DNA modifications, RNAs, and enzymes. We give a comprehensive review about the working principles and practical applications of these single-molecule biosensors. Additionally, we discuss the challenges and limitations of current single-molecule biosensors, and highlight the future directions.

Overweight and obesity promote diabetes and heart disease onset. Triglycerides are key biomarkers for cardiovascular disease, strokes, and other health issues. Scientists have devised methods and instruments for the detection of these molecules in liquid samples. In this study, an enzymatic biosensor was developed using an Arduino-based microfluidic platform, wherein a lipolytic enzyme was immobilized on an ethylene-vinyl acetate polymer through physical adsorption. This low-cost optical biosensor employed a spectrophotometric transducer and was assessed in liquid samples to indirectly detect triglycerides and fatty acids using p-nitrophenol as an indicator. The average triglyceride level detected in the conducted experiments was 47.727 mg/dL. The biosensor exhibited a percentage of recovery of 81.12% and a variation coefficient of 0.791%. Furthermore, the biosensor demonstrated the ability to detect triglyceride levels without the need for sample dilution, ranging from 7.6741 mg/dL to 58.835 mg/dL. This study successfully developed an efficient and affordable enzymatic biosensor prototype for triglyceride and fatty acid detection. The lipolytic enzyme immobilization on the polymer substrate provided a stable and reproducible detection system, rendering this biosensor an exciting option for the detection of these molecules. [ABSTRACT FROM AUTHOR]

Gold (Au) and glassy carbon electrodes have been decorated with gold nanodendrites (NDs) using galvanic replacement reactions. Modification of the ND surfaces by lipoic acid N-hydroxysuccinimide ester allows to immobilise selenate reductase to the electrode surface, rendering it selective for the catalytic reduction of selenate ( SeO 4 2 − , Se(VI)) to selenite ( SeO 3 2 − , Se(IV)). Electrode modifications have been characterized by electrochemical impedance spectroscopy and cyclic voltammetry (CV). For selenate detection, CV and differential pulse voltammetry measurements have been carried out in 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid buffer with pH 6.0. Under optimum conditions, the linear range for Au electrodes decorated with AuNDs was 0.3–203 µg/L Se with a limit of detection of 0.01 µg/L Se, which is a 274-fold improvement over using non-nanostructured surfaces for selenate detection. Other anions such as SO 4 2 − , NO 3 - , NO 2 − , PO 4 3 − , AsO 4 3 − , and SeO 3 2 − did not interfere with the detection of selenate. The electrochemical sensor was used for the detection of selenate in three different real samples with recovery between 98.5% and 102.0%. [ABSTRACT FROM AUTHOR]

The detection of small molecules has attracted enormous interest in various fields, including the chemical, biological, and healthcare fields. In order to achieve such detection with high accuracy, up to now, various types of biosensors have been developed. Among those biosensors, enzymatic biosensors have shown excellent sensing performances via their highly specific enzymatic reactions with small chemical molecules. As techniques used to implement the sensing function of such enzymatic biosensors, electrochemical and fluorescence techniques have been mostly used for the detection of small molecules because of their advantages. In addition, through the incorporation of nanotechnologies, the detection property of each technique-based enzymatic nanobiosensors can be improved to measure harmful or important small molecules accurately. This review provides interdisciplinary information related to developing enzymatic nanobiosensors for small molecule detection, such as widely used enzymes, target small molecules, and electrochemical/fluorescence techniques. We expect that this review will provide a broad perspective and well-organized roadmap to develop novel electrochemical and fluorescent enzymatic nanobiosensors. [ABSTRACT FROM AUTHOR]

Widespread use of pesticides and herbicides, and the contamination in river, lake and sea waters have been become a major environmental concern in recent years. A common example of such herbicides is atrazine and its derivatives, which have been widely used in recent years to control pests in agriculture and improve food production and meet the needs of the global population, which is increasing year by year. Most analytical methods are used to determine pesticides and herbicides in the environment which are usually highly reliable and sensitive, but they are often very complex and require advanced tools, and measurements should be performed directly in a lab. Atrazine electrochemical biosensors based on enzymatic biosensors, immunosensors, and aptasensors are reviewed in this study. For atrazine detection by enzymatic biosensors, tyrosinase commonly is used. Phenols and atrazine are the substrates and inhibitor of this enzyme, respectively. These enzymatic biosensors are based on sensing of decreasing current in the presence of atrazine. Immunosensors based on the analyte size generally categorized into two detection methods including competitive and noncompetitive that both of them were used for atrazine detection. The several aptamer sequences were used for atrazine aptasensing that could detect it in nano and picomolar concentrations.

Plant phenolic compounds demonstrate bioactive properties in vitro and/or in vivo, which creates demand for their precise determination in life sciences and industry. Measuring the concentration of individual phenolic compounds is a complex task, since approximately 9000 plant phenolic substances have been identified so far. The determination of the total phenolic content (TPC) is less laborious and is used for the qualimetric evaluation of complex multicomponent samples in routine analyses. Biosensors based on phenol oxidases (POs) have been proposed as alternative analytical devices for detecting phenolic compounds; however, their effectiveness in the analysis of food and vegetal matrices has not been addressed in detail. This review describes catalytic properties of laccase and tyrosinase and reports on the enzymatic and bienzymatic sensors based on laccase and tyrosinase for estimating the total phenolic index (TPI) in food-related samples (FRSs). The review presents the classification of biosensors, POs immobilization, the functions of nanomaterials, the biosensing catalytic cycle, interference, validation, and some other aspects related to TPI assessment. Nanomaterials are involved in the processes of immobilization, electron transfer, signal formation, and amplification, and they improve the performance of PO-based biosensors. Possible strategies for reducing interference in PO-based biosensors are discussed, namely the removal of ascorbic acid and the use of highly purified enzymes. [ABSTRACT FROM AUTHOR]

Fentanyl is a powerful synthetic opioid used to treat severe pain. New administration routes toward its illegal consumption for recreational purposes pose a growing threat to public health, either due to misuse or abuse of this substance. As a result, the rapid qualitative and quantitative determination of fentanyl in biofluids is of great interest. A novel enzymatic biosensor based on adsorptive-stripping cyclic voltammetry is proposed as a cost-effective, reliable, and efficient device for fentanyl determination in urine samples. Disposable screen-printed carbon electrodes modified with multi-walled carbon nanotubes and cytochrome c were used to develop the testing platform. The electrochemical behavior of fentanyl exhibited a well-defined anodic wave around 0.66 V vs. pseudo reference electrode. The experimental conditions were optimized to obtain the best analytical response, and linear regression analysis of increasing concentration standards was applied to estimate the performance parameters. The results suggest a simple method with a wide linearity range, high sensitivity, low limits of detection (0.086 μg/mL) and quantification, and satisfactory precision (2.9% RSD). The feasibility and applicability of the voltammetric approach were assessed by fentanyl-spiked urine samples by standard additions calibration curves in two levels of enrichment with an accuracy of 92% and 100%. [ABSTRACT FROM AUTHOR]

The temperature effect has been discussed in the past on pH sensors. In this study, the temperature effect is analyzed for the ascorbic acid (AA) biosensor based on enzymatic ascorbate oxidase (AO). To reduce this effect, a novel temperature compensation circuit was implemented by Taiwan Semiconductor Manufacturing Co., Ltd. (TSMC) 180 nm complementary metal-oxide-semiconductor (CMOS) process. By applying the proposed circuit, the temperature coefficients (TCs) with five concentrations of AA were suppressed below $201~\mathbf {\mu }\text{V}/\mathbf {^{\circ} }\text{C}$ . The TC of the normal level of AA concentration (0.0312 mM) in the human body was $188~\mathbf {\mu }\text{V}/\mathbf {^{\circ} }\text{C}$ , at the temperature range from 25°C to 55°C. The polyethylene terephthalate (PET) substrate was utilized. To confirm the stability of the fabricated AO/RuO2/PET AA biosensor, interference and hysteresis experiments were carried out. At present, the experiments were still in the stage of in vitro measurement. The results showed that the AO/RuO2/PET AA biosensor had good selectivity that effective against other interference that may exist in blood at either 25 °C or 37.5°C. Moreover, at the temperature of 37.5°C, the hysteresis voltage of the biosensor after applying the compensation circuit was reduced from 18.27 mV to 1.39 mV.

NADH is a cofactor used by a wide range of dehydrogenases. Measurement of the concentration of NADH is widely used to measure the activity of enzymes. Extensive efforts have been made to develop electrochemical sensors for NADH determination at low overpotentials to avoid interferences. The development of an enzymatic electrochemical biosensor for the detection of NADH is described. Nanoporous gold electrodes were utilised for the immobilization of diaphorase and osmium-based polymer Os(bpy)2(PVI). Nanoporous gold electrodes of different pore sizes were manufactured by varying the dealloying temperature. To optimise the enzymatic response, the concentrations of polymer and enzyme, average pore size and the operating temperature were examined with the optimal performance observed using 10 µL of Os(bpy)2(PVI) and 5 µL of diaphorase at concentrations of 6 and 10 mg/mL, respectively, on nanoporous gold electrodes with an average pore size of 5.9 nm. The biosensor showed a high sensitivity of 89.6 µA/cm2 mM, a low LOD of 0.8 µM and a linear range from 5 to 100 µM at a potential of 0.35 V vs Ag/AgCl at a temperature of 40 °C.

Overweight and obesity promote diabetes and heart disease onset. Triglycerides are key biomarkers for cardiovascular disease, strokes, and other health issues. Scientists have devised methods and instruments for the detection of these molecules in liquid samples. In this study, an enzymatic biosensor was developed using an Arduino-based microfluidic platform, wherein a lipolytic enzyme was immobilized on an ethylene-vinyl acetate polymer through physical adsorption. This low-cost optical biosensor employed a spectrophotometric transducer and was assessed in liquid samples to indirectly detect triglycerides and fatty acids using p-nitrophenol as an indicator. The average triglyceride level detected in the conducted experiments was 47.727 mg/dL. The biosensor exhibited a percentage of recovery of 81.12% and a variation coefficient of 0.791%. Furthermore, the biosensor demonstrated the ability to detect triglyceride levels without the need for sample dilution, ranging from 7.6741 mg/dL to 58.835 mg/dL. This study successfully developed an efficient and affordable enzymatic biosensor prototype for triglyceride and fatty acid detection. The lipolytic enzyme immobilization on the polymer substrate provided a stable and reproducible detection system, rendering this biosensor an exciting option for the detection of these molecules.

Photoelectrochemical (PEC) biosensors are a rather novel type of biosensors that utilize light to provide information about the composition of an analyte, enabling light‐controlled multi‐analyte measurements. For enzymatic PEC biosensors, amperometric detection principles are already known in the literature. In contrast, there is only a little information on H+‐ion sensitive PEC biosensors. In this work, we demonstrate the detection of H+ ions emerged by H+‐generating enzymes, exemplarily demonstrated with penicillinase as a model enzyme on a titanium dioxide photoanode. First, we describe the pH sensitivity of the sensor and study possible photoelectrocatalytic reactions with penicillin. Second, we show the enzymatic PEC detection of penicillin. [ABSTRACT FROM AUTHOR]

The indiscriminate use of pesticides in agriculture demands the development of devices capable of monitoring contaminations in food supplies, in the environment and biological fluids. Simplicity, easy handling, high sensitivities, and low limits-of-detection (LOD) and quantification are some of the required properties for these devices. In this work, we evaluated the effect of incorporating gold nanoparticles into indigo carmine-doped polypyrrole during the electropolymerization of films for use as an acetylcholinesterase (AChE) enzyme-based biosensor. As proof of concept, the pesticide methyl parathion was tested towards the inhibition of AChE. The enzyme was immobilized simply by drop-casting a solution, eliminating the need for any prior surface modification. The biosensors were characterized with cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The assays for the detection of methyl parathion with films containing polypyrrole, indigo carmine and AChE (PPy–IC–AChE) presented a sensitivity of 5.7 μA cm−2 g−1 mL and a LOD of 12 nmol L−1 (3.0 ng L−1) with a linear range from 1.3 x 10−7 mol L−1 to 1.0 x 10−5 mol L−1. The introduction of gold nanoparticles (AuNP) into the film (PPy–IC–AuNP-AChE) led to remarkable improvements on the overall performance, such as a lower redox potential for the enzymatic reaction, a 145 % increase in sensitivity (14 μA cm−2 g−1 mL), a wider detection dynamic range (from 1.3x10−7 to 1.0x10−3 mol L−1), and a very low LOD of 24 fmol L−1 (64 ag mL−1). These findings underscore the potential of using AuNPs to improve the enzymatic performance of biosensor devices. [Display omitted] • Gold nanoparticle in polypyrrole matrix enhance enzymatic electrochemical biosensing. • Enhanced enzyme activity of acetylcholinesterase with this novel approach. • Remarkable sensitivity: 145 % enhancement in sensitivity. • Wider sensing range: versatility and accuracy across a wide range of concentrations. • Femtomolar detection of the pesticide methyl parathion. [ABSTRACT FROM AUTHOR]

Diabetes is a chronic, systemic metabolic disease that leads to multiple complications, even death. Meanwhile, the number of people with diabetes worldwide is increasing year by year. Sensors play an important role in the development of biomedical devices. The development of efficient, stable, and inexpensive glucose sensors for the continuous monitoring of blood glucose levels has received widespread attention because they can provide reliable data for diabetes prevention and diagnosis. Electrospun nanofibers are new kinds of functional nanocomposites that show incredible capabilities for high-level biosensing. This article reviews glucose sensors based on electrospun nanofibers. The principles of the glucose sensor, the types of glucose measurement, and the glucose detection methods are briefly discussed. The principle of electrospinning and its applications and advantages in glucose sensors are then introduced. This article provides a comprehensive summary of the applications and advantages of polymers and nanomaterials in electrospun nanofiber-based glucose sensors. The relevant applications and comparisons of enzymatic and non-enzymatic nanofiber-based glucose sensors are discussed in detail. The main advantages and disadvantages of glucose sensors based on electrospun nanofibers are evaluated, and some solutions are proposed. Finally, potential commercial development and improved methods for glucose sensors based on electrospinning nanofibers are discussed.

The detection of small molecules has attracted enormous interest in various fields, including the chemical, biological, and healthcare fields. In order to achieve such detection with high accuracy, up to now, various types of biosensors have been developed. Among those biosensors, enzymatic biosensors have shown excellent sensing performances via their highly specific enzymatic reactions with small chemical molecules. As techniques used to implement the sensing function of such enzymatic biosensors, electrochemical and fluorescence techniques have been mostly used for the detection of small molecules because of their advantages. In addition, through the incorporation of nanotechnologies, the detection property of each technique-based enzymatic nanobiosensors can be improved to measure harmful or important small molecules accurately. This review provides interdisciplinary information related to developing enzymatic nanobiosensors for small molecule detection, such as widely used enzymes, target small molecules, and electrochemical/fluorescence techniques. We expect that this review will provide a broad perspective and well-organized roadmap to develop novel electrochemical and fluorescent enzymatic nanobiosensors.

A novel enzymatic electrochemical biosensor (mCuF/PANI‐nf/HA/Lacc/GCE) was designed for detection of bisphenol A (BPA). The copper ferrite nanoparticles was obtained by co‐precipitation and its surface was modified with ‐NH2 functional organosilane. Polyaniline nanofibers were also synthesized by cyclic voltammetry and characterized by FTIR, XRD, TGA, SEM and TEM, respectively. Then, it was crosslinked with hyaluronic acid as an immobilization matrix for Laccase to adhere to surface of the modified copper ferrites. Cyclic and differential pulse voltammetries were used to evaluate the electrochemical performances of the biosensor, which has a LOD value of 5.40 nM and a LOQ value of 16.20 nM in the 0.01–7.50 μM linear working range. The biosensor was successfully applied for determination of BPA in seawater, canned water and milk samples with recoveries ranging from 96.0 % and 100.7 %. In addition, accuracy of the voltammetric determination method in the real samples was carried out by HPLC and spike/recovery test. The layer‐by‐layer surface modification strategy of the designed mCuF/PANI‐nf/HA/Lacc/GCE biosensor opens a new perspective on both BPA determination and using biopolymer in the structure of enzymatic electrochemical biosensors. [ABSTRACT FROM AUTHOR]

Electrochemical sensors embedded in hydrogelbased contact lenses provide valuable health-related information, enabling non-invasive and real-time continuous monitoring. Recently, considerable progress has been made in tear based electrochemical sensors. The scope of reported analytes is continuously expanding. This review identifies key chemical biomarkers (including metabolites, ions, proteins) that can be electrochemically detected in tears. The working principles of i) amperometric enzymatic biosensors, ii) ion-selective sensors for pH and ions, iii) voltammetric sensors and iv) affinity sensors are summarized. This review provides guidelines for the future development of contact lens based electrochemical sensors. [ABSTRACT FROM AUTHOR]

Widespread use of pesticides and herbicides, and the contamination in river, lake and sea waters have been become a major environmental concern in recent years. A common example of such herbicides is atrazine and its derivatives, which have been widely used in recent years to control pests in agriculture and improve food production and meet the needs of the global population, which is increasing year by year. Most analytical methods are used to determine pesticides and herbicides in the environment which are usually highly reliable and sensitive, but they are often very complex and require advanced tools, and measurements should be performed directly in a lab. Atrazine electrochemical biosensors based on enzymatic biosensors, immunosensors, and aptasensors are reviewed in this study. For atrazine detection by enzymatic biosensors, tyrosinase commonly is used. Phenols and atrazine are the substrates and inhibitor of this enzyme, respectively. These enzymatic biosensors are based on sensing of decreasing current in the presence of atrazine. Immunosensors based on the analyte size generally categorized into two detection methods including competitive and noncompetitive that both of them were used for atrazine detection. The several aptamer sequences were used for atrazine aptasensing that could detect it in nano and picomolar concentrations. [ABSTRACT FROM AUTHOR]

The coronavirus disease2019 (COVID-19) pandemic has highlighted the need for disposable biosensors that can detect viruses in infected patients quickly due to fast response and also at a low cost. The present review provides an overview of the applications of disposable biosensors based on metal nanoparticles in enzymatic and nonenzymatic sensors with special reference to glucose and H2O2, immunosensors as well as genosensors (DNA biosensors in which the recognized event consists of the hybridization reaction)for point-of-care diagnostics. The disposable biosensors for COVID19 have also been discussed. [ABSTRACT FROM AUTHOR]

Tyrosine is a non-essential amino acid that presents in most fluids and all tissues in the human body and plays a crucial role in human body activities. Herein, an enzymatic biosensor based on the modification of glassy carbon electrode (GCE) with tyrosine hydroxylase (TryHAS) and reduced graphene oxide (rGO) fabricated and utilized to monitor tyrosine in food samples. The rGO/TryHAS/GCE offered powerful catalytic activity for sensing tyrosine with a linear dynamic range of 0.001–345 µM, and a detection limit of 0.7 nM. Furthermore, the selectivity of rGO/TryHAS/GCE was assessed for monitoring tyrosine in an aqueous solution, and the findings revealed a high selectivity in the sensing process. In the final step, rGO/TryHAS/GCE was utilized for the determination of tyrosine in real food samples including egg and cheese, with acceptable recovery data. [ABSTRACT FROM AUTHOR]

The coronavirus disease2019 (COVID-19) pandemic has highlighted the need for disposable biosensors that can detect viruses in infected patients quickly due to fast response and also at a low cost.The present review provides an overview of the applications of disposable biosensors based on metal nanoparticles in enzymatic and non-enzymatic sensors with special reference to glucose and H2O2, immunosensors as well as genosensors (DNA biosensors in which the recognized event consists of the hybridization reaction)for point-of-care diagnostics. The disposable biosensors for COVID19 have also been discussed.

Plant phenolic compounds demonstrate bioactive properties in vitro and/or in vivo, which creates demand for their precise determination in life sciences and industry. Measuring the concentration of individual phenolic compounds is a complex task, since approximately 9000 plant phenolic substances have been identified so far. The determination of the total phenolic content (TPC) is less laborious and is used for the qualimetric evaluation of complex multicomponent samples in routine analyses. Biosensors based on phenol oxidases (POs) have been proposed as alternative analytical devices for detecting phenolic compounds; however, their effectiveness in the analysis of food and vegetal matrices has not been addressed in detail. This review describes catalytic properties of laccase and tyrosinase and reports on the enzymatic and bienzymatic sensors based on laccase and tyrosinase for estimating the total phenolic index (TPI) in food-related samples (FRSs). The review presents the classification of biosensors, POs immobilization, the functions of nanomaterials, the biosensing catalytic cycle, interference, validation, and some other aspects related to TPI assessment. Nanomaterials are involved in the processes of immobilization, electron transfer, signal formation, and amplification, and they improve the performance of PO-based biosensors. Possible strategies for reducing interference in PO-based biosensors are discussed, namely the removal of ascorbic acid and the use of highly purified enzymes.

Biocompatible, industrially scalable, and opto/electrochemically active biomaterials are promising for biosensor platform design and application. Herein, cyclic oligosaccharide, β-cyclodextrin (BCD), is conjugated with Butein, a chalcone-type polyphenol, via dehydration reaction of the hydroxyl groups of BCD and the benzoyl ring of Butein. Functional group changes in the conjugated BCD-Butein were comprehensively studied using UV-visible absorbance, Fourier transform-infrared, and X-ray photoelectron spectroscopic techniques. The electrochemical characteristics of BCD-Butein were explored using cyclic voltammetry, showing the reversible redox behavior (2e - /2H + ) attributed to the catecholic OH group of Butein. The BCD-Butein-modified electrode exhibits a surface-confined redox process ( R 2 = 0.99, I pa and I pc ) at the interface, suitable for external mediatorless sensor studies. An enzymatic biomolecular sensor has been constructed using BCD-Butein-modified glassy carbon and a screen-printed electrode targeting sialic acid as the model clinical biomarker. With the enzyme sialic acid aldolase, BCD-Butein-modified substrate exhibited a selective conversion of sialic acid to N -acetyl-d-mannosamine and pyruvate, with a wide linear detection range (1-100 nM), the lowest detection limit of 0.2 nM, and a quantification limit of 0.69 nM, convenient for clinical threshold diagnosis.

An electroanalytical platform capable to take and dilute the sample has been designed in order to fully integrate the different steps of the analytical process in only one device. The concept is based on the addition of glass-fiber pads for sampling and diluting to an electrochemical cell combining a paper-based working electrode with low-cost connector headers as counter and reference electrodes. In order to demonstrate the feasibility of this all-in-one platform for biosensing applications, an enzymatic sensor for glucose determination (requiring a potential as low as −0.1 V vs. gold-plated wire by using ferrocyanide as mediator) was developed. Real food samples, such as cola beverages and orange juice, have been analyzed with the bioelectroanalytical lab-on-paper platform. As a proof-of-concept, and trying to go further in the integration of steps, sucrose was successfully detected by depositing invertase in the sampling strip. This enzyme hydrolyzes sucrose into fructose and glucose, which was determined using the enzymatic biosensor. This approach opens the pathway for the development of devices applying the lab-on-paper concept, saving costs and time, and making possible to perform decentralized analysis with high accuracy. [ABSTRACT FROM AUTHOR]

Herein we report a reliable and stable biosensor for the amperometric detection of creatinine through the ammonium produced in its reaction with creatinine deiminase linked to a Nafion®/polyaniline gold coated surface. The gold electrode array was produced using a low cost printed board circuit technology. A linear range of 1–1000 μM was obtained with standard deviations of less than 5 % (n=3) obtained. Stability studies were carried out and 80 % activity was maintained after one month. The sensors were tested with 142 serum samples from patients with renal dysfunction at different stage of the disease and validated using a commercial colorimetric method. [ABSTRACT FROM AUTHOR]

Herein a highly sensitive electrochemical enzymatic biosensor for the detection of neotame in soft drinks was developed based on multiwalled carbon nanotubes (MWCNTs) decorated with aloe vera‐derived gold nanoparticles (AuNPs) and carboxyl esterase (CaE) enzyme to support the wave strengthening strategy. The electrochemical biosensor revealed high sensitivity with a limit of detection (LOD) and limit of quantification (LOQ) of 27 μg L−1 and 83 μg L−1 respectively. The calibration curve showed a linear dependence of the cathodic peak current on the neotame concentration profile with a correlation factor of 0.9829, signifying an improved electrocatalytic property of the electrode. The good feasibility of the proposed strategy was confirmed by assessing the interactions between the analyte and the enzyme using computational tools. The density functional theory (DFT) calculations of neotame reveal a HOMO‐LUMO energy gap of −0.46618 eV, suggesting a great tendency to act as an electron donor. Furthermore, adsorption and analyte‐enzyme docking studies were carried out to better understand the redox mechanisms. These results revealed that neotame form hydrogen bonds with LEU 249 and GLU251 and other amino acids of the hydrophobic channel of the binding sites, thereby facilitating the redox reaction for the detection of neotame. These outcomes confirm that the aloe vera‐derived AuNPs are good platforms for immobilizing CaE because of its high surface area, promoting the electron transfer from neotame to form an enzyme‐substrate complex, contributing to an enhanced biosensing signal. Furthermore, the enhanced catalytic activity of this enzymatic biosensor for the detection of neotame in soft drinks has huge potential in the food and beverage industry. [ABSTRACT FROM AUTHOR]

The present work proposes a new electrochemical sulfite biosensor based on babassu mesocarp nanoparticles (BMNPs) immobilized on the surface of a pyrolytic graphite electrode (PGE). The synthesized nanoparticles had a size of 121.5 nm and a zeta potential of − 28.1 mV and were used as a support for the immobilization of chitosan (CHIT) and polyphenol oxidase (PPO) obtained from sweet potatoes (Ipomea batatas (L.)). The electrochemical activity of the PGE/BMNPs/CHIT/GA/PPO biosensor was measured using cyclic voltammetry (CV) and square wave voltammetry (SWV), and the biosensor was shown to have a sensitivity of 2.18 μA/μmol L−1, a detection limit of 0.151 μmol L−1, and quantitation limit of 0.452 μmol L−1 for sulfite. The principle of analysis for the developed biosensor is based on the inhibitory effect of sulfite on the activity of the PPO enzyme. This biosensor was successfully employed for the analysis of industrial juice, without the need to pre-treat the sample. [ABSTRACT FROM AUTHOR]

A patient at the fifth stage of chronic kidney disease usually needs dialysis or transplantation. The adequacy of dialysis can be assessed by the dimensionless parameter Kt/V, which depends on the concentration of urea in the blood. Kt/V is usually measured before and after treatment, or by an indirect measurement of dialysis fluid conductivity. For the real-time monitoring of the urea concentration during dialysis, this paper proposes a disposable biosensor that combines a pH sensitive reduced graphene oxide layer functionalized with 4-amino benzoic acid and urease. Urease is immobilized on reduced graphene oxide and catalyzes the hydrolysis of urea into carbon dioxide and ammonia. This catalysis increases the pH value locally and elicits a sensor response. Urea concentration was assessed in the plasma of five dialyzed patients using a potentiometric measurement. The response time was 120 s and the error was 6 ± 3% compared with standard clinical laboratory analysis. [ABSTRACT FROM AUTHOR]

MXenes are gaining immense attention owing to their robust conductivity, presence of favorable surface-functional groups and excellent hydrophilicity. Herein, a simple solution-based approach was adopted to functionalize few-layer thick MXene-Ti 3 C 2 T x with chitosan (Chi) molecules, creating a stable electro-active screen-printed electrode (SPE) platform for the detection of sarcosine (SAR), a new biomarker for prostate cancer. In comparison to pristine MXene, the chitosan-functionalized Ti 3 C 2 T x (MX-Chi/SPE) offered favorable surface functionalization for easy immobilization of sarcosine oxidase (SO x) enzymes, which led to the improved enzymatic oxidation of SAR. The detection mechanism relied upon the efficient reduction of enzymatically produced H 2 O 2 over MX-Chi/SPE, enabling selective detection of SAR both in low (0.1–0.3 µM) and high (1.5–3.5 µM) concentration ranges, with an estimated limit of detection (LOD) values of 0.012 µM and 0.14 µM (S/N = 3), respectively. Due to its robust enzymatic configuration, the biosensor enabled selective detection of SAR even in the presence of interfering species like ascorbic acid, uric acid, and glucose. Furthermore, the biosensor demonstrated excellent signal repeatability and stability and effectively recovered spiked SAR levels (98–106%) from artificial urine samples. This approach demonstrated the successful integration of MXenes as redox-active materials in clinical biosensors with a simple electrode preparation procedure, which has the potential to be extended to other MXene compositions. • Binder-free MX-Chi anode for sensitive enzymatic biosensing of the SAR biomarker. • Chitosan functionalized Ti 3 C 2 T x for high conductivity and linker-free immobalization of sacrocine oxidase. • Ti 3 C 2 T x and chitosan network creates a robust network with LOD of 0.012 µM for SAR. • MX-Chi Integrated SPE for SAR at low (0.1–0.3 µM) and high (1.5–3.5 µM) concentrations. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H 2 O 2) is a vital messenger molecule facilitating signal transmission within cellular systems. The accurate quantification of H 2 O 2 in complex environments, such as human serum, is instrumental in elucidating its diverse biological functions. In this study, we present the development of a robust electrode platform by integrating hemoglobin onto iron oxide (Fe 3 O 4) nanoparticles and reduced graphene oxide (rGO) as a conducting support for the sensitive detection of H 2 O 2 in human serum. The Fe 3 O 4 /rGO nanocomposite was synthesized via a facile single-step thermolysis reaction in the presence of oleylamine. Transmission electron microscopy (TEM) analysis revealed the formation of highly monodisperse Fe 3 O 4 nanoparticles that were uniformly dispersed over the reduced graphene surface. The rGO surface provided abundant active sites (Fe 3 O 4) for H 2 O 2 sensing. Consequently, the resulting Hb/Fe 3 O 4 @rGO modified electrode exhibited a wide linear range of H 2 O 2 concentrations from 1.5 to 2684 µM, demonstrating high sensitivity and low detection limit. Further characterization of the Hb/Fe 3 O 4 @rGO/GC electrode revealed a high surface coverage (τ = 3.0 × 10−9 mol cm−2), charge transfer coefficient (α = 0.83), and electron transfer rate constant (k s = 1.33 s−1). Subsequently, the Hb/Fe 3 O 4 @rGO/GC sensor probe was employed to analyze H 2 O 2 in real human serum samples, demonstrating excellent recovery rates ranging from 99.8 % to 104.0 %. The nanocomposite material, designed through the innovative combination of graphene oxide reduction, Fe 3 O 4 nanoparticle decoration, and oleylamine amide/amine bonding, serves as an excellent electrode material for H 2 O 2 concentration sensing. Thus, this study presents a promising platform for the future determination of H 2 O 2 biomarkers in clinical settings. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel and robust enzymatic biosensing platform with high sensitivity is developed based on facile one-step assembled bio-nanocomposites with enzymes-loaded polymeric nanoparticles decorating multi-walled carbon nanotubes (MWCNTs). An amphiphilic copolymer PAVE containing photo-cross-linkable coumarin segments and carboxylic groups was co-assembled with MWCNTs in aqueous solution while encapsulating the model enzyme namely glucose oxidase (GOx) simultaneously, generating necklace-like bio-nanocomposites (GOx@PAVE-CNTs) with GOx-loading polymeric nanoparticles as nanobeads and MWCNTs as conducting micron-string. Then the GOx@PAVE-CNTs bio-nanocomposites were electro-deposited onto electrode surface and a robust biosensing complex film with porous network structure was formed after following photo-cross-linking. Consequently, an enzymatic glucose biosensor was successfully constructed. The biosensor exhibited ultrafast response (<3 s) to glucose with a considerably wide linear range (1.0 μM ∼ 5 mM) and a low detection limit (0.36 μM) for glucose detection. High sensitivity and selectivity of the biosensor toward glucose were also well demonstrated. Furthermore, the biosensor showed exceptionally good stability and reproducibility. More importantly, the glucose biosensor was practically used for glucose detection from human urine and serum samples with satisfactory results. As a proof-of-concept strategy, this facile and effective strategy for biosensor fabrication is of considerable interest because of its versatility to be generalized to many other enzymatic biosensor systems, exhibiting promising and practical potential in bio-medical and life health applications. Image 1 • Necklace-like bio-sensing nanocomposite was developed by facile one step co-assembly of GOx, copolymer and MWCNTs. • A robust enzymatic biosensor was constructed by electrophoretic deposition of the bio-nanocomposite on electrode surface. • The biosensor showed fast response, high sensitivity and stability, good reproducibility towards glucose detection. • Satisfactory analytical results were obtained from real samples, demonstrating great potential in practical applications. [ABSTRACT FROM AUTHOR]

Abstract Highly sensitive phenol biosensor was developed by using well-dispersed carbon nanotubes (CNTs) in enzyme solution and adding CNTs in enzyme electrodes. First, the intact CNTs were dispersed in aqueous tyrosinase (TYR) solution, and TYR molecules were precipitated and crosslinked to prepare the sample of enzyme adsorption, precipitation and crosslinking (EAPC). EAPC exhibited 10.5- and 5.4-fold higher TYR activity per mg of CNTs as compared to enzyme adsorption (EA) and enzyme adsorption/crosslinking (EAC), respectively. EAPC retained 29% of its initial activity after incubation at 40 °C for 128 h, while EA and EAC showed no residual activities, respectively. In biosensing a model phenolic compound of catechol, the sensitivities of EA, EAC and EAPC electrodes on glassy carbon electrode (GCE) were 34, 281 and 675 µA/mM/cm2, respectively. When 90 w/w% CNTs were added to the enzyme electrodes, the sensitivities of EA, EAC, and EAPC electrodes were 146, 427, and 1160 µA/mM/cm2, respectively, and the EAPC electrode showed a 2.3-fold increase in sensitivity upon CNT addition. Catechol and phenol could also be detected by EAPC on the screen-printed electrode (SPE), with sensitivities of 1340 and 1170 µA/mM/cm2, respectively. The sensitivity of EAPC-SPE for phenol detection in the effluent from real municipal wastewater treatment plant was 1100 µA/mM/cm2. The sensitivity of EAPC-SPE retained 74% of its initial sensitivity after incubation at 40 °C for 12 h. The combination of EAPC immobilization and CNT addition has great potential for application in the development of sensitive enzyme biosensors for various analytes and phenols in water environments. Highlights • Phenol biosensor was developed by using well-dispersed CNTs in aqueous TYR solution. • High TYR loading and stability could be achieved by employing protocol of EAPC. • The TYR-EAPC on GCE with CNT addition achieved the highest sensitivity. • The EAPC electrode on SPE successfully detected phenol from municipal wastewater. [ABSTRACT FROM AUTHOR]

Highlights • A third-generation biosensor based on nitric oxide reductase (NOR) was developed. • A MWCNTs/BMIMBF 4 nanocomposite was optimized to entrap NOR. • PGE/[MWCNTs/BMIMBF 4 /NOR] direct electron transfer behavior was characterized. • High sensitivity was reached towards NO unmediated bioelectrocatalytic reduction. • The biosensor kept 79–116% of its initial response after one month. Abstract Nitric oxide (NO) has a crucial role in signaling and cellular physiology in humans. Herein, a novel third-generation biosensor based on the Marinobacter hydrocarbonoclasticus metalloenzyme (nitric oxide reductase (NOR)), responsible for the NO reduction in the denitrifying processes, was developed through the direct adsorption of a new nanocomposite (multiwalled carbon nanotubes (MWCNTs)/1 -n- butyl-3-methylimidazolium tetrafluoroborate (BMIMBF 4)/NOR) onto a pyrolytic graphite electrode (PGE) surface. The NOR direct electron transfer behavior (formal potential of -0.255 ± 0.003 V vs. Ag/AgCl) and electrocatalysis towards NO reduction (−0.68 ± 0.03 V vs. Ag/AgCl) of the PGE/[MWCNTs/BMIMBF 4 /NOR] biosensor were investigated in phosphate buffer at pH 6.0. Large enzyme loading (2.04 × 10−10 mol/cm2), acceptable electron transfer rate between NOR and the PGE surface (k s = 0.35 s-1), and high affinity for NO (K m = 2.17 μmol L-1) were observed with this biosensor composition. A linear response to NO concentration (0.23–4.76 μmol L-1) was perceived with high sensitivity (0.429 μA/μmolL-1), a detection limit of 0.07 μmol L-1, appropriate repeatability (9.1% relative standard deviations (RSD)), reproducibility (6.0–11% RSD) and 80–102% recoveries. The biosensor was stable during 1 month retaining 79–116% of its initial response. These data confirmed that NOR incorporated in the MWCNTs/BMIMBF 4 nanocomposite can efficiently maintain its bioactivity paving a new and effective way for NO biosensing. [ABSTRACT FROM AUTHOR]

In this paper, we investigated a novel functionalized polymeric film derived from 4-mercaptophenylacetic acid (MPAA). The polymerization was carried out through cyclic voltammetry (CV). Electrochemical, spectroscopic, and morphological analyses were used for characterization. Only acidic medium provided an efficient electrode modification as the electrochemical and morphological profiles obtained from treatment in alkaline solution resembles the unmodified electrode. The electrostatic repulsion between the carboxylate anions in the polymer and ferricyanide probe was verified by the current decrease in CV profiles and by the resistance of charge transfer increase through electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) images showed a complete and homogeneous coverage with a splinter-like morphology. The polymer presents stability under storage conditions until 35 days with no lixiviation during washing steps or loss of activity. The FT-IR measurements confirm the presence of the carboxyl group in the polymer suggesting a polymerization through the sulfur atom, which led to a mechanism proposal. The immobilization of enzyme tyrosinase over this platform and the detection of tyramine were performed successfully. 50 U of the enzyme for 18 h at pH 7.2 was the optimum parameters leading to a limit of detection and limit of quantification of 3.16 μmol L and 10.52 μmol L, respectively. With Kmapp of 62.11 μmol L and a recovery rate of 110.84% in a wine sample, the novel, stable, functionalized material formed over a low-cost electrode is suitable for further electrochemical applications exploiting the chemical reaction of carboxyl groups for biosensor purposing. [ABSTRACT FROM AUTHOR]

Abstract A newly modified electrode based on glassy carbon (GC) has been prepared and characterized electrochemically for application in electroanalytical chemistry. In particular, a GC screen-printed electrode (SPE) has been modified with nanostructures, namely multi-walled carbon nanotubes (MWCNTs), and TiO2 nanoparticles, and combined with a new generation of eco-friendly room-temperature ionic liquids (RTILs). The green RTILs here used are suitable for the immobilization of enzymes on the electrode surface and, additionally, facilitate the kinetics of electron transfer due to their intrinsic electrical conductivity. Upon evaluation of these newly modified electrodes we found an improvement in terms of electrochemically active area (Aea) with respect to the electrodes we previously reported. The modified SPEs were then used as substrates for the construction of two enzymatic biosensors for analytical applications: the first is an enzymatic biosensor based on alcohol dehydrogenase (ADH) for the analysis of ethyl alcohol; the second biosensor is based on lipase enzyme and has been tested for the analysis and the classification of Extra Virgin Olive Oil (EVOO). The performances of the here projected sensors appear comparable with biosensors having similar finalities. It is here envisaged that such a kind of electrodes could represent the starting tool for the construction and the definition of new portable devices for screening and field analyses. Graphical abstract fx1 Highlights • GC screen-printed electrodes modified with nanostructures and green ionic liquids. • Multi-walled CNT interaction with RTILs studied with chemometric instruments. • Further optimization of the platform was obtained by using TiO 2 nanoparticles. • Platform used to develop biosensors for ethyl alcohol and olive oils. • Discrimination of olive oils based on cultivar was obtained with proposed biosensor. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Enzyme-based fiber optic biosensor for halogenated environmental pollutant detection. • Indirect quantification of halocarbon levels based on NBC pH sensor colour change. • Acrylic microspheres for covalent binding of DhlA and physical adsorption of NBC. Abstract A reflectometric biosensor for enzymatic determination of halogenated organic pollutant in environmental water sample was developed. Polyacrylate microspheres modified with succinimide functional groups were employed as the substrate matrix for covalent immobilization of haloalkane dehalogenase (DhlA) enzyme, and ETH5294 Nile Blue chromoionophore (NBC) pH dye was physically immobilized on the acrylic micromatrix to function as an optical proton sensor. The hydrolytic dehalogenation of halocarbon catalyzed by the immobilized DhlA resulting in the release of a halogen and a proton, which protonated the immobilized NBC proton indicator, and a colour change of the biosensor from violet to blue was measured with a reflectance spectrophotometer for indirect quantification of the halogenated hydrocarbon concentration. The enzymatic halocarbon reflectance biosensor exhibited a dynamic linear response range of 1–30 mg L−1 1,2-dichloroethane (DCA) (R2 = 0.9762) with a detection limit of 0.3 mg L−1. The proposed enzymatic biosensor gave rapid response, within 2 min, towards the detection of 50 mg L−1 DCA at 662 nm, and demonstrated stable response up to 6 days of storage period at 4 °C and pH 8.0. Validation between the developed biosensor with standard gas chromatography–electron capture detector (GC-ECD) showed that both methods have a comparable accuracy in detecting halocarbon species. [ABSTRACT FROM AUTHOR]

Electrogenerated chemiluminescence (also called electrochemiluminescence (ECL)) has become a great focus of attention in different fields of analysis, mainly as a consequence of the potential remarkably high sensitivity and wide dynamic range. In the particular case of sensing applications, ECL biosensor unites the benefits of the high selectivity of biological recognition elements and the high sensitivity of ECL analysis methods. Hence, it is a powerful analytical device for sensitive detection of different analytes of interest in medical prognosis and diagnosis, food control and environment. These wide range of applications are increased by the introduction of screen-printed electrodes (SPEs). Disposable SPE-based biosensors cover the need to perform in-situ measurements with portable devices quickly and accurately. In this review, we sum up the latest biosensing applications and current progress on ECL bioanalysis combined with disposable SPEs in the field of bio affinity ECL sensors including immunosensors, DNA analysis and catalytic ECL sensors. Furthermore, the integration of nanomaterials with particular physical and chemical properties in the ECL biosensing systems has improved tremendously their sensitivity and overall performance, being one of the most appropriates research fields for the development of highly sensitive ECL biosensor devices.

Herein, a novel electrochemical glucose biosensor based on glucose oxidase (GOx) immobilized on a surface containing platinum nanoparticles (PtNPs) electrodeposited on poly(Azure A) (PAA) previously electropolymerized on activated screen-printed carbon electrodes (GOx-PtNPs-PAA-aSPCEs) is reported. The resulting electrochemical biosensor was validated towards glucose oxidation in real samples and further electrochemical measurement associated with the generated H2O2. The electrochemical biosensor showed an excellent sensitivity (42.7 μA mM−1 cm−2), limit of detection (7.6 μM), linear range (20 μM–2.3 mM), and good selectivity towards glucose determination. Furthermore, and most importantly, the detection of glucose was performed at a low potential (0.2 V vs. Ag). The high performance of the electrochemical biosensor was explained through surface exploration using field emission SEM, XPS, and impedance measurements. The electrochemical biosensor was successfully applied to glucose quantification in several real samples (commercial juices and a plant cell culture medium), exhibiting a high accuracy when compared with a classical spectrophotometric method. This electrochemical biosensor can be easily prepared and opens up a good alternative in the development of new sensitive glucose sensors.

Cholinergic signaling, i.e., neurotransmission mediated by acetylcholine, is involved in a host of physiological processes, including learning and memory. Cholinergic dysfunction is commonly associated with neurodegenerative diseases, including Alzheimer's disease. In the gut, acetylcholine acts as an excitatory neuromuscular signaler to mediate smooth muscle contraction, which facilitates peristaltic propulsion. Gastrointestinal dysfunction has also been associated with Alzheimer's disease. This research focuses on the preparation of an electrochemical enzyme-based biosensor to monitor cholinergic signaling in the gut and its application for measuring electrically stimulated acetylcholine release in the mouse colon ex vivo. The biosensors were prepared by platinizing Pt microelectrodes through potential cycling in a potassium hexachloroplatinate (IV) solution to roughen the electrode surface and improve adhesion of the multienzyme film. These electrodes were then modified with a permselective poly( m -phenylenediamine) polymer film, which blocks electroactive interferents from reaching the underlying substrate while remaining permeable to small molecules like H 2 O 2 . A multienzyme film containing choline oxidase and acetylcholinesterase was then drop-cast on these modified electrodes. The sensor responds to acetylcholine and choline through the enzymatic production of H 2 O 2 , which is electrochemically oxidized to produce an increase in current with increasing acetylcholine or choline concentration. Important figures of merit include a sensitivity of 190 ± 10 mA mol -1 L cm -2 , a limit of detection of 0.8 μmol L -1 , and a batch reproducibility of 6.1% relative standard deviation at room temperature. These sensors were used to detect electrically stimulated acetylcholine release from mouse myenteric ganglia in the presence and absence of tetrodotoxin and neostigmine, an acetylcholinesterase inhibitor.

In this work, an electrochemical approach using uricase (UOx) as an enzyme to detect uric acid (UA) for wound monitoring has been reported. UOx was entrapped in poly (vinyl alcohol) N‐methyl‐4(4'‐formylstyryl) pyridinium methosulfate acetal (PVA‐SbQ), a cationic polymer matrix. The polymer‐enzyme ratio for immobilization was calculated as 53.2 μg cm−2 : 0.25 U cm−2. UA was detected both optically as well as electrochemically. A redox electron shuttle, ferrocene carboxylic acid (FCA) was used to facilitate electron transfer. Entrapped UOx provided improved response to UA detection compared to physisorbed UOx. Sensor response was linear in the physiologically relevant ranges between 12 and 100 μM. The entrapped UOx biosensor was stable for 48 h and maintained 90 % activity until 5 days. This entrapped biosensor was used for UA measurements in biofluids of sweat and wounds. The sensor demonstrated a recovery of ∼102–107 %. These results show that entrapment of UA in such a polymer matrix is a preferred approach for UA measurements under physiological conditions. [ABSTRACT FROM AUTHOR]

The demand for developing novel materials to construct high-performance enzymatic glucose biosensors is rising, due to enzyme tend to denaturation and leaking from electrodes. Titanium carbide (TiC), as one of the most important transition metal carbides, exhibits good chemical stability and electrical conductivity, and electrocatalytic activity resembling that of metals, but is much cheaper. In this work, TiC–carbon nanofibers (CNFs) film (TCNFs) is synthesized by a one-step synthesis technique, which could maintain its structural integrity with robust adhesion, and could be produce in large quantity. Uniform TiC nanoparticles (NPs) are firmly embedded into the CNFs matrix. When TCNFs is applied for glucose oxidase (GOD) immobilization and biosensing, flexible TCNFs with good conductivity and porous nature facilitates electron transfer and GOD loading. The as-prepared glucose biosensor possesses excellent sensing performance, which exhibits a wide linear range (0.013–10.5 mM, R 2  = 0.999), a low detection limit (3.7 μM, S/N = 3), satisfactory reproducibility, good selectivity and anti-interference ability. Simple synthetic method and excellent electrochemical performance make TCNFs promising as an ideal substrate to fabricate effective electrochemical biosensors. [ABSTRACT FROM AUTHOR]

Abstract: Four various biosensors based on flow enzymatic mini‐reactors containing one of the two different mesoporous silica powders (SBA‐15 or MCM‐41) modified by one of the two enzymes (laccase or tyrosinase) were used for the determination of L‐DOPA, dopamine, noradrenaline, and adrenaline. Dependences of peak currents on detection potentials, flow rates, injected volumes, reactor volumes, and analyte concentrations were studied and optimized. The silica powder of MCM‐41 with covalently bonded laccase (Lac) was found to be the best filling for the detection of catecholamines. Relative current response of such biosensor was: 100 % for dopamine, 32.1 % for L‐DOPA, 26.2 % for noradrenaline, and 0.71 % for adrenaline. Statistical evaluation of parallel determinations of studied analytes with this biosensor proved its good accuracy (RSD=1.82–5.18 %) and sensitivity (5.46–15.5 μmol L−1). Life time of the studied biosensors is several months. The practical applicability of Lac‐MCM41 biosensor was successfully verified by the determination of dopamine and noradrenaline in medical solutions for infusions. [ABSTRACT FROM AUTHOR]

Abstract: Glutamate (Glu) is recognized as a vital neurotransmitter released via vesicular exocytosis and plays important roles in many physiological processes. Microelectrode amperometry has become a powerful method to study the secreted electroactive biochemicals via exocytosis, however, there was no means for direct monitoring of exocytosis of the non‐electroactive Glu so far. Herein, we developed an enzymatic micro‐biosensor by co‐modification of glutamate oxidase (GluOx) and Pt nanoparticles (Pt NPs) on the surface of a carbon fiber microelectrode. The Glu was enzymatically transformed by GluOx to an electroactive product, H2O2, which was then electrochemically detected by the Pt NPs. The prominent catalytic activity of enzyme and micrometer scale of microelectrode endow the sensor with high sensitivity and spatio‐temporal resolution, allowing real‐time monitoring Glu exocytosis from single hippocampal varicosities. The results demonstrate the capability of this biosensor in monitoring and quantification of the quantal release of neurotransmitter Glu, indicating its great potential in exploring the cellular mechanism of neuron communication and synaptic plasticity. [ABSTRACT FROM AUTHOR]

Laccase enzyme, a commonly used enzyme for the construction of biosensors for phenolic compounds was used for the first time to develop a new biosensor for the determination of the azo-dye tartrazine. The electrochemical biosensor was based on the immobilization of laccase on functionalized methacrylate-acrylate microspheres. The biosensor membrane is a composite of the laccase conjugated microspheres and gold nanoparticles (AuNPs) coated on a carbon-paste screen-printed electrode. The reaction involving tartrazine can be catalyzed by laccase enzyme, where the current change was measured by differential pulse voltammetry (DPV) at 1.1 V. The anodic peak current was linear within the tartrazine concentration range of 0.2 to 14 μM (R2 = 0.979) and the detection limit was 0.04 μM. Common food ingredients or additives such as glucose, sucrose, ascorbic acid, phenol and sunset yellow did not interfere with the biosensor response. Furthermore, the biosensor response was stable up to 30 days of storage period at 4 °C. Foods and beverage were used as real samples for the biosensor validation. The biosensor response to tartrazine showed no significant difference with a standard HPLC method for tartrazine analysis. [ABSTRACT FROM AUTHOR]

Peroxidase mimetics of bifunctional nanocomposite for dual mode electro-spectroscopic screening of cholesterol and hydrogen peroxide in real food samples and live cells. [Display omitted] • Developed a dual biosensing platform for cholesterol and H 2 O 2 using ChOx-BSA-AuNPs-MFOF. • The platform displayed a wide linear range concentration and nanomolar level detection limit. • The platform was found to be easy to use, rapid, interference-free, highly stable, and reproducible. • The platform was capable of detecting Chol and H 2 O 2 in real food samples and live cells. • To comply with JECFA and FAD guidelines for analyzing Chol in real food and juice samples. A simple and rapid screening of biomarkers in clinical and food matrices is urgently needed to diagnose cardiovascular diseases. The cholesterol (Chol) and hydrogen peroxide (H 2 O 2) are critical bio-indicators, which require more inventive detection techniques to be applied to real food, and bio-samples. In this study, a robust dual sensor was developed for Chol and H 2 O 2 using hybrid catalyst. Bovine serum albumin (BSA)-capped nanocatalyst was potentially catalyzed 3,3′,5,5′-tetramethylbenzidine (TMB), and H 2 O 2. The enzymatic nanoelectrocatalyst delivered a wide range of signaling concentrations from 250 nM to 3.0 mM and 100 nM to 10 mM, limit of detection (LOD) of 53.2 nM and 18.4 nM for Chol and H 2 O 2. The cholesterol oxidase-BSA-AuNPs-metal-free organic framework (ChOx-BSA-AuNPs-MFOF) based electrode surface effectively operated in live-cells and real-food samples. The enzymatic sensor exhibits adequate recovery of real-food samples (96.96–99.44%). Finally, the proposed system is a suitable choice for the potential applications of Chol and H 2 O 2 in clinical and food chemistry. [ABSTRACT FROM AUTHOR]