Recent developments in antibody-based assays for the detection of bacterial toxins

Functionalized metal-organic frameworks with biomolecules for sensing and detection applications of food contaminants

The increasing demand for toxin-free food, driven by the rise in fast food consumption and changing dietary habits, necessitates advanced and efficient detection methods to address the potential risks associated with contaminated food. Nanomaterial-based detection methods have shown significant promise, particularly using metal-organic frameworks (MOFs) combined with biomolecules. This review article provides an overview of recent advancements in using functionalized metal-organic frameworks (FMOFs) with biomolecules to detect various food contaminants, including heavy metals, antibiotics, pesticides, bacteria, mycotoxins and other chemical contaminants. We discuss the fundamental principles of detecting food contaminants, evaluate existing analytical techniques, and explore the development of biomacromolecule-functionalized MOF-based sensors encompassing colorimetric, optical, electrochemical, and portable variants. The review also examines sensing mechanisms, uses FMOFs as signal probes and carriers for capture probes, and assesses sensitivity. Additionally, we explore the opportunities and challenges in producing FMOFs with biomacromolecules for food contaminant assessment. Future directions include improving sensor sensitivity and specificity, developing more cost-effective production methods, and integrating these technologies into real-world food safety monitoring systems. This work aims to pave the way for innovative and reliable solutions to ensure the safety of our food supply.

Advances in phage display based nano immunosensors for cholera toxin

Cholera, a persistent global public health concern, continues to cause outbreaks in approximately 30 countries and territories this year. The imperative to safeguard water sources and food from Vibrio cholerae, the causative pathogen, remains urgent. The bacterium is mainly disseminated via ingestion of contaminated water or food. Despite the plate method's gold standard status for detection, its time-consuming nature, taking several days to provide results, remains a challenge. The emergence of novel virulence serotypes raises public health concerns, potentially compromising existing detection methods. Hence, exploiting Vibrio cholerae toxin testing holds promise due to its inherent stability. Immunobiosensors, leveraging antibody specificity and sensitivity, present formidable tools for detecting diverse small molecules, encompassing drugs, hormones, toxins, and environmental pollutants. This review explores cholera toxin detection, highlighting phage display-based nano immunosensors' potential. Engineered bacteriophages exhibit exceptional cholera toxin affinity, through specific antibody fragments or mimotopes, enabling precise quantification. This innovative approach promises to reshape cholera toxin detection, offering an alternative to animal-derived methods. Harnessing engineered bacteriophages aligns with ethical detection and emphasizes sensitivity and accuracy, a pivotal stride in the evolution of detection strategies. This review primarily introduces recent advancements in phage display-based nano immunosensors for cholera toxin, encompassing technical aspects, current challenges, and future prospects.

Phage display technology for fabricating a recombinant monoclonal ScFv antibody against tetanus toxin

Tetanus is a specific infectious disease, often associated with lower immunization in developing countries and catastrophic events (such as earthquakes). Millions of people, especially children, die every year from tetanus disease. Therefore, it is necessary to devise a rapid and sensitive detection method for tetanus toxin to ensure an early diagnosis and clinical treatment of tetanus. The current study looks at developing a novel, high specific, low-cost, and sensitive ScFv antibody. It is capable of tetanus detection immunoassays in clinical diagnosis, suspicious foods, and water monitoring. For this regard, a high-quality phage display antibody library (8.7 × 107 PFU/ml) was constructed. Tetanus-specific antibodies with high affinity retrieved from libraries. After phage rescue and four rounds of biopanning, clone screening was performed by phage ELISA. Recombinant antibodies expressed from the AC8 clone showed the highest affinity for tetanus. SDS-PAGE and western blotting confirmed the presence of a high-quality, pure ScFv band at 32 kDa. ELISA was used to determine the affinity value, estimated to be around 10-8 M. The results suggest that the proposed detection method by ScFv antibodies is an alternative diagnostic tool enabling rapid and specific detection of the tetanus toxin.

Multi-Probe Nano-Genomic Biosensor to Detect S. aureus from Magnetically-Extracted Food Samples

One of the most prevalent causes of foodborne illnesses worldwide is staphylococcal food poisoning. This study aimed to provide a robust method to extract the bacteria Staphylococcus aureus from food samples using glycan-coated magnetic nanoparticles (MNPs). Then, a cost-effective multi-probe genomic biosensor was designed to detect the nuc gene of S. aureus rapidly in different food matrices. This biosensor utilized gold nanoparticles and two DNA oligonucleotide probes combined to produce a plasmonic/colorimetric response to inform users if the sample was positive for S. aureus. In addition, the specificity and sensitivity of the biosensor were determined. For the specificity trials, the S. aureus biosensor was compared with the extracted DNA of Escherichia coli, Salmonella enterica serovar Enteritidis (SE), and Bacillus cereus. The sensitivity tests showed that the biosensor could detect as low as 2.5 ng/µL of the target DNA with a linear range of up to 20 ng/µL of DNA. With further research, this simple and cost-effective biosensor can rapidly identify foodborne pathogens from large-volume samples.

Rapid and sensitive detection of Staphylococcus aureus by using a long-period fiber grating immunosensor coated with egg yolk antibody

The rapid and reliable detection of bacteria plays an important role in clinical and veterinary practice. A stable, label free, compact, and sensitive long-period fiber grating (LPFG) sensor based on egg yolk antibody (IgY) was proposed for the detection of Staphylococcus aureus (S. aureus). LPFG was fabricated with laser writing technology, and specific IgY was further immobilized on the grating region and then combined with the corresponding bacteria. S. aureus was detected by tracking the change of resonance wavelength in the LPFG transmission spectrum caused by bacteria-antibody interaction induced by the increase of biological cover thickness and density after the immune reaction. The testing results showed that the proposed sensor was selective and sensitive to S. aureus measurement, and the detection limit is approximately 33 CFU/ml. The proposed antibody immobilization method is very simple, and the optical fiber can be manufactured in batch to reduce the cost. The detection time of the sensor is around 20 min, which is fast and suitable for detection. The assay was successfully applied for the quantitative analysis of S. aureus in natural waters and met the needs of on-site screening trace pathogenic bacteria in food safety control.

Quantum Dots as Biosensors in the Determination of Biochemical Parameters in Xenobiotic Exposure and Toxins

Quantum dots (QDs) have been exploited for a range of scientific applications where the analytes can be expected to have significant photoluminescent properties. Previously, the applications of QDs as nanosensors for the detection of toxics in biospecimens, especially in cases of poisoning, have been discussed. This review focuses on the applications of QDs as biosensors for the detection of phytotoxins, vertebrate and invertebrate toxins, and microbial toxins present in biospecimens. Further, the role of QDs in the measurement of biochemical parameters of patient/victim as an indirect method of poison detection is also highlighted.

Multiplex Immunoassay Techniques for On-Site Detection of Security Sensitive Toxins

Biological toxins are a heterogeneous group of high molecular as well as low molecular weight toxins produced by living organisms. Due to their physical and logistical properties, biological toxins are very attractive to terrorists for use in acts of bioterrorism. Therefore, among the group of biological toxins, several are categorized as security relevant, e.g., botulinum neurotoxins, staphylococcal enterotoxins, abrin, ricin or saxitoxin. Additionally, several security sensitive toxins also play a major role in natural food poisoning outbreaks. For a prompt response to a potential bioterrorist attack using biological toxins, first responders need reliable, easy-to-use and highly sensitive methodologies for on-site detection of the causative agent. Therefore, the aim of this review is to present on-site immunoassay platforms for multiplex detection of biological toxins. Furthermore, we introduce several commercially available detection technologies specialized for mobile or on-site identification of security sensitive toxins.

Modern Tools for Rapid Diagnostics of Antimicrobial Resistance

Fast, robust, and affordable antimicrobial susceptibility testing (AST) is required, as roughly 50% of antibiotic treatments are started with wrong antibiotics and without a proper diagnosis of the pathogen. Validated growth-based AST according to EUCAST or CLSI (European Committee on Antimicrobial Susceptibility Testing, Clinical Laboratory Standards Institute) recommendations is currently suggested to guide the antimicrobial therapy. Any new AST should be validated against these standard methods. Many rapid diagnostic techniques can already provide pathogen identification. Some of them can additionally detect the presence of resistance genes or resistance proteins, but usually isolated pure cultures are needed for AST. We discuss the value of the technologies applying nucleic acid amplification, whole genome sequencing, and hybridization as well as immunodiagnostic and mass spectrometry-based methods and biosensor-based AST. Additionally, we evaluate the potential of integrated systems applying microfluidics to integrate cultivation, lysis, purification, and signal reading steps. We discuss technologies and commercial products with potential for Point-of-Care Testing (POCT) and their capability to analyze polymicrobial samples without pre-purification steps. The purpose of this critical review is to present the needs and drivers for AST development, to show the benefits and limitations of AST methods, to introduce promising new POCT-compatible technologies, and to discuss AST technologies that are likely to thrive in the future.

A simple and fast protocol for the synthesis of 2-amino-4-(4-formylphenyl)-4H-chromene-3-carbonitrile to develop an optical immunoassay for the quantification of botulinum neurotoxin type F

In this study, a novel optical immunoassay platform using (S)-2-amino-4-(4-formylphenyl)-4H-chromene-3-carbonitrile, which was synthesized by an ultra-sonication method, as an optical probe.

Nanomaterials and nanocomposite applications in veterinary medicine

Nowadays, nanotechnology has made huge, significant advancements in biotechnology and biomedicine related to human and animal science, including increasing health safety, production, and the elevation of national income. There are various fields of nanomaterial applications in veterinary medicine such as efficient diagnostic and therapeutic tools, drug delivery, animal nutrition, breeding and reproduction, and valuable additives. Additional benefits include the detection of pathogens, protein, biological molecules, antimicrobial agents, feeding additives, nutrient delivery, and reproductive aids. There are many nanomaterials and nanocomposites that can be used in nanomedicine such as metal nanoparticles, liposomes, carbon nanotubes, and quantum dots. In the near future, nanotechnology research will have the ability to produce novel tools for improving animal health and production. Therefore, this chapter was undertaken to spotlight novel methods created by nanotechnology for application in the improvement of animal health and production. In addition, the toxicity of nanomaterials is fully discussed to avoid the suspected health hazards of toxicity for animal health safety.

Magnetic quantum dot based lateral flow assay biosensor for multiplex and sensitive detection of protein toxins in food samples

Protein toxins, such as botulinum neurotoxin type A (BoNT/A) and staphylococcal enterotoxin B (SEB), easily pollute food and water and are ultra-toxic to humans and animals, thus requiring a sensitive on-site detection method. In this study, we reported a novel lateral flow assay (LFA) strip on the basis of magnetic quantum dot nanoparticles (MagQD NPs) for sensitive and multiplex protein toxin detection in food samples. A new type of MagQD NP was prepared by fixing the dense carboxylated QDs on the surface of polyethyleneimine-modified Fe₃O₄ magnetic NPs (MNPs) and applied in LFA with the following functions: capture and enrich target toxins from sample solutions and serve as advanced fluorescent labels for the quantitative determination of targets on the strip. Through this strategy, the assay realized quantified BoNT/A and SEB detection in 30 min with the limits of detection of 2.52 and 2.86 pg/mL, respectively. The selectivity and the ability of quantitative analysis of the method were validated in real food samples, including milk and juice. This MagQD-LFA biosensor showed considerable potential as a point-of-care testing tool for the sensitive detection of trace toxins.

Sensitive and rapid detection of cholera toxin subunit B using magnetic frequency mixing detection

Cholera is a life-threatening disease caused by the cholera toxin (CT) as produced by some Vibrio cholerae serogroups. In this research we present a method which directly detects the toxin’s B subunit (CTB) in drinking water. For this purpose we performed a magnetic sandwich immunoassay inside a 3D immunofiltration column. We used two different commercially available antibodies to capture CTB and for binding to superparamagnetic beads. ELISA experiments were performed to select the antibody combination. The beads act as labels for the magnetic frequency mixing detection technique. We show that the limit of detection depends on the type of magnetic beads. A nonlinear Hill curve was fitted to the calibration measurements by means of a custom-written python software. We achieved a sensitive and rapid detection of CTB within a broad concentration range from 0.2 ng/ml to more than 700 ng/ml.

Utilization of Small RNA Genes to Distinguish Vibrio cholerae Biotypes via Multiplex Polymerase Chain Reaction

The diarrheal disease "cholera" is caused by Vibrio cholerae, and is primarily confined to endemic regions, mostly in Africa and Asia. It is punctuated by outbreaks and creates severe challenges to public health. The disease-causing strains are most-often members of serogroups O1 and O139. PCR-based methods allow rapid diagnosis of these pathogens, including the identification of their biotypes. However, this necessitates the selection of specific target sequences to differentiate even the closely related biotypes of V. cholerae. Oligonucleotides for selective amplification of small RNA (sRNA) genes that are specific to these V. cholerae subtypes were designed. The resulting multiplex PCR assay was validated using V. cholerae cultures (i.e., 19 V. cholerae and 22 non-V. cholerae isolates) and spiked stool samples. The validation using V. cholerae cultures and spiked stool suspensions revealed detection limits of 10-100 pg DNA per reaction and 1.5 cells/mL suspension, respectively. The multiplex PCR assay that targets sRNA genes for amplification enables the sensitive and specific detection, as well as the differentiation of V. cholerae-O1 classical, O1 El Tor, and O139 biotypes. Most importantly, the assay enables fast and cheaper diagnosis compared with classic culture-based methods.

Theranostics Aspects of Various Nanoparticles in Veterinary Medicine

Nanoscience and nanotechnology shows immense interest in various areas of research and applications, including biotechnology, biomedical sciences, nanomedicine, and veterinary medicine. Studies and application of nanotechnology was explored very extensively in the human medical field and also studies undertaken in rodents extensively, still either studies or applications in veterinary medicine is not up to the level when compared to applications to human beings. The application in veterinary medicine and animal production is still relatively innovative. Recently, in the era of health care technologies, Veterinary Medicine also entered into a new phase and incredible transformations. Nanotechnology has tremendous and potential influence not only the way we live, but also on the way that we practice veterinary medicine and increase the safety of domestic animals, production, and income to the farmers through use of nanomaterials. The current status and advancements of nanotechnology is being used to enhance the animal growth promotion, and production. To achieve these, nanoparticles are used as alternative antimicrobial agents to overcome the usage alarming rate of antibiotics, detection of pathogenic bacteria, and also nanoparticles being used as drug delivery agents as new drug and vaccine candidates with improved characteristics and performance, diagnostic, therapeutic, feed additive, nutrient delivery, biocidal agents, reproductive aids, and finally to increase the quality of food using various kinds of functionalized nanoparticles, such as liposomes, polymeric nanoparticles, dendrimers, micellar nanoparticles, and metal nanoparticles. It seems that nanotechnology is ideal for veterinary applications in terms of cost and the availability of resources. The main focus of this review is describes some of the important current and future principal aspects of involvement of nanotechnology in Veterinary Medicine. However, we are not intended to cover the entire scenario of Veterinary Medicine, despite this review is to provide a glimpse at potential important targets of nanotechnology in the field of Veterinary Medicine. Considering the strong potential of the interaction between the nanotechnology and Veterinary Medicine, the aim of this review is to provide a concise description of the advances of nanotechnology in Veterinary Medicine, in terms of their potential application of various kinds of nanoparticles, secondly we discussed role of nanomaterials in animal health and production, and finally we discussed conclusion and future perspectives of nanotechnology in veterinary medicine.

Rapid and Sensitive Detection of Staphylococcal Enterotoxin B by Recombinant Nanobody Using Phage Display Technology

Staphylococcal enterotoxin B, from Staphylococcus aureus (S. aureus), is one of the most potent bacterial superantigens with profound toxic effects on the immune system. It is associated with food poisoning, toxic shock, atopic dermatitis, asthma, and nasal polyps in humans. The current diagnostic methods for staphylococcal enterotoxin are mainly based on traditional monoclonal antibodies which hardly meet the requirements for clinical applications, and hybridoma clones lose their ability to secrete antibodies during time. The present study investigates the development of a novel, highly specific, low-cost, and sensitive nanobody capable of being used in immunoassays for Staphylococcal enterotoxin B (SEB) detection in suspicious foods. For this purpose, Camelus dromedarius was immunized against SEB toxin. After obtaining acceptable titration, a high-quality phage display nanobody library (4 × 10¹⁰ PFU/ml) was constructed. High-affinity SEB-specific nanobodies were retrieved from constructed libraries. After phage rescue and five round of biopanning, clone screening was performed by phage ELISA. Recombinant nanobodies which were expressed from C7 and C21 clone showed the highest affinity for SEB. The presence of high quality and pure nanobody band at ~ 15 kDa was confirmed by SDS-PAGE and western blotting. The affinity constant which was measured by ELISA was calculated to be around 10^-9 M. The results suggest that the proposed detection method by nanobodies is an alternative diagnostic tool enabling a rapid, inexpensive, and specific detection of the SEB.

Carbon dots based immunosorbent assay for the determination of GFAP in human serum

Glial fibrillary acidic protein (GFAP) is expressed in the central nervous system and the level of GFAP normally rises with brain injury and astroglial tumors. So, serum GFAP is used as a marker for diagnosing various types of brain damage and astroglial tumors. In this study, a new sensor based on carbon dots (CDs) linked with antibodies to specifically detect GFAP in human serum was developed. Anti-GFAP (Ab1) linked with protein A/G agarose resin (PA/G) as a capture antibody (PA/G-Ab1) and anti-GFAP (Ab2) labeled with CDs as a detection antibody (CDs-Ab2) were prepared firstly. Then the CD-linked antibody immunosorbent assay (CLAISA) method was constructed based on the sandwich conjunction reaction among PA/G-Ab1, GFAP, and CDs-Ab2. CLAISA, using the fluorescence of PA/G-Ab1-GFAP-Ab2-CDs as the direct signal, enabled the proposed immunosensor to detect GFAP sensitively with a linear range of 0.10-8.00 ng ml^-1 and a detection limit of 25 pg ml^-1. This method was applied to the determination of GFAP in human serum by the standard addition method, and the results showed high accuracy and precision. Considering the easy synthetic process and excellent performance of CLAISA, this method has great potential to be used to monitor GFAP in the clinic.

Proteomic Methods of Detection and Quantification of Protein Toxins

Biological toxins are a heterogeneous group of compounds that share commonalities with biological and chemical agents. Among them, protein toxins represent a considerable, diverse set. They cover a broad range of molecular weights from less than 1000 Da to more than 150 kDa. This review aims to compare conventional detection methods of protein toxins such as in vitro bioassays with proteomic methods, including immunoassays and mass spectrometry-based techniques and their combination. Special emphasis is given to toxins falling into a group of selected agents, according to the Centers for Disease Control and Prevention, such as Staphylococcal enterotoxins, Bacillus anthracis toxins, Clostridium botulinum toxins, Clostridium perfringens epsilon toxin, ricin from Ricinus communis, Abrin from Abrus precatorius or control of trade in dual-use items in the European Union, including lesser known protein toxins such as Viscumin from Viscum album. The analysis of protein toxins and monitoring for biological threats, i.e., the deliberate spread of infectious microorganisms or toxins through water, food, or the air, requires rapid and reliable methods for the early identification of these agents.

Current advances in aptamer-assisted technologies for detecting bacterial and fungal toxins

Infectious diseases are among the common leading causes of morbidity and mortality worldwide. Associated with the emergence of new infectious diseases, the increasing number of antimicrobial-resistant isolates presents a serious threat to public health and hospitalized patients. A microbial pathogen may elicit several host responses and use a variety of mechanisms to evade host defences. These methods and mechanisms include capsule, lipopolysaccharides or cell wall components, adhesions and toxins. Toxins inhibit phagocytosis, cause septic shock and host cell damages by binding to host surface receptors and invasion. Bacterial and fungal pathogens are able to apply many different toxin-dependent mechanisms to disturb signalling pathways and the structural integrity of host cells for establishing and maintaining infections Initial techniques for analysis of bacterial toxins were based on in vivo or in vitro assessments. There is a permanent demand for appropriate detection methods which are affordable, practical, careful, rapid, sensitive, efficient and economical. Aptamers are DNA or RNA oligonucleotides that are selected by systematic evolution of ligands using exponential enrichment (SELEX) methods and can be applied in diagnostic applications. This review provides an overview of aptamer-based methods as a novel approach for detecting toxins in bacterial and fungal pathogens.

The principles and applications of avidin-based nanoparticles in drug delivery and diagnosis

Avidin-biotin interaction is one of the strongest non-covalent interactions in the nature. Avidin and its analogues have therefore been extensively utilized as probes and affinity matrices for a wide variety of applications in biochemical assays, diagnosis, affinity purification, and drug delivery. Recently, there has been a growing interest in exploring this non-covalent interaction in nanoscale drug delivery systems for pharmaceutical agents, including small molecules, proteins, vaccines, monoclonal antibodies, and nucleic acids. Particularly, the ease of fabrication without losing the chemical and biological properties of the coupled moieties makes the avidin-biotin system a versatile platform for nanotechnology. In addition, avidin-based nanoparticles have been investigated as diagnostic systems for various tumors and surface antigens. In this review, we will highlight the various fabrication principles and biomedical applications of avidin-based nanoparticles in drug delivery and diagnosis. The structures and biochemical properties of avidin, biotin and their respective analogues will also be discussed.