Detect toxins in fish and shellfish with your mobile phone

A biosensor connected to the mobile phone will allow the detection of toxins in fish and shellfish linked to food poisoning.

Researchers from the Rovira i Virgili University (URV) in Tarragona and the Institute of Agrifood Research and Technology (IRTA) dependent on the Government of Catalonia, are developing, through the CELLECTRA project, new biotechnological tools to detect toxins in seafood. The objective is to create reliable and sensitive methodologies to detect ciguatoxins and tetrodotoxins in fish and shellfish, two toxins typical of tropical places that have been spreading to temperate waters of the Atlantic and the Mediterranean, possibly due to the influence of global climate change. To this we must add that, due to the globalization of trade, in the market we find species of fish and shellfish from different seas.

Thanks to this project, the research team will produce biosensors, devices that can detect toxins from purified samples of shellfish and fish. Biosensors are based on three types of elements that will allow toxins to be recognized: in cells, which allow toxicological screening of toxins; and in receptors and in aptamers —single chain nucleic acids—, with which, based on the chemical structure of the toxins, they can be specifically detected. The device will be able to connect to the mobile phone and will immediately provide the results of the analysis. “Faced with the increase in intoxications, we need a fast, sensitive, efficient and, above all, portable system, because it must be easy to use by producers, fish distribution points, supermarkets and food safety agencies,” says Mònica Campàs, researcher of the Marine and continental waters program of the IRTA and coordinator of the project.

In the first year of CELLECTRA, scientists focused on the early stages of biosensor design. They have managed to immobilize cells on electrodes, which are the ones that will give the answer for the analysis of toxic samples. They have also obtained receptors from mammalian neuronal cells, and in the laboratory they have produced aptamers that recognize tetrodotoxin. Lastly, cyclodextrins have been synthesized, sugar-based compounds that are capable of capturing ciguatoxins from samples and concentrating them to make them easier to detect. “The combination of all these elements makes the biosensor very reliable,” remarks Ciara K. O’Sullivan, ICREA researcher who leads the project at the URV, together with researcher Alex Fragoso.

Ciara O’Sullivan, in the image, leads the project, together with Alex Fragoso, at the URV. (Photo: URV)

Ciguatera, the most common marine toxin poisoning

Ciguatoxins are neurotoxins produced by dinoflagellate microalgae of the Gambierdiscus and Fukuyoa genera that accumulate in fish and other marine animals, mainly in tropical areas. People who eat seafood containing ciguatoxins can get food poisoning called ciguatera. The symptoms of this intoxication can be gastrointestinal, cardiovascular and neurological. Ciguatoxins are heat stable, that is, they are not eliminated when they are cooked or frozen. In addition, they are colorless, odorless and tasteless. At a chemical level, their structures are very complex, making them very difficult to detect. “In recent years, outbreaks have increased in areas where previously they had not been detected, which is why surveillance programs must be carried out and tools available to detect them,” warns Campàs.

Tetrodotoxin, beyond the puffer fish

The majority of poisonings due to this neurotoxin are due to the consumption of puffer fish (Fugu), which, in fact, is prohibited in Europe. However, it has also been detected in other marine animals such as sea urchins and mussels, and even in land animals such as insects, newts and frogs. The diversity of ecosystems where tetrodotoxins exist means that their origin is still unclear. It is known that there are some bacteria associated with these species that produce it, but it has not yet been scientifically resolved if it is a symbiotic relationship or if these animals are also capable of producing it. (Source: URV)