ESR3 Massimo Picardo

Project: Suspect screening of natural toxins in surface water reservoirs

Principal supervisor: Dr. Marinella Farré

Intro to project: 

Natural toxins in the aquatic ecosystem can be produced by different organisms, including bacteria, plants and fungi, thus grouping a wide variety of structures and physicochemical properties and toxicological effects. The risk of water contamination by natural toxins generates environmental and public health issues. In some cases, natural toxins can be accumulated in aquatic organisms and transferred throughout the aquatic food chain to humans. Most of the reported toxic compounds in environmental samples are cyanotoxins of which are reported different compounds and congeners: hepatotoxic peptides called microcystins (almost 80 congeners), nodularins, neurotoxic, cytotoxic and dermatotoxic alkaloids. However, scarce consideration has been given for other compounds such as phytotoxins and mycotoxins which have been rarely reported as environmental natural contaminants. In addition, only microcystin-LR was regulated by the European Union to 1 µg/L in drinking water. 

Since natural toxins have been recognized as dangerous and harmful for humans, many authors have conducted studies on the occurrence and distribution into the aquatic environment. In order to determine and quantify toxins content, lots of analytical methods have been reported. However, most of them have been reported to be specific for a low number of target compounds. https://doi.org/10.1016/j.trac.2018.12.017. Nevertheless, the number of natural toxins is huge and most of the dedicated target methods cannot keep up with their different chemical-physical characteristics. 

Outputs: This project aimed first to collect information from online libraries to create one dedicated dataset of the most reported natural toxins with all known and unknown mass spectrums reported in the literature, in order to allow a fast and efficient determination with further instrumental analysis. 

A previous purification and concentration step using a triple solid-phase extraction (SPE) was proposed to retain a wide range of toxins with different polarities.

Then we developed and optimized an LC-HRMS/MS method using data-dependent acquisition for the tentative identification of natural toxins in surface water reservoirs (https://doi.org/10.1016/j.chemosphere.2020.127888).

The method was then applied to analyse water samples coming from a sampling campaign from March to September 2018 along the Ter River in Catalonia (ES). Here the results showed the presence of a high number of phytotoxins with a minor presence of mycotoxins and cyanotoxins. the occurrence was driven by the botanical diversity and the anthropization of the area both with the chemical physic characteristics of the river (Suspect and target screening of natural toxins in the Ter River catchment area and prioritisation by their toxicity, Toxins, ISSN 2072-6651). 

Further improvements allowed further customization of the previously published screening method with a data-independent acquisition approach. Here the mass spectrums acquisition was carried out with an LC-HRMS/MS under All Ion Fragmentation mode. The Following step considers the characterization of natural toxins structures using Compound Discoverer 3.1 as a primary filter, followed by the comparison of the MS/MS spectrums with MzCloud, and fragmentation prediction with Metfrag. The method was applied in real samples coming from Spain, Italy and the Czech Republic.

PhD thesis will be discussed in January 2021