Comparison of two fabricated aptasensors based on modified carbon paste/oleic acid and magnetic bar carbon paste/Fe3O4@oleic acid nanoparticle electrodes for tetracycline detection

Fluorescent Sensors for Tetracycline Detection in Aqueous Medium: A Mini-Review

Tetracycline (TC) is a commonly used antibiotic in human therapy and animal husbandry. Public concerns about TC residues inflated due to their negative impact on the environment, food, and human health concerns. To ensure human health and safety, there is a need for fluorogenic chemosensors that can easily detect TC antibiotics with high selectivity and sensitivity in the aqueous medium. This mini-review discusses the progress and achievements in several fluorometric antibiotic tetracycline detection methods. Fluorogenic chemosensors for tetracycline antibiotics with easy-to-use, high selectivity, and sensitivity have been essentially required to regulate food safety and secure human health and safety. Moreover, we gave more attention to the practical applicability of chemosensors for tetracycline antibiotics in food and water quality assessment. This article starts with a section that constitutes an overview of the problems of antibiotics and the typical features of traditional techniques of antibiotic detection. It then goes on to describe up-to-date optical methods for the selective detection and efficient removal of TC. These methods involve a variety of platforms, like tetraphenylethylene polymers, metal complexes, self-assembled CuNCs, and hydrogel. The article also discusses the practical applicability of chemosensors for tetracycline antibiotics in food and water quality.

Novel electrochemical biosensor for breast cancer detection, based on a nanocomposite of carbon nanofiber, metal-organic framework, and magnetic graphene oxide

In this study, we present the newly developed a novel microRNA biosensor based on magnetic rod carbon paste electrodes for breast cancer detection by using a relatively new MOF structure as a substrate. The major goal of manufacturing biosensors, suitable for clinical diagnostics, is to measure very low amount of microRNA 155 in complex environments. Therefore, we used a combination of different materials, including carbon nanofibers, CuBTC-AIA (CuMOF), and Fe@rGO, to improve the electrode surface-to-volume ratio and facilitate the electron transfer process. In this method, 1-pyrenebutyric acid N-hydroxysuccinimide ester was used to bind the microRNAs to the electrode surface. The hybridization process on the modified electrode surface was investigated using cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry across the potential range, in which the accumulated hematoxylin was electroactive. Under optimal conditions, a very low detection limit of 0.08 fM and an adequate dynamic range of 0.2 fM-500 pM were achieved. The fabricated sensor was reported to be reproducible and selective when tested using different types of mismatched target sequences. And finally, the real human serum samples were used to confirm the capability of the nanobiosensor to detect microRNA 155 without any significant interference from other molecules and components.

Functionalities of electrochemical fluoroquinolone sensors and biosensors

Fluoroquinolones (FQs) are a class of broad-spectrum antimicrobial agents that are used to treat variety of infectious diseases. This class of antibiotics was being used for patients exhibiting early symptoms of a human respiratory disease known as the COVID-19 virus. As a result, this outbreak causes an increase in drug-resistant strains and environmental pollution, both of which pose serious threats to biota and human health. Thus, to ensure public health and prevent antimicrobial resistance, it is crucial to develop effective detection methods for FQs determination in water bodies even at trace levels. Due to their characteristics like specificity, selectivity, sensitivity, and low detection limits, electrochemical biosensors are promising future platforms for quick and on-site monitoring of FQs residues in a variety of samples when compared to conventional detection techniques. Despite their excellent properties, biosensor stability continues to be a problem even today. However, the integration of nanomaterials (NMs) could improve biocompatibility, stability, sensitivity, and speed of response in biosensors. This review concentrated on recent developments and contemporary methods in FQs biosensors. Furthermore, a variety of modification materials on the electrode surface are discussed. We also pay more attention to the practical applications of electrochemical biosensors for FQs detection. In addition, the existing challenges, outlook, and promising future perspectives in this field have been proposed. We hope that this review can serve as a bedrock for future researchers and provide new ideas for the development of electrochemical biosensors for antibiotics detection in the future.

A novel magneto-mediated electrochemical biosensor integrated DNAzyme motor and hollow nanobox-like Pt@Ni-Co electrocatalyst as dual signal amplifiers for vanilla detection

Herein, a novel magneto-mediated electrochemical aptasensor using the signal amplification technologies of DNAzyme motor and electrocatalyst for vanilla (VAN) detection was fabricated. The D/B duplex, formed by the DNAzyme motor that was each silenced by a blocker, and hairpin DNA1 (H1) containing adenosine ribonucleotide (rA) site were tethered on the sites of the gold nanoparticles@hollow porphyrinic-Metal-organic framework/polyethyleneimine-reduced graphene oxide (AuHPCN-222/PEI-rGO)-modified gold electrode (AuE). Then, after homogeneous and specific recognition in the presence of the VAN, trigger DNA was released and enriched by magnetic separation technique and introduced to the sensing platform to activate the DNAzyme motor, which efficiently improved target recognition capability and avoided the obstacle of multiple DNA strands tangling. More interestingly, the activated DNAzyme motor could repeatedly bind to and cleave H1 in the presence of Mg2+, leading to the exposure of a plethora of capture probes. The thionine (Thi) functionalized hairpin DNA2 (H2)-Pt@Ni-Co as signal probes could hybridize with capture probes. Additionally, the Pt@Ni-Co electrocatalysts presented catalytic activity towards Thi to obtain stronger electrochemical signals. VAN with concentrations ranging from 1 × 10-6 to 10 μM was determined and a detection limit was down to 0.15 pM. The designed electrochemical sensor was highly selective with specificity, stability, reproducibility, and reliable capability for monitoring the VAN in real samples.

Preparation of an electrochemical sensor utilizing graphene-like biochar for the detection of tetracycline

Tetracycline (TC), which is ubiquitous in the aquatic environment, can cause ecological imbalance and adversely affect human health. Therefore, a quick, inexpensive, and easy method for the detection of TC in water systems is highly desirable. This study reports the development of a novel electrochemical sensor from waste peanut shell for the quick detection of TC in water. Raman and TEM lattice mapping analyses confirmed the successful preparation of graphene -like biochar from waste peanut shells (PSs) via hydrothermal and pyrolysis processes. An electrochemical sensor, PS@glassy carbon electrode (PS@GCE), was then developed by coating the prepared graphene-like biochar on the surface of a glass electrode to enhance its conductivity. The feasibility of using this sensor for the detection of TC in the aqueous system was investigated. The PS@GCE sensor exhibited excellent sensitivity with a low detection limit of 3.6 × 10--9 nM and a linear range of 10-10-102 μM. These results were attributed to the large specific surface area and high conductivity, of the PS biochar. The stability of the PS@GCE sensor was also investigated in the presence of TC (10-4 M) and interfering species (10-2 M) and recovery rates in the range of 86.4%-116.0% were achieved, thus indicating the absence of an interference range of range of 84.3%-98.2% with relative standard deviation lower than 6% were achieved upon the detection of TC in natural water samples using the designed sensor, thus confirming the superior repeatability of the PS@GCE sensor. Consequently, the designed electrode has a high potential for application in the detection of TC in natural aqueous systems.

3D rhombohedral microcrystals metal-organic frameworks for electrochemical and fluorescence sensing of tetracycline

Zirconium-based metal-organic frameworks (MOF) exhibiting 3D rhombohedral microcrystals were synthesized by the solvothermal method. The structure, morphology, composition, and optical properties of the synthesized MOF were carried out using different spectroscopic, microscopic, and diffraction techniques. Synthesized MOF was rhombohedral in shape and the cage structure of these crystalline molecules was the active binding site of the analyte, tetracycline (TET). The electronic property and size of the cages are chosen such that a specific interaction with TET was observed. Sensing of the analyte was demonstrated by both the electrochemical and fluorescent techniques. The MOF had significant luminescent properties and exhibited excellent electro-catalytic activity due to embedded zirconium metal ions. An electrochemical and fluorescence sensor was fabricated towards TET where TET binds via hydrogen bond to MOF, and causes fluorescence quenching due to the transfer of electrons. Both approaches exhibited high selectivity and good stability in the presence of interfering molecules such as antibiotics, biomolecules, and ions; and showed excellent reliability in tap water and wastewater sample analysis.

Iron/iron oxide-based magneto-electrochemical sensors/biosensors for ensuring food safety: recent progress and challenges in environmental protection

Foodborne diseases have arisen due to the globalization of industry and the increase in urban population, which has led to increased demand for food and has ultimately endangered the quality of food. Foodborne diseases have caused some of the most common public health problems and led to significant social and economic issues worldwide. Food quality and safety are affected by microbial contaminants, growth-promoting feed additives (β-agonists and antibiotics), food allergens, and toxins in different stages from harvesting to storage and marketing of products. Electrochemical biosensors, due to their reduced size and portability, low cost, and low consumption of reagents and samples, can quickly provide valuable quantitative and qualitative information about food contamination. In this regard, using nanomaterials can increase the sensitivity of the assessment. Magnetic nanoparticle (MNP)-based biosensors, especially, are receiving significant attention due to their low-cost production, physicochemical stability, biocompatibility, and eco-friendly catalytic characteristics, along with magnetic, biological, chemical and electronic sensing features. Here, we provide a review on the application of iron-based magnetic nanoparticles in the electrochemical sensing of food contamination. The types of nanomaterials used in order to improve the methods and increase the sensitivity of the methods have been discussed. Then, we stated the advantages and limitations of each method and tried to state the research gaps for each platform/method. Finally, the role of microfluidic and smartphone-based methods in the rapid detection of food contamination is stated. Then, various techniques like label-free and labelled regimes for the sensitive monitoring of food contamination were surveyed. Next, the critical role of antibody, aptamer, peptide, enzyme, DNA, cells and so on for the construction of specific bioreceptors for individual and simultaneous recognition by electrochemical methods for food contamination were discussed. Finally, integration of novel technologies such as microfluidic and smartphones for the identification of food contaminations were investigated. It is important to point out that, in the last part of each sub-section, attained results of different reports for each strategy were compared and advantages/limitations were mentioned.

An electrochemical aptasensor for detection of streptomycin based on signal amplification assisted by functionalized gold nanoparticles and hybridization chain reaction

A ratiometric electrochemical aptasensor based on gold nanoparticles (AuNPs) functionalization and hybridization chain reaction (HCR) assisted signal amplification has been for the first time designed for the detection of streptomycin (STR). The double-stranded DNA (dsDNA) formed by the hybridization of ferrocene (Fc)-labeled STR aptamer (Apt) and capture probe (CP) is first immobilized on the gold electrode (GE) surface via Au-S reaction. The specific binding of the target and Apt results in numerous Fc detachment from the sensing interface. Then, the remaining single-stranded CP is combined with AuNPs modified with initiator DNA (iDNA) by auxiliary DNA (aDNA). Among them, the iDNA triggers HCR between two hairpin probes (H1/H2), thus capturing a large number of methylene blue (MB) electrochemical probe, which generates a strong electrochemical signal of MB and a weak electrochemical signal of Fc. Signals are collected by square wave voltammetry (the potential window ranging from -0.5 V to 0.6 V, vs. Ag/AgCl ), and the oxidation peak currents at -0.200 V (MB) and 0.416 V (Fc) are recorded. The use of the ratiometric method has effectively improved the accuracy and reliability of the analysis. The successful application of AuNPs and HCR greatly improves the sensitivity of the sensor, and the detection limit is as low as 0.08 pM. It can sensitively determine STR in the range 0.1 pM to 10 nM. In addition, the designed aptasensor has been successfully applied to the detection of STR in milk and honey 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.

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.

A high-performance electrochemical sensor for sensitive detection of tetracycline based on a Zr-UiO-66/MWCNTs/AuNPs composite electrode

Herein, a high-performance electrochemical sensor was constructed based on a metal-organic framework (Zr-UiO-66)/multi-carbon nanotubes/gold nanoparticles (Zr-UiO-66/MWCNTs/AuNPs) composite modified glassy carbon electrode for sensitive determination of tetracycline. The morphology, structure, and performance of Zr-UiO-66/MWCNTs/AuNPs were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and electrochemical techniques. The Zr-UiO-66/MWCNTs/AuNPs nanohybrids exhibited excellent electrocatalytic activity towards the oxidation of tetracycline, mainly because of the synergistic effect of the MOFs, MWCNTs, and gold nanoparticles. The electrochemical kinetics and catalytical mechanism of tetracycline were demonstrated, proving that tetracycline's electrocatalytic oxidation reaction was an absorption-controlled two-step process involving the transfer of two protons and two electrons, respectively. Furthermore, a simple and facile method was used to achieve the regeneration of the absorbed saturated electrode. A low concentration of tetracycline was detected by amperometry with the linear ranges of 5 × 10^-7 to 2.25 × 10^-4 mol L^-1 (R² = 0.9941), the sensitivity was 45.4 mA L mol^-1, and the limit of detection was as low as 1.67 × 10^-7 mol L^-1 (S/N = 3). In addition, the composite electrode demonstrated high selectivity (interference deviation of ± 5%), satisfactory reproductivity (RSD of 5.31%), and long-term stability (easy regeneration) and was successfully applied in the analysis of tetracycline antibiotics in actual samples. Thus, the proposed electrode provides a promising and prospective MOFs-based sensing platform for the detection of tetracyclines in the environment.

Recent Advances and Perspectives on the Sources and Detection of Antibiotics in Aquatic Environments

Water quality and safety are vital to the ecological environment, social development, and ecological susceptibility. The extensive use and continuous discharge of antibiotics have caused serious water pollution; antibiotics are widely found in freshwater, drinking water, and reservoirs; and this pollution has become a common phenomenon and challenge in global water ecosystems, as water polluted by antibiotics poses serious risks to human health and the ecological environment. Therefore, the antibiotic content in water should be identified, monitored, and eliminated. Nevertheless, there is no single method that can detect all different types of antibiotics, so various techniques are often combined to produce reliable results. This review summarizes the sources of antibiotic pollution in water, covering three main aspects: (1) wastewater discharges from domestic sewage, (2) medical wastewater, and (3) animal physiology and aquaculture. The existing analytical techniques, including extraction techniques, conventional detection methods, and biosensors, are reviewed. The electrochemical biosensors have become a research hotspot in recent years because of their rapid detection, high efficiency, and portability, and the use of nanoparticles contributes to these outstanding qualities. Additionally, the comprehensive quality evaluation of various detection methods, including the linear detection range, detection limit (LOD), and recovery rate, is discussed, and the future of this research field is also prospected.

Electrochemically reduced graphene oxide/Cu-MOF/Pt nanoparticles composites as a high-performance sensing platform for sensitive detection of tetracycline

A promising sensing platform was constructed based on an electrochemically reduced graphene oxide (ErGO)/copper metal-organic framework (Cu-MOF)/platinum nanoparticles (ErGO/Cu-MOF/PtNPs) modified glassy carbon electrode for the detection of tetracycline. The ErGO/Cu-MOF/PtNPs composite electrode possessed an excellent electrochemical performance to tetracycline detection mainly due to the synergistic effect of ErGO, Cu-MOF and PtNPs. The electrochemical kinetics and catalytical mechanism of tetracycline were systematically studied, showing that tetracycline's electrocatalytic oxidation reaction was an absorption-controlled two-step process involving two electrons and one proton transfer, respectively. Low concentration of tetracycline was detected by amperometry with the a linear range of 1 ~ 200 μM (R² = 0.9900) and a detection limit of 0.03 μM (S/R = 3). The proposed sensor was successfully applied to the detection of tetracycline in the real water samples with recoveries of 93.5% ~ 106%, and relative standard deviations (RSD) of 4.65% ~ 5.21% (n = 3). Furthermore, acceptable stability, repeatability and reproducibility were verified for continuous determination of tetracycline under optimized conditions. The ErGO/Cu-MOF/PtNPs composite electrode also demonstrated better anti-interference performance compared to other types of antibiotics than that of similar structural tetracyclines. Therefore, the proposed ErGO/Cu-MOF/PtNPs composites might provide a potential sensing platform for detecting analogous tetracyclines or total tetracyclines in the environment.

Tandem Förster resonance energy transfer induced visual ratiometric fluorescence sensing of tetracyclines based on zeolitic imidazolate framework-8 incorporated with carbon dots and safranine T

With increasing TC concentration, tandem FRET1 from CDs to TC, then FRET2 from TC to safranine T were occurred. TC could be easily recognized by naked eye. Besides, we could perform on-site detection of TC with the help of a mobile phone.

Green synthetic nitrogen-doped graphene quantum dot fluorescent probe for the highly sensitive and selective detection of tetracycline in food samples

Tetracycline (TC) is a broad-spectrum antibiotic. When humans consume too much food containing tetracycline residues, it can be a serious health hazard. Therefore, it is essential to develop a strategy to detect TC. In this study, we prepared light blue-green luminescent nitrogen-doped graphene quantum dots (N-GQDs) by a hydrothermal method using the natural products potato straight-chain starch and urea as precursors; the fluorescence quantum yield of the prepared N-GQDs was 5.2%. We investigated the detection of tetracycline (TC) by this N-GQD fluorescent sensor based on the internal filtration effect (IFE) of TC on N-GQDs. The reaction is green, simple and no other contaminating products are present. A good linear relationship was established between the relative fluorescence intensity ratio of the system and the logarithm of the TC concentration of 2.5 × 10⁻¹⁰ to 5 × 10⁻⁶ M (R² = 0.9930), with a detection limit of 9.735 × 10⁻¹³ M. The method has been used to analyze TC in three real food samples (whole milk, skim milk, honey) with low detection limits (3.750 × 10⁻¹¹ to 2.075 × 10⁻⁹ M), wide linear range, and satisfactory recoveries of 93.80–109.20% were obtained. In conclusion, the proposed method is a green, rapid, highly sensitive and selective method for the detection of tetracycline in real food samples, demonstrating the potential application of N-GQDs in food detection.

Tetracycline (TC) is a broad-spectrum antibiotic.

Recent trends in nanomaterial-based signal amplification in electrochemical aptasensors

Ultrasensitive biosensors have become a necessity in the world of scientific research, and several signal enhancement strategies have been employed to attain exceptionally low detection limits. Nanotechnology turns out to be a strong contender for signal amplification, as they can be employed as platform modifiers, catalysts, carriers or labels. Here, we have described the most recent advancements in the utilization of nanomaterials as signal amplification components in aptamer-based electrochemical biosensors. We have briefly reviewed the methods that utilized nanomaterials, namely gold and carbon, as well as nanocomposites such as: graphene, carbon nanotubes, quantum dots, and metal-organic frameworks.

Magnetic molecularly imprinted polymers for extraction of S-phenylmercapturic acid from urine samples followed by high-performance liquid chromatography

In this study, magnetic molecularly imprinted polymers (MMIPs) were prepared and used as sorbents for extraction of S-phenylmercapturic acid (S-PMA) from urine samples, followed by high-performance liquid chromatography ultraviolet-visible (HPLC-UV/Vis) analysis. The MMIPs were synthesized by the copolymerization reaction of (phenylthio) acetic acid (template molecule), methacrylic acid (functional monomers) and ethylene glycol dimethacrylate (cross-linkers). The morphology, structure property and surface groups of the prepared MMIPs were characterized by scan electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray diffraction pattern, thermogravimetric analyses, Brunauer-Emmett-Teller and vibrating sample magnetometer. The selectivity of the MMIPs was investigated in the presence of interferents. Various parameters affecting the S-PMA extraction efficiency were investigated, including MMIPs amount, pH, sample volume, desorption solvent, as well as extraction and desorption time. The obtained optimal parameters were as follows: MMIPs amount (20 mg), pH (3.0), sample volume (5 mL), desorption solvent (methanol/acetic acid [9/1, v/v]), extraction time (30 minutes) and desorption time (2 minutes). The method was validated according to the Food and Drug Administration Guidance for Industry on Bioanalytical Method Validation. The calibration curve for the analyte was linear in the concentration range of 0.030-1.0 mg/L (r = 0.9995). The LOD and LOQ of the method were 0.0080 and 0.0267 mg/L, respectively. The enrichment factor of the MMIPs was 5. The relative standard deviations of intra- and inter-day tests were in the range of 3.8-5.1% and 3.9-6.3%, respectively. The recoveries at three different concentrations of 0.10, 0.50 and 0.80 mg/L ranged between 95.2% and 98.6%. In addition, the MMIPs could be reused for at least eight times. The proposed method was successfully applied to the determination of S-PMA in urine samples. In addition, this developed method could be used as a tool in the early screening and clinical diagnosis of benzene intoxication.

Tetracycline Antibiotics: Elucidating the Electrochemical Fingerprint and Oxidation Pathway

Herein, a complete study of the electrochemical behavior of the most commonly used tetracycline antibiotics (TCs) on unmodified carbon screen-printed electrodes (SPEs) is presented. In addition, the oxidation pathway of TCs on SPE is elucidated, for the first time, with liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). Square wave voltammetry (SWV) was used to study the electrochemical fingerprint (EF) of the antibiotics shaping the different oxidation processes of the TCs in a pH range from 2 to 12. Their characteristic structure and subsequent EF offer the possibility of distinguishing this class of antibiotics from other types. Under the optimized parameters, calibration curves of tetracycline (TET), doxycycline (DOXY), oxytetracycline (OXY), and chlortetracycline (CHL) in a Britton Robinson buffer solution (pH 9) exhibited a linear range between 5 and 100 µM with excellent reproducibilities (RSDTET = 3.01%, RSDDOXY = 3.29%, RSDOXY = 9.78% and RSDCHL = 6.88% at 10 µM, N = 3) and limits of detection (LOD) of LODTET = 4.15 µM, LODDOXY = 2.14 µM, LODOXY = 3.07 µM and LODCHL = 4.15 µM. Furthermore, binary, tertiary, and complex mixtures of all TCs were analyzed with SWV to investigate the corresponding EF. A dual pH screening (pH 4 and pH 9), together with the use of a custom-made Matlab script for data treatment, allowed for the successful confirmation of a single presence of TCs in the unknown samples. Overall, this work presents a straightforward study of the electrochemical behavior of TCs in SPE, allowing for the future on-site identification of residues of tetracycline antibiotics in real samples.

The Role of Aryldiazonium Chemistry in Designing Electrochemical Aptasensors for the Detection of Food Contaminants

Food safety monitoring assays based on synthetic recognition structures such as aptamers are receiving considerable attention due to their remarkable advantages in terms of their ability to bind to a wide range of target analytes, strong binding affinity, facile manufacturing, and cost-effectiveness. Although aptasensors for food monitoring are still in the development stage, the use of an electrochemical detection route, combined with the wide range of materials available as transducers and the proper immobilization strategy of the aptamer at the transducer surface, can lead to powerful analytical tools. In such a context, employing aryldiazonium salts for the surface derivatization of transducer electrodes serves as a simple, versatile and robust strategy to fine-tune the interface properties and to facilitate the convenient anchoring and stability of the aptamer. By summarizing the most important results disclosed in the last years, this article provides a comprehensive review that emphasizes the contribution of aryldiazonium chemistry in developing electrochemical aptasensors for food safety monitoring.

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.

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.

Electrochemical methods for the determination of antibiotic residues in milk: A critical review

Several antibiotics have been applied to veterinary medicine due to their broad-spectrum of antibacterial activity and prophylactic power. Residues of these antibiotics can be accumulated in dairy cattle, in addition to promoting contamination of the environment and, in more serious cases, in milk, causing a public health problem. Different regulatory agencies establish maximum residue limits for these antibiotics in milk, so it becomes important to develop sensitive analytical methods for monitoring these compounds. Electrochemical techniques are important analytical tools in analytical chemistry because they present low cost, simplicity, high sensitivity, and adequate analytical frequency (sample throughput) for routine analyses. In this sense, this review summarizes the state of the art of the main electrochemical sensors and biosensors, instrumental techniques, and sample preparation used for the development of analytical methods, published in the last five years, for the monitoring of different classes of antibiotics: aminoglycosides, amphenicols, beta-lactams, fluoroquinolones, sulfonamides, and tetracyclines, in milk samples. The different strategies to develop electrochemical sensors and biosensors are critically compared considering their analytical features. The mechanisms of electrochemical oxidation/reduction of the antibiotics are revised and discussed considering strategies to improve the selectivity of the method. In addition, current challenges and future prospects are discussed.

The Application of Nanomaterials for the Electrochemical Detection of Antibiotics: A Review

Antibiotics can accumulate through food metabolism in the human body which may have a significant effect on human safety and health. It is therefore highly beneficial to establish easy and sensitive approaches for rapid assessment of antibiotic amounts. In the development of next-generation biosensors, nanomaterials (NMs) with outstanding thermal, mechanical, optical, and electrical properties have been identified as one of the most hopeful materials for opening new gates. This study discusses the latest developments in the identification of antibiotics by nanomaterial-constructed biosensors. The construction of biosensors for electrochemical signal-transducing mechanisms has been utilized in various types of nanomaterials, including quantum dots (QDs), metal-organic frameworks (MOFs), magnetic nanoparticles (NPs), metal nanomaterials, and carbon nanomaterials. To provide an outline for future study directions, the existing problems and future opportunities in this area are also included. The current review, therefore, summarizes an in-depth assessment of the nanostructured electrochemical sensing method for residues of antibiotics in different systems.

Magnetic nanoparticles in developing electrochemical sensors for pharmaceutical and biomedical applications

A revolutionary impact on the pharmaceutical and biomedical applications has been arisen in the few years to come as a result of the advances made in magnetic nanoparticles (MNPs) research. The use of MNPs opens wide opportunities in diagnostics, drug and gene delivery, in vivo imaging, magnetic separation, and hyperthermia therapy, etc. Besides, their possible integration in sensors makes them an ideal essential element of innovative pharmaceutical and biomedical applications. Nowadays, MNPs-based electrochemical sensors have attracted great attention to pharmaceutical and biomedical applications owing to their high sensitivity, stability. Selectivity towards the target as well as their simplicity of manufacture. Therefore, this review focus on recent advances with cutting-edge approaches dealing with the synthesis, design, and advantageous analytical performance of MNPs in the electrochemical sensors utilized for pharmaceutical and biomedical applications between 2015 and 2020. The challenges existing in this research area and some potential strategies/future perspectives for the rational design of electrochemical sensors are also outlined.

Application of magnetic nanomaterials in electroanalytical methods: A review

Magnetic nanomaterials (MNMs) have gained high attention in different fields of studies due to their ferromagnetic/superparamagnetic properties and their low toxicity and high biocompatibility. MNMs contain magnetic elements such as iron and nickel in metallic, bimetallic, metal oxide, and mixed metal oxide. In electroanalytical methods, MNMs have been applied as sorbents for sample preparation before the electrochemical detection (sorbent role), as the electrode modifier (catalytic role), and the integration of the above two roles (as both sorbent and catalytic agent). In this paper, the application of MNMs in electroanalytical methods have been classified based on the main role of the nanomaterial and discussed separately. Furthermore, catalytic activities of MNMs in electroanalytical methods such as redox electrocatalytic, nanozymes catalytic (peroxidase, catalase activity, oxidase activity, superoxide dismutase activity), catalyst gate, and nanocontainer have been discussed.

Detection of pollutants in water bodies: electrochemical detection or photo-electrochemical detection?

The massive discharge of pollutants including endocrine-disrupting chemicals (EDCs), heavy metals, pharmaceuticals and personal care products (PPCPs) into water bodies is endangering the ecological environment and human health, and needs to be accurately detected. Both electrochemical and photo-electrochemical detection methods have been widely used for the detection of these pollutants, however, which one is better for the detection of different environmental pollutants? In this feature article, different electrochemical and photo-electrochemical detection methods are summarized, including the principles, classification, common catalysts, and applications. By summarizing the advantages and disadvantages of different detection methods, this review provides a guide for other researchers to detect pollutants in water bodies by using electrochemical and photo-electrochemical analysis.

Pinacho D. Personalized Medicine for Antibiotics: The Role of Nanobiosensors in Therapeutic Drug Monitoring

Due to the high bacterial resistance to antibiotics (AB), it has become necessary to adjust the dose aimed at personalized medicine by means of therapeutic drug monitoring (TDM). TDM is a fundamental tool for measuring the concentration of drugs that have a limited or highly toxic dose in different body fluids, such as blood, plasma, serum, and urine, among others. Using different techniques that allow for the pharmacokinetic (PK) and pharmacodynamic (PD) analysis of the drug, TDM can reduce the risks inherent in treatment. Among these techniques, nanotechnology focused on biosensors, which are relevant due to their versatility, sensitivity, specificity, and low cost. They provide results in real time, using an element for biological recognition coupled to a signal transducer. This review describes recent advances in the quantification of AB using biosensors with a focus on TDM as a fundamental aspect of personalized medicine.

Magneto-Impedance Biosensor Sensitivity: Effect and Enhancement

Biosensors based on magneto-impedance (MI) effect are powerful tools for biomedical applications as they are highly sensitive, stable, exhibit fast response, small in size, and have low hysteresis and power consumption. However, the performance of these biosensors is influenced by a variety of factors, including the design, geometry, materials and fabrication procedures. Other less appreciated factors influencing the MI effect include measuring circuit implementation, the material used for construction, geometry of the thin film sensing element, and patterning shapes compatible with the interface microelectronic circuitry. The type magnetic (ferrofluid, Dynabeads, and nanoparticles) and size of the particles, the magnetic particle concentration, magnetic field strength and stray magnetic fields can also affect the sensor sensitivity. Based on these considerations it is proposed that ideal MI biosensor sensitivity could be achieved when the sensor is constructed in sandwich thick magnetic layers with large sensing area in a meander shape, measured with circuitry that provides the lowest possible external inductance at high frequencies, enclosed by a protective layer between magnetic particles and sensing element, and perpendicularly magnetized when detecting high-concentration of magnetic particles.

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.

Impedimetric Aptamer-Based Biosensors: Applications

Impedimetric aptamer-based biosensors show high potential for handheld devices and point-of-care tests. In this review, we report on recent advances in aptamer-based impedimetric biosensors for applications in biotechnology. We detail on analytes relevant in medical and environmental biotechnology as well as food control, for which aptamer-based impedimetric biosensors were developed. The reviewed biosensors are examined for their performance, including sensitivity, selectivity, response time, and real sample validation. Additionally, the benefits and challenges of impedimetric aptasensors are summarized.

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.

Development of Immunochromatographic Assay for Determination of Tetracycline in Human Serum

Determining antibiotic concentration in human blood provides useful pharmacokinetic information. Commonly used methods such as ELISA require a long time to obtain results and thus cannot be applied when information is needed immediately. In this study, a novel antibody-based lateral flow technique was developed for tetracycline detection in human serum. Contrary to tests developed to analyze food samples, the features of work with serum as analyzed probe were studied for the first time here. The application of labeled and unlabeled specific antibodies was compared. For this purpose, specific and anti-species antibodies were labeled with gold nanoparticles and used for antigen⁻antibody interaction on the membrane surface with observed staining in the test zone. For both schemes, optimal conditions were established to provide the best sensitivity. The developed assay has a limit of visual detection as low as 35 and 11 ng/mL for the direct and indirect labeled antibodies, respectively. The limit of instrumental detection is from 0.4 to 3.5 ng/mL for diluted and undiluted sera. The use of indirect antibody labeling showed a small increase in sensitivity compared to traditional direct antibody labeling. The developed method showed no cross-reactivity with antibiotics of other classes. The method was used to test samples of serum. The results showed high correlation with the data obtained by ELISA (R² = 0.98968). The assay provides a quick assessment of the amount of antibiotics in the blood and keeps them under control throughout the duration of therapy.

Critical Review: DNA Aptasensors, Are They Ready for Monitoring Organic Pollutants in Natural and Treated Water Sources?

There is a growing need to monitor anthropogenic organic contaminants detected in water sources. DNA aptamers are synthetic single-stranded oligonucleotides, selected to bind to target contaminants with favorable selectivity and sensitivity. These aptamers can be functionalized and are used with a variety of sensing platforms to develop sensors, or aptasensors. In this critical review, we (1) identify the state-of-the-art in DNA aptamer selection, (2) evaluate target and aptamer properties that make for sensitive and selective binding and sensing, (3) determine strengths and weaknesses of alternative sensing platforms, and (4) assess the potential for aptasensors to quantify environmentally relevant concentrations of organic contaminants in water. Among a suite of target and aptamer properties, binding affinity is either directly (e.g., organic carbon partition coefficient) or inversely (e.g., polar surface area) correlated to properties that indicate greater target hydrophobicity results in the strongest binding aptamers, and binding affinity is correlated to aptasensor limits of detection. Electrochemical-based aptasensors show the greatest sensitivity, which is similar to ELISA-based methods. Only a handful of aptasensors can detect organic pollutants at environmentally relevant concentrations, and interference from structurally similar analogs commonly present in natural waters is a yet-to-be overcome challenge. These findings lead to recommendations to improve aptasensor performance.

Bifunctional aptasensor based on novel two-dimensional nanocomposite of MoS2 quantum dots and g-C3N4 nanosheets decorated with chitosan-stabilized Au nanoparticles for selectively detecting prostate specific antigen

A novel nanostructured biosensing platform was designed based on two-dimensional (2D) nanocomposite of graphitic carbon nitride (g-C₃N₄) nanosheets and MoS₂ quantum dots (MoS₂ QDs), followed by decoration with chitosan-stabilized Au nanoparticles (CS-AuNPs) (denoted as MoS₂QDs@g-C₃N₄@CS-AuNPs), of which CS-AuNPs were prepared by plasma enhanced-chemical vapor deposition. Owning to the good surface plasmon performance of the CS-AuNPs and excellent electrochemical activity of MoS₂QDs@g-C₃N₄ nanosheets, the as-obtained 2D MoS₂QDs@g-C₃N₄@CS-AuNPs nanocomposite was simultaneously explored to construct both surface plasmon resonance spectroscopy (SPR) sensor and electrochemical aptasensor. The MoS₂QDs@g-C₃N₄@CS-AuNPs-based aptasensor shows strong bio-binding affinity toward the prostate specific antigen (PSA) targeted aptamer strands as compared to the individual component, including MoS₂ QDs, g-C₃N₄, and CS-AuNPs. When detecting PSA, the low limit of detection (LOD) of 0.71 pg mL^-1 deduced by electrochemical aptasensor is three orders of magnitude lower than that deduced by SPR sensor (0.77 ng mL^-1). As expected, both SPR sensor and electrochemical aptasensor demonstrate good selectivity, highly stability, acceptable reproducibility, and well consistent applicability in human serum. The satisfactory results suggest potential application of the MoS₂QDs@g-C₃N₄@CS-AuNPs in bifunctional biosensing fields and clinical monitoring of cancer markers.