Immunorecognition magnetic supports for the development of an electrochemical immunoassay for azaspiracid detection in mussels

A highly sensitive point-of-care detection platform for Salmonella typhimurium by integrating magnetic enrichment and fluorescent CsPbBr3@SiO2

A platform was designed based on Fe3O4 and CsPbBr3@SiO2 for integrated magnetic enrichment-fluorescence detection of Salmonella typhimurium, which significantly simplifies the detection process and enhances the working efficiency. Fe3O4 served as a magnetic enrichment unit for the capture of S. typhimurium. CsPbBr3@SiO2 was employed as a fluorescence-sensing unit for quantitative signal output, where SiO2 was introduced to strengthen the stability of CsPbBr3, improve its biomodificability, and prevent lead leakage. More importantly, the SiO2 shell shows neglectable absorption or scattering towards fluorescence, making the CsPbBr3@SiO2 exhibit a high quantum yield of 74.4%. After magnetic enrichment, the decreasing rate of the fluorescence emission intensity of the CsPbBr3@SiO2 supernatant at 527 nm under excitation light at UV 365 nm showed a strong linear correlation with S. typhimurium concentration of 1 × 102~1 × 108 CFU∙mL-1, and the limit of detection (LOD) reached 12.72 CFU∙mL-1. This platform has demonstrated outstanding stability, reproducibility, and resistance to interference, which provides an alternative for convenient and quantitative detection of S. typhimurium.

Automated Patch Clamp for the Detection of Tetrodotoxin in Pufferfish Samples

Tetrodotoxin (TTX) is a marine toxin responsible for many intoxications around the world. Its presence in some pufferfish species and, as recently reported, in shellfish, poses a serious health concern. Although TTX is not routinely monitored, there is a need for fast, sensitive, reliable, and simple methods for its detection and quantification. In this work, we describe the use of an automated patch clamp (APC) system with Neuro-2a cells for the determination of TTX contents in pufferfish samples. The cells showed an IC50 of 6.4 nM for TTX and were not affected by the presence of muscle, skin, liver, and gonad tissues of a Sphoeroides pachygaster specimen (TTX-free) when analysed at 10 mg/mL. The LOD achieved with this technique was 0.05 mg TTX equiv./kg, which is far below the Japanese regulatory limit of 2 mg TTX equiv./kg. The APC system was applied to the analysis of extracts of a Lagocephalus sceleratus specimen, showing TTX contents that followed the trend of gonads > liver > skin > muscle. The APC system, providing an in vitro toxicological approach, offers the advantages of being sensitive, rapid, and reliable for the detection of TTX-like compounds in seafood.

Current Research Status of Azaspiracids

The presence and impact of toxins have been detected in various regions worldwide ever since the discovery of azaspiracids (AZAs) in 1995. These toxins have had detrimental effects on marine resource utilization, marine environmental protection, and fishery production. Over the course of more than two decades of research and development, scientists from all over the world have conducted comprehensive studies on the in vivo metabolism, in vitro synthesis methods, pathogenic mechanisms, and toxicology of these toxins. This paper aims to provide a systematic introduction to the discovery, distribution, pathogenic mechanism, in vivo biosynthesis, and in vitro artificial synthesis of AZA toxins. Additionally, it will summarize various detection methods employed over the past 20 years, along with their advantages and disadvantages. This effort will contribute to the future development of rapid detection technologies and the invention of detection devices for AZAs in marine environmental samples.

Detection of Ciguatoxins and Tetrodotoxins in Seafood with Biosensors and Other Smart Bioanalytical Systems

The emergence of marine toxins such as ciguatoxins (CTXs) and tetrodotoxins (TTXs) in non-endemic regions may pose a serious food safety threat and public health concern if proper control measures are not applied. This article provides an overview of the main biorecognition molecules used for the detection of CTXs and TTXs and the different assay configurations and transduction strategies explored in the development of biosensors and other biotechnological tools for these marine toxins. The advantages and limitations of the systems based on cells, receptors, antibodies, and aptamers are described, and new challenges in marine toxin detection are identified. The validation of these smart bioanalytical systems through analysis of samples and comparison with other techniques is also rationally discussed. These tools have already been demonstrated to be useful in the detection and quantification of CTXs and TTXs, and are, therefore, highly promising for their implementation in research activities and monitoring programs.

Facile immunochromatographic assay based on metal-organic framework-decorated polydopamine for the determination of hydrochlorothiazide adulteration in functional foods

Herein, a novel immunochromatographic assay (ICA) based on metal-organic framework-decorated polydopamine (MOF@PDA) was firstly developed for the determination of hydrochlorothiazide (HCTZ) adulteration in functional foods. The coupling rate of MOF@PDA carrier to HCTZ antibody was as high as 91.7 %. The detection limits of the developed MOF@PDA-ICA in functional tablets and capsules were 5.93 and 4.72 μg/kg, the linear ranges were 11.2-91.91 μg/kg and 9.11-86.78 μg/kg, respectively. The sensitivity was 27-fold higher than that of the reported ICA. The recovery was 82.5-116.6 %, and coefficient of variation was 6.9-14.2 %. The results can be achieved and analyzed in 8 min with the smartphone-based detection device. The parallel tests of 23 commercial functional tablets and capsules showed that the results of the MOF@PDA-ICA were consistent with that of the LC-MS/MS (R² > 0.99). Therefore, our method is facile, sensitive, portable, and can provide a reliable technical mean for the detection of HCTZ adulteration in functional foods.

Emerging Marine Biotoxins in European Waters: Potential Risks and Analytical Challenges

Harmful algal blooms pose a challenge regarding food safety due to their erratic nature and forming circumstances which are yet to be disclosed. The best strategy to protect human consumers is through legislation and monitoring strategies. Global warming and anthropological intervention aided the migration and establishment of emerging toxin producers into Europe's temperate waters, creating a new threat to human public health. The lack of information, standards, and reference materials delay effective solutions, being a matter of urgent resolution. In this work, the recent findings of the presence of emerging azaspiracids, spirolildes, pinnatoxins, gymnodimines, palitoxins, ciguatoxins, brevetoxins, and tetrodotoxins on European Coasts are addressed. The information concerning emerging toxins such as new matrices, locations, and toxicity assays is paramount to set the risk assessment guidelines, regulatory levels, and analytical methodology that would protect the consumers.

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.

Ensuring seafood safe to spoon: a brief review of biosensors for marine biotoxin monitoring

With harmful algal blooms, marine food poisoning caused by marine biotoxins frequently occurs and is life-threatening if severe. However, the conventional detection methods of marine toxins have a few limitations: low sensitivity and high-cost. Therefore, it is necessary to establish a fast and sensitive on-site detection method for real seafood sample. Biosensors based on aptamers, antibodies, and cells have been applied in marine toxins monitoring. This review presents the classification and toxic effects of marine toxins, and recent biosensor for marine toxin detection. In addition, we have compared the superiority and limitation of these biosensors. Finally, challenges and opportunities of biosensors in food safety detection were discussed. Considering the excellent results achieved by the aptasensor in the field of detection, it seems ready to be put into practical applications.

Magnetic Beads in Marine Toxin Detection: A Review

Due to the expanding occurrence of marine toxins, and their potential impact on human health, there is an increased need for tools for their rapid and efficient detection. We give an overview of the use of magnetic beads (MBs) for the detection of marine toxins in shellfish and fish samples, with an emphasis on their incorporation into electrochemical biosensors. The use of MBs as supports for the immobilization of toxins or antibodies, as signal amplifiers as well as for target pre-concentration, is reviewed. In addition, the exploitation of MBs in Systematic Evolution of Ligands by Exponential enrichment (SELEX) for the selection of aptamers is presented. These MB-based strategies have led to the development of sensitive, simple, reliable and robust analytical systems for the detection of toxins in natural samples, with applicability in seafood safety and human health protection.

Magnetic nanoparticles for smart electrochemical immunoassays: a review on recent developments

This review (with 129 refs) summarizes the progress in electrochemical immunoassays combined with magnetic particles that was made in the past 5 years. The specifity of antibodies linked to electrochemical transduction (by amperometry, voltammetry, impedimetry or electrochemiluminescence) gains further attractive features by introducing magnetic nanoparticles (MNPs). This enables fairly easy preconcentration of analytes, minimizes matrix effects, and introduces an appropriate label. Following an introduction into the fundamentals of electrochemical immunoassays and on nanomaterials for respective uses, a large chapter addresses method for magnetic capture and preconcentration of analytes. A next chapter discusses commonly used labels such as dots, enzymes, metal and metal oxide nanoparticles and combined clusters. The large field of hybrid nanomaterials for use in such immunoassays is discussed next, with a focus on MNPs composites with various kinds of graphene variants, polydopamine, noble metal nanoparticles or nanotubes. Typical applications address clinical markers (mainly blood and urine parameters), diagnosis of cancer (markers and cells), detection of pathogens (with subsections on viruses and bacteria), and environmental and food contaminants as toxic agents and pesticides. A concluding section summarizes the present status, current challenges, and highlights future trends. Graphical abstract Magnetic nanoparticles (MNP) with antibodies (Ab) capture and preconcentrate analyte from sample (a) and afterwards become magnetically (b) or immunospecifically (c) bound at an electrode. Signal either increases due to the presence of alabel (b) or decreases as the redox probe is blocked (c).

A Practical ELISA for Azaspiracids in Shellfish via Development of a New Plate-Coating Antigen

Azaspiracids (AZAs) are a group of biotoxins that appear periodically in shellfish and can cause food poisoning in humans. Current methods for quantifying the regulated AZAs are restricted to LC-MS but are not well suited to detecting novel and unregulated AZAs. An ELISA method for total AZAs in shellfish was reported recently, but unfortunately, it used relatively large amounts of the AZA-1-containing plate-coating conjugate, consuming significant amounts of pure AZA-1 per assay. Therefore, a new plate-coater, OVA-cdiAZA1 was produced, resulting in an ELISA with a working range of 0.30-4.1 ng/mL and a limit of quantification of 37 μg/kg for AZA-1 in shellfish. This ELISA was nearly twice as sensitive as the previous ELISA while using 5-fold less plate-coater. The new ELISA displayed broad cross-reactivity toward AZAs, detecting all available quantitative AZA reference materials as well as the precursors to AZA-3 and AZA-6, and results from shellfish analyzed with the new ELISA showed excellent correlation ( R² = 0.99) with total AZA-1-10 by LC-MS. The results suggest that the new ELISA is suitable for screening samples for total AZAs, even in cases where novel AZAs are present and regulated AZAs are absent, such as was reported recently from Puget Sound and the Bay of Naples.

Self-assembled monolayer-based immunoassays for okadaic acid detection in seawater as monitoring tools

Rapid and cost-effective methods to monitor the presence of diarrhetic shellfish poisoning (DSP) toxins in seawater samples in an easy and reliable manner are required to protect human health and avoid economic losses to shellfish industry. Immunoassays for the detection of okadaic acid (OA) and dinophysistoxin-1 and dinophysistoxin-2 are developed by immobilising OA on self-assembled monothiols or dithiols in an ordered and oriented way, providing an effective limit of detection of ∼1 ng OA equiv./mL seawater. The immunoassays are applied to the analysis of the particulate fraction of seawater samples from two Catalan harbours (NW Mediterranean) and samples collected periodically from the Galician Rias (E Atlantic), as well as a reference mussel sample. Results are in agreement with LC-MS/MS and the certified values. OA concentration in seawater correlates with Dinophysis cell abundance, with a 1-2 weeks lag. The immunoassays provide powerful high-throughput analytical methods potentially applicable as alternative monitoring tools.

Rapid screening and multi-toxin profile confirmation of tetrodotoxins and analogues in human body fluids derived from a puffer fish poisoning incident in New Caledonia

In August 2014, a puffer fish poisoning incidence resulting in one fatality was reported in New Caledonia. Although tetrodotoxin (TTX) intoxication was established from the patients' signs and symptoms, the determination of TTX in the patient's urine, serum or plasma is essential to confirm the clinical diagnosis. To provide a simple cost-effective rapid screening tool for clinical analysis, a maleimide-based enzyme-linked immunosorbent assay (mELISA) adapted for the determination of TTX contents in human body fluids was assessed. The mELISA was applied to the analysis of urine samples from two patients and a response for the presence of TTX and/or structurally similar analogues was detected in all samples. The analysis by LC-MS/MS confirmed the presence of TTX but also TTX analogues (4-epiTTX, 4,9-anhydroTTX and 5,6,11-trideoxyTTX) in the urine. A change in the multi-toxin profile in the urine based on time following consumption was observed. LC-MS/MS analysis of serum and plasma samples also revealed the presence of TTX (32.9 ng/mL) and 5,6,11-trideoxyTTX (374.6 ng/mL) in the post-mortem plasma. The results provide for the first time the TTX multi-toxin profile of human samples from a puffer fish intoxication and clearly demonstrate the implication of TTX as the causative agent of the reported intoxication case.

Advances in human chorionic gonadotropin detection technologies: a review

Human chorionic gonadotropin (HCG) is a glycoprotein secreted by placental trophoblast cells in pregnancy. HCG is a heterodimer composed of two different α- and β-subunits, with the latter being unique to HCG. As well as being the most important diagnostic markers for pregnancy, HCG is also a tumor marker, therefore, quantitative detection of HCG is of great value. Numerous advanced technologies have been developed for HCG concentration detection including electrochemical immunoassay, chemiluminescent immunoassay, fluorescence immunoassay, resonance scattering spectrometry, atomic emission spectrometry, radioimmunoassay, MS and so on. Some have pursued simple and easy operation, while others have emphasized on accuracy and applications in clinical medicine. This review provides a comprehensive summary of various methods of detecting HCG.