Designing and fabrication of a novel sensitive electrochemical aptasensor based on poly (L-glutamic acid)/MWCNTs modified glassy carbon electrode for determination of tetracycline

Disposable biosensor based on ionic liquid, carbon nanofiber and poly(glutamic acid) for tyramine determination

In this study, an electrochemical biosensor based on carbon nanofibers (CNF), ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (IL), poly(glutamic acid) (PGA) and tyrosinase (Tyr) modified screen printed carbon electrode (SPE) was constructed for tyramine determination. Optimum experimental parameters such as CNF and IL amount, polymerization conditions of glutamic acid, enzyme loading, pH of test solution and operating potential were explored. The construction steps of the Tyr/PGA/CNF-IL/SPE were pursued by scanning electron microscopy and cyclic voltammetry. The Tyr/PGA/CNF-IL/SPE biosensor exhibited linear response to tyramine in the range of 2.0 × 10-7 - 4.8 × 10-5 M with a low detection limit of 9.1 × 10-8 M and sensitivity of 302.6 μA mM-1. The other advantages of Tyr/PGA/CNF-IL/SPE include its high reproducibility, good stability and anti-interference ability. The presented biosensor was also applied for tyramine determination in malt drink and pickle juice samples and mean analytical recoveries of spiked tyramine were calculated as 100.6% and 100.4% respectively.

Modified electrochemical aptasensor for ultrasensitive detection of tetracycline: In silico and in vitro studies

An ultrasensitive electrochemical aptasensor based on a glassy carbon electrode, modified by carbon nanofibers and carboxylated multi-walled carbon nanotubes was fabricated to detect tetracycline in food samples. The affinity of antibiotics, including kanamycin, tetracycline, ampicillin, and sulfadimethoxine toward desired sequences of aptamers and the stability of antibiotic-aptamer complexes were studied using molecular docking and molecular dynamic simulations. Moreover, the highest affinity and most stable complex were observed for tetracycline in complex with kanamycin-specific aptamer (KAP). Finally, KAP was used to develop an aptasensor. The central composite design (CCD) was used to optimize effective parameters. The biosensor achieved a wide dynamic linear range (1.0 × 10^-17-1.0 × 10^-5 M) and a low limit of detection (2.28 × 10^-18 M) under optimized conditions using differential pulse voltammetry. Using the developed aptasensor, tetracycline residues in milk samples were determined.

Lab-made 3D-printed electrochemical sensors for tetracycline determination

Antibiotics such as tetracycline (TC) are widely prescribed to treat humans or dairy animals. Therefore, it is important to establish affordable devices in laboratories with minimal infrastructure. 3D printing has proven to be a powerful and cost-effective tool that revolutionizes many applications in electrochemical sensing. In this work, we employ a conductive filament based on graphite (Gr) and polylactic acid (PLA) (40:60; w/w; synthesized in our lab) to manufacture 3D-printed electrodes. This electrode was used "as printed" and coupled to batch injection analysis with amperometric detection (BIA-AD) for TC sensing. Preliminary studies by cyclic voltammetry and differential pulse voltammetry revealed a mass transport governed by adsorption of the species and consequent fouling of the redox products on the 3D printed surface. Thus, a simple strategy (solution stirring and application of successive potentials, +0.95 V followed by +1.2 V) was associated with the BIA-AD system to solve this effect. The proposed electrode showed analytical performance comparable to costly conventional electrodes with linear response ranging from 0.5 to 50 μmol L^-1 and a detection limit of 0.19 μmol L^-1. Additionally, the developed method was applied to pharmaceutical, tap water, and milk samples, which required minimal sample preparation (simple dilution). Recovery values of 92-117% were obtained for tap water and milk samples, while the content found of TC in the capsule was close to the value reported by the manufacturer. These results indicate the feasibility of the method for routine analysis involving environmental, pharmaceutical, and food samples.

Bibliometrics Analysis of Research Progress of Electrochemical Detection of Tetracycline Antibiotics

Tetracycline is a broad-spectrum class of antibiotics. The use of excessive doses of tetracycline antibiotics can result in their residues in food, posing varying degrees of risk to human health. Therefore, the establishment of a rapid and sensitive field detection method for tetracycline residues is of great practical importance to improve the safety of food-derived animal foods. Electrochemical analysis techniques are widely used in the field of pollutant detection because of the simple detection principle, easy operation of the instrument, and low cost of analysis. In this review, we summarize the electrochemical detection of tetracycline antibiotics by bibliometrics. Unlike the previously published reviews, this article reviews and analyzes the development of this topic. The contributions of different countries and different institutions were analyzed. Keyword analysis was used to explain the development of different research directions. The results of the analysis revealed that developments and innovations in materials science can enhance the performance of electrochemical detection of tetracycline antibiotics. Among them, gold nanoparticles and carbon nanotubes are the most used nanomaterials. Aptamer sensing strategies are the most favored methodologies in electrochemical detection of tetracycline antibiotics.

Label free flexible electrochemical DNA biosensor for selective detection of Shigella flexneri in real food samples

An effective tool for early-stage selective detection of the foodborne bacterial pathogen Shigella flexneri (S. flexneri) is essential for diagnosing infectious diseases and controlling outbreaks. Here, a label-free electrochemical DNA biosensor for monitoring S. flexneri is developed. To fabricate the biosensor, detection probe (capture probe) is immobilized on the surface of poly melamine (P-Mel) and poly glutamic acid (PGA), and disuccinimidyl suberate (DSS) functionalized flexible indium tin oxide (ITO) electrode. Anthraquinone-2-sulfonic acid monohydrate sodium salt (AQMS) is used as a signal indicator for the detection of S. flexneri. The proposed DNA biosensor exhibits a wide dynamic range with concentration of the targets ranging from 1 × 10^-6 to 1 × 10^-21 molL^-1 with a limit of detection (LOD) of 7.4 × 10^-22 molL^-1 in the complementary linear target of S. flexneri, and a detection range of 8 × 10¹⁰-80 cells/ml with a LOD of 10 cells/ml in real S. flexneri sample. The proposed flexible biosensor provides high specificity for the detection of S. flexneri compared to other target signals such as discrete base mismatches and different bacterial species. The developed biosensor displayed excellent recoveries in detecting S. flexneri in spiked food samples. Therefore, the proposed biosensor can serve as a model methodology for the detection of other pathogens in a broad span of industries.

Selective Antibody-Free Sensing Membranes for Picogram Tetracycline Detection

As an antibody-free sensing membrane for the detection of the antibiotic tetracycline (TC), a liquid PVC membrane doped with the ion-pair tetracycline/θ-shaped anion [3,3'-Co(1,2-C₂B₉H₁₁)₂]^- ([o-COSAN]^-) was formulated and deposited on a SWCNT modified gold microelectrode. The chosen transduction technique was electrochemical impedance spectroscopy (EIS). The PVC membrane was composed of: the tetracycline/[o-COSAN]^- ion-pair, a plasticizer. A detection limit of 0.3 pg/L was obtained with this membrane, using bis(2-ethylhexyl) sebacate as a plasticizer. The sensitivity of detection of tetracycline was five times higher than that of oxytetracycline and of terramycin, and 22 times higher than that of demeclocycline. A shelf-life of the prepared sensor was more than six months and was used for detection in spiked honey samples. These results open the way to having continuous monitoring sensors with a high detection capacity, are easy to clean, avoid the use of antibodies, and produce a direct measurement.

Fabrication of a label-free electrochemical aptasensor to detect cytochrome c in the early stage of cell apoptosis

A label-free direct electrochemical aptasensor is presented for the identification of cytochrome c (Cyt c) at the nM concentration level. Carbon nanofibers (CNF), as a highly conductive material, were used to modify a glassy carbon electrode (GCE) and thus increase its conductivity. Moreover, to enhance the immobilization of aptamers (Apt) on the electrode surface, graphene oxide functionalized with aspartic acid (GOAsp) was added to the surface. Aspartic acid with countless carboxyl groups (-COOH) on its surface caused more aptamers to be immobilized on the electrode surface. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) were used to monitor the step-by-step fabrication of the label-free direct electrochemical aptasensor. The label-free quantification of Cyt c was also done by the direct electron transfer between the Fe(III)/Fe(II)-heme redox-active sites which were selectively bound to the aptamers on the GCE and the surface of the electrode. Under optimum conditions, the peak currents of differential pulse voltammograms at 0.26 V (vs. Ag/AgCl) were used for calibration. The proposed aptasensor performs in a wide dynamic range from 10 nM to 100 µM with a low detection limit of 0.74 nM for cytochrome c. It also has high selectivity as well as acceptable stability. These advantages make the biosensor capable of detecting early-stage apoptotic cells that contribute to early cancer diagnosis.

Detection of Oxytetracycline Using an Electrochemical Label-Free Aptamer-Based Biosensor

One of the most effective ways to detect and measure antibiotics is to detect their biomarkers. The best biomarker for the control and detection of oxytetracycline (OTC) is the OTC-specific aptamer. In this study, a novel, rapid, and label-free aptamer-based electrochemical biosensor (electrochemical aptasensor) was designed for OTC determination based on a newly synthesized nanocomposite including multi-walled carbon nanotubes (MWCNTs), gold nanoparticles (AuNPs), reduced graphene oxide (rGO), and chitosan (CS), as well as nanosheets to modify a glassy carbon electrode, which extremely enhanced electrical conductivity and increased the electrode surface to bind well with the amine-terminated OTC-specific aptamer through self-assembly. The (MWCNTs-AuNPs/CS-AuNPs/rGO-AuNPs) nanocomposite modified electrode was synthesized using a layer- by-layer modification method which had the highest efficiency for better aptamer stabilization. Differential pulse voltammetry (DPV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) techniques were used to investigate and evaluate the electrochemical properties and importance of the synthesized nanocomposite in different steps. The designed aptasensor was very sensitive for measuring the OTC content of milk samples, and the results were compared with those of our previously published paper. Based on the calibration curve, the detection limit was 30.0 pM, and the linear range was 1.00-540 nM for OTC. The repeatability and reproducibility of the aptasensor were obtained for 10.0 nM of OTC with a relative standard deviation (RSD%) of 2.39% and 4.01%, respectively, which were not affected by the coexistence of similar derivatives. The measurement in real samples with the recovery range of 93.5% to 98.76% shows that this aptasensor with a low detection limit and wide linear range can be a good tool for detecting OTC.

Development of electrochemical aptasensors detecting phosphate ions on TMB substrate with epoxy-based mesoporous silica nanoparticles

This study, it is aimed to develop an electrochemical aptasensor that can detect phosphate ions using 3.3'5.5' tetramethylbenzidine (TMB). It is based on the principle of converting the binding affinity of the target molecule phosphate ion (PO₄^3-) into an electrochemical signal with specific aptamer sequences for the aptasensor to be developed. The aptamer structure served as a gate for the TMB to be released and was used to trap the TMB molecule in mesoporous silica nanoparticles (MSNPs). The samples for this study were characterized by transmission electron spectroscopy (TEM), Brunner-Emmet-Teller, dynamic light scattering&electrophoretic light scattering, and induction coupled plasma atomic emission spectroscopy. According to TEM analysis, MSNPs have a morphologically hexagonal structure and an average size of 208 nm. In this study, palladium-carbon nanoparticles (Pd/C NPs) with catalytic reaction were used as an alternative to the biologically used horseradish peroxidase (HRP) enzyme for the release of TMB in the presence of phosphate ions. The limit of detection (LOD) was calculated as 0.983 μM, the limit of determination (LOQ) was calculated as 3.276 μM, and the dynamic linear phosphate range was found to be 50-1000 μM. The most important advantage of this bio-based aptasensor assembly is that it does not contain molecules such as a protein that cannot be stored for a long time at room temperature, so its shelf life is very long compared to similar systems developed with antibodies. The proposed sensor shows good recovery in phosphate ion detection and is considered to have great potential among electrochemical sensors.

A REVIEW ON DETERMINATION OF THE VETERINARY DRUG RESIDUES IN FOOD PRODUCTS

In this paper, we discuss veterinary medicine and its applications in the food field as well as its risk to the health of humans and animals by the residues. We review how the veterinary residues enter and cause some detrimental effects. We also mention two techniques to determine the residue of veterinary medication that existed in food originating from animals, including classic and advanced techniques. Finally, we discuss the potential of various developed methods compared to some traditional techniques.

Highly Sensitive Detection of Trace Tetracycline in Water Using a Metal-Organic Framework-Enabled Sensor

Due to the abuse application of antibiotics in the recent decades, a high level of antibiotics has been let out and remains in our environment. Electrochemical sensing is a useful method to sensitively detect antibiotics, and the key factor for a successful electrochemical sensor is the active electrode materials. In this study, a sensitive electrochemical sensing platform based on a metal-organic framework (MOF) of MIL-53 (Fe) was facilely fabricated. It shows highly selective and sensitive detection performance for trace tetracycline. Differential pulse voltammetry (DPV) was applied to analyze the detection of tetracycline. The linear range of tetracycline detection was 0.0643 μmol/L-1.53 μmol/L, and the limit of detection (LOD) is 0.0260 μmol/L. Furthermore, the MOF-enabled sensor can be effectively used in actual water bodies. The results indicate that the electrochemical sensor is a high potential sensing platform for tetracycline.

Signal amplification of novel sandwich-type genosensor via catalytic redox-recycling on platform MWCNTs/Fe3O4@TMU-21 for BRCA1 gene detection

The MWCNTs/Fe₃O₄@TMU-21 as a novel electrochemical sandwich-type genosensor was fabricated to detect the BRCA1 gene using the redox-cycling ferrocene functionalized reporter label probe (r-Fc-DNA). In the designed genosensor, the capture probe (cDNA) and r-Fc-DNA were used to detect the BRCA1 gene in sandwich-type genosensor, in which DNA sequences are well -hybridized with the BRCA1 gene (t-DNA). The cDNA was immobilized on the multiwall carbon nanotube and metal-organic framework with Fe₃O₄ nanoparticle core, which is the sensor platform. Target DNA was assayed by redox-recycling reporter probe (r-Fc-DNA) using the electro-catalytic activity of ferri/ferrocyanide, which results in significantly enhanced the oxidation peak current of r-Fc-DNA. The electrochemical redox cycling led to a high signal-to-noise ratio for gene assay. MWCNTs and Fe₃O₄@TMU-21 were applied to increase the platform conductivity and suitable binding of the recognition elements. This constructed genosensor plays an influential role in increasing the sensitivity of BRCA1 gene sequence recognition. So that under optimal conditions, this genosensor illustrated a wide linear range from 1.0×10^-15 to 1.0×10^-10 M with a detection limit of 0.57 × 10^-15 M. Moreover, the genosensor exhibited high selectivity, stability, and reproducibility. The obtained recoveries (between 91 and 105%) of the BRCA1 gene assay in human blood samples satisfactory, which can be used for BRCA1 gene measurement in the laboratory.

Fabrication of an ultrasensitive aptasensor for precise electrochemical detection of the trace amounts of streptomycin in milk

Designing a sensitive method for the detection of streptomycin residues in animal products is essential for controlling consumer health risk. In this study, a high-purity pencil lead graphite electrode coated with inner graphene layers and outer surface-adsorbed gold nanoparticles attached to streptomycin-specific thiolated aptamer was used as an electrochemical aptasensor. The aptasensor electrode fabrication steps were investigated by scanning electron microscope (SEM) and Fourier-transform infrared spectrophotometer (FTIR). Moreover, aptasensor performance during fabrication and binding of aptamer to streptomycin were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. After the binding of sreptomycin to it's specific aptamer as a component of the aptasensor a decrease in the current and an increase in the charge transfer resistance (R_ct) were recorded using the above-mentioned techniques. Under optimal conditions, the novel ultra-sensetive designed aptansensor detects streptomycin in the range of  10^-8 to  10^-16 M with a LOD of 0.8×10^-18 M. The aptansensor demonstrates a high selectivity, good reproducibility and acceptable stability for the specific detection of streptomycin. According to the results, the manufactured aptansensor is a fast, low-cost, highly sensitive and selective device and thus the aptasensor can detect the trace amounts of streptomycin in milk in dairy industries.

Advances and perspectives of aptasensors for the detection of tetracyclines: A class of model compounds of food analysis

The residual tetracyclines in food are frequently applied as the model compounds to develop aptasensors. Until now, more than 100 advanced aptasensors towards tetracyclines have been developed and published in English. This review summarizes and discusses comprehensively these advanced aptasensors, in terms of the principle designs, applied frontier transducers/materials, working performance, and advantages/disadvantages. The aptasensors are classified according to the inherent transduction techniques, i.e., optics, optics-electricity, optics-mass, and electricity-mass. Moreover, the present challenges such as the limited specificity and limited affinity of the aptamers, the future prospects and trends such as further combination with other advanced materials and technologies, and the urgent need of expanding the practical application were discussed and prospected. We hope this review can serve as a powerful tool for both tracing the development progresses of aptasensors and providing adequate references for further development of aptasensing methods for food-related analytes.

Fabrication and application of a novel electrochemical biosensor based on a mesoporous carbon sphere@UiO-66-NH2/Lac complex enzyme for tetracycline detection

The overuse of tetracycline results in a threat to human, poultry and livestock health. An enzymatic electrochemical biosensor is an ideal alternative method for accurate and rapid tetracycline detection, while the unstable and easily deactivated nature of the enzyme limits its development. To overcome these limitations, a highly sensitive enzymatic electrochemical biosensor for the determination of tetracycline is developed in this work based on a complex enzyme which was constructed using a mesoporous carbon sphere@UiO-66-NH2 (MCS@UiO-66-NH2) core-shell composite with embedded laccase (Lac). Compared to pure MCS and UiO-66-NH2, the MCS@UiO-66-NH2 core-shell composite has an advantageous mesoporous structure (pore diameter >8 nm), which is suitable for the immobilization of small laccase. The biosensor based on the complex enzyme exhibits a superior activity and enhanced stability as compared with that made using a pure enzyme because the mesoporous structure of the MCS@UiO-66-NH2 composite can effectively protect the laccase against inactivation and denaturation. Besides, its high specific surface area and good conductivity are beneficial to enzyme immobilization and electron transfer in the modified electrode. The biosensor based on this complex enzyme exhibits a relatively low detection limit of 8.94 × 10-7 mol L-1 and a detection range of 1.0 × 10-6-6.0 × 10-5 mol L-1 for tetracycline detection. Furthermore, the developed biosensor possesses good long-term stability, selectivity and reproducibility, indicating its potential application for tetracycline determination in actual food. This research work provides a prospective solution to resolve the stability and inactivation problems of enzymatic electrochemical biosensors in different application scenarios.

A novel and disposable GP- based impedimetric biosensor using electropolymerization process with PGA for highly sensitive determination of leptin: Early diagnosis of childhood obesity

This study presents a novel, single-use electrochemical biosensor for the leptin biomarker, which may have potential use for early diagnosis of childhood obesity. The graphite paper working electrode was used for the first time in impedimetric biosensors. All immobilization procedure, investigation of the optimal parameters and characterization of biosensors were followed and evaluated using Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV). The Scanning Electron Microscope (SEM) was utilized to visualize the morphology of the electrode surface during the immobilization steps of the immunosensor. Moreover, the characterization of the interactions between anti-leptin and leptin was investigated by using Single Frequency Technique (SFI). The applicability of the designed biosensor for real serum samples was tested for clinical use. It was observed that the biosensor allows high sensitivity in the analyte detection (leptin) in real serum samples. Moreover, it was suggested that the developed biosensor presents advantages such as long shelf life (5% loss of activity after 8 weeks and 60% loss after 10 weeks), ability to determine analyte concentrations at picogram level (0.2 pg mL^-1 -20 pg mL^-1), low limit of detection (0.00813 pg mL^{- 1}), reproducibility, reusability (12 times) and high sensitivity.

Fabrication of low-cost sustainable electrocatalyst: a diagnostic tool for multifunctional disorders in human fluids

In purine metabolism, the xanthine oxidoreductase enzyme converts hypoxanthine (HXN) to xanthine (XN) and XN to uric acid (UA). This leads to the deposition of UA crystals in several parts of the body and the serum UA level might be associated with various multifunctional disorders. The dietary intake of caffeine (CF) and ascorbic acid (AA) decreases the UA level in the serum, which leads to cellular damage. Hence, it is highly needed to monitor the UA level in the presence of AA, XN, HXN, and CF and vice versa. Considering this sequence of complications, the present paper reports the fabrication of an electrochemical sensor using low-cost N-doped carbon dots (CDs) for the selective and simultaneous determination of UA in the presence of AA, XN, HXN, and CF at the physiological pH. The colloidal solution of CDs was prepared by the pyrolysis of asparagine and fabricated on a GC electrode by cycling the potential from -0.20 to +1.2 V in a solution containing CDs and 0.01 M H2SO4. Here, the surface -NH2 functionalities of CDs were used to make a thin film of CDs on the GC electrode. FT-IR spectroscopy confirmed the involvement of the -NH2 group in the formation of the CD film. HR-TEM analysis depicts that the formed CDs showed spherical particles with a size of 1.67 nm and SEM analysis exhibits the 89 nm CD film on the GC electrode surface. The fabricated CD film was successfully used for the sensitive and selective determination of UA. The determination of UA was achieved selectively in a mixture consisting of AA, XN, HXN, and CF with 50-fold high concentration. The CDs-film fabricated electrode has several benefits over the bare electrode: (i) well-resolved oxidation peaks for five analytes, (ii) boosted sensitivity, (iii) shifted oxidation as well as on-set potentials toward less positive potentials, and (iv) high stability. The practical utility of the present sensor was tested by simultaneously determining the multifactorial disorders-causing agents in human fluids. The electrocatalyst developed in the present study is sustainable and can be used for multiple analyses; besides, the electrochemical method used for the fabrication of the CD film is environmentally benign.

Advances in Electrochemical Aptasensors Based on Carbon Nanomaterials

Carbon nanomaterials offer unique opportunities for the assembling of electrochemical aptasensors due to their high electroconductivity, redox activity, compatibility with biochemical receptors and broad possibilities of functionalization and combination with other auxiliary reagents. In this review, the progress in the development of electrochemical aptasensors based on carbon nanomaterials in 2016–2020 is considered with particular emphasis on the role of carbon materials in aptamer immobilization and signal generation. The synthesis and properties of carbon nanotubes, graphene materials, carbon nitride, carbon black particles and fullerene are described and their implementation in the electrochemical biosensors are summarized. Examples of electrochemical aptasensors are classified in accordance with the content of the surface layer and signal measurement mode. In conclusion, the drawbacks and future prospects of carbon nanomaterials’ application in electrochemical aptasensors are briefly discussed.

High-Performance Voltammetric Aptasensing Platform for Ultrasensitive Detection of Bisphenol A as an Environmental Pollutant

Bisphenol A (BPA) as a pervasive endocrine-disrupting compound (EDC) has been shown to cause multiple detrimental effects including cardiovascular disorders, pregnancy complications, obesity, glucose metabolism disorders, and reproductive toxicity even at a concentration as low as tolerable daily intake (TDI) (4 μg/kg/day). In the present study, a novel ultra-sensitive, electrochemical aptasensor was designed using a screen-printed carbon electrode (SPCE) modified by gold nanoparticles (Au NPs) conjugated to thiolated aptamers for accurate determination of BPA in biological, industrial and environmental samples. To characterize the electrochemical properties of the aptasensor, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were implemented. Detection of BPA was also performed through differential pulse voltammetry (DPV) in [Fe(CN)₆]^3–/4– electrolyte solution. Under optimum condition, the present electrochemical aptasensor demonstrated an outstanding linear response in the concentration range of 1 pM to 10 nM with a remarkably low limit of detection of 0.113 pM. Due to the superb affinity between anti-BPA aptamers and BPA molecules, the designed aptasensor did not show any significant interaction with other analytes in real samples. Also, fabricated biosensor remained perfectly stable in long-term storage. The analytical results of the fabricated aptasensor are well compatible with those obtained by the ELISA method, indicating the trustworthiness and reasonable accuracy of the application of aptasensor in real samples. Overall, the proposed aptasensor would be a credible and economical method of precise, reproducible, and highly selective detection of minimum levels of BPA in food containers and clinical samples. This would be a promising strategy to enhance the safety of food products and reduce the risk of BPA daily exposure.

Recent advances and challenges in electrochemical biosensors for emerging and re-emerging infectious diseases

The rise of emerging infectious diseases (EIDs) as well as the increase in spread of existing infections is threatening global economies and human lives, with several countries still fighting repeated onslaught of a few of these epidemics. The catastrophic impact a pandemic has on humans and economy should serve as a reminder to be better prepared to the advent of known and unknown pathogens in the future. The goal of having a set of initiatives and procedures to tackle them is the need of the hour.

Rapid detection and point-of-care (POC) analysis of pathogens causing these diseases is not only a problem entailing the scientific community but also raises challenges in tailoring appropriate treatment strategies to the healthcare sector. Among the various methods used to detect pathogens, Electrochemical Biosensor Technology is at the forefront in the development of POC devices. Electrochemical Biosensors stand in good stead due to their rapid response, high sensitivity and selectivity and ease of miniaturization to name a few advantages.

This review explores the innovations in electrochemical biosensing based on the various electroanalytical techniques including voltammetry, impedance, amperometry and potentiometry and discusses their potential in diagnosis of emerging and re-emerging infectious diseases (Re-EIDs), which are potential pandemic threats.

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This review offers a detailed description of the latest developments in electrochemical biosensors for emerging and re-emerging infectious diseases.

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Advantages and limitations of various types of electrochemical biosensor techniques are demonstrated.

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Discusses the latest electrochemical biosensors for COVID-19.

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Challenges and future prospects of electrochemical biosensors have been discussed in this review.

Development of an electrochemical biosensor for impedimetric detection of tetracycline in milk

Abstract

This study dealt with the fabrication of an impedimetric biosensor based on nanomaterial modified with pencil graphite electrode for the detection of tetracycline (TET) in milk samples. For response of the impedimetric aptasensor to be improved, the influence of different parameters (immobilization time of reduced grapheme oxide, time of aptamer, and TET binding, and concentration of aptamer) was optimized. In optimum conditions, the aptasensor provided a concentration range within 1 × 10^-16 - 1 × 10^-6 M and with a limit of detection of 3 × 10^-17 M TET. The proposed impedimetric aptasensor was then used in milk samples analysis, and the acceptable recovery was achieved ranging from 92.8 to 102.1%. According to this study, the combination of an aptamer and electrochemical impedance spectroscopy is a promising method for detection of TET in milk samples with high reproducibility and stability.

Graphic abstract

Indirect Competitive Determination of Tetracycline Residue in Honey Using an Ultrasensitive Gold-Nanoparticle-Linked Aptamer Assay

Tetracycline residue in honey has become an increasingly important food safety problem. In this work, an ultrasensitive gold nanoparticles (AuNPs)-linked aptamer assay was developed to determine the tetracycline residue in honey. First, a tetracycline–bovine serum albumin conjugate coating was applied to a microplate. Then, with the incubation of AuNPs-linked aptamer, the fixed tetracycline in the microplate competed for the limited aptamer with the free tetracycline in the sample. Higher amounts of free tetracycline in the sample were associated with more competitive binding of aptamer-AuNPs, and the aptamer-AuNPs binding with tetracycline-BSA was lower. Finally, as a kind of nanozyme, AuNPs exhibited peroxidase activity and oxidized 3,3′,5,5′-tetramethylbenzidine, transforming it from colorless to blue, and achieving the measurement at 652 nm. The analytical performance—including linearity, limit of detection, selectivity, precision, repeatability, and accuracy—has been investigated. It was successfully applied to the determination of tetracycline in honey samples with high accuracy and sensitivity.

An interdigitated microelectrode based aptasensor for real-time and ultratrace detection of four organophosphorus pesticides

With increasing industrialization of food production, residues of organophosphorus pesticides (OPs) are more frequently found in the environment including rivers, lakes and soils. Extended exposure to OPs, even at a level below 1 nM, may lead to liver and central nervous system damages in humans and animals, while existing detection methods are not sensitive enough to detect OPs at trace levels. We presented a simple-to-use aptasensor to rapidly detect broad-spectrum OPs with high sensitivity. DNA aptamer was modified on the surface of a micro interdigitated electrode chip, and AC electrokinetics was employed to accelerate the binding of OP molecules to the aptamer probe. The sensing strategy directly measured the interfacial capacitance whose change rate was adopted as a quantitative indicator of recognition events, with a sample to result detection time of 30 s. This aptasensor had a wide linear range of (fM ~ nM), and the detection limit reached (0.24-1.67) fM for four highly-toxic OPs, with good specificity. It still showed good activity after being stored in non-refrigerated environment for at least 14 days. This aptasensor as well as the detection method offer a promising solution for on-site and real-time sensitive OP detection.

Highly sensitive determination of tetracycline in chicken meat and eggs using AuNP/ MWCNT-modified glassy carbon electrodes

Glassy carbon electrodes (GCE) were modified with gold nanoparticles (AuNPs) and multi-walled carbon nanotubes (MWCNTs) by means of sputtering and electrodeposition. The electrodeposited MWCNT on gold coated GCE exhibited the optimum performance as characterized using cyclic voltammetry. The limit of detection and limit of quantitation were found to be 42 ppb and 139 ppb, respectively. The modified electrode was used as working electrode in differential pulse voltammetry to detect tetracycline (TET) residues in the eggs, wings, liver, breast, and thigh, of organic as well as non-organic chicken bought from a local supermarket. The highest concentration in the eggs, wings, liver, breast, and thigh were found to be 5.9 ppm, 2.0 ppm, 1.4 ppm, 1.3 ppm, and 1.2 ppm for organic chicken and 8.70 ppm, 4.8 ppm, 4.3 ppm, 3.3 ppm, and 2.7 ppm for the corresponding parts in non-organic chicken, respectively. The obtained concentrations were remarkably greater compared to the maximum residual limit released by the Codex Alimentarius Commission.

Sensitive electrochemical sensor based on poly(l-glutamic acid)/graphene oxide composite material for simultaneous detection of heavy metal ions

Heavy metal pollution can be toxic to humans and wildlife, thus it is of great significance to develop rapid and sensitive methods to detect heavy metal ions. Here, a novel type of electrochemical sensor for the simultaneous detection of heavy metal ions has been prepared by using poly(l-glutamic acid) (PGA) and graphene oxide (GO) composite materials to modify the glassy carbon electrode (GCE). Due to the good binding properties of poly(l-glutamic acid) (PGA) for the heavy metal ions (such as Cu²⁺, Cd²⁺, and Hg²⁺) as well as good electron conductivity of graphene oxide (GO), the heavy metal ions, Cu²⁺, Cd²⁺, and Hg²⁺ in aqueous solution can be accurately detected by using differential pulse anodic stripping voltammetry method (DPASV). Under the optimized experiment conditions, the modified GCE shows excellent electrochemical performance toward Cu²⁺, Cd²⁺, and Hg²⁺, and the linear range of PG/GCE for Cu²⁺, Cd²⁺, and Hg²⁺ is 0.25–5.5 μM, and the limits of detection (LODs, S/N ≥ 3) Cu²⁺, Cd²⁺, and Hg²⁺ are estimated to be 0.024 μM, 0.015 μM and 0.032 μM, respectively. Moreover, the modified GCE is successfully applied to the determination of Cu²⁺, Cd²⁺, and Hg²⁺ in real samples. All obtained results show that the modified electrode not only has the advantages of simple preparation, high sensitivity, and good stability, but also can be applied in the field of heavy metal ion detection.

A novel electrochemical sensor with high stability and good reproducibility for the simultaneous detection of heavy metal ions was prepared by using PGA/GO to modify the GCE, showing high sensitivity of superior to most of the reported values.

Dual-aptamer based electrochemical sandwich biosensor for MCF-7 human breast cancer cells using silver nanoparticle labels and a poly(glutamic acid)/MWNT nanocomposite

This paper reports on a sensitive and selective method for the detection of Michigan Cancer Foundation-7 (MCF-7) human breast cancer cells and MUC1 biomarker by using an aptamer-based sandwich assay. A biocompatible nanocomposite consisting of multiwall carbon nanotubes (MWCNT) and poly(glutamic acid) is placed on a glassy carbon electrode (GCE). The sandwich assay relies on the use of a mucin 1 (MUC1)-binding aptamer that is first immobilized on the surface of modified GCE. Another aptamer (labeled with silver nanoparticles) is applied for secondary recognition of MCF-7 cells in order to increase selectivity and produce an amplified signal. Differential pulse anodic stripping voltammetry was used to follow the electrochemical signal of the AgNPs. Under the optimal condition, the sensor responds to MCF-7 cells in the concentration range from 1.0 × 10² to 1.0 × 10⁷ cells·mL^-1 with a detection limit of 25 cells. We also demonstrate that the MUC1 tumor marker can be detected by the present biosensor. The assay is highly selective and sensitive, acceptably stable and reproducible. This warrants the applicability of the method to early diagnosis of breast cancer. Graphical abstract Schematic of the fabrication of an aptamer-based sandwich biosensor for Michigan Cancer Foundation-7 cells (MCF-7). A MWCNT-poly(glutamic acid) nanocomposite was used as a biocompatible matrix for MUC1-aptamer immobilization. Stripping voltammetry analysis of AgNPs was performed using aptamer conjugated AgNPs as signalling probe.