Determination of DSP toxins: comparative study of HPLC and bioassay to reduce the observation time of the mouse bioassay

Okadaic acid meet and greet: an insight into detection methods, response strategies and genotoxic effects in marine invertebrates

Harmful Algal Blooms (HABs) constitute one of the most important sources of contamination in the oceans, producing high concentrations of potentially harmful biotoxins that are accumulated across the food chains. One such biotoxin, Okadaic Acid (OA), is produced by marine dinoflagellates and subsequently accumulated within the tissues of filtering marine organisms feeding on HABs, rapidly spreading to their predators in the food chain and eventually reaching human consumers causing Diarrhetic Shellfish Poisoning (DSP) syndrome. While numerous studies have thoroughly evaluated the effects of OA in mammals, the attention drawn to marine organisms in this regard has been scarce, even though they constitute primary targets for this biotoxin. With this in mind, the present work aimed to provide a timely and comprehensive insight into the current literature on the effect of OA in marine invertebrates, along with the strategies developed by these organisms to respond to its toxic effect together with the most important methods and techniques used for OA detection and evaluation.

First direct fluorescence polarization assay for the detection and quantification of spirolides in mussel samples

In 2009, we achieve the first inhibition FP assay to detect imine cyclic toxins. In the present paper we propose a new FP assay for direct quantify spirolides. This new method has resulted in significant improvement of sensitivity, rapidity and accessibility. In the method design, nicotinic acetylcholine receptor from Torpedo marmorata membranes labelled with a derivative of fluorescein was used. Spirolides, 13-desmethyl spirolide C (13-desMeC) and 13,19-didesmethyl spirolide C (13,19-didesMeC) were extracted and purified from cultures of the Alexandrium ostenfeldii dinoflagellate. Data showed the decrease of FP when toxin concentration was increased. Thus, a relationship between the FP units and the spirolides amount present in a sample was obtained. This direct assay is a reproducible, simple and very sensitive method with a detection limit about 25 nM for 13-desMeC and 150 nM for 13,19-didesMeC. The procedure was used to measure spirolides in mussel samples using an extraction and clean up protocol suitable for the FP assay. Results obtained show that this method is able to quantify 13-desMeC in the range of 50-350 μg kg(-1) meat. Other liposoluble toxins did not interfere with the assay, proving a specific method. Moreover, the matrix do not affect in the range of toxin concentrations that involving risk of spirolides intoxication.

A comparison of the mouse bioassay with liquid chromatography-mass spectrometry for the detection of lipophilic toxins in shellfish from Scottish waters

Some lipophilic shellfish toxins (LSTs) can cause human illness due to eating shellfish that have become naturally contaminated following filter feeding on toxin producing algae. A mouse bioassay (MBA) is widely used to detect LSTs in regulatory monitoring of shellfish. However, the MBA is imprecise giving only a positive or negative result and is prone to interference from other compounds. In this study, liquid chromatography-mass spectrometry (LC-MS) was compared to the MBA, with the aim of substituting the in vivo assay for monitoring shellfish from Scottish waters. Overall, it was not feasible to demonstrate equivalence of LC-MS with the MBA, but due to the detection of a range of LSTs, it is considered that LC-MS methods capable of detecting multiple analogues are accepted by international markets of shellfish to assure consumer protection.

Okadaic acid, a causative toxin of diarrhetic shellfish poisoning, in green-lipped mussels Perna viridis from Hong Kong fish culture zones: method development and monitoring

Green-lipped mussels (Perna viridis) were collected from seven fish culture zones (FCZs) in Hong Kong and analyzed for okadaic acid (OA). A conventional HPLC method was modified by incorporating a proteinase K digestion step. Results suggest that a higher recovery (2.5 times higher) of OA was obtained from spiked samples after the addition of 1.08 mg proteinase K in comparison with samples incubated without the proteolytic enzyme. For the hepatopancreas (HP) of individual field-collected mussels, the additional digestion step can enhance OA extraction by 3.1 times. Spatial and temporal variations in OA concentrations in the mussels from various FCZs were investigated. The highest concentration of OA in mussel HP samples was 1164.9 ng/g HP wet wt. With respect to OA concentrations in whole mussel tissues from seven sites and four seasonal samplings, the concentrations were between 70.0 and 131.0 ng/g wet wt., which did not exceed the generally recognized international regulatory criteria (>200 ng/g) for OA.

Fluorescent microplate cell assay to measure uptake and metabolism of glucose in normal human lung fibroblasts

This is the first report of a fluorimetric microplate assay to assess glucose uptake and metabolism in eukaryotic cells. The assay was carried out incubating normal human lung fibroblasts in the wells of microtiter trays with a fluorescent D-glucose derivative, 2-N-7-(nitrobenz-2-oxa-1,3-diazol-4-yl)amino-2-deoxy-D-glucose (2-NBDG). This dye could be incorporated by glucose transporting systems in living cells. Substrate uptake was determined by analysing the data obtained with a fluorescence microplate reader. Variables studied in the development of the assay included dye concentration and incubation period. We found that this cell assay is very sensitive, reproducible, provides fast results and graphical display of data. It requires small sample volumes and allows handling of a large number of samples simultaneously. Okadaic acid was used to assess this microplate assay in the field of cytotoxicity. This diarrhetic shellfish toxin is a tumour promoter and a specific inhibitor of protein phosphatases 1 and 2A. The exposition of cells to okadaic acid (0.1 nM-1 microM) at different time intervals causes a decrease in intracellular glucose (40-50% over controls). Results obtained with okadaic acid are the starting point to evaluate application of the method to routine toxicity probes.

Improvement on sample clean-up for high-performance liquid chromatographic-fluorimetric determination of diarrhetic shellfish toxins using 1-bromoacetylpyrene

Okadaic acid (OA) and dinophysistoxin-2, two of the main diarrhetic shellfish toxins, can be determined by high-performance liquid chromatography coupled to fluorimetry as pyrenacyl esters. Toxin fluorescent derivatives were obtained after quantitative derivatization with 1-bromoacetylpyrene in acetonitrile. An efficient improvement in the silica gel clean-up procedure of the pyrenacyl derivatives is reported. The clean-up cartridge is washed with hexane-dichloromethane (1:1, v/v), dichloromethane-ethyl acetate (8:2, v/v), and finally the pyrenacyl esters were eluted with dichloromethane-methanol (9:1, v/v). We compare this procedure with other methods already described. Good results were obtained with mussels, scallops and clams. The clean-up procedure showed good robustness when checked against silica and solvents activity. Using samples of mussel hepatopancreas with an OA concentration ranging from 0 to 2 micrograms OA/g hepatopancreas, the inter-assay relative standard deviation ranged from 5.5 to 12.6%.