Nano-sensor for pharma-free water
-
<ic:message key='Bild vergrößern' />
- The basic principle of the sensor is energy transfer between fluorescent dyes: If a specific substance blocks this transfer by binding to an aptamer, the sensor turns green instead of red. Source: Sander Münster/3Dkosmos.de
01.11.2013 -
The proportion of drug residues in water is steadily increasing. This is a problem both for humans and for the environment. On the other hand, the metal residues found in industrial process water are valuable, and can be recycled. Scientists at the Helmholtz Centres for Environmental Research in Leipzig (UFZ) and Dresden-Rossendorf (FZD), working together with the University of Rostock and the ProAqua GmbH & Co. KG Mainz, have developed a sensor concept that enables pharmaceuticals and heavy metals to be selectively detected in water samples. The underlying principle of the technology is nano-surfaces covered with fluorescent bacterial proteins. The Aptasens joint project, funded by the Federal Ministry of Research since 2009, has now come to an end. Building on these results, the sensor will now be further developed for eventual application.
“As a basic principle, our colour sensor approach is suitable for the detection of all possible substances,” explains Katrin Pollmann, Head of the Biotechnology Working Group at the FZD. The problem of drug residues is growing as a result of demographic change and the subsequent increase in consumption of medicines, says the biologist. Another important research topic at the Helmholtz Institute Freiberg for Resource Technology (HIF) at the FZD is the recycling of strategic metals in process water from industrial plants. Because the new sensor technology is so versatile, both of these differing requirements could be pursued profitably.
| More on biotechnologie.de |
BMBF subsidy for good water quality
Against this backdrop, researchers at the HZDR, the UFZ and colleagues from the University of Rostock and the water treatment specialists Proaqua GmbH & Co. KG Mainz have joined forces in the cooperative project Aptasens. Their objective is to give life to the new concept, which could eventually find application on an industrial scale. From 2009 to 2013, the joint research project was supported with a total of approximately €1.9 million from the BMBF.
Red: negative, green: positive
The sensor turns green if the target substance is detected in a water sample. A red colour indicates that the sample is free of the substance. As the scientists have reported in the journal Sensors and Actuators B: Chemical (2013, online prepublication), this is made possible through a nano-structured surface on the insides of the sensor. This is covered with bacterial proteins. The dye molecules are so densely packed together that an energy transfer, known in physics as fluorescence resonance energy transfer (FRET), can take place between them. It works like this: If the nano surface is irradiated with light of a specific wavelength, typically using a laser, the green dye molecules are energetically stimulated. Via the FRET effect, they pass on this energy to the red dyes, causing them to shine. “But this energy transfer only takes place if the water sample is ‘clean’. If foreign substances in the sample, such as a medication, become deposited between the colour molecules at the specific binding sites, the transfer is interrupted,” explains lead author Ulrike Weinert from HZDR. This means that only the green dyes shine when irradiated by the laser.
| Aptasens project partners |
HZDR website UFZ website University of Rostock website Proaqua GmbH & Co. KG website |
Wide range of applications
The second important component is the specific binding sites on the nano-surface. The scientists have designed short single strands of DNA in such a way that they can specifically bind to a wide range of substances. These DNA segments are known as aptamers, which bind highly specifically to their target molecules in the manner of antibodies. This means that it could be possible to produce binding sites for any number of molecules. The combination of the sensor principle and the aptamers has resulted in the name Aptasens for the joint project.
Dress rehearsal using antibiotics
Beate Strehlitz from the UFZ and her team have developed such an aptamer for kanamycin, an antibiotic that is used for bacterial infections of the eye, as well as in veterinary medicine. It is also frequently used in microbiological laboratory experiments in the cultivation of genetically modified microorganisms. For the sensor to become operational, in a final step the bacterial proteins and the kanamycin receptor are integrated onto a sensor chip at the nano-surface.
The function of the sensor can now be tested using the kanamycin. “The testing include a laser light source that activates the chip and a detector that measures the colour change,” explains Katrin Pollman. The scientists are now applying for funding for a follow-up project.
The development of detection methods that can quickly, inexpensively and highly specifically detect substances in samples is an important branch of research for medicine and industry. The early detection of cancer, a rapid test for specific allergens in food, or the quality assurance of drinking water, are just a few examples in a wide range of potential applications.
© biotechnologie.de/bs
