Electrochemical biosensors for pathogenic microorganisms detection based on recognition elements

The worldwide spread of pathogenic microorganisms poses a significant risk to human health. Electrochemical biosensors have emerged as dependable analytical tools for the point-of-care detection of pathogens and can effectively compensate for the limitations of conventional techniques. Real-time analysis, high throughput, portability, and rapidity make them pioneering tools for on-site detection of pathogens. Herein, this work comprehensively reviews the recent advances in electrochemical biosensors for pathogen detection, focusing on those based on the classification of recognition elements, and summarizes their principles, current challenges, and prospects. This review was conducted by a systematic search of PubMed and Web of Science databases to obtain relevant literature and construct a basic framework. A total of 171 publications were included after online screening and data extraction to obtain information of the research advances in electrochemical biosensors for pathogen detection. According to the findings, the research of electrochemical biosensors in pathogen detection has been increasing yearly in the past 3 years, which has a broad development prospect, but most of the biosensors have performance or economic limitations and are still in the primary stage. Therefore, significant research and funding are required to fuel the rapid development of electrochemical biosensors. The overview comprehensively evaluates the recent advances in different types of electrochemical biosensors utilized in pathogen detection, with a view to providing insights into future research directions in biosensors.

Chimeric Protein Switch Biosensors

Rapid detection of protein and small-molecule analytes is a valuable technique across multiple disciplines, but most in vitro testing of biological or environmental samples requires long, laborious processes and trained personnel in laboratory settings, leading to long wait times for results and high expenses. Fusion of recognition with reporter elements has been introduced to detection methods such as enzyme-linked immunoassays (ELISA), with enzyme-conjugated secondary antibodies removing one of the many incubation and wash steps. Chimeric protein switch biosensors go further and provide a platform for homogenous mix-and-read assays where long wash and incubation steps are eradicated from the process. Chimeric protein switch biosensors consist of an enzyme switch (the reporter) coupled to a recognition element, where binding of the analyte results in switching the activity of the reporter enzyme on or off. Several chimeric protein switch biosensors have successfully been developed for analytes ranging from small molecule drugs to large protein biomarkers. There are two main formats of chimeric protein switch biosensor developed, one-component and multi-component, and these formats exhibit unique advantages and disadvantages. Genetically fusing a recognition protein to the enzyme switch has many advantages in the production and performance of the biosensor. A range of immune and synthetic binding proteins have been developed as alternatives to antibodies, including antibody mimetics or antibody fragments. These are mainly small, easily manipulated proteins and can be genetically fused to a reporter for recombinant expression or manipulated to allow chemical fusion. Here, aspects of chimeric protein switch biosensors will be reviewed with a comparison of different classes of recognition elements and switching mechanisms.

Recent advances in biosensors for antibiotic detection: Selectivity and signal amplification with nanomaterials

Antibiotics are widely used in the prevention and treatment of infectious diseases in animals due to its bactericidal or bacteriostatic action. Residual antibiotics and their metabolites pose great threats to human and animal health, such as potential carcinogenic and mutagenic effects, and bacterial resistances. Therefore, it is necessary and urgent to accurately monitor trace amounts of antibiotics in food samples. Up to now, many analytical methods have been reported for the determination of antibiotics. Biosensors with the advantages of high sensitivity, rapid response, easy miniaturization, and low price have been widely applied to the detection of antibiotics residues in past decades. This review offered an in-depth evaluation of recognition elements for antibiotic residues in diverse food matrices. In addition, it presented a systematical and critical review on signal amplification via various materials, focusing on recently developed nanomaterials. Finally, the review provided an outlook on the future concepts to help upgrade the sensing techniques for antibiotics in food.

The potential application of electrochemical biosensors in the COVID-19 pandemic: A perspective on the rapid diagnostics of SARS-CoV-2

Electrochemical biosensors combine the selectivity of electrochemical signal transducers with the specificity of biomolecular recognition strategies. Although they have been broadly studied in different areas of diagnostics, they are not yet fully commercialized. During the COVID-19 pandemic, electrochemical platforms have shown the potential to address significant limitations of conventional diagnostic platforms, including accuracy, affordability, and portability. The advantages of electrochemical platforms make them a strong candidate for rapid point-of-care detection of SARS-CoV-2 infection by targeting not only viral RNA but antigens and antibodies. Herein, we reviewed advancements in electrochemical biosensing platforms towards the detection of SARS-CoV-2 through studying similar viruses.

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The complicated nature of conventional tests restricted the availability and distribution of COVID-19 tests.

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Electrochemical detection methods can stand as potential rapid tests for the diagnosis of COVID-19.

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Electrochemical biosensors combine signal selectivity and molecular specificity for rapid accurate detection of SARS-CoV-2.

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The electrochemical biosensors demonstrate trail-blazing sensitivity and specificity, outmatching conventional assays.

A nanocomposite prepared from bifunctionalized ionic liquid, chitosan, graphene oxide and magnetic nanoparticles for aptamer-based assay of tetracycline by chemiluminescence

A nanocomposite was prepared from a bifunctionalized ionic liquid, chitosan on magnetic nanoparticle-modified graphene oxide (IL/Chit@MGO). It was used in a chemiluminescencc (CL) assay for tetracycline. The materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray powder diffraction, nitrogen adsorption-desorption isotherm, vibrating sample magnetometry and zeta potentials. Subsequently, a tetracycline-binding aptamer (TC-Apt) acting as a recognition element, and G-quadruplex DNAzyme (G-DNAzyme) acting as a signal amplification component were modified on IL/Chit@MGO. So, the bifunctional G-DNAzyme/TC-Apt/IL/Chit@MGO was prepared. The IL/Chit@MGO is found to possess excellent loading capability for TC-Apt. This is attributed to the large specific surface and abundant charge on the surface of IL/Chit@MGO. The composite was used to construct a CL assay for tetracycline. Tetracycline binds to TC-Apt and causes the release of the G-DNAzyme. The latter catalyzes the CL of luminol-H₂O₂ CL system at pH 7.4. Under optimized conditions, the blue CL at the emission wavelength of 425 nm increases linearly in the 0.16 pM to 2.0 nM concentration range, and the detection limit is 21 fM (at 3σ). The assay is selective, reproducible and stable. The assay was applied to tetracycline detection in practical samples. The apparent recoveries are 98.0% to 101.3% for the milk sample and 97.0% to 102.2% for the water sample. Graphical abstractG-quadruplex DNAzyme (G-DNAzyme) and tetracycline aptamer (TC-Apt) bifunctionalized ionic liquid/chitosan@magnetic graphene oxide (IL/Chit@MGO) was prepared. The nanocomposite was used to construct a chemiluminescence (CL) assay for tetracycline.

Recent progress in the development of recognition bioelements for polychlorinated biphenyls detection: Antibodies and aptamers

Polychlorinated biphenyls (PCBs) are persistent pollutants, which have expanded in foods and the environment. Detection of PCBs is considered essential due to recognized side-effects of PCBs on health and the public concerns in this regard. On the other hand, due to the trace levels of these organic chlorine compounds, reliable and sensitive assays must be developed. Recognition elements are essential parts of analytical detection assays and sensors of PCBs since these elements are involved in the selective identification of the analytes of interest. Understanding the fundamentals of the recognition elements of PCBs and the benefits of the sensor strategies result in the development of next-generation recognition devices. This review aimed to highlight the recent progress in the recognition elements as key parts of biosensors. We initially, focused on the developed antibody-based biosensors for the detection of PCBs, followed by discussing the aptamers as novel recognition elements. Furthermore, the recent advancement in the development of aptamer-based solid phase extractions has been evaluated. These findings could contribute to improving the design of commercial PCB-kits in the future.

Bioinspired recognition elements for mycotoxin sensors

Mycotoxins are low molecular weight molecules produced as secondary metabolites by filamentous fungi that can be found as natural contaminants in many foods and feeds. These toxins have been shown to have adverse effects on both human and animal health, and are the cause of significant economic losses worldwide. Sensors for mycotoxin analysis have traditionally applied elements of biological origin for the selective recognition purposes. However, since the 1970s there has been an exponential growth in the use of genetically engineered or synthetic biomimetic recognition elements that allow some of the limitations associated with the use of natural receptors for the analyses of these toxins to be circumvented. This review provides an overview of recent advances in the application of bioinspired recognition elements, including recombinant antibodies, peptides, aptamers, and molecularly imprinted polymers, to the development of sensors for mycotoxins based on different transduction elements. Graphical abstract Novel analytical methods based on bioinspired recognition elements, such as recombinant antibodies, peptides, aptamers, and molecularly imprinted polymers, can improve the detection of mycotoxins and provide better tools than their natural counterparts to ensure food safety.

Lysozyme as a recognition element for monitoring of bacterial population

Bacterial infections remain a significant challenge in biomedicine and environment safety. Increasing worldwide demand for point-of-care techniques and increasing concern on their safe development and use, require a simple and sensitive bioanalysis for pathogen detection. However, this goal is not yet achieved. A design for fluorescein isothiocyanate-labeled lysozyme (FITC-LYZ), which provides quantitative binding information for gram-positive bacteria, Micrococcus luteus, and detects pathogen concentration, is presented. The functional lysozyme is used not only as the pathogenic detection platform, but also as a tracking reagent for microbial population in antibacterial tests. A nonlinear relationship between the system response and the logarithm of the bacterial concentration was observed in the range of 1.2×10(2)-1.2×10(5) cfu mL(-1). The system has a potential for further applications and provides a facile and simple method for detection of pathogenic bacteria. Meanwhile, the fluorescein isothiocyanate -labeled lysozyme is also employed as the tracking agent for antibacterial dynamic assay, which show a similar dynamic curve compared with UV-vis test.