Express high-sensitive detection of ochratoxin A in food by a lateral flow immunoassay based on magnetic biolabels

Nanolabels for biosensors based on lateral flow immunoassays

The COVID-19 outbreak was an important turning point in the development of a new generation of biosensing technologies. The synergistic combination of an immunochromatographic test (lateral flow immunoassays, LFIA) and signal transducers provides enhanced sensitivity and the ability to quantify in the rapid tests. This is possible due to the variety of nanoparticles that can be used as reporter labels. In this review, we first present an overview on the principles of a LFIA and its different formats. We analyze cutting-edge work on these platforms based on different types of nanoparticles used as labels and on the highly sensitive transducers to which they can be coupled. The works discussed herein have a beneficial impact on the fields of clinical analysis, food safety or environmental control, thus highlighting the relevance of the biosensors. Last, we provide insights into the barriers that need to be overcome when designing laboratory prototypes accessible to the society.

Mimotope peptides for nanobodies: A nontoxic alternative to ochratoxin A and its application in chemiluminescence immunoassays for analysis of pepper samples

Ochratoxin A (OTA) is a common food contaminant and poses a significant threat to human health, which requires rigorous monitoring. Mimotope peptides (MPs) are commonly used as non-toxic alternatives to toxic small molecules in eco-friendly immunoassays. Herein, with an anti-OTA nanobody as the target protein, cyclic 7-mer MPs of OTA were screened using phage display and immunomagnetic separation. The phage MPs (PMP) with the highest sensitivity and its alkaline phosphatase-tagged MP fusion (ALP-MP) were used to develop a PMP-based chemiluminescent immunoassay (PMP-CLIA) and an ALP-MP-based CLIA (AMP-CLIA). After optimization, PMP-CLIA and AMP-CLIA exhibited a limit of detection of 0.128 ng/mL and 0.232 ng/mL. Good accuracy and selectivity were confirmed for both CLIAs by recovery experiments and cross-reactions. Moreover, they were validated by high performance liquid chromatography in detecting real pepper samples. Thus, two CLIAs based on the nanobody and MPs were demonstrated as reliable tools for monitoring OTA in pepper.

Ochratoxin A in food commodities: A review of occurrence, toxicity, and management strategies

Ochratoxin A (OTA) is a potent mycotoxin produced by species of Aspergillus and Penicillium that contaminate agricultural products and pose significant health risks to both humans and animals. This review examines the mechanisms of OTA toxicity, its occurrence in various food commodities, and the implications for public health and trade. Literature pertaining to OTA was sourced from Google Scholar, covering the period from 2004 to 2024. OTA exposure is linked to multiple adverse health effects, including teratogenicity, immunotoxicity, and hepatotoxicity, with a primary impact on kidney function, and it is classified as a possible human carcinogen (Group 2B). Its toxic effects are attributed to several mechanisms, including lipid peroxidation, inhibition of protein synthesis, DNA damage, oxidative stress, and mitochondrial dysfunction. Notable findings included the presence of OTA in 46.7 % of cocoa products in Turkey, 32 % of cocoa samples in Côte d'Ivoire exceeding the OTA threshold of 2 μg/kg, and 91.5 % of ready-to-sell cocoa beans in Nigeria testing positive for OTA. Coffee beans are particularly susceptible to OTA contamination, which underscores the need for vigilant monitoring. Additionally, OTA contamination impacts agricultural productivity and food safety, leading to significant economic consequences, particularly in regions reliant on exports, such as cocoa and coffee. Several countries regulate the OTA levels in food products to safeguard public health. However, these regulations can impede trade, particularly in countries with high levels of contamination. Balancing regulatory compliance with economic viability is crucial for affected nations. Current strategies for managing OTA include improved agronomic practices, such as the use of biocontrol agents for pest management, enhanced storage conditions to prevent mould growth, and the implementation of detoxification techniques to reduce OTA levels in food products. Despite these strategies, OTA remains a significant threat to public health and the agricultural economy worldwide. The complexity of contamination in food products requires robust prevention, control, and management strategies to mitigate its impact. Continuous research and regulatory initiatives are essential for safeguarding consumers and ensuring food safety.

Pen direct writing of SERRS-based lateral flow assays for detection of penicillin G in milk

Direct pen writing offers versatile opportunities for development of low-cost tests for point-of-care applications. In this work a lateral flow immunoassay (LFIA) test was fabricated by hand "writing" immunoprobes onto hand-cut nitrocellulose strips with a commercial fountain pen. The qualitative capabilities of the test were extended by addition of a Raman reporter and consequent design and fabrication of a Surface Enhanced Resonant Raman Scattering (SERRS)-LFIA test. As proof-of-concept, dual detection of penicillin G was achieved in milk with a visual LOD of 20 ppm and a dynamic range of 0.03-97.5 ppm. Evaluation against equivalent tests performed with conventionally prepared LFIA strips showed comparable results, thus demonstrating the validity of the test. These results demonstrate the potential for further decrease in cost and consequent broader use of LFIA tests in remote regions and resource-limited environments.

Probing binding mode between sodium acid pyrophosphate and albumin: multi-spectroscopic and molecular docking analysis

Sodium acid pyrophosphate (SAPP) food additive is widely used as a preservative, bulking agent, chelating agent, emulsifier and pH regulator. It is also used as an improver of color and water retention capacity in the processing of various types of seafood, canned food, cooked meat and flour products. For the first time, we evaluated the SAPP interaction with bovine serum albumin (BSA) using spectroscopic methods including UV-Vis absorption, fluorescence spectroscopy, and surface plasmon resonance, and docking analysis to understand the mechanisms of complex formation and binding. The fluorescence intensity of BSA reduces when titrated with various concentrations of SAPP by forming a complex with BSA via a static quenching mechanism. The binding constant between BSA and SAPP decreased from 123,300 to 15,800 (M-1) with rising temperature, which indicates a decrement in complex formation owing to the interaction of SAPP with BSA. A negative ΔG° value means that SAPP binds spontaneously to BSA at all temperatures, and both ΔH° and ΔS° negative values indicate that hydrogen bonds (H-bonding) and van der Waals forces are the primary forces involved in the binding processes. The UV-Vis spectrum of BSA reduced upon increasing SAPP concentrations due to forming a new ground state complex between SAPP and BSA. Molecular docking study shows that residues Arg256, Ser259, Ser286, Ile 289 and Ala 290 play an important role in SAPP binding process to site I (subdomain IIA) of BSA through H-bonding and van der Waals forces, which is supported by the thermodynamic study.Communicated by Ramaswamy H. Sarma.

Advances in identifying and managing emerging contaminants in aquatic ecosystems: Analytical approaches, toxicity assessment, transformation pathways, environmental fate, and remediation strategies

Emerging contaminants (ECs) are increasingly recognized as threats to human health and ecosystems. This review evaluates advanced analytical methods, particularly mass spectrometry, for detecting ECs and understanding their toxicity, transformation pathways, and environmental distribution. Our findings underscore the reliability of current techniques and the potential of upcoming methods. The adverse effects of ECs on aquatic life necessitate both in vitro and in vivo toxicity assessments. Evaluating the distribution and degradation of ECs reveals that they undergo physical, chemical, and biological transformations. Remediation strategies such as advanced oxidation, adsorption, and membrane bioreactors effectively treat EC-contaminated waters, with combinations of these techniques showing the highest efficacy. To minimize the impact of ECs, a proactive approach involving monitoring, regulations, and public education is vital. Future research should prioritize the refining of detection methods and formulation of robust policies for EC management.

Magnetic nanoparticle-based immunosensors and aptasensors for mycotoxin detection in foodstuffs: An update

Mycotoxin contamination of food crops is a global challenge due to their unpredictable occurrence and severe adverse health effects on humans. Therefore, it is of great importance to develop effective tools to prevent the accumulation of mycotoxins through the food chain. The use of magnetic nanoparticle (MNP)-assisted biosensors for detecting mycotoxin in complex foodstuffs has garnered great interest due to the significantly enhanced sensitivity and accuracy. Within such a context, this review includes the fundamentals and recent advances (2020-2023) in the area of mycotoxin monitoring in food matrices using MNP-based aptasensors and immunosensors. In this review, we start by providing a comprehensive introduction to the design of immunosensors (natural antibody or nanobody, random or site-oriented immobilization) and aptasensors (techniques for aptamer selection, characterization, and truncation). Meanwhile, special attention is paid to the multifunctionalities of MNPs (recoverable adsorbent, versatile carrier, and signal indicator) in preparing mycotoxin-specific biosensors. Further, the contribution of MNPs to the multiplexing determination of various mycotoxins is summarized. Finally, challenges and future perspectives for the practical applications of MNP-assisted biosensors are also discussed. The progress and updates of MNP-based biosensors shown in this review are expected to offer readers valuable insights about the design of MNP-based tools for the effective detection of mycotoxins in practical applications.

Highly Sensitive Magnetic-Nanoparticle-Based Immunochromatography Assay for Rapid Detection of Amantadine in Chicken and Eggs

Amantadine (AMD) is an antiviral drug that is prohibited for use in livestock and poultry. In this study, carboxyl-modified magnetic nanoparticles (MNPs) were synthesized using the solvothermal method in one step with harmless and inexpensive regents, and they were used to label monoclonal antibodies (mAbs) of AMD in microwells with electrostatic adsorption. Then, a magnetic immunochromatography assay (MICA) method was successfully established. Under optimal conditions, the MICA showed a good performance, with a linear range of 0.2~10.0 µg/L. The limit of detection (LOD) was 0.068 µg/L with the instrument, and the visual LOD (vLOD) was 0.5 µg/L. There was no cross-reaction with rimantadine and ribavirin. The vLOD in real samples was 1.0 µg/kg. The developed MICA has the advantages of convenience, speed, and sensitivity, which make it suitable for the on-site rapid detection of AMD residues in chicken tissues and eggs.

Quantitative Rapid Magnetic Immunoassay for Sensitive Toxin Detection in Food: Non-Covalent Functionalization of Nanolabels vs. Covalent Immobilization

In this study, we present a novel and ultrasensitive magnetic lateral flow immunoassay (LFIA) tailored for the precise detection of zearalenone, a mycotoxin with significant implications for human and animal health. A versatile and straightforward method for creating non-covalent magnetic labels is proposed and comprehensively compared with a covalent immobilization strategy. We employ the magnetic particle quantification (MPQ) technique for precise detection of the labels and characterization of their functionality, including measuring the antibody sorption density on the particle surface. Through kinetic studies using the label-free spectral phase interferometry, the rate and equilibrium constants for the binding of monoclonal antibodies with free (not bound with carrier protein) zearalenone were determined to be kon = 3.42 × 105 M-1s-1, koff = 7.05 × 10-4 s-1, and KD = 2.06 × 10-9 M. The proposed MPQ-LFIA method exhibits detection limits of 2.3 pg/mL and 7.6 pg/mL when employing magnetic labels based on covalent immobilization and non-covalent sorption, with dynamic ranges of 5.5 and 5 orders, correspondingly. We have successfully demonstrated the effective determination of zearalenone in barley flour samples contaminated with Fusarium graminearum. The ease of use and effectiveness of developed test systems further enhances their value as practical tools for addressing mycotoxin contamination challenges.

Recognition-Activated Primer-Mediated Exponential Rolling Circle Amplification for Signal Probe Production and Ultrasensitive Visual Detection of Ochratoxin A with Nucleic Acid Lateral Flow Strips

We proposed a visual strategy for rapid and ultrasensitive detection of ochratoxin A (OTA) by integration of primer-mediated exponential rolling circle amplification (P-ERCA) with a designed nucleic acid lateral flow strip (LFS). The recognition component was preimmobilized in the tube by hybridization between the immobilized functionalized aptamer and complementary ssDNA. Recognition of OTA induces the release of complementary ssDNA from the tube, which will also act as the primer of the designed P-ERCA. Three nicking sites on the template P-ERCA could contribute to the production of enormous signal probes based on the simultaneous amplification-nicking model, which can be visually measured directly with the constructed nucleic acid LFS. Importantly, the nicked signal probe can also act as the trigger of the new-round RCA, achieving exponential growth of signal probes for measurement and signal enhancement. Taking advantage of the extraordinary amplification efficiency of P-ERCA and the simplicity of LFS, this P-ERCA-LFS method demonstrates ultrasensitive detection of OTA with a visual limit of detection as low as 100 fg/mL for qualitative screening and a limit of detection of 35 fg/mL for semiquantitative analysis. This designed strategy could also be utilized as a universal method for detection of other chemical analytes with the replacement of the aptamer for recognition, and the nucleic acid LFS unit could also be a useful protocol for direct ssDNA analysis.

Isothermal Amplification and Hypersensitive Fluorescence Dual-Enhancement Nucleic Acid Lateral Flow Assay for Rapid Detection of Acinetobacter baumannii and Its Drug Resistance

Acinetobacter baumannii (A. baumannii) is among the main pathogens that cause nosocomial infections. The ability to rapidly and accurately detect A. baumannii and its drug resistance is essential for blocking secondary infections and guiding treatments. In this study, we reported a nucleic acid fluorescent lateral flow assay (NFLFA) to identify A. baumannii and carbapenem-resistant A. baumannii (CRAB) in a rapid and quantitative manner by integrating loop-mediated isothermal amplification (LAMP) and silica-based multilayered quantum dot nanobead tag (Si@MQB). First, a rapid LAMP system was established and optimised to support the effective amplification of two bacterial genes in 35 min. Then, the antibody-modified Si@MQB was introduced to capture the two kinds of amplified DNA sequences and simultaneously detect them on two test lines of a LFA strip, which greatly improved the detection sensitivity and stability of the commonly used AuNP-based nucleic acid LFA. With these strategies, the established LAMP-NFLFA achieved detection limits of 199 CFU/mL and 287 CFU/mL for the RecA (house-keeping gene) and blaOXA-23 (drug resistance gene) genes, respectively, within 43 min. Furthermore, the assay exhibited good repeatability and specificity for detecting target pathogens in real complex specimens and environments; thus, the proposed assay undoubtedly provides a promising and low-cost tool for the on-site monitoring of nosocomial infections.

Advancing Mycotoxin Detection: Multivariate Rapid Analysis on Corn Using Surface Enhanced Raman Spectroscopy (SERS)

Mycotoxin contamination on food and feed can have deleterious effect on human and animal health. Agricultural crops may contain one or more mycotoxin compounds; therefore, a good multiplex detection method is desirable to ensure food safety. In this study, we developed a rapid method using label-free surface-enhanced Raman spectroscopy (SERS) to simultaneously detect three common types of mycotoxins found on corn, namely aflatoxin B1 (AFB1), zearalenone (ZEN), and ochratoxin A (OTA). The intrinsic chemical fingerprint from each mycotoxin was characterized by their unique Raman spectra, enabling clear discrimination between them. The limit of detection (LOD) of AFB1, ZEN, and OTA on corn were 10 ppb (32 nM), 20 ppb (64 nM), and 100 ppb (248 nM), respectively. Multivariate statistical analysis was used to predict concentrations of AFB1, ZEN, and OTA up to 1.5 ppm (4.8 µM) based on the SERS spectra of known concentrations, resulting in a correlation coefficient of 0.74, 0.89, and 0.72, respectively. The sampling time was less than 30 min per sample. The application of label-free SERS and multivariate analysis is a promising method for rapid and simultaneous detection of mycotoxins in corn and may be extended to other types of mycotoxins and crops.

Aflatoxin detection technologies: recent advances and future prospects

Aflatoxins have posed serious threat to food safety and human health. Therefore, it is important to detect aflatoxins in samples rapidly and accurately. In this review, various technologies to detect aflatoxins in food are discussed, including conventional ones such as thin-layer chromatography (TLC), high performance liquid chromatography (HPLC), enzyme linked immunosorbent assay (ELISA), colloidal gold immunochromatographic assay (GICA), radioimmunoassay (RIA), fluorescence spectroscopy (FS), as well as emerging ones (e.g., biosensors, molecular imprinting technology, surface plasmon resonance). Critical challenges of these technologies include high cost, complex processing procedures and long processing time, low stability, low repeatability, low accuracy, poor portability, and so on. Critical discussion is provided on the trade-off relationship between detection speed and detection accuracy, as well as the application scenario and sustainability of different technologies. Especially, the prospect of combining different technologies is discussed. Future research is necessary to develop more convenient, more accurate, faster, and cost-effective technologies to detect aflatoxins.

A label-free fluorescent aptasensor based on a novel exponential rolling circle amplification for highly sensitive ochratoxin A detection

Rapid and sensitive analysis of ochratoxin A (OTA) plays an important role in food safety. Here, an aptasensor based on novel exponential rolling circle amplification (ERCA) was proposed for ultrasensitive and label-free fluorescence detection of OTA. The attachment of OTA to its aptamer could release H and rapidly hybridize with CT to initiate rolling circle amplification (RCA). The amplicons could further displace H from APH to initiate recycled RCA, achieving exponential growth of amplification products that contained G4 dimers for lighting up ThT. Benefiting from the exponential amplification efficiency of the ERCA strategy and the high fluorescence quantum yield of G4 dimer/ThT, this strategy exhibited a wide linear range from 10 fg/mL to 10 ng/mL with a detection limit of 4.3 fg/mL. In addition, the aptasensor displayed satisfactory recoveries in real sample analysis. We believe that this novel aptasensor possesses promising application prospects in food safety and medicine detection.

Experimental Validation and Prediction of Super-Enhancers: Advances and Challenges

Super-enhancers (SEs) are cis-regulatory elements of the human genome that have been widely discussed since the discovery and origin of the term. Super-enhancers have been shown to be strongly associated with the expression of genes crucial for cell differentiation, cell stability maintenance, and tumorigenesis. Our goal was to systematize research studies dedicated to the investigation of structure and functions of super-enhancers as well as to define further perspectives of the field in various applications, such as drug development and clinical use. We overviewed the fundamental studies which provided experimental data on various pathologies and their associations with particular super-enhancers. The analysis of mainstream approaches for SE search and prediction allowed us to accumulate existing data and propose directions for further algorithmic improvements of SEs' reliability levels and efficiency. Thus, here we provide the description of the most robust algorithms such as ROSE, imPROSE, and DEEPSEN and suggest their further use for various research and development tasks. The most promising research direction, which is based on topic and number of published studies, are cancer-associated super-enhancers and prospective SE-targeted therapy strategies, most of which are discussed in this review.

Ultra-sensitive determination of Ochratoxin A in coffee and tea samples using a novel semi-automated in-syringe based coagulant-assisted fast mycotoxin extraction (FaMEx) technique coupled with UHPLC-MS/MS

In this study, we demonstrated a novel semi-automated in-syringe-based coagulant-assisted liquid-liquid microextraction (IS-CGA-LLME) as fast mycotoxin extraction (FaMEx) technique coupled with ultra-high-performance liquid chromatography connected with a tandem-mass spectrometer (UHPLC-MS/MS) for the quantification of mycotoxin (Ochratoxin A, OT-A) in coffee and tea samples. IS-CGA-LLME is a three-step extraction process that includes extraction of OT-A from sample matrix using low-volume solvent extraction, then the extractant was cleaned-up using a coagulation process, and finally, the decolorized/matrix removed sample solution was processed for LLME for target analyte's pre-concentration. The final extractant was analyzed using UHPLC-MS/MS for OT-A quantification. Under the optimized experimental conditions, highly sensitive detection and quantification limits were obtained at 0.001 and 0.003 ng g^-1 for OT-A with excellent extraction recovery (93-111%) and precision <10%. These results proved that the developed method is a simple, highly sensitive, semi-automated, low-matrix effect and efficient procedure for the determination of mycotoxins in food samples.

Latest strategies for rapid and point of care detection of mycotoxins in food: A review

Mycotoxins contaminated in agricultural products are often highly carcinogenic and genotoxic to humans. With the streamlining of the food industry chain and the improvement of food safety requirements, the traditional laboratory testing mode is constantly challenged due to the expensive equipment, complex operation steps, and lag in testing results. Therefore, rapid detection methods are urgently needed in the food safety system. This review focuses on the latest strategies that can achieve rapid and on-site testing, with particular attention to the nanomaterials integrated biosensors. To provide researchers with the latest trends and inspiration in the field of rapid detection, we summarize several strategies suitable for point of care testing (POCT) of mycotoxins, including enzyme-linked immunoassay (ELISA), lateral flow assay (LFA), fluorescence, electrochemistry, and colorimetry assay. POCT-based strategies are all developing towards intelligence and portability, especially when combined with smartphones, making it easier to read signals for intuitive access and analysis of test data. Detection performance of the devices has also improved considerably with the integration of biosensors and nanomaterials.

A SERS-based lateral flow immunochromatographic assay using Raman reporter mediated-gap AuNR@Au nanoparticles as the substrate for the detection of enrofloxacin in food samples

A lateral flow immunochromatographic assay (LFIA) based on surface-enhanced Raman scattering (SERS) for sensitive and specific detection of antibiotic enrofloxacin (ENR) in food samples was developed. 1,4-benzenedithiol (BDT) was selected as the Raman reporter, and the BDT mediated-gap AuNR@Au nanoparticles (NPs) were synthesized, characterized and used as the substrate in SERS-LFIA due to the existence of the anisotropic gold nanorods (AuNRs) and the nano-gap with the high SERS enhancement. AuNRs were prepared, then covered by monolayer BDT. Under reduction condition and in presence of HAuCl₄, the reduced gold was deposited and grown on AuNRs to form AuNR^BDT@Au NPs. As the two thiol groups on para-positions in BDT were respectively linked to AuNR (core) and Au (shell), the gap size inside the NPs was uniform. The immunoprobe (e.g. AuNR^BDT@Au-Ab) was obtained by immobilizing Ab against ENR on the surface of AuNR^BDT@Au NPs. The performance of SERS-LFIA was similar to that in colloidal gold based-LFIA, and the entire assay time was within 15 min. After LFIA procedures, the specific SERS intensity of BDT at 1560 cm^-1 on the test line was measured for the quantitative detection of ENR. The IC₅₀ and limit of detection (LOD) of the LFIA for ENR were 59 pg mL^-1 and 0.12 pg mL^-1 (e.g. 71 pg g^-1 and 0.14 pg g^-1 in real sample), respectively. There was no cross-reactivity (CR) of the LFIA with other five antibiotics. The recoveries of ENR from spiked food samples were in range of 89.2%-102.4% with the relative standard deviation (RSD) of 1.70%-6.38%. It was proven that the proposed method was able to simply and rapidly detect ENR in food samples with high sensitivity, specificity, accuracy and precision. The platform can be also an alternative platform for the detection of other target analytes using corresponding Abs.

Magnetic Nanoseparation Technology for Efficient Control of Microorganisms and Toxins in Foods: A Review

Outbreaks of foodborne diseases mediated by food microorganisms and toxins remain one of the leading causes of disease and death worldwide. It not only poses a serious threat to human health and safety but also imposes a huge burden on health care and socioeconomics. Traditional methods for the removal and detection of pathogenic bacteria and toxins in various samples such as food and drinking water have certain limitations, requiring a rapid and sensitive strategy for the enrichment and separation of target analytes. Magnetic nanoparticles (MNPs) exhibit excellent performance in this field due to their fascinating properties. The strategy of combining biorecognition elements with MNPs can be used for fast and efficient enrichment and isolation of pathogens. In this review, we describe new trends and practical applications of magnetic nanoseparation technology in the detection of foodborne microorganisms and toxins. We mainly summarize the biochemical modification and functionalization methods of commonly used magnetic nanomaterial carriers and discuss the application of magnetic separation combined with other instrumental analysis techniques. Combined with various detection techniques, it will increase the efficiency of detection and identification of microorganisms and toxins in rapid assays.

Kinetic Analysis of Prostate-Specific Antigen Interaction with Monoclonal Antibodies for Development of a Magnetic Immunoassay Based on Nontransparent Fiber Structures

Prostate cancer is the second most common cancer diagnosed in men worldwide. Measuring the prostate-specific antigen (PSA) is regarded as essential during prostate cancer screening. Early diagnosis of this disease relapse after radical prostatectomy requires extremely sensitive methods. This research presents an approach to development of an ultrasensitive magnetic sandwich immunoassay, which demonstrates the limit of PSA detection in human serum of 19 pg/mL at a dynamic range exceeding 3.5 orders of concentration. Such attractive performance stems, inter alia, from the kinetic analysis of monoclonal antibodies (mAbs) against free PSA to select the mAbs exhibiting best kinetic characteristics and specificity. The analysis is carried out with a label-free multiplex spectral-correlation interferometry compatible with inexpensive single-use glass sensor chips. The high sensitivity of developed PSA immunoassay is due to electronic quantification of magnetic nanolabels functionalized by the selected mAbs and three-dimension porous filters used as an extended solid phase. The assay is promising for PSA monitoring after radical prostatectomy. The proposed versatile approach can be applied for the rational design of highly sensitive tests for detection of other analytes in many fields, including in vitro diagnostics, veterinary, food safety, etc.

Highly Sensitive Nanomagnetic Quantification of Extracellular Vesicles by Immunochromatographic Strips: A Tool for Liquid Biopsy

Extracellular vesicles (EVs) are promising agents for liquid biopsy-a non-invasive approach for the diagnosis of cancer and evaluation of therapy response. However, EV potential is limited by the lack of sufficiently sensitive, time-, and cost-efficient methods for their registration. This research aimed at developing a highly sensitive and easy-to-use immunochromatographic tool based on magnetic nanoparticles for EV quantification. The tool is demonstrated by detection of EVs isolated from cell culture supernatants and various body fluids using characteristic biomarkers, CD9 and CD81, and a tumor-associated marker-epithelial cell adhesion molecules. The detection limit of 3.7 × 105 EV/µL is one to two orders better than the most sensitive traditional lateral flow system and commercial ELISA kits. The detection specificity is ensured by an isotype control line on the test strip. The tool's advantages are due to the spatial quantification of EV-bound magnetic nanolabels within the strip volume by an original electronic technique. The inexpensive tool, promising for liquid biopsy in daily clinical routines, can be extended to other relevant biomarkers.

Multiplex Label-Free Kinetic Characterization of Antibodies for Rapid Sensitive Cardiac Troponin I Detection Based on Functionalized Magnetic Nanotags

Express and highly sensitive immunoassays for the quantitative registration of cardiac troponin I (cTnI) are in high demand for early point-of-care differential diagnosis of acute myocardial infarction. The selection of antibodies that feature rapid and tight binding with antigens is crucial for immunoassay rate and sensitivity. A method is presented for the selection of the most promising clones for advanced immunoassays via simultaneous characterization of interaction kinetics of different monoclonal antibodies (mAb) using a direct label-free method of multiplex spectral correlation interferometry. mAb-cTnI interactions were real-time registered on an epoxy-modified microarray glass sensor chip that did not require activation. The covalent immobilization of mAb microdots on its surface provided versatility, convenience, and virtually unlimited multiplexing potential. The kinetics of tracer antibody interaction with the “cTnI—capture antibody” complex was characterized. Algorithms are shown for excluding mutual competition of the tracer/capture antibodies and selecting the optimal pairs for different assay formats. Using the selected mAbs, a lateral flow assay was developed for rapid quantitative cTnI determination based on electronic detection of functionalized magnetic nanoparticles applied as labels (detection limit—0.08 ng/mL, dynamic range > 3 orders). The method can be extended to other molecular biomarkers for high-throughput screening of mAbs and rational development of immunoassays.