Comparative evaluation of enzyme-linked immunoassay and reference methods for the detection of shellfish hydrophilic toxins in several presentations of seafood

Spectroscopic ellipsometry methods for brevetoxin detection

The spectroscopic ellipsometry (SE), and attenuated internal reflection spectroscopic ellipsometry (TIRE) are promising methods in label-free biosensing applications. An ellipsometer running under surface plasmon resonance (SPR) conditions has unique advantages over other SPR-based methods in terms of sensitivity and real-time/label-free measurement capability. In this study, both SE and TIRE-based brevetoxin B (BTX) sensors were developed using two anti-BTX aptamers reported before. A new aptamer sequence was also derived from these two antiBTX aptamers using predictive modeling tools and an exclusion method. All three antiBTX aptamers' analytical performances were quite competitive in terms of both detecting range and detection limits. However, the selectivity of the previously reported aptamers against analogs of BTX was poor at low detection ranges, especially for okadaic acid. Furthermore, the selectivity of the derived aptamer was lower than its predecessors. The sensors were capable of detecting BTX in the range of 0.05 nM-1600 nM in the TIRE and 0.5 nM-2000 nM in the SE configuration. The detection limits of the sensors were 1.48 nM (1.32 ng/mL) and 0.80 nM (0.72 ng/mL) for SE and TIRE configurations, respectively. Both configurations have been used successfully to detect BTX standards spiked into real fish and shrimp samples.

Allelopathic inhibitory effect of the macroalga Pyropia haitanensis (Rhodophyta) on harmful bloom-forming Pseudo-nitzschia species

The blooms of harmful microalgae represent a prominent threat to fisheries, public health, and economies throughout the world. Recent studies have shown that certain macroalgae release allelochemicals that can inhibit the growth of bloom-forming microalgae. In this study, we found that the macroalga Pyropia haitanensis significantly inhibited growth of the harmful bloom-forming microalgae Pseudo-nitzschia pungens and Pseudo-nitzschia multiseries. The inhibitory-effect of the live thali of P. haitanensis was highest, followed by that of dry powder, water-soluble extract, and culture medium filtrate. The Pseudo-nitzschia species died 96 h after exposure to 5-10 g fresh-weight L^-1 of P. haitanensis live thalli. Furthermore, an aqueous extract of P. haitanensis suppressed the growth of P. pungens and P. multiseries, thereby indicating that P. haitanensis contains stable allelopathic substances that cause the observed inhibitory-effects. On the basis of these findings, we conclude that the macroalga P. haitanensis would have potential utility in controlling the blooms of Pseudo-nitzschia species.

First determination of extracellular paralytic shellfish poisoning toxins in the culture medium of toxigenic dinoflagellates by HILIC-HRMS

Paralytic shellfish poisoning (PSP) toxins have received considerable attention in recent years because of their adverse effects on marine breeding industries and human health. In this study, a reliable method for the analysis of extracellular PSP toxins in the culture medium of marine toxic dinoflagellates was developed for the first time using graphitized carbon black-solid-phase extraction and hydrophilic interaction liquid chromatography-high-resolution mass spectrometry. The limit of quantification of typical PSP toxins in algal culture medium ranged from 0.072 μg/L to 0.151 μg/L under optimal conditions. Satisfactory absolute recoveries (87.5%-102.4%), precision (relative standard deviation ≤ 7.6%), and linearity (R² ≥ 0.9998) were also achieved. In addition, the proposed method was applied to screen and determine the extracellular PSP toxins of two typical toxigenic dinoflagellates, Alexandrium minutum and Alexandrium tamarense. The total concentrations of the extracellular PSP toxins in A. minutum and A. tamarense over the whole growth period were within 2.0-735.5 and 2.0-19.2 μg/L, respectively. The concentrations of extracellular PSP toxins varied remarkably in the different growth stages of A. minutum and A. tamarense, and the contents of some extracellular PSP toxins were substantially higher than those of intracellular PSP toxins. Therefore, the extracellular PSP toxins released by toxigenic red tide algae cannot be ignored, and their environmental fate, bioavailability, and potential harm to aquatic environment need to be investigated in future studies.

Saxitoxin aptasensor based on attenuated internal reflection ellipsometry for seafood

In this study, we proposed label-free saxitoxin (STX) sensor using STX specific aptamer in combination with spectroscopic ellipsometry (SE) and attenuated internal reflection (AIR) spectroscopic ellipsometry method which is operated under surface plasmon resonance (SPR) conditions. Besides the other surface plasmon resonance-based applications, AIR-SE applications have unique advantages in terms of sensitivity and it was used herein for real-time detection of STX in real samples. Another method, SE, was also used and compared with AIR-SE. Analytical performances were satisfactory with low detection limits and a wide detection range. Limit of detection was 0.01 ng/mL for AIR-SE and 0.11 ng/mL for SE. Both proposed sensors were operable in 0.01 nM-1000 nM STX range. These methods were also used for the accurate, selective, and sensitive detection of STX from fish and shrimp samples.

Pseudo-nitzschia Blooms in a Coastal Upwelling System: Remote Sensing Detection, Toxicity and Environmental Variables

The NW coast of the Iberian Peninsula is dominated by extensive shellfish farming, which places this region as a world leader in mussel production. Harmful algal blooms in the area frequent lead to lengthy harvesting closures threatening food security. This study developed a framework for the detection of Pseudo-nitzschia blooms in the Galician rias from satellite data (MERIS full-resolution images) and identified key variables that affect their abundance and toxicity. Two events of toxin-containing Pseudo-nitzschia were detected (up to 2.5 μg L−1 pDA) in the area. This study suggests that even moderate densities of Pseudo-nitzschia in this area might indicate high toxin content. Empirical models for particulate domoic acid (pDA) were developed based on MERIS FR data. The resulting remote-sensing model, including MERIS bands centered around 510, 560, and 620 nm explain 73% of the pDA variance (R2 = 0.73, p < 0.001). The results show that higher salinity values and lower Si(OH)4/N ratios favour higher Pseudo-nitzschia spp. abundances. High pDA values seem to be associated with relatively high PO43, low NO3− concentrations, and low Si(OH)4/N. While MERIS FR data and regionally specific algorithms can be useful for detecting Pseudo-nitzschia blooms, nutrient relationships are crucial for predicting the toxicity of these blooms.

Use of biosensors for the detection of marine toxins

Increasing occurrences of harmful algal blooms (HABs) in the ocean are a major concern for countries around the globe, and with strong links between HABs and climate change and eutrophication, the occurrences are only set to increase. Of particular concern with regard to HABs is the presence of toxin-producing algae. Six major marine biotoxin groups are associated with HABs. Ingestion of such toxins via contaminated shellfish, fish, or other potential vectors, can lead to intoxication syndromes with moderate to severe symptoms, including death in extreme cases. There are also major economic implications associated with the diverse effects of marine biotoxins and HABs. Thus, effective monitoring programmes are required to manage and mitigate their detrimental global effect. However, currently legislated detection methods are labour-intensive, expensive and relatively slow. The growing field of biosensor diagnostic devices is an exciting area that has the potential to produce robust, easy-to-use, cost-effective, rapid and accurate detection methods for marine biotoxins and HABs. This review discusses recently developed biosensor assays that target marine biotoxins and their microbial producers, both in harvested fish/shellfish samples and in the open ocean. The effective deployment of such biosensor platforms could address the pressing need for improved monitoring of HABs and marine biotoxins, and could help to reduce their global economic impact.

Enzymes in Fish and Seafood Processing

Enzymes have been used for the production and processing of fish and seafood for several centuries in an empirical manner. In recent decades, a growing trend toward a rational and controlled application of enzymes for such goals has emerged. Underlying such pattern are, among others, the increasingly wider array of enzyme activities and enzyme sources, improved enzyme formulations, and enhanced requirements for cost-effective and environmentally friendly processes. The better use of enzyme action in fish- and seafood-related application has had a significant impact on fish-related industry. Thus, new products have surfaced, product quality has improved, more sustainable processes have been developed, and innovative and reliable analytical techniques have been implemented. Recent development in these fields are presented and discussed, and prospective developments are suggested.

A feedback mechanism to control apoptosis occurs in the digestive gland of the oyster crassostrea gigas exposed to the paralytic shellfish toxins producer Alexandrium catenella

To better understand the effect of Paralytic Shellfish Toxins (PSTs) accumulation in the digestive gland of the Pacific oyster, Crassostrea gigas, we experimentally exposed individual oysters for 48 h to a PSTs producer, the dinoflagellate Alexandrium catenella. In comparison to the effect of the non-toxic Alexandrium tamarense, on the eight apoptotic related genes tested, Bax and BI.1 were significantly upregulated in oysters exposed 48 h to A. catenella. Among the five detoxification related genes tested, the expression of cytochrome P450 (CYP1A) was shown to be correlated with toxin concentration in the digestive gland of oysters exposed to the toxic dinoflagellate. Beside this, we observed a significant increase in ROS production, a decrease in caspase-3/7 activity and normal percentage of apoptotic cells in this tissue. Taken together, these results suggest a feedback mechanism, which may occur in the digestive gland where BI.1 could play a key role in preventing the induction of apoptosis by PSTs. Moreover, the expression of CYP1A, Bax and BI.1 were found to be significantly correlated to the occurrence of natural toxic events, suggesting that the expression of these genes together could be used as biomarker to assess the biological responses of oysters to stress caused by PSTs.

Open-sandwich immunoassay for sensitive and broad-range detection of a shellfish toxin gonyautoxin

At present, the analytical method for paralytic shellfish poisoning (PSP) toxins in shellfish is the mouse bioassay (MBA), which is an official method of the Association of Analytical Communities (AOAC [8]). However, the low sensitivity and concerns over the number of live animals required for testing have been cited as the major reason for seeking its replacement. In this report, we employed an open-sandwich immunoassay (OS-IA) to detect gonyautoxin (GTX2/3), a kind of PSP toxins. OS-IA, which utilizes the antigen-induced enhancement of antibody VH/VL interaction, can measure a small molecule antigen in a noncompetitive format. Hence it has a wider working range and shorter measurement time. We isolated anti-GTX2/3 antibody gene from a hybridoma GT-13A by screening a Fab-displaying phage library. Then the vectors for OS-IA were constructed, and examined for antigen concentration-dependency of the VH/VL interaction by OS-ELISA. As a result, in each case, signal intensity increases notably in a wide concentration range (0.1 to >1000 ng mL(-1)) of free GTX2/3, which was enough to cover its regulation value (80 μg 100 g(-1)) in many countries. So OS-IA will be widely applicable to detect PSP toxins in shellfish meats and in drinking water.

The effect of fish matrix on the enzyme-linked immunosorbent assay of antibiotics

BACKGROUND

The matrix effect is considered to be a problem in the immunoassay of foodstuffs. However, information on the interference from aquatic products, as well as the mechanism involved, is very limited. In this study, using three flatfishes (Scophthalmus maximus, Paralichthys olivaceus and Cymoglossus robustus) as samples, the effect of the fish matrix on the competitive indirect enzyme-linked immunosorbent assay (ci-ELISA) of antibiotic (norfloxacin) residues was investigated. The mechanism of the observed matrix effect is also preliminarily discussed.

RESULTS

Within the working range of the calibration curves, a significant (P = 0.05) but irregular variation in the inhibition ratio was observed in the presence of fish extracts. Further experiments revealed that such a matrix effect could be caused by some water-soluble fish proteins with a wide range of molecular weight (from below 14.4 kDa to about 116.0 kDa), and the ions from fish muscles may also contribute to the interference. The results of western blotting indicated that some fish protein components might effectively bind with antibody reagents used.

CONCLUSION

Significant interference in the immunoassay of norfloxacin was observed in the presence of fish matrix. Some proteins and ions were demonstrated to contribute to the matrix effect investigated. Although the detailed mechanism is still unclear, the non-specific interaction between fish proteins and immunoglobulin G (IgG) or horseradish peroxidase (HRP) labelled IgG was assumed to be an important source of the matrix effect in immunoassays.

Contributions of pesticide residue chemistry to improving food and environmental safety: past and present accomplishments and future challenges

The principles of modern pesticide residue chemistry were articulated in the 1950s. Early authors pointed out the advantages of systematizing and standardizing analytical methods for pesticides so that they could be widely practiced and the results could be reproduced from one laboratory to the next. The availability of improved methods has led to a much more complete understanding of pesticide behavior and fate in foods and the environment. Using methods based largely upon gas chromatography (GC) and high-performance liquid chromatography (HPLC) coupled increasingly with mass spectrometry (MS) and MS(n) as the detection tool, residues can be measured at parts per billion levels and below in a variety of food and environmental matrices. Development of efficient extraction and cleanup methods, techniques such as ELISA, efficient sample preparation techniques such as QuEChERS, and automated laboratory and field instrumentation has also contributed to the tools available for use in modern pesticide residue analysis. As a result, great strides have been made in improving food and worker safety and in understanding environmental behavior and fate of pesticides. There are many challenges remaining in the field of pesticide residue chemistry that will continue to stimulate analytical chemists. New chemistries are emerging, often patterned on complex natural products. Analyzing for the parent chemicals and potentially multiple breakdown products will require analytical ingenuity. The development of more sensitive bioassays and knowledge of unintended side effects will challenge residue chemistry as well, as in the case of following the fate of environmental endocrine disruptors associated with some pesticides as well as nonpesticide contaminants from packaging materials and other familiar articles. Continued funding and other resources to ensure better training, international cooperation, and accelerated research and development activities will be a constant need in pesticide residue chemistry as it is for all areas of science that aim to mitigate or eliminate contaminants that can affect human and environmental health and safety.