Amperometric biogenic amine biosensors based on Prussian blue, indium tin oxide nanoparticles and diamine oxidase– or monoamine oxidase–modified electrodes

Recent advancements in chemosensors for the detection of food spoilage

The need for reliable sensors has become a major requirement to confirm the quality and safety of food commodities. Chemosensors are promising sensing tools to identify contaminants and food spoilage to ensure food safety. Chemosensing materials are evolving and becoming potential mechanisms to enable onsite and real-time monitoring of food safety. This review summarizes the information about the basic four types of chemosensors (colorimetric, optical, electrochemical, and piezoelectric) employed in the food sector, the latest advancements in the development of chemo-sensing mechanisms, and their food applications, with special emphasis on the future outlook of them. In this review, we discuss the novel chemosensors developed from the year 2018 to 2022 to detect spoilage in some common types of food like fish, meat, milk, cheese and soy sauce. This work will provide a fundamental step toward further development and innovations of chemosensors targeting different arenas in the food industry.

Material Breakthroughs in Smart Food Monitoring: Intelligent Packaging and On-Site Testing Technologies for Spoilage and Contamination Detection

Despite extensive commercial and regulatory interventions, food spoilage and contamination continue to impose massive ramifications on human health and the global economy. Recognizing that such issues will be significantly eliminated by the accurate and timely monitoring of food quality markers, smart food sensors have garnered significant interest as platforms for both real-time, in-package food monitoring and on-site commercial testing. In both cases, the sensitivity, stability, and efficiency of the developed sensors are largely informed by underlying material design, driving focus toward the creation of advanced materials optimized for such applications. Herein, a comprehensive review of emerging intelligent materials and sensors developed in this space is provided, through the lens of three key food quality markers - biogenic amines, pH, and pathogenic microbes. Each sensing platform is presented with targeted consideration toward the contributions of the underlying metallic or polymeric substrate to the sensing mechanism and detection performance. Further, the real-world applicability of presented works is considered with respect to their capabilities, regulatory adherence, and commercial potential. Finally, a situational assessment of the current state of intelligent food monitoring technologies is provided, discussing material-centric strategies to address their existing limitations, regulatory concerns, and commercial considerations.

A do-it-yourself electrochemical cell based on pencil leads and transparency sheets: Application to the enzymatic determination of histamine

The availability of more efficient analytical methods that answer the world's demands is a challenge and their development continues to be a difficult task. In this work the construction of an electrochemical cell, based on low-cost and accessible materials, that can be easily constructed and used for electroanalytical purposes, is described. Pencil leads were used as electrodes and a transparency sheet as the base. This cell was used as transducer for developing an amperometric biosensor for the quantification of histamine, which is the only biogenic amine regulated by law. The analysis was based on the use of diamine oxidase as biorecognition element, hexacyanoferrate(III) as electron-transfer mediator, and chronoamperometry, at +0.5 V during 100 s, to record the analytical signal. A linear relationship between histamine concentration and the analytical signal was established between 5.0 and 35 mg L-1 and a low limit of detection (1.0 mg L-1) was achieved. The analysis of different fish species (sardine and tuna) was performed, obtaining recovery values between 102% and 110%. The stability of the sensor is noteworthy: it maintained 95% of the initial analytical signal after 15 days.

Immobilization of Enzyme Electrochemical Biosensors and Their Application to Food Bioprocess Monitoring

Electrochemical biosensors based on immobilized enzymes are among the most popular and commercially successful biosensors. The literature in this field suggests that modification of electrodes with nanomaterials is an excellent method for enzyme immobilization, which can greatly improve the stability and sensitivity of the sensor. However, the poor stability, weak reproducibility, and limited lifetime of the enzyme itself still limit the requirements for the development of enzyme electrochemical biosensors for food production process monitoring. Therefore, constructing sensing technologies based on enzyme electrochemical biosensors remains a great challenge. This article outlines the construction principles of four generations of enzyme electrochemical biosensors and discusses the applications of single-enzyme systems, multi-enzyme systems, and nano-enzyme systems developed based on these principles. The article further describes methods to improve enzyme immobilization by combining different types of nanomaterials such as metals and their oxides, graphene-related materials, metal-organic frameworks, carbon nanotubes, and conducting polymers. In addition, the article highlights the challenges and future trends of enzyme electrochemical biosensors, providing theoretical support and future perspectives for further research and development of high-performance enzyme chemical biosensors.

Recent Advances in Electrochemical Enzyme-Based Biosensors for Food and Beverage Analysis

Food analysis and control are crucial aspects in food research and production in order to ensure quality and safety of food products. Electrochemical biosensors based on enzymes as the bioreceptors are emerging as promising tools for food analysis because of their high selectivity and sensitivity, short analysis time, and high-cost effectiveness in comparison to conventional methods. This review provides the readers with an overview of various electrochemical enzyme-based biosensors in food analysis, focusing on enzymes used for different applications in the analysis of sugars, alcohols, amino acids and amines, and organic acids, as well as mycotoxins and chemical contaminants. In addition, strategies to improve the performance of enzyme-based biosensors that have been reported over the last five years will be discussed. The challenges and future outlooks for the food sector are also presented.

The Peroxidase-like Nanocomposites as Hydrogen Peroxide-Sensitive Elements in Cholesterol Oxidase-Based Biosensors for Cholesterol Assay

Catalytically active nanomaterials, in particular, nanozymes, are promising candidates for applications in biosensors due to their excellent catalytic activity, stability and cost-effective preparation. Nanozymes with peroxidase-like activities are prospective candidates for applications in biosensors. The purpose of the current work is to develop cholesterol oxidase-based amperometric bionanosensors using novel nanocomposites as peroxidase (HRP) mimetics. To select the most electroactive chemosensor on hydrogen peroxide, a wide range of nanomaterials were synthesized and characterized using cyclic voltammetry (CV) and chronoamperometry. Pt NPs were deposited on the surface of a glassy carbon electrode (GCE) in order to improve the conductivity and sensitivity of the nanocomposites. The most HRP-like active bi-metallic CuFe nanoparticles (nCuFe) were placed on a previously nano-platinized electrode, followed by conjugation of cholesterol oxidase (ChOx) in a cross-linking film formed by cysteamine and glutaraldehyde. The constructed nanostructured bioelectrode ChOx/nCuFe/nPt/GCE was characterized by CV and chronoamperometry in the presence of cholesterol. The bionanosensor (ChOx/nCuFe/nPt/GCE) shows a high sensitivity (3960 A·M^-1·m^-2) for cholesterol, a wide linear range (2-50 µM) and good storage stability at a low working potential (-0.25 V vs. Ag/AgCl/3 M KCl). The constructed bionanosensor was tested on a real serum sample. A detailed comparative analysis of the bioanalytical characteristics of the developed cholesterol bionanosensor and the known analogs is presented.

Application of Electrochemical Biosensors for Determination of Food Spoilage

Food security is significantly affected by the mass production of agricultural produce and goods, the growing number of imported foods, and new eating and consumption habits. These changed circumstances bring food safety issues arising from food spoilage to the fore, making food safety control essential. Simple and fast screening methods have been developed to detect pathogens and biomarkers indicating the freshness of food for safety. In addition to the traditional, sequential, chemical analytical and microbiological methods, fast, highly sensitive, automated methods suitable for serial tests have appeared. At the same time, biosensor research is also developing dynamically worldwide, both in terms of the analytes to be determined and the technical toolkit. Consequently, the rapid development of biosensors, including electrochemical-based biosensors, has led to significant advantages in the quantitative detection and screening of food contaminants. These techniques show great specificity for the biomarkers tested and provide adequate analytical accuracy even in complex food matrices. In our review article, we summarize, in separate chapters, the electrochemical biosensors developed for the most important food groups and the food safety issues they can ensure, with particular respect to meat and fish products, milk and dairy products, as well as alcoholic and non-alcoholic beverages.

Humanoid shaped optical fiber plasmon biosensor functionalized with graphene oxide/multi-walled carbon nanotubes for histamine detection

Histamine is a biologically active molecule that serves as a reliable predictor of the quality of fish. In this work, authors have developed a novel humanoid-shaped tapered optical fiber (HTOF) biosensor based on the localized surface plasmon resonance (LSPR) phenomenon to detect varying histamine concentrations. In this experiment, a novel and distinctive tapering structure has been developed using a combiner manufacturing system and contemporary processing technologies. Graphene oxide (GO)/multi-walled carbon nanotubes (MWCNTs) are immobilized on the HTOF probe surface to increase the biocompatibility of biosensor. In this instance, GO/MWCNTs are deployed first, then gold nanoparticles (AuNPs). Consequently, the GO/MWCNTs help to give abundant space for the immobilization of nanoparticles (AuNPs in this case) as well as increase surface area for the attachment of biomolecules to the fiber surface. By immobilizing AuNPs on the surface of the probe, the evanescent field can stimulate the AuNPs and excite the LSPR phenomena for sensing the histamine. The surface of the sensing probe is functionalized with diamine oxidase enzyme in order to enhance the histamine sensor's particular selectivity. The proposed sensor is demonstrated experimentally to have a sensitivity of 5.5 nm/mM and a detection limit of 59.45 µM in the linear detection range of 0-1000 µM. In addition, the probe's reusability, reproducibility, stability, and selectivity are tested; the results of these indices show that the probe has a high application potential for detecting histamine levels in marine products.

Electrochemical (bio)sensors based on carbon quantum dots, ionic liquid and gold nanoparticles for bisphenol A

Electrochemical (bio)sensors were developed for bisphenol A (BPA) determination. Screen printed carbon electrode (SPCE) was modified with ionic liquid 1- butyl-3-methylimidazolium tetrafluoroborate (IL), carbon quantum dots (CQD) and gold nanoparticles (AuNP) for the fabrication of the BPA sensor. Electrode surface composition was optimized for the deposition time of AuNP, amount of CQD and percentage of IL using the central composite design (CCD) method. The results of the CCD study indicated that maximum amperometric response was recorded when 9.8 μg CQD, 3% IL and 284 s AuNP deposition time were used in modification. Tyrosinase (Ty) was further modified on the AuNP/CQD-IL/SPCE to fabricate the biosensor. Analytical performance characteristics of the BPA sensor were investigated by differential pulse anodic adsorptive stripping voltammetry and the AuNP/CQD-IL/SPCE sensor exhibited a linear response to BPA in the range of 2.0 × 10^-8 - 3.6 × 10^-6 M with a detection limit of 1.1 × 10^-8 M. Amperometric measurements showed that the linear dynamic range and detection limit of the Ty/AuNP/CQD-IL/SPCE were 2.0 × 10^-8 - 4.0 × 10^-6 M and 6.2 × 10^-9 M, respectively. Analytical performance characteristics such as sensitivity, reproducibility and selectivity were investigated for the presented (bio)sensors. The analytical applicability of the (bio)sensors to the analysis of BPA in mineral water samples was also tested.

A Review on Bio- and Chemosensors for the Detection of Biogenic Amines in Food Safety Applications: The Status in 2022

This article provides an overview on the broad topic of biogenic amines (BAs) that are a persistent concern in the context of food quality and safety. They emerge mainly from the decomposition of amino acids in protein-rich food due to enzymes excreted by pathogenic bacteria that infect food under inappropriate storage conditions. While there are food authority regulations on the maximum allowed amounts of, e.g., histamine in fish, sensitive individuals can still suffer from medical conditions triggered by biogenic amines, and mass outbreaks of scombroid poisoning are reported regularly. We review first the classical techniques used for selective BA detection and quantification in analytical laboratories and focus then on sensor-based solutions aiming at on-site BA detection throughout the food chain. There are receptor-free chemosensors for BA detection and a vastly growing range of bio- and biomimetic sensors that employ receptors to enable selective molecular recognition. Regarding the receptors, we address enzymes, antibodies, molecularly imprinted polymers (MIPs), and aptamers as the most recent class of BA receptors. Furthermore, we address the underlying transducer technologies, including optical, electrochemical, mass-sensitive, and thermal-based sensing principles. The review concludes with an assessment on the persistent limitations of BA sensors, a technological forecast, and thoughts on short-term solutions.

Recent advances in development of electrochemical biosensors for the detection of biogenic amines

Biogenic amines (BAs) are widely found in food as a consequence of diverse factors including free amino acid availability, microbial production of decarboxylases, and variations in processing and storage conditions. Hence, BAs are considered as an important marker for determining the freshness and quality of food. Owing to the documentation of BAs in different dietary products, their numerous negative impacts on human health have reported to be a serious concern in past few decades. Therefore, the quantification of these chemical species in food becomes crucial as it can immensely contributes toward control of new episodes on food intoxication in humans. In this line, various chromatographic and colorimetric methods have been developed to detect BAs. However, these methods are in use from a longer time, still are limited by high cost, lengthy procedures, huge infrastructure and skilled personnel requirements that hinder their on-field application. In pursuit of a reliable method offering accurate detection of BAs, this review presents the state-of-the-art of electrochemical strategies for BAs sensing in food. The core of the review discusses about the widely employed electrochemical transducers, such as amperometric, potentiometric, impedimetric and conductometric-based BAs biosensors with significant findings of research work conducted previously. The application of electrochemical sensors to analyze BAs in different fields including food systems (fermented and non-fermented types) and smart packaging systems has been reviewed. Moreover, existing challenges and further available prospects for the development of rapid, facile, and sensitive electrochemical strategies for on-site determination of BAs have also been discussed.

A Multipurpose and Multilayered Microneedle Sensor for Redox Potential Monitoring in Diverse Food Analysis

This work presents a multipurpose and multilayered stainless steel microneedle sensor for the in situ redox potential monitoring in food and drink samples, termed MN redox sensor. The MN redox sensor was fabricated by layer-by-layer (LbL) approach. The in-tube multilayer coating comprised carbon nanotubes (CNTs)/cellulose nanocrystals (CNCs) as the first layer, polyaniline (PANI) as the second layer, and the ferrocyanide redox couple as the third layer. Using cyclic voltammetry (CV) as a transduction method, the MN redox sensor showed facile electron transfer for probing both electrical capacitance and redox potential, useful for both analyte specific and bulk quantification of redox species in various food and drink samples. The bulk redox species were quantified based on the anodic/cathodic redox peak shifts (E_a/E_c) on the voltammograms resulting from the presence of redox-active species. The MN redox sensor was applied to detect selected redox species including ascorbic acid, H₂O₂, and putrescine, with capacitive limits of detection (LOD) of 49.9, 17.8, and 263 ng/mL for each species, respectively. For the bulk determination of redox species, the MN redox sensor displayed LOD of 5.27 × 10³, 55.4, and 25.8 ng/mL in ascorbic acid, H₂O₂, and putrescine equivalents, respectively. The sensor exhibited reproducibility of ~ 1.8% relative standard deviation (%RSD). The MN redox sensor was successfully employed for the detection of fish spoilage and antioxidant quantification in king mushroom and brewed coffee samples, thereby justifying its potential for food quality and food safety applications. Lastly, the portability, reusability, rapid sampling time, and capability of in situ analysis of food and drink samples makes it amenable for real-time sensing applications.

Applications of Gelatin in Biosensors: Recent Trends and Progress

Gelatin is a natural protein from animal tissue with excellent biocompatibility, biodegradability, biosafety, low cost, and sol-gel property. By taking advantage of these properties, gelatin is considered to be an ideal component for the fabrication of biosensors. In recent years, biosensors with gelatin have been widely used for detecting various analytes, such as glucose, hydrogen peroxide, urea, amino acids, and pesticides, in the fields of medical diagnosis, food testing, and environmental monitoring. This perspective is an overview of the most recent trends and progress in the development of gelatin-based biosensors, which are classified by the function of gelatin as a matrix for immobilized biorecognition materials or as a biorecognition material for detecting target analytes.

Immobilizing diamine oxidase on electroactive phase-change microcapsules to construct thermoregulatory smart biosensor for enhancing detection of histamine in foods

Aiming at enhancing the biosensing detection of histamine in foods at high temperature, we developed a thermoregulatory biosensor based on diamine oxidase-immobilized phase-change microcapsules consisting of an n-docosane core, a TiO₂ shell, and an electroactive polyaniline/ZnO composite coating layer. The microcapsules exhibit a satisfactory latent heat capacity of over 112 J/g for thermo-temperature regulation. Through an innovative integration of electroactive phase-change microcapsules and biological enzyme in the working electrode, the biosensor obtained a thermoregulatory function through reversible phase transitions by the n-docosane core under high-temperature environments. This enables the biosensor to achieve a higher response sensitivity of 28.57 µA⋅mM^-1⋅cm^-2 and a lower detection limit of 0.473 µmol/L at the high assay temperatures compared to conventional histamine biosensors. With enhanced electrochemical biosensing performance through in-situ thermo-temperature regulation, the smart biosensor developed in this study has found practical applications for high-sensitive detection and high-accurate quantitive determination of histamine in foods across a broad temperature range.

Recent Advancements in Enzyme‐Incorporated Nanomaterials: Synthesis, Mechanistic Formation and Applications

Over the past decade, nanotechnology has been developed and employed across various entities. Among the numerous nanostructured material types, enzyme‐incorporated nanomaterials have shown great potential in various fields, as an alternative to biologically derived as well as synthetically developed hybrid structures. The mechanism of incorporating enzyme onto a nanostructure depends on several factors including the method of immobilization, type of nanomaterial, as well as operational and environmental conditions. The prospects of enzyme‐incorporated nanomaterials have shown promising results across various applications, such as biocatalysts, biosensors, drug therapy, and wastewater treatment. This is due to their excellent ability to exhibit chemical and physical properties such as high surface‐to‐volume ratio, recovery and/or reusability rates, sensitivity, response scale, and stable catalytic activity across wide operating conditions. In this review, the evolution of enzyme‐incorporated nanomaterials along with their impact on our society due to its state‐of‐the‐art properties, and its significance across different industrial applications are discussed. In addition, the weakness and future prospects of enzyme‐incorporated nanomaterials were also discussed to guide scientists for futuristic research and development in this field.

The Application of Polyurethane-LiClO4 to Modify Screen-Printed Electrodes Analyzing Histamine in Mackerel Using a Voltammetric Approach

Histamine is an important substance that can be applied as a parameter for allergic reactions and food freshness. This study develops a method to produce a histamine sensor based on electrodes modified using polyurethane-LiClO₄. A sensor method was developed where this sensor was produced from polyurethane. The application of 4,4'-diphenylmethane diisocyanate (hard compound) and palm kernel oil-based monoester polyol (soft compound) to produce polyurethane (PU) based on bio-polyol. The addition of lithium perchlorate (LiClO₄) was done in order to increase the conductivity of PU. The oxidation process was detected using cyclic voltammetry, whereas the electrochemical impedance spectroscopy was used to analyze the conductivity of the polymer. The polyurethane-LiClO₄ was attached on a screen-printed electrode (SPE) within 45 min. Moreover, the 1% LiClO₄-PU-SPE presented satisfactory selectivity for the detection of histamine in the pH 7.5 solution. The LiClO₄-PU-SPE presented a good correlation coefficient (R = 0.9991) in the range 0.015-1 mmol·L^-1. The detection limit was 0.17 mmol·L^-1. Moreover, the histamine concentration of mackerel samples was detected by the PU-SEP-LiClO₄. Several amine compounds were chosen to study the selectivity of histamine detection using SPE-PU-LiClO₄. The interference was from several major interfering compounds such as aniline, cadaverine, hexamine, putrescine, and xanthine. The technique showed a satisfactory selective analysis compared to the other amines. A satisfactory recovery performance toward varying concentrations of histamine was obtained at 94 and 103% for histamine at 0.01 and 0.1 mmol·L^-1, respectively. The application of PU-SEP-LiClO₄ as an electrochemical sensor has a great prospect to analyze histamine content in fish mackerel as a consequence of PU-SEP-LiClO₄ having good selectivity and simplicity.

Questions in the Chemical Enzymology of MAO

We have structure, a wealth of kinetic data, thousands of chemical ligands and clinical information for the effects of a range of drugs on monoamine oxidase activity in vivo. We have comparative information from various species and mutations on kinetics and effects of inhibition. Nevertheless, there are what seem like simple questions still to be answered. This article presents a brief summary of existing experimental evidence the background and poses questions that remain intriguing for chemists and biochemists researching the chemical enzymology of and drug design for monoamine oxidases (FAD-containing EC 4.1.3.4).

An enzymatic histamine biosensor based on a screen-printed carbon electrode modified with a chitosan-gold nanoparticles composite cryogel on Prussian blue-coated multi-walled carbon nanotubes

A histamine biosensor was developed based on a screen-printed carbon electrode modified with Prussian blue (PB) electrodeposited on multi-walled carbon nanotubes covered with a macroporous layer of chitosan-gold nanoparticles composite cryogel (CS-AuNPs Cry). With its high specific surface area and conductivity, CS-AuNPs Cry proved an excellent supporting material for diamine oxidase (DAO) immobilization. PB acted as a redox mediator to promote electron transfer between hydrogen peroxide and the electrode surface. The PB reduction current was measured during the hydrogen peroxide-releasing oxidation of histamine catalyzed by DAO. The proposed biosensor displayed two linear ranges: 2.50-125.0 µmol L^-1 and 125.0-400.0 µmol L^-1. The limit of detection was 1.81 µmol L^-1. Reproducibility was good (RSD = 5.46%), operational stability high, long-term stability excellent, and selectivity good. The biosensor determined histamine levels in fish and shrimps with satisfactory recoveries, and the obtained results agreed with those obtained by ELISA.

Schiff base complex/TiO2 chemosensor for visual detection of food freshness level

Histamine is one of the important biomarkers for food spoilage in the food sectors. In the present study, a rapid and simple analytical tool has been developed to detect histamine as an indirect strategy to monitor food freshness level. Optical histamine sensor with carboxyl-substituted Schiff base zinc(II) complex with hydroxypropoxy side chain deposited onto titanium dioxide nanoparticles was fabricated and was found to respond successfully to histamine. The Schiff base zinc(II) complex-histamine binding generated an enhancement of the fluorescent signal. Under the optimal reaction condition, the developed sensor can detect down to 2.53 × 10^-10 M in the range of between 1.0 × 10^-9 and 1.0 × 10^-5 M (R² = 0.9868). Selectivity performance of the sensor towards histamine over other amines was confirmed. The sensor also displayed good reproducibility performances with low relative standard deviation values (1.45%-4.95%). Shelf-life studies suggested that the developed sensor remains stable after 60 days in histamine detection. More importantly, the proposed sensor has been successfully applied to determine histamine in salmon fillet with good recoveries. This strategy has a promising potential in the food quality assurance sectors, especially in controlling the food safety for healthy consumption among consumers.

Screen-Printed Electrode-Based Sensors for Food Spoilage Control: Bacteria and Biogenic Amines Detection

Food spoilage is caused by the development of microorganisms, biogenic amines, and other harmful substances, which, when consumed, can lead to different health problems. Foodborne diseases can be avoided by assessing the safety and freshness of food along the production and supply chains. The routine methods for food analysis usually involve long analysis times and complex instrumentation and are performed in centralized laboratories. In this context, sensors based on screen-printed electrodes (SPEs) have gained increasing importance because of their advantageous characteristics, such as ease of use and portability, which allow fast analysis in point-of-need scenarios. This review provides a comprehensive overview of SPE-based sensors for the evaluation of food safety and freshness, focusing on the determination of bacteria and biogenic amines. After discussing the characteristics of SPEs as transducers, the main bacteria, and biogenic amines responsible for important and common foodborne diseases are described. Then, SPE-based sensors for the analysis of these bacteria and biogenic amines in food samples are discussed, comparing several parameters, such as limit of detection, analysis time, and sample type.

Disposable biogenic amine biosensors for histamine determination in fish

This study presents the development of disposable biosensors employed in the determination of histamine in fish samples. Screen printed carbon electrodes (SPCEs) were first modified with a mixture of titanium dioxide nanoparticles (TiO₂), carboxylated multiwalled carbon nanotubes (c-MWCNTs), hexaammineruthenium(iii) chloride (RU) and chitosan (CS). Diamine oxidase (DAO) or monoamine oxidase (MAO) enzymes were further immobilized onto the TiO₂-c-MWCNT-RU-CS/SPCEs via 1-ethyl-3-(dimethylaminopropyl) carbodiimide hydrochloride (EDC) and hydroxysuccinimide (NHS) chemistry for the fabrication of the biosensors. The morphological and electrochemical properties of the proposed biosensors were studied using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS). A performance comparison of two biosensors indicated that the one based on DAO had a linear concentration range from 9.9 × 10^-6 to 1.1 × 10^-3 M and the other based on MAO, from 5.6 × 10^-5 to 1.1 × 10^-3 M for histamine. The sensitivity of the DAO based biosensor was almost 1.5 times higher than that of the MAO based biosensor. The proposed biosensors were successfully employed to determine histamine in fish samples and the recoveries were between 100.0% and 104.6%.

An amperometric biosensor based on poly(L-aspartic acid), nanodiamond particles, carbon nanofiber, and ascorbate oxidase-modified glassy carbon electrode for the determination of L-ascorbic acid

An amperometric L-ascorbic acid biosensor utilizing ascorbate oxidase (AOx) immobilized onto poly(L-aspartic acid) (P(L-Asp)) film was fabricated on carbon nanofiber (CNF) and nanodiamond particle (ND)-modified glassy carbon electrode (GCE). Effects of AOx, ND, and CNF amounts were investigated by monitoring the response currents of the biosensor at different amounts of AOx, ND, and CNF. The electropolymerization step of L-aspartic acid on CNF-ND/GCE surface was also optimized. Scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques were used to enlighten the modification steps of the biosensor. The effects of pH and applied potential were studied in detail to achieve the best analytical performance. Under optimized experimental conditions, the AOx/P(L-Asp)/ND-CNF/GCE biosensor showed a linear response to L-ascorbic acid in the range of 2.0 × 10^-7-1.8 × 10^-3 M with a detection limit of 1.0 × 10^-7 M and sensitivity of 105.0 μAmM^-1 cm^-2. The novel biosensing platform showed good reproducibility and selectivity. The strong interaction between AOx and the P(L-Asp)/ND-CNF matrix was revealed by the high repeatability (3.4%) and good operational stability. The AOx/P(L-Asp)/ND-CNF/GCE biosensor was successfully applied to the determination of L-ascorbic acid in vitamin C effervescent tablet and pharmaceutical powder containing ascorbic acid with good results, which makes it a promising approach for quantification of L-ascorbic acid. Graphical abstract.