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A tiny wire with a memory to diagnose cancer

17.08.16 - EPFL researchers have used a nanowire to detect prostate cancer with greater accuracy than ever before. Their device is ten times more sensitive than any other biosensor available.

One indicator that a cancer has started to develop is the presence of biomarkers. These are molecules that are produced by the cancer and pass into the bloodstream.

Researchers at EPFL's Integrated Systems Laboratory (LSI/STI) have developed a new type of sensor that can detect tiny quantities of these markers and thus improve diagnostic accuracy. The sensor comes in the form of a tiny wire and is ten times more sensitive than any other biosensor ever realized. It is therefore capable of detecting cancer at a very early stage so that patients can receive better treatment. The researchers' work has been published in Nano Letters.

An electrical component with a memory
When doctors suspect that a patient has cancer, they look for biomarkers in their body. But it's not easy to detect these molecules in very small quantities – blood is a very dense fluid, full of molecules and cells that get in the way.

EPFL researchers have managed to get around this obstacle by inventing a new detection technique. The trick is to trap the molecules of interest by the blood sample and then detect them in a dry environment, where measurements won’t be disturbed by all the molecules. To do this, the researchers used a Memristor – a new electrical component that can “remember” all the electrical currents that pass through it. The device has been successfully tested on the biomarker for prostate cancer, known as the Prostate Specific Antigen (PSA).

A nanowire, DNA fragments and an electric current
To begin with, fragments of modified DNA are grafted onto a silicon nanowire. The DNA is used to trap the molecules. It is modified so that it traps only the biomarkers for prostate cancer.

The wire is dipped into a cancer sample for close to an hour, giving the DNA time to get hold of the molecules. It is then dried and an electric charge is first sent through it. If there are molecules on the wire, they create resistance, which alters the wire's conductivity in places. But this alone is not enough to accurately detect the biomarkers.

It is only when the same charge is sent through the wire a second time in the opposite direction that the molecules can be properly detected. "If the wire had no memory, the two currents' curves would be superimposed, which means there's no memory effect," said Sandro Carrara, from the Integrated Systems Lab.

If the right biomarkers are trapped at the wire surface, then at the exact spot where the current reverse during the phases of sending charges into the wire, there will be a difference in the curve known as a voltage gap. It is this phenomenon that makes it possible to detect the biomarkers with so high sensitivity together with the use of modified DNA to trap the biomarkers.

"It's the first time a Memristor has been used to make such type of biosensor," said Carrara.

For now, the technique has only been used to detect biomarkers for prostate cancer. But it could be used for all types of markers. "We are also working with the Ludwig Institute and the CHUV hospital, which are providing us with samples and tumor extracts. Our next step is to use the same technique to detect breast cancer."


Project partners:

Experimental Oncology Group, Ludwig Institute for Cancer Research (Lausanne)
Senology Unit, Department of Obstetrics and Gynecology, CHUV hospital (Lausanne)
Department of Electronic & Electrical Engineering, University of Bath (United Kingdom)
Department of Informatics and Microsystem Technology, University of Applied Sciences Kaiserslautern, Zweibrücken (Germany)

Reference: Label-Free Ultrasensitive Memristive Aptasensor

EPFL news
Identifying pesticides in hair

15.08.16 - Summer series on student projects – For her Master’s project in environmental sciences, Christelle Oltramare collected 110 hair samples in Burkina Faso and came up with a process for identifying several types of pesticides.

She left with an empty suitcase and came back with one full of hair! Christelle Oltramare decided to do her Master’s project - EPFL Central Environmental Laboratory - in Burkina Faso – somewhat off the beaten path. For two months, she took hair samples from volunteers in several villages in order to measure how farmers are affected by their livelihood. She also wanted her research to include people who were not in direct contact with pesticides.

 “I did an internship last summer in occupational health, and I was really fascinated to discover how the environment can affect human health. Working with hair was an interesting new approach.” Many pesticides are known for being endocrine disruptors, or are assumed or known carcinogens. These toxic compounds are found in the environment, water and food.

Burkina Faso does not have the same regulations or oversight that Switzerland does when it comes to using dangerous products. “Most of the farmers don’t know how to read and they don’t differentiate – a pesticide is a pesticide whether it's meant for cotton or vegetables. And they often apply the same quantity of the product to their patch of land – measuring no more than 100 square meters – that an industrial farm would use for a hectare.”

Hair can now be analyzed for trace amounts of drugs, and there is a protocol. But in the absence of an accepted procedure for identifying pesticides, Oltramare took a method of extracting pesticides from fruits and vegetables and applied it to hair.

She had to play with several parameters in order to properly analyze the samples, washing the hair first to remove any dust and then dipping the hair into a solvent for the purposes of extraction. “We ran several trials to find the best solvent and the best phase for purification while at the same time ensuring no fatty acids remained in our sample and spoiled the analysis.”

She analyzed 73 samples. Her results showed that people are exposed to a number of pesticides, and that this is not due solely to their work. The farmers are affected the most, but the village's inhabitants were also exposed to pesticides through other vectors, like food and water.

EPFL news
All brawn, little brains: EPFL students' table-football robot

11.08.16 - A robot developed by EPFL students was able to compete against human players with average skills in table football. The next step will be to program the robot with some strategy and organise a competition among robots.

Do you think you could win a game of table football against a robot developed by EPFL students? Some people have tried, and it was harder than they thought. Even with a very simple strategy, the robot is able to beat players with an average skill level. What’s its secret? Speed and shooting power.

The robot, which was designed as a research platform for Bachelor’s and Master’s students, reached a milestone recently. After several years of development in the Automatic Control Laboratory, it is now faster, more accurate and more powerful than ever before.

Much more efficient industrial motors
The robot was provided with brand new ‘arms’, which are powerful and agile. They use high dynamic linear motors, the same type found in manufacturing. They can position the player very quickly on the field and then engage a rotational movement with the help of another motor to shoot. These motors are precise to less than a millimetre and can generate 9g in acceleration: the robot moves faster than a human being.

The robot also has excellent eyesight. A high-speed camera located under the game’s transparent floor follows the ball’s movement. The camera collects 300 images per second, which are then processed by a computer. Léo Sibut, a Master’s student, spent six months working on data acquisition and actuator control. “I learned a lot about image processing, which is a field I didn’t know very well,” he said. His work improved the robot’s precision and reliability.

Plenty of brawn but just a little brain!
The system is currently able to detect the ball, stop it and then shoot towards the goal. “It’s a very basic strategy, but it works surprisingly well,” said Christophe Salzmann, the scientist in charge of the project.

Yet he thinks it’s too simple. “At this stage, the system is like a bodybuilder with a tiny brain,” he jokes. “But in addition to being strong, we want the robot to be able to fake out the opponent, steer clear of the opponent, and predict the ball’s path and the opponent’s position.” The students have started working on these improvements by installing lasers that can detect the position of the opponents’ handles. This is what the robot needs to be able to apply a real strategy.

Competing software
In the meantime, Salzmann would like to quickly put together a table football competition between robots. The aim would be for the participants to program some strategy into the software and then have the machines square off.

EPFL news
AEROWORKS project at ISVC16

The EU-funded AEROWORKS project is co-organising a special track session at the 12th International Symposium on Visual Computing that will take place in Las Vegas, United States, from 12 to 14 December 2016.

ESBF_2, ZEEUS and ELIPTIC projects at 2016 Annual Polis conference

The EU-funded ESBF_2, ZEUUS and ELIPTIC projects will be presented at the 2016 Annual Polis conference that will take place in Rotterdam, the Netherlands, from 1 to 2 December 2016.

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