The Red Tide is a natural phenomenon occurring in many coasts around the globe. It consists in a rapid increase of toxic microalgae, being the most important the ones near the extraction zones of where we get our seafood. When the shellfish eat these toxic algae, they become poisonous to us, so the government (or the respective responsible entity) needs to analyze all the seafood extracted to make sure our food is not contaminated, which means thousands of analysis per week worldwide.

Scientists around the world have developed a very reliable method of analysis: The Bioassay. Keeping it simple, they blend a sample of the shellfish meant to be sold, mix it with special chemicals and inject it directly into 3 different mice's stomachs. After a while, they can see the results: if 2 or more of them die, they say the shellfish is poisoned, so we can't eat them.

The most remarkable feature of this method is that it is effective (Ref. 1), so effective that there are rarely some cases of intoxicated people around the world. But there are two big problems:

First, it's the logistics. It needs to be done in a laboratory, which sometimes is located far away from the extraction zones. It also needs to have the right equipment to keep the mice in good shape to be used in the assays. Another problem is that it needs to be done by an expert team of scientists that can precisely inject the mice and see the results.

Second, and most importantly: Ethics. We are talking of thousands of analysis per week, each one taking at least 3 mice to be correctly done. And let us clarify: If the sample resulted not to be contaminated, which is the most cases (more than 99%) the mice need to be sacrificed anyway. In other words, thousands of animals are dying for nothing.

Additionally, all of the problems listed above involve a lot of money; starting with the transfer of the shellfish sample to the laboratory, to the mice themselves.

There have been efforts to make protein-based kits for the detection of the toxins, but they have their own flaws: Due to the protein-based nature of the detection tools, they still need a lot of equipment in the laboratory, along with trained scientists to perform the assays. Also, proteins are easily degraded, so the results are not always consistent, meaning that they have a dangerous amounts of false negative results (Ref. 2).

As you can see, there is an urge to develop an alternative method for the detection of the toxins, mainly because of the ethical problem. In Chile, professor Benjamín Suárez, who is the Director of the Marine Toxins Laboratory of the University of Chile (and also one of our main advisors) along with his experts team, have sent a formal petition to the government, asking for the number of mice to be reduced, from 3 to 2, for each assay (Ref 3). In the document, they basically explain that the third mouse is not necessary, because 2 are enough for the detection of a toxin concentration that is dangerous for humans, and the third one will only indicate if the concentration is way up the mentioned threshold. This document is currently under revision, but even if they manage to convince the authorities, it will only be a little step for the solving of the problem.

With all this in mind, we designed our project, knowing it would be a difficult task for a bunch of undergraduate students, but also that we had professor Benjamin and professor Francisco Chávez (Director of the Systems Microbiology Laboratory of the University of Chile) supporting our work.

Here we present to you Tenzyme Vilú, a portable device for the detection of marine toxins.

This biosensor does not use any living organisms nor the mentioned problematic proteins, it uses a novel system of molecular detection called Aptazymes. We designed Tenzyme Vilú to specifically solve the problems listed above.

As said, our device solves the logistic problems as it can be used directly into the extraction zone, due to its portable and ergonomic design. The biggest feature of our device is that it gives a colorimetric response to the presence of the toxins, meaning that anyone with a normal functioning vision can see and interpret the results. All you need to do is put the shellfish in the grinder, mix it with the chemicals we provide and put this mix in the paper included in our device. After a few minutes the paper will change its color to turquoise if toxins were present in the sample, but if not, it will remain colorless.

As you can see, the key element of our device is the paper matrix. It contains our molecular tool, which is the one responsible for both the sensing of the toxin and the chemical reaction that causes the solution to change its color. This is the reason why we made the paper matrix disposable, so you won't have to dispose all the device after an assay, you just need to wash the chassis and change the paper. You will find further information about the device design in our Design section.

Our detection method has another feature: it can detect a lower concentration of the marine toxins than the bioassay. It means a lot, because the increase in the concentration of the toxin in the shellfish is gradual, so the sooner you detect it the better you can respond, which will make sense later.

We (and maybe you) know that replacing the mice bioassay is an almost impossible task, due to the international regulations on the subject. That's why we want to keep clear that the main goal of our project is not to replace this method, but to function as a fast and reliable screening method: A "filter". We mentioned that the most important problem to solve is the one involving the deaths of thousands of animals per year, so what we want to achieve is that the regulatory entities acknowledge our device as a valid method for detecting the absence of toxins in the shellfish samples. That is, if the user get ambiguous or positive results, then they can use the bioassay to assure the consumer safety. This way we will stop wasting thousands of precious animals lives just to find the samples had no toxins on them.

In South America, and specially in Chile, science is not a priority for the government to fund. That's why we need to prove that our work will have a huge impact in our society, and Tenzyme Vilú is not an exception.

In the south of our country there are hundreds of families that make a living out of the shellfish extraction. When problems like the red tide strike those localities, these families are left with no economical income for a week or two, if the losses are low. With a tool like ours, they can anticipate the appearance of higher concentrations (as said before) and prepare a better response for when the shellfish reach a dangerous concentration. You can find a better description of how Tenzyme Vilú helps our community in the Human Practices section.