The Preparation and Identification of a Monoclonal Antibody against Domoic Acid and Establishment of Detection by Indirect Competitive ELISA

Rapid determination of domoic acid in seafood by fluorescence polarization immunoassay using a portable analyzer

Monitoring phycotoxin accumulation in marine products such as edible shellfish is a regulatory requirement in many countries. Therefore, a simple and rapid onsite quantification method is sought. Herein, we present a fluorescence polarization immunoassay (FPIA), a well-known one-step immunoassay, using a portable fluorescence polarization analyzer for domoic acid (DA), widely referred to as the primary toxin of amnesic shellfish poisoning (ASP). To establish FPIA for DA, the matrix effect of methanol, which is widely used to extract DA from shellfish, on FPIA was investigated. To validate this method, we performed a spike recovery test using oysters containing DA at a concentration equivalent to the regulatory limits of North America and the European Union (20 mg/kg). The recovery rate was found to be 79.4-114.7%, which is equivalent to that of the commercially available enzyme-linked immunosorbent assay (ELISA). We expect that this FPIA system will enable the quantitative onsite analysis of DA and significantly contribute to the safety of marine products.

Palladium nanoclusters as a label to determine GFAP in human serum from donors with stroke by bimodal detection: inductively coupled plasma-mass spectrometry and linear sweep voltammetry

Water-soluble, stable, and monodisperse palladium nanoclusters (PdNCs) were synthesized using NaBH4 as a reductant and lipoic acid as a ligand. PdNCs, measured by high-resolution transmission electron microscopy, showed a round shape and a diameter of 2.49 ± 0.02 nm. It was found that each PdNC contains 550 Pd atoms on average. These PdNCs offer high amplification as a label of biochemical reactions when inductively coupled plasma-mass spectrometry (ICP-MS) is used as a detector. In addition, PdNCs have catalytic activity on electrochemical reactions, allowing detection by linear sweep voltammetry (LSV). As a proof of applicability, a competitive immunoassay based on PdNC labels was developed for the determination of glial fibrillary acidic protein (GFAP) in human serum, comparing ICP-MS and LSV detection. GFAP is a biomarker for differentiating between patients with ischemic stroke (IS) and hemorrhagic stroke (HS). The limit of detection (LoD), corresponding to IC10 (4-parameter logistic curve), was 0.03 pM of GFAP, both by ICP-MS and LSV, being lower than the 0.31 pM LoD provided by the ELISA commercial kit. Using the error profile method, 0.03 pM and 0.11 pM LoDs were obtained respectively by ICP-MS and LSV: LoD is lower by ICP-MS due to the better precision of the measurements. The analyses of human serum samples from IS, HS, and control (CT) donors using PdNC labels and detection by ICP-MS and LSV were validated with a commercial ELISA kit (for CT donors only ICP-MS provided enough sensitivity). Results point out toward the future use of PdNCs as a label in other immunoprobes for the determination of specific proteins requiring very low LoDs as well as the development of electrochemical decentralized methodologies.

Development and In-House Validation of an Enzyme-Linked Immunosorbent Assay and a Lateral Flow Immunoassay for the Dosage of Tenofovir in Human Saliva

Highly active antiretroviral therapy (HAART) includes very potent drugs that are often characterized by high toxicity. Tenofovir (TFV) is a widely used drug prescribed mainly for pre-exposure prophylaxis (PreP) and the treatment of human immunodeficiency virus (HIV). The therapeutic range of TFV is narrow, and adverse effects occur with both underdose and overdose. The main factor contributing to therapeutic failure is the improper management of TFV, which may be caused by low compliance or patient variability. An important tool to prevent inappropriate administration is therapeutic drug monitoring (TDM) of compliance-relevant concentrations (ARCs) of TFV. TDM is performed routinely using time-consuming and expensive chromatographic methods coupled with mass spectrometry. Immunoassays, such as enzyme-linked immunosorbent assays (ELISAs) and lateral flow immunoassays (LFIAs), are based on antibody-antigen specific recognition and represent key tools for real-time quantitative and qualitative screening for point-of-care testing (POCT). Since saliva is a non-invasive and non-infectious biological sample, it is well-suited for TDM. However, saliva is expected to have a very low ARC for TFV, so tests with high sensitivity are required. Here, we have developed and validated a highly sensitive ELISA (IC50 1.2 ng/mL, dynamic range 0.4-10 ng/mL) that allows the quantification of TFV in saliva at ARCs and an extremely sensitive LFIA (visual LOD 0.5 ng/mL) that is able to distinguish between optimal and suboptimal ARCs of TFV in untreated saliva.

Design of a Diagnostic Immunoassay for Aflatoxin M1 Based on a Plant-Produced Antibody

A new green competitive ELISA for aflatoxin M1 quantification in raw milk was developed. This diagnostic tool is based on an anti AFM1 mAb produced by plant molecular farming in alternative to classical systems. Our assay, showing an IC₅₀ below 25 ng/L, fits with the requirements of EU legislation limits for AFM1 (50 ng/L). Optimal accuracy was achieved in correspondence of the decision levels (25 and 50 ng/L), and the assay enabled AFM1 quantification in the range 5-110 ng/L, with limit of detection 3 ng/L. Moreover, to evaluate a real applicability in diagnostics, raw milk-spiked samples were analysed, achieving satisfactory recovery rates of AFM1. In conclusion, an efficient and ready-to-use diagnostic assay for the quantification of aflatoxin M1 in milk, based on a plant-produced recombinant mAb, has been successfully developed.

Rapid and sensitive detection of tenuazonic acid in agricultural by-products based on gold nano-flower lateral flow

Tenuazonic acid (TA) is a highly toxic mycotoxin mainly generated by the fungi of Alternaria genus and widely contaminates agricultural by-products. Given the threat of TA to food-security, it is very important to develop rapid and sensitive detection methods for TA monitoring. In this study, gold nano-particles (AuNP) with average diameter near 17.25 nm were prepared, and the developed AuNP-based strip has an assay time of 15 min with visual limit of detection (LOD) of 12.5 ng/ml and threshold of 100 ng/ml. To further improve sensitivity, multi-branched gold nano-flowers (AuNF) with average diameter near 50 nm were prepared and characterized by UV-VIS and TEM, and the established AuNF-based strip has visual LOD of 0.78 ng/ml and threshold of 50 ng/ml within 15 min. Both assays were applied to determine TA in apple juice and tomato ketchup, and the results were consistent with that of UHPLC-MS/MS. Thus, these assays could be applied for rapid determination of trace TA in real samples.

Rapid electrochemical detection of domoic acid based on polydopamine/reduced graphene oxide coupled with in-situ imprinted polyacrylamide

Domoic acid, namely amnesic shellfish toxin, is a highly neurotoxic substance to marine animals and humankind. To reduce the incidence of poisoning accidents, the exploitation of specific and rapid detection method for domoic acid monitoring is highly required. Herein, an electrochemical molecularly imprinted polymer (MIP) sensor based on polydopamine-reduced graphene oxide/polyacrylamide composite (PDA-rGO/PAM) was constructed successfully to detect domoic acid. The domoic acid molecule could be recognized in imprinted cavities of PAM reversibly through hydrogen bonding. PDA-rGO promoted the loading capacity of PAM and improved the charge transfer rate, which amplified the electrical signal response of the MIP sensor. The screen-printed electrode (SPE) modified with PDA-rGO/PAM displayed satisfactory response toward toxin contaminated sample at a linear range from 1 to 600 nM and a low detection limit of 0.31 nM, demonstrating the prospective application of the transducer as a portable sensing platform for the on-site detection of hazardous marine biotoxin. Moreover, benefiting from the superior specificity and stability of MIP, the fabricated sensor could be utilized to detect the domoic acid content in mussel extracts directly without complex pretreatment operation.

High affinity monoclonal antibody targeting Siglec-15 for cancer immunotherapy

BACKGROUND AND AIM

Recently, Siglec-15 has been proved as a novel immune suppressor and a potential target for normalization cancer immunotherapy, which is non-redundant to the well-known PD-L1/PD-1 pathway. Herein, anti-Siglec-15 mAb, a monoclonal antibody (mAb) with a high affinity against Siglec-15, was prepared.

METHODS

The engineered CHO-K1 Siglec-15 cell line was constructed to heterologously expressed Siglec-15 for the affinity test with the mAb. Antigens Siglec-15-mIgG and Siglec-15-his were recombinantly expressed by 293F cells and purified by high-performance liquid chromatography (HPLC). Hybridoma cell line against Siglec-15 was prepared and validated by enzyme-linked immunoabsorbant assay (ELISA) and fluorescent-activated cell sorting (FACS). Finally, the anti-Siglec-15 mAb was produced, purified, and confirmed by SDS-PAGE, ELISA, and FACS.

RESULTS

The EC₅₀ of the anti-Siglec-15 mAb with Siglec-15 is 76.65 ng/mL, lower than that of the positive control 5G12 (90.7 ng/mL), indicating a high affinity of the anti-Siglec-15 mAb. In vitro and in vivo studies verified that the anti-Siglec-15 mAb blocks the Siglec-15-mediated suppression of T cell and moderately prevents the tumor growth.

CONCLUSIONS

The anti-Siglec-15 mAb can be considered as an effective immunotherapy for tumor suppression.

RELEVANCE FOR PATIENTS

The anti-Siglec-15 mAb prepared in this study is useful as an immune checkpoint inhibitor against Siglec-15 for normalization cancer immunotherapy. This immunotherapy provides an alternative treatment for cancer patients who are refractory to the well-known PD-L1/PD-1-targeting therapies.

Molecularly imprinted nanoparticle-based assay (MINA): Potential application for the detection of the neurotoxin domoic acid

Domoic acid (DA) is a natural amino acid and water-soluble neurotoxic biotoxin primarily produced by the microalgae Pseudo-nitzschia. DA can cause poisoning in humans and a wide variety of marine species. In this work, a molecularly imprinted nanoparticle-based assay (MINA) was developed as an alternative to enzyme-linked immunosorbent assay (ELISA) for selective detection of DA. In contrast with ELISA, MINA uses molecularly imprinted polymer nanoparticles (nanoMIPs) as plastic antibodies due to its higher stability and lower production costs. In this work, dihydrokainic acid (DKA) was used as a dummy template because this molecule is structurally similar to DA but less toxic. The developed MINA had a high linear response for DKA and DA, showing detection limits of 2.12 nmol L^-1 and 4.32 nmol L^-1, respectively. Additionally, q-RMN studies demonstrated that DKA - nanoMIPs were selective for DKA, since they presented the best association parameters with a high loading load capacity of 175% and an association efficiency of 18%. No cross-reactivity towards 1, 3, 5 - pentanetricarboxylic acid was observed. These results suggest that MINA could be a more robust, more sensitive, and less expensive alternative to ELISA. The assay developed with DKA - nanoMIPs has strong potential for the detection of domoic acid in real samples of red tide.

A high sensitive platinum-modified colloidal gold immunoassay for tenuazonic acid detection based on monoclonal IgG

Due to the threat of tenuazonic acid (TA) to public health, it is urgent to establish rapidly effective and sensitive assay methods for TA. In this study, a TA-specific IgG monoclonal antibody (McAb) with high affinity (Kaff was 1.72 × 10¹⁰ L/mol) was screened, and the developed icELISA for TA detection has IC₅₀ of 2.50 ng/mL and LOD of 0.17 ng/mL. Platinum-modified gold nanoparticle (Au@PtNP) was optimized as Au@Pt_0.4NP, and the resulted Au@Pt_0.4NP-McAb probe was designed to catalyze precipitation-type tetramethylbenzidine for visual detection of trace TA with visual LOD of 0.39 ng/mL. The sensitivity of this established Au@Pt_0.4NP-McAb strip was highly increased when compared with the existing colloidal gold strip. The developed strip was used to detect trace TA in apple juice and tomato ketchup which were consistent with the results from UHPLC-MS/MS. Therefore, this developed strip could be used for rapid detection of trace TA in real samples.

Current Trends and Challenges for Rapid SMART Diagnostics at Point-of-Site Testing for Marine Toxins

In the past twenty years marine biotoxin analysis in routine regulatory monitoring has advanced significantly in Europe (EU) and other regions from the use of the mouse bioassay (MBA) towards the high-end analytical techniques such as high-performance liquid chromatography (HPLC) with tandem mass spectrometry (MS). Previously, acceptance of these advanced methods, in progressing away from the MBA, was hindered by a lack of commercial certified analytical standards for method development and validation. This has now been addressed whereby the availability of a wide range of analytical standards from several companies in the EU, North America and Asia has enhanced the development and validation of methods to the required regulatory standards. However, the cost of the high-end analytical equipment, lengthy procedures and the need for qualified personnel to perform analysis can still be a challenge for routine monitoring laboratories. In developing regions, aquaculture production is increasing and alternative inexpensive Sensitive, Measurable, Accurate and Real-Time (SMART) rapid point-of-site testing (POST) methods suitable for novice end users that can be validated and internationally accepted remain an objective for both regulators and the industry. The range of commercial testing kits on the market for marine toxin analysis remains limited and even more so those meeting the requirements for use in regulatory control. Individual assays include enzyme-linked immunosorbent assays (ELISA) and lateral flow membrane-based immunoassays (LFIA) for EU-regulated toxins, such as okadaic acid (OA) and dinophysistoxins (DTXs), saxitoxin (STX) and its analogues and domoic acid (DA) in the form of three separate tests offering varying costs and benefits for the industry. It can be observed from the literature that not only are developments and improvements ongoing for these assays, but there are also novel assays being developed using upcoming state-of-the-art biosensor technology. This review focuses on both currently available methods and recent advances in innovative methods for marine biotoxin testing and the end-user practicalities that need to be observed. Furthermore, it highlights trends that are influencing assay developments such as multiplexing capabilities and rapid POST, indicating potential detection methods that will shape the future market.

Recent progress in micro/nano biosensors for shellfish toxin detection

Shellfish toxins, as one kind of marine toxin, have attracted worldwide attention due to their severe threat to food safety and human health. Therefore, it is highly essential and urgent to develop a low-cost and convenient method to detect these toxins. With the rapid advance in microfabrication processes, micro/nano biosensors provide novel approaches to address this issue. In addition to their features of low cost, portability, easy operation, high efficiency and high bioactivity, micro/nano biosensors have great potential to realize on-the-spot, rapid detection of shellfish toxins. This review focuses on the most recent advances in the development of micro/nano biosensors for shellfish toxin detection. These biosensors are mainly classified into five categories according to their transducer detection principles, which include optical devices, electrochemical sensors, electrochemiluminescence, field-effect transistors, and acoustic devices. Sensor strategies, toxin analytes, biosensitive elements, coupling methods and field detection performance are highlighted to discuss the applications of shellfish toxin detection. With advances in sensor technology, biomaterials, microfabrication and miniaturized electronics, micro/nano biosensors applied to in-field fast detection of shellfish toxins are expected to play a critical role in food safety, environmental monitoring, and foreign trade in the foreseeable future. Finally, the current challenges and future development trends of micro/nano biosensors for shellfish toxin detection are discussed.

A McAb-Based Direct Competitive ELISA to Detect O:9 Salmonella Infection in Chicken

Salmonella enteritidis and Salmonella pullorum belonging to Group O₉Salmonella are major causative agents of infectious diseases in chicken. O₉ antigen as a part of lipopolysaccharide (LPS) is a predominant detected target for Salmonella infection. To identify the infection, an anti-O₉ monoclonal antibody (McAb)-based direct competitive enzyme-linked assay (O₉ Dc-ELISA) was developed after constraints were optimized; the establishment and application of O₉ Dc-ELISA, compared to two commercial kits and plate agglutination test (PAT), showed that O₉ Dc-ELISA could screen out more positive samples than the PAT method could and produce the same agreement rates with commercial kits in terms of sensitivity in addition to strong specificity to clinical serum samples.

Enzyme Immunoassay for Measuring Aflatoxin B1 in Legal Cannabis

The diffusion of the legalization of cannabis for recreational, medicinal and nutraceutical uses requires the development of adequate analytical methods to assure the safety and security of such products. In particular, aflatoxins are considered to pose a major risk for the health of cannabis consumers. Among analytical methods that allows for adequate monitoring of food safety, immunoassays play a major role thanks to their cost-effectiveness, high-throughput capacity, simplicity and limited requirement for equipment and skilled operators. Therefore, a rapid and sensitive enzyme immunoassay has been adapted to measure the most hazardous aflatoxin B1 in cannabis products. The assay was acceptably accurate (recovery rate: 78–136%), reproducible (intra- and inter-assay means coefficients of variation 11.8% and 13.8%, respectively), and sensitive (limit of detection and range of quantification: 0.35 ng mL⁻¹ and 0.4–2 ng mL⁻¹, respectively corresponding to 7 ng g⁻¹ and 8–40 ng g⁻¹ ng g⁻¹ in the plant) and provided results which agreed with a HPLC-MS/MS method for the direct analysis of aflatoxin B1 in cannabis inflorescence and leaves. In addition, the carcinogenic aflatoxin B1 was detected in 50% of the cannabis products analyzed (14 samples collected from small retails) at levels exceeding those admitted by the European Union in commodities intended for direct human consumption, thus envisaging the need for effective surveillance of aflatoxin contamination in legal cannabis.

Development of an ic-ELISA and immunochromatographic strip based on IgG antibody for detection of ω-conotoxin MVIIA

ω-conotoxin MVIIA(ω-CTX MVIIA) is a peptide consisting of 25 amino acid residues secreted mainly by Conus magus. In view of the toxin threat to humans and animals and defined application in analgesic therapy, it is necessary to develop a rapid, effective and accuracy method for the quantification and analysis of ω-CTX MVIIA in real samples. In the present study, a hybridoma cell named 2E5 stable secreting IgG antibody against ω-CTX MVIIA was selected successfully, and the subtype of Mab 2E5 was IgG1. The purified monoclonal antibody(Mab) 2E5 has high affinity (about 2.79 × 10⁹ L/mol), and shows high specificity to ω-CTX MVIIA antigen. The linear range of ic-ELISA to detect ω-CTX MVIIA was 0.20˜7.22 μg/mL, with a lower detection limit (LOD) of 0.14 ng/mL. The average recovery of intra- and inter-assay were (85.45 ± 2.28)% and (88.03 ± 4.80)% respectively, with a coefficient of variation from 2.59% to 5.42%. The LOD of colloidal strip by naked eye was 1 μg/mL, and the detection time was less than 10 min without any equipment. The developed ELISA and colloidal test strips based on this IgG antibody could be used to detect ω-CTX MVIIA residue in real Conus samples.