Multiplex Lateral Flow Assay and the Sample Preparation Method for the Simultaneous Detection of Three Marine Toxins

Aptamer-antibody sandwich lateral flow test for rapid visual detection of tetrodotoxin in pufferfish

Tetrodotoxin (TTX) is a highly potent marine toxin which can cause severe poisoning following consumption of contaminated fish and seafood. Thus, a sensitive, reliable and simple test is required for rapid screening of samples and prevention of intoxication. Herein, we translated a previously reported microtiter plate hybrid aptamer-antibody assay into a rapid lateral flow assay (LFA) test. The test relies on an aptamer immobilized on the membrane and an antibody conjugated with gold nanoparticles to provide a visual result when TTX is present in the sample. The optimized test is simple (one-step), rapid (<20 min), highly sensitive (visual limit of detection of 0.3 ng/mL TTX in buffer corresponding to 0.78 mg TTX/kg tissue), specific, reproducible and with long storage life. It was validated by analyzing contaminated pufferfish tissue extracts and it successfully detected TTX below the current limits set by official bodies. The analysis performed with this device in combination with a simple LFA reader for quantification was in excellent agreement with other established methods, further demonstrating the value of this test as a simple, low-cost and reliable analytical tool to ensure food safety, protect human health, and broaden the knowledge on the correlation between biological parameters and environmental data.

Past, Current and Future Techniques for Monitoring Paralytic Shellfish Toxins in Bivalve Molluscs

Paralytic shellfish poisoning is a threat to human health caused by the consumption of shellfish contaminated with toxins of the saxitoxin class. Human health is protected by the setting of regulatory limits and the analysis of shellfish prior to sale. Both robust toxicity data, generated from experiments fitting into the ethical 3R framework, and appropriate analysis methods are required to ensure the success of this approach. A literature review of in vivo animal bioassays and in vitro and analytical methods showed that in vitro methods are the best option to screen shellfish for non-regulatory purposes. However, since neither the receptor nor antibody binding of paralytic shellfish toxin analogues correlate with toxicity, these assays cannot accurately quantify toxicity in shellfish nor be used to calculate toxicity equivalence factors. Fully replacing animals in testing is rightfully the ultimate goal, but this cannot be at a cost to human health. More modern technology, such as organ-on-a-chip, represent an exciting development, but animal bioassays cannot currently be replaced in the determination of toxicity. Analytical methods that employ toxicity equivalence factors calculated using oral animal toxicity data result in an accurate assessment of the food safety risk posed by paralytic shellfish toxin contamination in bivalve molluscs.

Ultrasensitive "Hunter of Target": Rabbit Monoclonal Antibody-Based Competitive Lateral Flow Immunoassay for Saxitoxin

The rapid, sensitive, and accurate detection of paralytic shellfish toxins (PSTs), such as saxitoxin (STX), is critical for protecting human health due to the frequent occurrence of toxic red tides. In this work, to address the low affinity of traditional mouse monoclonal antibodies (m-mAbs), rabbit monoclonal antibodies (r-mAbs) against STX were produced by a single B-cell sorting culture and a cross-selection strategy. The r-mAbs showed 100-fold improvement in sensitivity (IC50 = 0.018 ng/mL), improved stability under strong acid/alkali resistance (pH = 3-12), and high tolerance to organic solvent (MOH, 30%) in comparison with m-mAbs. The structural analysis of PSTs shows that the r-mAbs primarily interacted with common functional groups in PSTs, including guanidine, amide, and alcoholic hydroxyl groups (-OH). R-mAbs3C3 recognized STX, GTX2/3, C1/C2, NEO, and dcSTX with broad specificity through hydrogen bonding facilitated by Asp93, Gln27, Ser27A, and Asp95 in the complementarity-determining region (CDR) pocket. In contrast, r-mAbs3C7 displayed high specificity for STX, mediated by Ser98, Leu96, Ser30, Tyr97, and Ser53, which formed hydrogen bonds and hydrophobic interactions. The lack of interaction with Asp93 and Asp95 in r-mAbs3C7 likely contributed to its enhanced specificity. The anti-STX r-mAbs3C3 was then used to develop an ultrasensitive lateral flow immunoassay (LFIA) for the detection of STX with a cutoff value of 100 pg/mL. The LFIA demonstrated recovery rates ranging from 86.6 to 106.3% in food samples (mussels, nassariidae, bullacta exarata, and fresh water). Given its high target selectivity and sensitivity, this study provides a sight for rapid, sensitive, and accurate monitoring of food toxins.

Simultaneous Detection of Five Infectious Diseases in a Single Strip: Oligo dT-Utilized Lateral Flow Immunoassay

The need for accurate and simultaneous diagnosis of multiple respiratory infectious diseases has become increasingly critical due to ongoing viral mutations and the similarity of symptoms among various viruses. Here, we have advanced our detection capabilities by developing a multiplex lateral flow immunoassay (LFA) platform that integrates oligonucleotides and antibodies, enabling the simultaneous detection of five respiratory viruses: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), Influenza A (FluA), Influenza B (FluB), Respiratory syncytial virus (RSV), and Adenovirus (ADV), on a single membrane. By applying the oligonucleotide and antibody-conjugated AuNPs, the platform enables highly sensitive and specific detection. In addition, signal amplification using RPA70A-conjugated gold nanoparticles that developed in the previous study can further be applied optionally for low-concentration biomarkers. Our interferences and cross-reactivity tests confirmed that these complexes do not produce false positives, substantiating the assay's utility in clinical settings. This platform, therefore, provides a robust solution for the precise and rapid diagnosis of complex viral infections, positioning it as suitable for application in pandemic response scenarios.

Multi-dimensional microfluidic paper-based analytical devices (μPADs) for noninvasive testing: A review of structural design and applications

The rapid emergence of microfluidic paper-based devices as point-of-care testing (POCT) tools for early disease diagnosis and health monitoring, particularly in resource-limited areas, holds immense potential for enhancing healthcare accessibility. Leveraging the numerous advantages of paper, such as capillary-driven flow, porous structure, hydrophilic functional groups, biodegradability, cost-effectiveness, and flexibility, it has become a pivotal choice for microfluidic substrates. The repertoire of microfluidic paper-based devices includes one-dimensional lateral flow assays (1D LFAs), two-dimensional microfluidic paper-based analytical devices (2D μPADs), and three-dimensional (3D) μPADs. In this comprehensive review, we provide and examine crucial information related to paper substrates, design strategies, and detection methods in multi-dimensional microfluidic paper-based devices. We also investigate potential applications of microfluidic paper-based devices for detecting viruses, metabolites and hormones in non-invasive samples such as human saliva, sweat and urine. Additionally, we delve into capillary-driven flow alternative theoretical models of fluids within the paper to provide guidance. Finally, we critically examine the potential for future developments and address challenges for multi-dimensional microfluidic paper-based devices in advancing noninvasive early diagnosis and health monitoring. This article showcases their transformative impact on healthcare, paving the way for enhanced medical services worldwide.

Tetrodotoxin and the state-of-the-art progress of its associated analytical methods

Tetrodotoxin (TTX), which is found in various marine organisms, including pufferfish, shellfish, shrimp, crab, marine gastropods, and gobies, is an effective marine toxin and the cause of many seafood poisoning incidents. Owing to its toxicity and threat to public health, the development of simple, rapid, and efficient analytical methods to detect TTX in various food matrices has garnered increasing interest worldwide. Herein, we reviewed the structure and properties, origin and sources, toxicity and poisoning, and relevant legislative measures of TTX. Additionally, we have mainly reviewed the state-of-the-art progress of analytical methods for TTX detection in the past five years, such as bioassays, immunoassays, instrumental analysis, and biosensors, and summarized their advantages and limitations. Furthermore, this review provides an in-depth discussion of the most advanced biosensors, including cell-based biosensors, immunosensors, and aptasensors. Overall, this study provides useful insights into the future development and wide application of biosensors for TTX detection.

Toward Sensitive and Reliable Immunoassays of Marine Biotoxins: From Rational Design to Food Analysis

Marine biotoxins are metabolites produced by algae that can accumulate in shellfish or fish and enter organisms through the food chain, posing a serious threat to biological health. Therefore, accurate and rapid detection is an urgent requirement for food safety. Although various detection methods, including the mouse bioassay, liquid chromatography-mass spectrometry, and cell detection methods, and protein phosphatase inhibition assays have been developed in the past decades, the current detection methods cannot fully meet these demands. Among these methods, the outstanding immunoassay virtues of high sensitivity, reliability, and low cost are highly advantageous for marine biotoxin detection in complex samples. In this work, we review the recent 5-year progress in marine biotoxin immunodetection technologies such as optical immunoassays, electrochemical immunoassays, and piezoelectric immunoassays. With the assistance of immunoassays, the detection of food-related marine biotoxins can be implemented for ensuring public health and preventing food poisoning. In addition, the immunodetection technique platforms including lateral flow chips and microfluidic chips are also discussed. We carefully investigate the advantages and disadvantages for each immunoassay, which are compared to demonstrate the guidance for selecting appropriate immunoassays and platforms for the detection of marine biotoxins. It is expected that this review will provide insights for the further development of immunoassays and promote the rapid progress and successful translation of advanced immunoassays with food safety detection.

Fortified Dual-Spectral Overlap with Enhanced Colorimetric/Fluorescence Dual-Response Immunochromatography for On-Site Bimodal-Type Gentamicin Monitoring

Immunochromatography (ICA) remains untapped toward enhanced sensitivity and applicability for fulfilling the nuts and bolts of on-site food safety surveillance. Herein, we report a fortified dual-spectral overlap with enhanced colorimetric/fluorescence dual-response ICA for on-site bimodal-type gentamicin (Gen) monitoring by employing polydopamine (PDA)-coated AuNPs (APDA) simultaneously serving as a colorimetric reporter and a fluorescence quencher. Availing of the enhanced colorimetric response that originated from the PDA layer, the resultant APDA exhibits less required antibody and immunoprobes in a single immunoassay, which facilitates improved antibody utilization efficiency and immuno-recognition in APDA-ICA. Further integrated with the advantageous features of fortified excitation and emission dual-spectral overlap for the Arg/ATT-AuNCs, this APDA-ICA with a "turn on/off" pattern achieves the visual limits of detection of 1.0 and 0.5 ng mL-1 for colorimetric and fluorescence patterns (25- and 50-fold lower than standard AuNPs-ICA). Moreover, the excellent self-calibration and satisfactory recovery of 79.03-118.04% were shown in the on-site visual colorimetric-fluorescence analysis for Gen in real environmental media (including real river water, an urban aquaculture water body, an aquatic product, and an animal byproduct). This work provides the feasibility of exploiting fortified dual-spectral overlap with an enhanced colorimetric/fluorescence dual response for safeguarding food safety and public health.

Precautions for seafood consumers: An updated review of toxicity, bioaccumulation, and rapid detection methods of marine biotoxins

Seafood products are globally consumed, and there is an increasing demand for the quality and safety of these products among consumers. Some seafoods are easily contaminated by marine biotoxins in natural environments or cultured farming processes. When humans ingest different toxins accumulated in seafood, they may exhibit different poisoning symptoms. According to the investigations, marine toxins produced by harmful algal blooms and various other marine organisms mainly accumulate in the body organs such as liver and digestive tract of seafood animals. Several regions around the world have reported incidents of seafood poisoning by biotoxins, posing a threat to human health. Thus, most countries have legislated to specify the permissible levels of these biotoxins in seafood. Therefore, it is necessary for seafood producers and suppliers to conduct necessary testing of toxins in seafood before and after harvesting to prohibit excessive toxins containing seafood from entering the market, which therefore can reduce the occurrence of seafood poisoning incidents. In recent years, some technologies which can quickly, conveniently, and sensitively detect biological toxins in seafood, have been developed and validated, these technologies have the potential to help seafood producers, suppliers and regulatory authorities. This article reviews the seafood toxins sources and types, mechanism of action and bioaccumulation of marine toxins, as well as legislation and rapid detection technologies for biotoxins in seafood for official and fishermen supervision.

Evaluation of biotoxins and toxic metal risks in mussels from the Sea of Marmara following marine mucilage

The mucilage phenomenon observed in the Sea of Marmara in 2021, has raised public concern about seafood safety. Mediterranean mussels serve as a vehicle in food chain, enabling the transfer of pollutants. Farmed and wild mussels were collected from 4 different stations throughout the fishing season. Biotoxins causing amnesic, paralytic, or diarrhetic shellfish poisonings (ASP, PSP, or DSP) were examined during monthly samplings. Potential health risks posed by cadmium, lead and arsenic were assessed. Health risks were evaluated considering 150 g/week mussel consumption, accounting for the different age groups of consumers (50, 60, 70 kg). Estimated Weekly Intake calculations of metals were determined to be lower than Provisional Tolerable Weekly Intake at all age groups throughout the sampling period in all stations. Target Hazard QuotientCd of mussels captured from Istanbul Strait was always determined <1, while it was equal to 1 for 50 kg individuals in Gelibolu samples. All THQAs were >1. Target carcinogenic Risk was evaluated for Pb and iAs, which were found to be negligible and acceptable, respectively. No biotoxins responsible for ASP, PSP, or DSP were detected. Hg levels were under detectable limits. Excluding Cd, the results did not reveal any risks associated with mussel consumption during mucilage.

A bispecific nanobody with high sensitivity/efficiency for simultaneous determination of carbaryl and its metabolite 1-naphthol in the soil and rice samples

The simultaneous determination of carbaryl and its metabolite 1-naphthol is essential for risk assessment of pesticide exposure in agricultural and environmental samples. Herein, several bispecific nanobodies (BsNbs) with different lengths of hydrophilic linkers and junction sites were prepared and characterized for the simultaneous recognition of carbaryl and its metabolite 1-naphthol. It was found that the affinity of BsNbs to the analytes could be regulated by controlling linker length and linking terminal. Additionally, molecular simulation revealed that linker lengths affected the conformation of BsNbs, leading to alteration in sensitivity. The BsNb with G4S linker, named G4S-C-N-VHH, showing good thermal stability and sensitivity was used to develop a bispecific indirect competitive enzyme-linked immunosorbent assay (Bic-ELISA). The assay demonstrated a limit of detection of 0.8 ng/mL for carbaryl and 0.4 ng/mL for 1-naphthol in buffer system. Good recoveries from soil and rice samples were obtained, ranging from 80.0% to 112.7% (carbaryl) and 76.5%-110.8% (1-naphthol), respectively. Taken together, this study firstly provided a BsNb with high sensitivity and efficiency against environmental pesticide and its metabolite, and firstly used molecular dynamics simulation to explore the influence of linker on recognition. The results are valuable for the application of immunoassay with high efficiency in the fields of environment and agriculture.

Enhanced sensitivity and accuracy via gold nanoparticles based multi-line lateral flow immunoassay strip for Salmonella typhimurium detection in milk and orange juice

Food borne pathogens threaten food safety and affect human health. The lateral flow immunoassays (LFIAs) are widely concerned because of simplicity, low cost and user friendliness, and have broad application prospects in pathogen detection. However, the sensitivity of LFIAs is limited. Herein, multi-line LFIAs are introduced into pathogen detection for the first time. Compared with traditional single-line LFIAs, the overall signal strength of multi-line LFIAs has been significantly improved. It is particularly noteworthy that multi-line LFIAs detection accuracy of 10³ CFU/mL pathogen has been improved by about 55%. The proposed multi-line LFIAs reduce the possibility of judging a positive result as a false negative result. The LFIAs strip was validated in real samples of milk and orange juice. This strategy has great potential for rapid detection of pathogens in real samples, and provides new insights for improving the accuracy and sensitivity of LFIAs strips.

Variation profile of diarrhetic shellfish toxins and diol esters derivatives of Prorocentrum lima during growth by high-resolution mass spectrometry

Prorocentrum lima is a widely distributed toxigenic benthic dinoflagellate whose production of diarrhetic shellfish toxins threatens the shellfish industry and seafood safety. Current research primarily assesses the difference between free and post-hydrolysis total toxin methods, ignoring the impact of different detection methods on technical accuracy. After removing matrix interference with SPE extraction, a thorough HRMS strategy was created in this study. Alkaline hydrolysis could release the diol esters and played a crucial role in obtaining an accurate assessment of toxin levels, achieving satisfactory recoveries (74.0-147.0%) and repeatability (relative deviation <12.3%). The HRMS approach evaluated toxin profile variation during the growth of three P. lima strains from China. A total of 24 toxin contents varying in composition, content, and a high proportion were detected. The SHG, HN, and 3XS strains had total toxin contents of 23.3 ± 1.74, 19.8 ± 1.25, and 19.5 ± 1.58 pg cell^-1, respectively. The diol esters proportion varied among the strains, with SHG having 58.9-69.9, HN having 75.4-86.5, and 3XS having 91.0-91.7%. The variety of toxins produced by distinct P. lima strains highlighted the significance of this method for appropriately measuring the risks connected with DSTs manufacturing. The proposed approach provides a technical basis for gathering comprehensive and accurate data on the potential risks of P. lima DSTs production, with significant implications for ensuring food safety and preventing harmful toxins from spreading in the marine ecosystem.