Liquid Chromatography−Tandem Mass Spectrometry Application, for the Determination of Extracellular Hepatotoxins in Irish Lake and Drinking Waters

Antioxidant micropeptins from a Microcoleus autumnalis-dominated benthic cyanobacterial mat from Western Ireland

Exploring the chemical diversity present in cyanobacterial mats increasingly frequent in fresh and marine waters is imperative for both evaluating risks associated with these diverse biofilms and their potential for biodiscovery. During a project aimed at the study of the (eco)toxicity of benthic cyanobacteria blooming in some lakes of the West of Ireland, three previously undescribed ahp-cyclodepsipeptides micropeptin LOF941 (1), micropeptin LOF925 (2) and micropeptin LOF953 (3) were isolated from the Microcoleus autumnalis-dominated benthic cyanobacterial biofilm collected from the shore of Lough O'Flynn, Co. Roscommon, Ireland. Their structures remain consistent in their amino acid sequence with the presence of an unusual methionine, and differ by their exocyclic side chains. The planar structures of the previously undescribed micropeptins were elucidated by 1D and 2D NMR and HRESIMS analyses, and their 3D configurations assessed by ROESY NMR and Marfey's analyses. The three isolated compounds showed no cytotoxic effects and all three compounds were shown to exhibit antioxidant properties, with 1 showing the highest bioactivity. Additionally, several micropeptin analogues are proposed from the methanolic fraction of the biofilm extract by UHPLC-HRESIMS/MS analysis and molecular networking. Notably, the known cyanotoxins anatoxin-a and dihydroanatoxin-a were annotated in the molecular network therefore raising issues about the toxicity of this cyanobacterial mat.

Self-powered Aptasensors Made with the In2O3-In2S3-Ti3C2 Composite for Dual-mode Detection of Microcystin-LR

A dual-mode self-powered aptasensing platform of photoelectrochemical (PEC) and photofuel cell (PFC) was constructed for Microcystin-LR (MC-LR) detection. Specifically, the In₂O₃-In₂S₃-Ti₃C₂ (IO-IS-TC) composite was facilely assembled on the base of MOF-derived In₂O₃ hollow tubulars, and the integrated mechanism and photoconversion efficiency are proposed and discussed in detail. Herein, a promising dual-mode sensing platform was constructed using the IO-IS-TC composite as a photoanode matrix with higher output power and obvious photocurrent response. Moreover, the dual-mode sensing platform did not require external bias and the addition of sacrificial agents under visible light irradiation. The enhanced PEC properties can be attributed to the matched energy level of ternary components and the improved separation of photogenerated carriers. Moreover, aptamer-based recognition was adopted to catch MC-LR molecules, which realized the highly sensitive and selective detection. The PFC aptasensor was exhibited at 50-5 × 10⁵ pmol/L with a detection limit of 17.4 pmol/L, and the PEC aptasensor was realized from 0.5 to 4 × 10⁵ pmol/L with a detection limit of 0.169 pmol/L. The proposed aptasensing platform showed good specificity, reproducibility, and stability, which paved the way for the construction of a fast and ultrasensitive PEC sensing methodology for environmental analysis.

Quantification of 17 Endogenous and Exogenous Steroidal Hormones in Equine and Bovine Blood for Doping Control with UHPLC-MS/MS

A simple and fast analytical method able to simultaneously identify and quantify 17 endogenous and exogenous steroidal hormones was developed in bovine and equine blood using UHPLC-MS/MS. A total amount of 500 µL of sample was deproteinized with 500 µL of a mixture of methanol and zinc sulfate and evaporated. The mixture was reconstituted with 50 µL of a solution of 25% methanol and injected in the UHPLC-MS/MS triple quadrupole. The correlation coefficients of the calibration curves of the analyzed compounds were in the range of 0.9932–0.9999, and the limits of detection and quantification were in the range of 0.023–1.833 and 0.069–5.5 ppb, respectively. The developed method showed a high sensitivity and qualitative aspects allowing the detection and quantification of all steroids in equine and bovine blood. Moreover, the detection limit of testosterone (50 ppt) is half of the threshold admitted in plasma (100 ppt). Once validated, the method was used to quantify 17 steroid hormones in both bovine and equine blood samples. The primary endogenous compounds detected were corticosterone (range 0.28–0.60 ppb) and cortisol (range 0.44–10.00 ppb), followed by androstenedione, testosterone and 11-deoxycortisol.

Harmful Algal Bloom Toxins in Aerosol Generated from Inland Lake Water

Harmful algal blooms (HABs) caused by cyanobacteria in freshwater environments produce toxins (e.g., microcystin) that are harmful to human and animal health. HAB frequency and intensity are increasing with greater nutrient runoff and a warming climate. Lake spray aerosol (LSA) released from freshwater lakes has been identified on lakeshores and after transport inland, including from lakes with HABs, but little is known about the potential for HAB toxins to be incorporated into LSA. In this study, freshwater samples were collected from two lakes in Michigan: Mona Lake during a severe HAB with microcystin concentrations (>200 μg/L) well above the Environmental Protection Agency (EPA) recommended "do not drink" level (1.6 μg/L) and Muskegon Lake without a HAB (<1 μg/L microcystin). Microcystin toxins were identified in freshwater, as well as aerosol particles generated in the laboratory from Mona Lake water by liquid chromatography-tandem mass spectrometry (LC-MS/MS) at atmospheric concentrations up to 50 ± 20 ng/m³. Enrichment of hydrophobic microcystin congeners (e.g., microcystin-LR) was observed in aerosol particles relative to bulk freshwater, while enrichment of hydrophilic microcystin (e.g., microcystin-RR) was lower. As HABs increase in a warming climate, understanding and quantifying the emissions of toxins into the atmosphere is crucial for evaluating the health consequences of HABs.

Development and single-laboratory validation of a UHPLC-MS/MS method for quantitation of microcystins and nodularin in natural water, cyanobacteria, shellfish and algal supplement tablet powders

A simple, rapid UHPLC-MS/MS method has been developed and optimised for the quantitation of microcystins and nodularin in wide variety of sample matrices. Microcystin analogues targeted were MC-LR, MC-RR, MC-LA, MC-LY, MC-LF, LC-LW, MC-YR, MC-WR, [Asp3] MC-LR, [Dha7] MC-LR, MC-HilR and MC-HtyR. Optimisation studies were conducted to develop a simple, quick and efficient extraction protocol without the need for complex pre-analysis concentration procedures, together with a rapid sub 5min chromatographic separation of toxins in shellfish and algal supplement tablet powders, as well as water and cyanobacterial bloom samples. Validation studies were undertaken on each matrix-analyte combination to the full method performance characteristics following international guidelines. The method was found to be specific and linear over the full calibration range. Method sensitivity in terms of limits of detection, quantitation and reporting were found to be significantly improved in comparison to LC-UV methods and applicable to the analysis of each of the four matrices. Overall, acceptable recoveries were determined for each of the matrices studied, with associated precision and within-laboratory reproducibility well within expected guidance limits. Results from the formalised ruggedness analysis of all available cyanotoxins, showed that the method was robust for all parameters investigated. The results presented here show that the optimised LC-MS/MS method for cyanotoxins is fit for the purpose of detection and quantitation of a range of microcystins and nodularin in shellfish, algal supplement tablet powder, water and cyanobacteria. The method provides a valuable early warning tool for the rapid, routine extraction and analysis of natural waters, cyanobacterial blooms, algal powders, food supplements and shellfish tissues, enabling monitoring labs to supplement traditional microscopy techniques and report toxicity results within a short timeframe of sample receipt. The new method, now accredited to ISO17025 standard, is simple, quick, applicable to multiple matrices and is highly suitable for use as a routine, high-throughout, fast turnaround regulatory monitoring tool.

A pM leveled photoelectrochemical sensor for microcystin-LR based on surface molecularly imprinted TiO2@CNTs nanostructure

A simple and highly sensitive photoelectrochemical (PEC) sensor towards Microcystin-LR (MC-LR), a kind of typical cyanobacterial toxin in water samples, was developed on a surface molecular imprinted TiO₂ coated multiwalled carbon nanotubes (MI-TiO₂@CNTs) hybrid nanostructure. It was synthesized using a feasible two-step sol-gel method combining with in situ surface molecular imprinting technique (MIT). With a controllable core-shell tube casing structure, the resultant MI-TiO₂@CNTs are enhanced greatly in visible-light driven response capacity. In comparison with the traditional TiO₂ (P25) and non-imprinted (NI-)TiO₂@CNTs, the MI-TiO₂@CNTs based PEC sensor showed a much higher photoelectric oxidation capacity towards MC-LR. Using this sensor, the determination of MC-LR was doable in a wide linear range from 1.0pM to 3.0nM with a high photocurrent response sensitivity. An outstanding selectivity towards MC-LR was further achieved with this sensor, proven by simultaneously monitoring 100-fold potential co-existing interferences. The superiority of the obtained MC-LR sensor in sensitivity and selectivity is mainly attributed to the high specific surface area and excellent photoelectric activity of TiO₂@CNTs heterojunction structure, as well as the abundant active recognition sites on its functionalized molecular imprinting surface. A promising PEC analysis platform with high sensitivity and selectivity for MC-LR has thus been provided.

Homogeneous time-resolved fluoroimmunoassay of microcystin-LR using layered WS2 nanosheets as a transducer

A homogeneous time-resolved fluoroimmunoassay method for rapid and sensitive detection of microcystin-LR (MC-LR) in water samples was developed based on the interaction between water-soluble WS₂ nanosheets and the conjugate of MC-LR with a luminescent Eu³⁺ complex BHHBCB-Eu³⁺ (BHHBCB: 1,2-bis[4'-(1″,1″,1″,2″,2″,3″,3″-heptafluoro-4″,6″-hexanedion-6″-yl)- benzyl]-4-chlorosulfobenzene). The large lateral dimensions and high surface areas of two-dimensional layered WS₂ nanosheets enable easy adsorption of the MC-LR-BHHBCB-Eu³⁺ conjugate, that lead to efficient quenching of the luminescence of Eu³⁺ complex via energy transfer or electron transfer process. However, the addition of monoclonal anti-MC-LR antibody can induce the formation of MC-LR-BHHBCB-Eu³⁺/antibody immune complex, which prevents the interaction between WS₂ nanosheets and MC-LR-BHHBCB-Eu³⁺ to result in the restoration of Eu³⁺ luminescence. This signal transduction mechanism made it possible for analysis of the target MC-LR in a homogeneous system. The present method has advantages of rapidity and simplicity since the B/F (bound reagent/free reagent) separation steps, the solid-phase carrier and antibody labeling or modification process are not necessary. The proposed immunosensing system displayed a wide linear range, good precision and accuracy, and comparable sensitivity with a detection limit of 0.3 μg l^-1, which satisfied the World Health Organization (WHO) provisional guideline limit of 1.0 μg l^-1 for MC-LR in drinking water.

Development and application of a UHPLC-MS/MS method for the simultaneous determination of 17 steroidal hormones in equine serum

A new, fast and simple analytical method that is able to identify and quantify simultaneously 17 steroid hormones and metabolites (pregnenolone, 17-OH-pregnenolone, progesterone, 17-OH-progesterone, androsterone, androstenedione, dehydroepiandrosterone, dehydroepiandrosterone sulfate, testosterone, cortisol, corticosterone, aldosterone, 11-deoxycortisol, 11-deoxycorticosterone, dihydrotestosterone, estrone and estradiol) has been developed in equine serum using the ultra-high-performance liquid chromatography-tandem mass spectrometry technique. A total of 400 µl of sample was deproteinized with 1000 µl of acetonitrile, evaporated, restored with 50 µl of a solution of 25% methanol and injected in ultra-high-performance liquid chromatography-tandem mass spectrometry triple quadrupole. The recovery percentage obtained by spiking the matrix at two different concentrations with a standard mixture of steroid hormones was in all cases higher than 85.60% and with the percentage of coefficient of variation lower than 8.37%. The range of the correlation coefficients of the calibration curves of the analyzed compounds was 0.9922-0.9986, and the limits of detection and limits of quantification were in the range of 0.002-2 and 0.0055-5.5 ng ml^-1 , respectively. The detected limit of quantification for testosterone (i.e. 50 pg ml^-1 ) is twofold lower with respect to its threshold admitted in geldings plasma (100 pg ml^-1 free testosterone). The high sensitivity and the quantitative aspect of the method permitted to detect most of the steroids in equine serum. Once validated, the method was used to quantify 17 steroid hormones in mare, stallion and gelding serum samples. The main steroids detected were corticosterone (range 37.25-51.26 ng ml^-1 ) and cortisol (range 32.57-52.24 ng ml^-1 ), followed by 17-OH-pregnenolone, dihydrotestosterone and pregnenolone. Copyright © 2016 John Wiley & Sons, Ltd.

Electrospun polymer nanofibres as solid-phase extraction sorbents for extraction and quantification of microcystins

Electrospun polymer nanofibres were used as novel solid-phase extraction (SPE) sorbents to extract and quantify the microcystins (MCs) including microcystin-RR (MC-RR) and microcystin-LR (MC-LR) from in-suit water samples. The parameters that influenced the extraction efficiency were studied, including the amount of nanofibre, eluted solvent, eluted volume, pH, and the water sample volume. Under optimized conditions, a linear response for MC-RR and MC-LR over the range of 0.25-4 µg/L was achieved with r(2) values of 0.998 and 0.997, respectively. The extraction recovery of MC-RR and MC-LR was 97-102% and 98-100%, respectively, when the MC concentration was 0.25-4 µg/L. When their concentrations ranged from 0.05  to 0.25 µg/L, the MCs could be detected with high accuracy by the nanofibre SPE sorbent combined with nitrogen gas. Due to its simplicity, environment-friendliness, high efficiency, reusability, and sensitivity, the electrospun polymer nanofibre can be applied as a novel SPE sorbent to extract and detect the MCs from in-suit water samples.

Investigation of targeted pyrrolizidine alkaloids in traditional Chinese medicines and selected herbal teas sourced in Ireland using LC-ESI-MS/MS

Publications linking hepatotoxicity to the use of herbal preparations are escalating. Herbal teas, traditional Chinese medicines (TCMs) and dietary supplements have been shown to contain pyrrolizidine alkaloids (PAs). Acute PA toxicosis of the liver can result in sinusoidal-obstruction syndrome, also known as veno-occlusive disease (VOD). This paper describes a sensitive and robust method for the detection of targeted PAs and their N-oxides (PANOs) in herbal products (selected herbal teas and TCMs) sourced within Ireland. The sample preparation includes a simple acidic extraction with clean-up via solid-phase extraction (SPE). Sample extracts were accurately analysed by using LC-ESI-MS/MS applying for the first time a pentafluorophenyl (PFP) core-shell column to the chromatographic separation of PAs and PANOs. The method was validated for selectivity, taking into consideration matrix effects, specificity, linearity, precision and trueness. Limits of detection (LOD) and limits of quantitation (LOQ) were quantified for all PAs and PANOs ranging from 0.4 to 1.9 µg kg⁻¹ and from 1.3 to 6.3 µg kg⁻¹, respectively. In this study 10 PAs and four PANOs were targeted because they are commercially available as reference standards. Therefore, this study can only report the levels of these PAs and PANOs analysed in the herbal teas and TCMs. The results reported represent the minimum levels of PAs and PANOs present in the samples analysed; commercially available herbal teas (n = 18) and TCMs (n = 54). A total of 50% herbal teas and 78% Chinese medicines tested positive for one or more PAs and/or PANOs included within this study, ranging from 10 to 1733 and from 13 to 3668 µg kg⁻¹, respectively.

Determination of microcystins and nodularin (cyanobacterial toxins) in water by LC-MS/MS. Monitoring of Lake Marathonas, a water reservoir of Athens, Greece

A method for the determination of the hepatotoxic cyanotoxins microcystins (MCs, i.e. MC-LR, MC-RR, MC-YR, MC-LA) and nodularin (NOD) in water was developed using liquid chromatography with electrospray ionization triple quadrupole mass spectrometry (LC-ESI-MS/MS) after solid phase extraction (SPE). New patterns of fragmentation of MC-LA were observed under the experimental conditions used. The method was fully validated to meet accreditation criteria. Mean recoveries at three concentration levels (0.006, 0.1 and 1 μg L(-1)) ranged between 70 and 114% with %RSD values generally below 20%. Detection limits were 2 ng L(-1) for all hepatotoxins. The method was applied to study the occurrence of MCs and NOD in Lake Marathonas, a water reservoir of Athens, over a period from July 2007 to December 2010. The protein phosphatase inhibition assay (PPIA) was additionally used for fast screening of samples. MC-YR, MC-LR and MC-RR were detected and found to vary seasonally with consistent peaks during early autumn, having maximum concentrations of 717, 451 and 174 ng L(-1), respectively. The results of this study constitute the first report on the presence, concentration levels and seasonal variations of MCs in Lake Marathonas. None of the target cyanotoxins were detected in treated drinking water samples during the period of the study.

Monitoring approaches for a toxic cyanobacterial bloom

Cyanobacterial blooms, dominated by Microcystis sp. and associated microcystin variants, have been implicated in illnesses of humans and animals. Little is known regarding the formation of blooms and the presence of cyanotoxin variants in water bodies. Furthermore, the role played by ecological parameters, in regulating Microcystis blooms is complicate and diverse. Local authorities responsible for water management are often faced with the challenging task of dealing with cyanobacterial blooms. Therefore, the development of suitable monitoring approaches to characterize cyanobacterial blooms is an important goal. Currently, various biological, biochemical and physicochemical methods/approaches are being used to monitor cyanobacterial blooms and detect microcystins in freshwater bodies. Because these methods can vary as to the information they provide, no single approach seemed to be sufficient to accurately monitor blooms. For example, immunosensors are more suited for monitoring the presence of toxins in clear water bodies while molecular methods are more suited to detect potentially toxic strains. Thus, monitoring approaches should be tailored for specific water bodies using methods based on economic feasibility, speed, sensitivity and field applicability. This review critically evaluates monitoring approaches that are applicable to cyanobacterial blooms, especially those that focus on the presence of Microcystis, in freshwater bodies. Further, they were characterized and ranked according to their cost, speed, sensitivity and selectivity. Suggested improvements were offered as well as future research endeavors to accommodate anticipated environmental changes.

Simultaneous quantification of microcystins and nodularin in aerosol samples using high-performance liquid chromatography/negative electrospray ionization tandem mass spectrometry

RATIONALE

Cyanobacteria are a small group of photosynthetic planktonic bacteria, producing a large group of strong hepatotoxins called microcystins (MCs). Many studies have been conducted to evaluate the presence of MCs and nodularin (NOD) in water or in marine organisms, but little research has been done on the atmospheric environment. Waterborne toxins can be found in the aerosol phase due to bubble-bursting processes.

METHODS

The aim of this study was to obtain a sensitive method for the simultaneous determination of trace concentrations of individual cyanotoxins in aerosol samples, using liquid chromatography coupled with a triple quadrupole (HPLC/MS/MS). During method development improved electrospray ionization was found in negative ion mode. In contrast with other authors, we have developed a chromatographic separation using alkaline conditions, thus achieving good resolution, improved electrospray ionization and therefore better sensitivity.

RESULTS

A sensitive analytical method was set up to simultaneously measure trace concentrations of cyanotoxins in aerosol samples in a single chromatographic analysis using the internal standard method. The limit of detection for all the toxins was determined to be between 1 fg/μL (MC LA and LF) and 9 fg/μL (NOD).

CONCLUSIONS

The method was applied to ten aerosol samples from the Venice Lagoon. In these samples, trace concentrations of MC-LA ranging between 90 fg m(-3) and 706 fg m(-3), MC-LF between n.d. and 369 fg m(-3) and MC-LW between n.d. and 262 fg m(-3). This is the first study to quantify the cyanotoxins in Venetian aerosol samples using the HPLC/(-)ESI-MS/MS.

Initial studies on the occurrence of cyanobacteria and microcystins in Irish lakes

We report the results of a synoptic survey at 14 sites across the north of Ireland undertaken to determine the occurrence of cyanobacteria and their constituent microcystin cyanotoxins. Seven microcystin toxins were tested for, and five of which were found, with MC-LR, MC-RR, and MC-YR being the most prevalent. Gomphosphaeria spp and Microcystis aeruginosa were the most dominant cyanobacterial species encountered. Together with Aphanizomenon flos-aquae, these were the cyanobacteria associated with the highest microcystin concentrations. The occurrence of several microcystin toxins indicates that there may potentially be more than one cyanobacteria species producing microcystins at many sites. Total microcystin concentrations varied over three orders of magnitude dividing the sites into two groups of high (>1000 ngMC/μgChla, six sites) or low toxicity (<200 ngMC/μgChla, eight sites).

Facile and rapid access to linear and truncated microcystin analogues for the implementation of immunoassays

A series of simplified microcystin-LR analogues based on Adda [(2S,3S,8S,9S,4E,6E)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldecadienoic acid] or its corresponding aldol precursor linked to a polypeptide moiety have been synthesised and assessed for their binding affinity by the monoclonal antibody mAb MC159, an anti-microcystin-LR mAb recently selected by us for the detection of microcystins through various immunoassay formats. Some modifications have been brought to the enantiospecific synthesis of N-Boc-Adda developed by Pearson et al. (Org. Lett., 2000, 2, 2901) which enabled us to access in an economical and time-saving manner a small library of MC-LR linear analogues. Among which Adda was chosen to synthesise, as an illustrative example, a fluorescent probe derived from this beta-amino acid. This probe was subsequently solid-phase immobilised by means of oxime ligation in order to lead to biochips suitable for microcystin detection through the SPIT-FRI method.