Developing New Strategies for Cyanotoxin Determination using High Resolution Mass Spectrometry

Dr Audrey Roy-Lachapelle, Postdoctoral Fellow at Environment and Climate Change Canada

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Environment and Climate Change Canada

SelectScience^® spoke with Dr Audrey Roy-Lachapelle, Postdoctoral Fellow at Environment and Climate Change Canada, to learn how she works to improve cyanotoxin risk assessment to safeguard human health and the environment.

Cyanotoxins are secondary metabolites that form when populations of cyanobacteria reproduce exponentially, creating bacterial blooms in water sources. They include some of the most poisonous toxins known and Dr Roy-Lachapelle notes that they are linked with neurodegenerative diseases, as well as being harmful to animals and the environment. Dr Roy-Lachapelle works closely with the University of Montreal, under the direction of Prof. Sébastien Sauvé, who’s laboratory “focuses on the study of the bioavailability and speciation of trace elements in soils and water”, explains Dr Roy-Lachapelle.

One cyanotoxin in particular, β-Methylamino-L-alanine (BMAA), is “a non-proteinogenic amino acid linked to ALS and Parkinson's Disease”, she describes. By using a variety of sample preparation techniques including derivatization, Dr Roy-Lachapelle and her team have been able to facilitate chromatography of BMAA and “three other cyanotoxins for the first time”,. She informs us that, once separated, it is possible to selectively detect BMAA from its conformation isomers, allowing identification of the possible structures of the derivative fragments. The team was then able to successfully apply this new method and report BMAA in lake water for the first time in the province of Quebec in Canada.

The need for determination

Despite making significant grounds towards effective cyanotoxin determination, “overall, cyanotoxins detection methods are not sufficient to assess the global risk from a toxic cyanobacterial bloom”, Dr Roy-Lachapelle explains. According to her, there are a number of different cyanotoxin types, the most widespread being microcystins, which also include many varying congeners. As a result, complete determination of all toxins within a sample can be very difficult. Current microcystin determination capabilities are not sufficient as there are “more than 100 congeners known but only about 12 standards are available for analysis”, Dr Roy-Lachapelle comments. This lack of understanding can lead to harmful consequences to public safety.

Challenges of detection

The occurrence of cyanobacterial blooms is dependent on a number of conditions, such as temperature, light and nutrients. However, predicting the time and place of their appearances, as well as the genera and strain of bacteria that occur, is “almost impossible”, Dr Roy-Lachapelle states. “With this in mind, we cannot target specific cyanotoxins and be sure we have evaluated the global toxicity of the bloom”,. Other factors such as differing structural diversity “complicates the extraction, chromatographic and analysis conditions”,. This emphasizes the need for analytical detection method that encompasses the broadest range of toxins possible.

Validation by high resolution mass spectrometry

To facilitate targeted screening and quantification, Dr Roy-Lachapelle uses the Thermo Scientific™ Q Exactive™ Hybrid Quadrupole-Orbitrap™ Mass Spectrometer, which enables her to selectively detect cyanotoxins, following sample derivatization or oxidation. In one experiment, they were able to isolate a common moiety in over 100 microcystin congeners using oxidation. Once identified, high resolution mass spectrometry can be employed to “estimate the concentration of all the congeners for a better risk assessment”, Dr Roy-Lachapelle explains.

A key benefit of this technology is its ability to “overcome isobaric interferences which cannot be avoided using low resolution triple quadrupole”, Dr Roy-Lachapelle remarks. High resolution mass spectrometry also brings about another key advantage over traditional techniques, in that it enables detection of compounds without the use of certified standards, which “is very useful for us, considering that the majority of cyanotoxins are not available as standards”, she adds.

The future

Dr Roy-Lachapelle concludes by highlighting that “it is important to continue the study of these toxins, to have a better understanding of their occurrence, nature and toxicity. The future of our research resides on the improvement of their detection, and also a better understanding of their degradation, using a metabolomics approach”.

“With improved mass spectrometric technologies that are more accessible, and the potential miniaturization for portable devices used in the field, it will be possible to directly analyze the risk of algal blooms, by investigating all toxins and congeners, to assess actual toxicity. With high resolution mass spectrometry, it is now possible to detect and validate the presence of untargeted compounds without the use of certified standards, and this is a big step for the study of emerging contaminants”, she finishes.

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