Capacity of the potentially toxic diatoms Pseudo-nitzschia mannii and Pseudo-nitzschia hasleana to tolerate polycyclic aromatic hydrocarbons

This study investigates the effects of polycyclic aromatic hydrocarbons (PAHs) on two potentially toxic Pseudo-nitzschia hasleana and P. mannii, isolated from a PAH contaminated marine environment. Both species, maintained in non-axenic cultures, have been exposed during 144 h to increasing concentrations of a 15 PAHs mixture. Analysis of the domoic acid, showed very low concentrations. Dose-response curves for growth and photosynthesis inhibition were determined. Both species have maintained their growth until the end of incubation even at the highest concentration tested (120 µg l^-1), Nevertheless, P mannii showed faster growth and seemed to be more tolerant than P. hasleana. To reduce PAH toxicity, both species have enhanced their biovolume, with a higher increase for P. mannii relative to P hasleana. Both species were also capable of bio-concentrating PAHs and were able to degrade them probably in synergy with their associated bacteria. The highest biodegradation was observed for P. mannii, which could harbored more efficient hydrocarbon-degrading bacteria. This study provides the first evidence that PAHs can control the growth and physiology of potentially toxic diatoms. Future studies should investigate the bacterial community associated with Pseudo-nitzschia species, as responses to pollutants or to other environmental stressors could be strongly influence by associated bacteria.

Occurrence of cyclic imines in European commercial seafood and consumers risk assessment

Cyclic imines constitute a quite recently discovered group of marine biotoxins that act on neural receptors and that bioaccumulate in seafood. They are grouped together due to the imino group functioning as their common pharmacore, responsible for acute neurotoxicity in mice. Cyclic imines (CIs) have not been linked yet to human poisoning and are not regulated in the European Union (EU), although the European Food Safety Authority (EFSA) requires more data to perform conclusive risk assessment for consumers. Several commercial samples of bivalves including raw and processed samples from eight countries (Italy, Portugal, Slovenia, Spain, Ireland, Norway, The Netherlands and Denmark) were obtained over 2 years. Emerging cyclic imine concentrations in all the samples were analysed on a LC-3200QTRAP and LC-HRMS QExactive mass spectrometer. In shellfish, two CIs, pinnatoxin G (PnTX-G) and 13-desmethylspirolide C (SPX-1) were found at low concentrations (0.1-12µg/kg PnTX-G and 26-66µg/kg SPX-1), while gymnodimines and pteriatoxins were not detected in commercial (raw and processed) samples. In summary, SPX-1 (n: 47) and PnTX-G (n: 96) were detected in 9.4% and 4.2% of the samples, respectively, at concentrations higher than the limit of quantification (LOQ), and in 7.3% and 31.2% of the samples at concentrations lower than the LOQ (25µg/kg for SPX-1 and 3µg/kg for PnTX-G), respectively. For the detected cyclic imines, the average exposure and the 95th percentile were calculated. The results obtained indicate that it is unlikely that a potential health risk exists through the seafood diet for CIs in the EU. However, further information about CIs is necessary in order to perform a conclusive risk assessment.

Evaluation of tetrodotoxins in puffer fish caught along the Mediterranean coast of Spain. Toxin profile of Lagocephalus sceleratus

Although consumption of Tetraodontidae species is prohibited in the EU, intoxications are still reported. The evaluation of tetrodotoxins (TTXs) by mass spectrometry (LC-MS/MS and LC-HRMS) and a screening immunoassay (mELISA) in tetraodontid fishes caught along the Western Mediterranean Sea revealed high concentrations of TTXs in Lagocephalus sceleratus while no TTXs were identified in L. lagocephalus and Sphoeroides pachygaster individuals. The high TTXs content found in the L. sceleratus analysed herein demonstrate the occurrence of highly toxic puffer fish in the Western Mediterranean Sea. Being L. sceleratus a recent invasive species in the Mediterranean, surveillance, risk assessment and risk management measures are necessary. The strategy used within this research work could be a valuable tool for future food safety monitoring.

Identification of ciguatoxins in a shark involved in a fatal food poisoning in the Indian Ocean

Severe food poisoning events after the consumption of sharks have been reported since the 1940s; however, there has been no clear understanding of their cause. Herein, we report for the first time the presence of ciguatoxins (CTXs) in sharks. The identification by mass spectrometry of CTXs, including two new analogues, in a bull shark (Carcharhinus leucas) that was consumed by humans, causing the poisoning and death of 11 people in Madagascar in 2013 is described. Typical neurotoxic ciguatera symptoms were recorded in patients, and toxicological assays on extracts of the shark demonstrated CTX-like activity. These results confirm this episode as a ciguatera poisoning event and expand the range of pelagic fish species that are involved in ciguatera in the Indian Ocean. Additionally, gambieric acid D, a molecule originally described in CTX-producing microalgae, was identified for the first time in fish. This finding can contribute to a better understanding of trophic relations within food webs. The present work confirms that consumption of sharks from the Indian Ocean should be considered a ciguatera risk, and actions should be taken to evaluate its magnitude and risk in order to manage shark fisheries.

Effects of nitrogen supply on Pseudo-nitzschia calliantha and Pseudo-nitzschia cf. seriata: field and laboratory experiments

The effects of inorganic and organic nitrogen supply on the growth and domoic acid (DA) production of Pseudo-nitzschia cf. seriata and Pseudo-nitzschia calliantha from Bizerte Lagoon (SW Mediterranean Sea) were studied during field and laboratory experiments. Nitrogen enrichments (40 µM NO3 (-); 10 µM NH4 (+); 20 µM CH4N2O) and a control, with no added N, were carried out in separate carboys with seawater collected from Bizerte Lagoon. In the field experiments, all N-enrichments resulted in significant increases in chlorophyll a concentration, and maintained exponential growth until the end of the experiment. The initial diatom community was dominated by a bloom of P. cf. seriata (9.3 × 10(5) cells l(-1)). After 6 days of incubation, the abundance of P. cf. seriata was greatest in the urea addition (1.52 × 10(6) cells l(-1)), compared to the ammonium treatment (0.47 × 10(6) cells l(-1)), nitrate treatment (0.70 × 10(6) cells l(-1)) and control (0.36 × 10(6) cells l(-1)). The specific growth rates, calculated from increases in chlorophyll a and cell abundance, were statistically different across all treatments, with the highest in the urea and nitrate additions. Similar results were obtained from the laboratory experiments. These were carried out with P. calliantha isolated from Bizerte Lagoon and grown in f/2 medium enriched with 40 µM nitrate, 10 µM ammonium and 20 µM urea. The exponential growth rate was significantly faster for the cells cultured with urea (1.50 d(-1)) compared to the nitrate (0.90 d(-1)) and ammonium (0.80 d(-1)) treatments and the control (0.40 d(-1)). Analysis of DA, performed at the beginning and the end of the both experiments in all treatments, revealed very low concentrations (below the limit of quantification, 0.02- 1.310(-7) pg cell(-1), respectively).The field and laboratory experiments demonstrate that P.cf. seriata and P. calliantha are able to grow efficiently on the three forms of N, but with a preference for urea.

Ostreopsis cf. ovata from western Mediterranean Sea: Physiological responses under different temperature and salinity conditions

The dinoflagellate Ostreopsis cf. ovata proliferates seasonally in the Mediterranean Sea, producing palytoxin-like compounds (ovatoxins) which are considered among the most potent marine toxins. Blooms have been related to several toxic events in which respiratory problems in humans and mortality of benthic marine organisms have been observed. In the coming decades, an increase in temperature and salinity is predicted in the Mediterranean Sea as a consequence of global warming that may provoke alterations in the dynamics of marine microorganisms. In this study, the physiological effects of changes in water temperature and salinity were analyzed, and their interaction through a multi-factorial experiment using two strains of O. cf. ovata in culture that had been isolated from the western Mediterranean Sea. In order to perform an accurate and reliable estimation of cell abundance, hydrochloric acid and sodium-ethylenediaminetetraacetic acid treatments were evaluated for the purpose of disaggregating cell clumps, with the former providing lower counting errors, especially after the stationary phase. Results of the physiological study showed that growth was inhibited at 19°C for all salinities. The highest growth rates were registered at 24°C for both strains (0.48±0.05divday^-1), and a significant variability in growth rate was found among salinities at 24°C and 28°C. Two groups were distinguished by cell size in all high temperature conditions and a positive correlation was found between the amount of small cells and growth rate. The concentration of palytoxin-like compounds in the cultures increased with time and significantly higher amounts of toxin were found at 28°C in comparison to 24°C. The results suggest that climate change may not affect intensity of blooms, but their toxicity may be enhanced.

Detection of Tetrodotoxins in Puffer Fish by a Self-Assembled Monolayer-Based Immunoassay and Comparison with Surface Plasmon Resonance, LC-MS/MS, and Mouse Bioassay

The increasing occurrence of puffer fish containing tetrodotoxin (TTX) in the Mediterranean could represent a major food safety risk for European consumers and threaten the fishing industry. The work presented herein describes the development of a new enzyme linked immunosorbent assay (mELISA) based on the immobilization of TTX through dithiol monolayers self-assembled on maleimide plates, which provides an ordered and oriented antigen immobilization and favors the antigen-antibody affinity interaction. The mELISA was found to have a limit of detection (LOD) of TTX of 0.23 mg/kg of puffer fish matrix. The mELISA and a surface plasmon resonance (SPR) immunosensor previously developed were employed to establish the cross-reactivity factors (CRFs) of 5,6,11-trideoxy-TTX, 5,11-deoxy-TTX, 11-nor-TTX-6-ol, and 5,6,11-trideoxy-4-anhydro-TTX, as well as to determine TTX equivalent contents in puffer fish samples. Results obtained by both immunochemical tools were correlated (R(2) = 0.977). The puffer fish samples were also analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the corresponding CRFs were applied to the individual TTX contents. Results provided by the immunochemical tools, when compared with those obtained by LC-MS/MS, showed a good degree of correlation (R(2) = 0.991 and 0.979 for mELISA and SPR, respectively). The mouse bioassay (MBA) slightly overestimated the CRF adjusted TTX content of samples when compared with the data obtained from the other techniques. The mELISA has been demonstrated to be fit for the purpose for screening samples in monitoring programs and in research activities.

Assessment of acylation routes and structural characterisation by liquid chromatography/tandem mass spectrometry of semi-synthetic acyl ester analogues of lipophilic marine toxins

RATIONALE

Esterification is one of the most important metabolic routes of lipophilic marine toxins in shellfish. In this work we assessed several chemical acylation reactions aimed at obtaining acyl ester analogues via partial synthesis from the free toxins. The procedures developed including sensitive and selective methods based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) can be applied to obtain reference materials that may be used as analytical standards (internal/external) for method development and calibration, as well as to perform toxicological in vitro and in vivo studies.

METHODS

Acylation systems involved both anhydrous and non-anhydrous fatty acid or acid halides as a source of the acyl radical, and several catalysers of the reaction. A series of mass spectrometric experiments involving product ion scans and multiple reaction monitoring (MRM) were used to confirm the identity and to elucidate the fragmentation pathways of the synthesised products.

RESULTS

Reaction yields regarding reaction time and temperature were examined at sub-nmol scale for the acylation system consisting of palmitic anhydride and 4-(dimethylamino)pyridine (DMAP) in anhydrous pyridine, showing the best conditions at 75 °C for 60 min, 75 °C for 120 min and 100 °C for 270 min for cyclic imines, azaspiracid-1 and pectenotoxin-2, respectively. The esterification approach was verified at a larger scale for the esterification of gymnodimine-A (GYM-A), which kept a good yield >90% for the synthesis of 10-O-palmitoyl-GYM-A.

CONCLUSIONS

Acyl ester analogues of lipophilic marine toxins have been synthesised and their structure elucidated by LC/MS/MS. For acyl ester analogues identical to natural metabolites, the procedures developed have potential to be applied for the semi-synthesis of metabolites in a sustainable, scalable and controlled way, avoiding extensive and tedious isolation and purification procedures from naturally contaminated shellfish. For the semi-synthetic esters structurally different than those found in shellfish, they may have applicability as internal standards for accurate quantifications of natural metabolites present in complex matrices.

Controlled gelation of poly(3-alkylthiophene)s in bulk and in thin-films using low volatility solvent/poor-solvent mixtures

Low volatility solvent/non-solvent mixtures were utilized to engineer the structure of poly(3-alkylthiophene) (P3AT) organogels. The ratio of solvent to poor-solvent was manipulated to systematically control the kinetics of self-assembly. Specific solvent mixtures were utilized to produce similar gelation kinetics with polymers of differing alkyl chain length. Simultaneous small angle neutron scattering (SANS) and dielectric spectroscopy was used to probe the structure and the electronic properties of isothermally self-assembled P3ATs. It was determined that alkyl chain length has a dominant effect on the relationship between fiber development and conductivity. Furthermore, using transmission electron microscopy (TEM) and SANS we demonstrate that, for P3HT organogels, lower poor-solvent content leads to fewer fibers with larger nucleation centers while higher poor-solvent amounts results in more fibers and nucleation centers that are smaller and more abundant. This leads to opposing effects in terms of the contribution of the solvent quality to the electrical conductivity. An optimum in conductivity is found at different amounts of poor-solvent for each type of polymer. It is also shown that low volatility solvent mixtures allow for the formation of thermoreversible conjugated polymer organogels in thin-films at room temperature. This work highlights the potential to engineer the structure of conjugated polymer organogels while enabling the use of interconnected gel structures in thin-film organic electronic devices.

Confirmation of pinnatoxins and spirolides in shellfish and passive samplers from Catalonia (Spain) by liquid chromatography coupled with triple quadrupole and high-resolution hybrid tandem mass spectrometry

Cyclic imines are lipophilic marine toxins that bioaccumulate in seafood. Their structure comprises a cyclic-imino moiety, responsible for acute neurotoxicity in mice. Cyclic imines have not been linked yet to human poisonings and are not regulated in Europe, although the European Food Safety Authority requires more data to perform a conclusive risk assessment for consumers. This work presents the first detection of pinnatoxin G (PnTX-G) in Spain and 13-desmethyl spirolide C (SPX-1) in shellfish from Catalonia (Spain, NW Mediterranean Sea). Cyclic imines were found at low concentrations (2 to 60 µg/kg) in 13 samples of mussels and oysters (22 samples analyzed). Pinnatoxin G has been also detected in 17 seawater samples (out of 34) using solid phase adsorption toxin tracking devices (0.3 to 0.9 µg/kg-resin). Pinnatoxin G and SPX-1 were confirmed with both low and high resolution (<2 ppm) mass spectrometry by comparison of the response with that from reference standards. For other analogs without reference standards, we applied a strategy combining low resolution MS with a triple quadrupole mass analyzer for a fast and reliable screening, and high resolution MS LTQ Orbitrap® for unambiguous confirmation. The advantages and limitations of using high resolution MS without reference standards were discussed.

Flow-induced structured phase in nonionic micellar solutions

In this work, we consider the flow of a nonionic micellar solution (precursor) through an array of microposts, with focus on its microstructural and rheological evolution. The precursor contains polyoxyethylene(20) sorbitan monooleate (Tween-80) and cosurfactant monolaurin (ML). An irreversible flow-induced structured phase (NI-FISP) emerges after the nonionic precursor flows through the hexagonal micropost arrays, when subjected to strain rates ~10(4) s(-1) and strain ~10(3). NI-FISP consists of close-looped micellar bundles and multiconnected micellar networks as evidenced by transmission electron microscopy (TEM) and cryo-electron microscopy (cryo-EM). We also conduct small-angle neutron scattering (SANS) measurements in both precursor and NI-FISP to illustrate the structural transition. We propose a potential mechanism for the NI-FISP formation that relies on the micropost arrays and the flow kinematics in the microdevice to induce entropic fluctuations in the micellar solution. Finally, we show that the rheological variation from a viscous precursor solution to a viscoelastic micellar structured phase is associated with the structural evolution from the precursor to NI-FISP.

An analytical perspective on detection, screening, and confirmation in phycology, with particular reference to toxins and toxin-producing species

Knowledge concerning the ability of microalgae to produce metabolites of interest such as toxins or high-value secondary metabolites requires exhaustive details to be supplied on how the research was conducted. These should include the microalgal species and strain characterization, the culture conditions, the cell density, and physiological state at the time of harvesting, the harvesting method, the sample pre-treatment protocol, and the subsequent instrumental analytical separation/detection system. In this comment, we discuss issues that affect algal research from an analytical chemistry perspective, particularly (i) the need to specify detection capabilities of the entire method (i.e., limits of detection or threshold detection levels), which we illustrate in relation to classification of a species or strain as being "toxin producing" or "non-toxin producing"; and (ii) the requirements that have to be satisfied to confirm a microalgal species (new or not) as a producer of a particular chemical of interest for phycologists, which again we illustrate in relation to toxins. A successful collaboration among phycologists and analytical chemists will only be achieved as a result of a synergistic collaboration between the two disciplines, with a reciprocal understanding at least at a background level.

Worming their way into shape: toroidal formations in micellar solutions

We report the formation of nanostructured toroidal micellar bundles (nTMB) from a semidilute wormlike micellar solution, evidenced by both cryogenic-electron microscopy and transmission electron microscopy images. Our strategy for creating nTMB involves a two-step protocol consisting of a simple prestraining process followed by flow through a microfluidic device containing an array of microposts, producing strain rates in the wormlike micelles on the order of 10(5) s(-1). In combination with microfluidic confinement, these unusually large strain rates allow for the formation of stable nTMB. Electron microscopy images reveal a variety of nTMB morphologies and provide the size distribution of the nTMB. Small-angle neutron scattering indicates the underlying microstructural transition from wormlike micelles to nTMB. We also show that other flow-induced approaches such as sonication can induce and control the emergence of onion-like and nTMB structures, which may provide a useful tool for nanotemplating.

Management of domoic acid monitoring in shellfish from the Catalan coast

Monitoring of amnesic shellfish poisoning (ASP) toxins in shellfish from the Catalan coast started in 2001. No ASP toxins were detected in any of the analyses performed before 2008. On 22 January 2008, domoic acid (DA) was detected in Donax trunculus (0.5 mg kg(-1)) and confirmed by rapid resolution liquid chromatography-tandem mass spectrometry (0.6 mg kg(-1)). A total of 974 shellfish samples were analyzed from January 2008 to December 2011, covering all the Catalan production areas and the most important marketed species. DA was detected in 23.8 % of the samples and was recorded every month in all areas and all species, except Ostrea edulis, although the percentage of samples with DA and DA content varied widely among samples. DA exceeded the regulatory level of 20 mg kg(-1) twice: in Callista chione sampled on February 2008 and in D. trunculus sampled on April 2010. DA content in Bolinus brandaris appeared constant and close to 4.5 mg kg(-1) for months in 2009. Mytilus galloprovincialis, Crassostrea gigas, and Ruditapes sp. presented very low concentrations of DA in the Ebro Delta bays, despite 113 alert situations according to Pseudo-nitzschia spp. abundances and the high number of shellfish samples analyzed. The origin of DA in Catalan shellfish remains unknown.

Inhibition equivalency factors for dinophysistoxin-1 and dinophysistoxin-2 in protein phosphatase assays: applicability to the analysis of shellfish samples and comparison with LC-MS/MS

The protein phosphatase inhibition assay (PPIA) is a well-known strategy for the determination of diarrheic shellfish poisoning (DSP) lipophilic toxins, which deserves better characterization and understanding to be used as a routine screening tool in monitoring programs. In this work, the applicability of two PPIAs to the determination of okadaic acid (OA), dinophysistoxin-1 (DTX-1), dinophysistoxin-2 (DTX-2), and their acyl ester derivatives in shellfish has been investigated. The inhibitory potencies of the DSP toxins on a recombinant and a wild PP2A have been determined, allowing the establishment of inhibition equivalency factors (IEFs) (1.1 and 0.9 for DTX-1, and 0.4 and 0.6 for DTX-2, for recombinant and wild PP2A, respectively). The PPIAs have been applied to the determination of OA equivalent contents in spiked and naturally contaminated shellfish samples. Results have been compared to those obtained by LC-MS/MS analysis, after application of the IEFs, showing good agreements.

High-throughput analysis of amnesic shellfish poisoning toxins in shellfish by ultra-performance rapid resolution LC-MS/MS

The application of ultra-performance rapid resolution LC on a 1.8 microm particle-size column coupled with tandem MS (RRLC-MS/MS) is described for the analysis of amnesic shellfish poisoning (ASP) toxins in shellfish. Complete resolution among domoic acid (DA) and the isomers was achieved in less than 3 min. The method was intralaboratory validated for direct analysis of crude extracts without further cleanup. It showed LODs ranging from 0.05 to 0.09 mg/kg and a working range that complied with the current regulatory level for DA of 20 mg/kg, and with the level of 4.5 mg/kg recently proposed by the European Food Safety Authority. Confirmatory capabilities were demonstrated according to the Commission Decision 2002/657/EC criteria. The results obtained by RRLC-MS/MS agreed with those provided by the reference LC-UV method, both intralaboratory for the analysis of blind samples (R2 = 0.9751) and interlaboratory through participation in the proficiency test for ASP toxins during 2009 (z-score = -0.962 and 0.177 for low- and high-contaminated samples, respectively). RRLC-MS/MS provided fast analysis and additional confirmatory capabilities for direct analysis of crude extracts while the performance and reliability of the results were maintained, even in very complex matrixes.

Update on methodologies available for ciguatoxin determination: perspectives to confront the onset of ciguatera fish poisoning in Europe

Ciguatera fish poisoning (CFP) occurs mainly when humans ingest finfish contaminated with ciguatoxins (CTXs). The complexity and variability of such toxins have made it difficult to develop reliable methods to routinely monitor CFP with specificity and sensitivity. This review aims to describe the methodologies available for CTX detection, including those based on the toxicological, biochemical, chemical, and pharmaceutical properties of CTXs. Selecting any of these methodological approaches for routine monitoring of ciguatera may be dependent upon the applicability of the method. However, identifying a reference validation method for CTXs is a critical and urgent issue, and is dependent upon the availability of certified CTX standards and the coordinated action of laboratories. Reports of CFP cases in European hospitals have been described in several countries, and are mostly due to travel to CFP endemic areas. Additionally, the recent detection of the CTX-producing tropical genus Gambierdiscus in the eastern Atlantic Ocean of the northern hemisphere and in the Mediterranean Sea, as well as the confirmation of CFP in the Canary Islands and possibly in Madeira, constitute other reasons to study the onset of CFP in Europe [1]. The question of the possible contribution of climate change to the distribution of toxin-producing microalgae and ciguateric fish is raised. The impact of ciguatera onset on European Union (EU) policies will be discussed with respect to EU regulations on marine toxins in seafood. Critical analysis and availability of methodologies for CTX determination is required for a rapid response to suspected CFP cases and to conduct sound CFP risk analysis.

Colorimetric and electrochemical phosphodiesterase inhibition assays for yessotoxin detection: development and comparison with LC-MS/MS

This work describes the development and applicability of two functional assays for the detection of yessotoxin (YTX), a polycyclic ether marine toxin produced by dinoflagellates. The assays are based on the interaction between this toxin and the phosphodiesterase (PDE) enzyme and the subsequent measurement of the enzyme activity by colorimetric and electrochemical methods. Firstly, several enzyme substrates were tested in order to select those able to be detected by colorimetry or electrochemistry after enzymatic hydrolysis. The substrates that provided the highest absorbance values and density currents were p-nitrophenyl phenylphosphonate and alpha-naphthyl phosphate, respectively. After optimisation of the experimental parameters, limits of detection of 0.8 and 0.6 microM were attained by colorimetry and electrochemistry, respectively. An inhibitory effect of YTX on the PDE activity was observed. The assays have been applied to the analysis of YTX production by Protoceratium reticulatum cultures, and results were compared with liquid chromatography-tandem mass spectrometry analysis.

Evaluation of the production of paralytic shellfish poisoning toxins by extracellular bacteria isolated from the toxic dinoflagellate Alexandrium minutum

The purpose of the study was to determine if paralytic shellfish poisoning (PSP) toxins are present in extracellular bacteria isolated from a toxic strain of the dinoflagellate Alexandrium minutum. A quantitative analysis was carried out of viable culturable bacteria attached to the surface of dinoflagellates and of bacteria present in dinoflagellate culture medium. A numerical taxonomy study was undertaken for presumptive identification of bacteria attached to the surface of dinoflagellates. Members of the following genera were detected on the cell surface of A. minutum: Cellulophaga, Marinomonas, Pseudoalteromonas, and Vibrio. The presence of intracellular PSP toxins in bacteria isolated from the cell surface of dinoflagellates was analysed by high-performance liquid chromatography with fluorescence detection (HPLC-FLD). Compounds that eluted at the same time as the standards of the PSP toxins GTX-2, GTX-3, GTX-4, dcGTX-2, and dcGTX-3 were present in some of the bacterial cell extracts. Natural fluorescent bacterial compounds, coeluting with some PSP toxins, were also detected. The results obtained showed that the fluorescent compounds, identified as putative PSP toxins by HPLC-FLD, did not correspond to any PSP analogue. This allowed us to reject the hypothesis that extracellular bacteria attached to the surface of dinoflagellates produce PSP toxins.

NG108-15 cell-based and protein phosphatase inhibition assays as alternative semiquantitative tools for the screening of lipophilic toxins in mussels. Okadaic acid detection

We report the application of a cell-based assay (CBA) using NG108-15 a hybridoma cell strain and a protein phosphatase inhibition-based assay (PPIA) as alternative toxicological or functional semiquantitative tools, respectively, for the screening of lipophilic toxins in mussels (Mytilusgalloprovincialis). Acetonic extracts were directly tested by CBA and PPIA but severe matrix effects were observed. As a solution, a simple 17-fraction protocol with solid-phase extraction (SPE) cartridges was optimised and applied as a previous step to the CBA or the PPIA. LC-MS/MS analyses were performed in parallel to determine the lipophilic toxins content in mussel extracts. Evaluation of the SPE protocol by LC-MS/MS showed okadaic acid (OA) recovery above 90% and negligible effects of mussel matrix on the SPE performance. The whole methods provided limits of detection of 47 and 45mug OA equivalents/kg for CBA and PPIA, respectively. The combined strategy permitted the identification of OA toxicity in two fractions, and allowed us to clearly distinguish between negative and positive samples, the latter being either OA-spiked or naturally-contaminated samples at levels equal or above the regulatory limit. The combination of fractioning with CBA or PPIA allows the quantification of the toxic and functional effects of samples above these concentrations.

Determination of dissolved domoic acid in seawater with reversed-phase extraction disks and rapid resolution liquid chromatography tandem mass spectrometry with head-column trapping

Domoic acid (DA) is the principal neurotoxin responsible for amnesic shellfish poisoning (ASP) and is produced, among other species, by marine diatoms of the genus Pseudo-nitzschia. In this work, a method for the determination of dissolved DA and its isomers present in seawater has been developed, based on a solid-phase extraction (SPE) disks followed by rapid resolution liquid chromatography coupled with tandem mass spectrometry. SPE provided sample desalting and 20-fold concentration of dissolved DA, while complete resolution between DA and its isomers was achieved in less than 3 min with rapid resolution chromatography thus providing high sample throughput. Additionally, a simple on-column chromatographic procedure allowed head-column trapping of DA providing 15-fold higher sensitivity. The conditions developed in this work have shown appropriate quality parameters in a within-laboratory validation. The detection limit was 0.02 ng mL(-1) for the whole method, while trueness ranged between 92.1% and 110.6% recovery and precision between 8.4% and 19.0% relative standard deviation. Expanded uncertainty measured was 1.92, 0.23 and 0.03 for 10.0, 1.0 and 0.1 ng mL(-1) DA concentrations, respectively, which demonstrated the accuracy of this method for confirmation and quantification of DA present at very low concentration levels in seawater.

Advanced studies for the application of high-performance capillary electrophoresis for the analysis of yessotoxin and 45-hydroxyyessotoxin

Yessotoxins (YTXs) are a group of polyether toxins which have been previously reported as responsible for seafood contamination in several places worldwide. Despite their toxicity, which is not yet fully discussed, YTXs have been reported as an interference in the success of mouse bioassay for the determination of diarrhetic shellfish poisoning (DSP) toxins, and therefore, efficient and reliable analytical methodologies are required to evaluate their presence, avoiding false positives for DSP. High-performance capillary electrophoresis (HPCE) is presented in this work as an alternative to HPLC technique widely used for the analysis of YTXs. Improvements in the applicability of HPCE have been carried out through the development of different CE modes as well as different detection modes. With this aim, micellar electrokinetic chromatography (MEKC) has been considered for an increased selectivity while an increased sensitivity was achieved by using sample stacking. Moreover, the coupling of CE with mass spectrometry allowed the confirmation of YTXs present in the contaminated samples evaluated in this work. The results obtained showed the potential of CE as an alternative to HPLC for the analysis of YTXs present in naturally contaminated samples.