Doctor Wolfgang Fritzsche;
Reason enough for the Institute of Photonic Technology in Jena to hold a symposium on the topic ”Nanotechnologies for Clean Drinking Water – DNA Nanosensors“. COMPAMED.de asked Doctor Wolfgang Fritzsche, which projects the Institute is currently working on and what the subject is currently doing.
COMPAMED.de: Dr. Fritzsche, how is the purity of drinking water in Germany and other industrial nations?
Wolfgang Fritzsche: All drinking water equipment is in danger of having bacteria growing in it. Legionella bacteria for instance are bacteria that particularly love warm water. They thrive very well at 40 degrees Celsius and can only reliably be killed at 60 degrees. In drinking water equipment that is not heated to more than 60 degrees, they can definitely be found – and this way get into the respiratory tracts via your shower water for instance, where it can lead to infections.
That is why besides control regulations that specify how often and how detailed the drinking water has to be tested, we are very keen to develop testing methods for water quality that are quicker and more cost-efficient than the traditional methods – and that can be taken out of the microbiological laboratories and brought home to the user. These were the driving forces that motivated this project.
COMPAMED.de: The project highlights two different techniques. On the one hand, is the chip-based method and on the other hand, the so-called Raman spectroscopy. Why these two different methods?
Fritzsche: For us it was about finding quicker methods than the previously established cultivation methods, since currently the standard is bacteria cultures where bacteria are visually identified. Our approaches are entirely different. On the one hand, we would like to develop a chip that works based on extracted nucleic acid. Initially we will work with bacterial DNA and then change over to RNA. The principles of polymerase chain reaction, PCR in short, are being applied here. A specific bacterium can be confirmed with the aid of a DNA or RNA chip.
Close-up of the bio chips; © IPHT
However, our technique has the advantage of us being able to multiply several sequences at the same time and then afterwards with the help of the DNA chip being able to differentiate this sequence again. Therefore, we only perform one multiplication reaction, but in doing so are able to distinguish and identify several components if they exist.
With regard to the Raman spectroscopy, the idea of the project is to distinguish bacteria to the point of category and type by utilizing the possibility of vibrational spectroscopy. This is similar to the infrared spectroscopy, however this requires preliminary investigations, for example building a spectral library, so that you know what spectrum belongs to which type and category –this is a so-called chemometric approach. You recognize a specific type by the specific pattern. This method was developed by the University of Jena at the Institute of Physical Chemistry and now is meant to be established with the current project for this specific case of application, that being to detect pathogens in drinking water equipment. Aside from pathogen recognition however, sample preparation is also an issue, because the pathogens are not necessarily isolated in drinking water equipment, but primarily exist in biofilms. This is a complex layer, which on the one hand makes isolation more difficult and on the other hand limits the removal through chemical intervention. This project is meant to find solutions for these issues.
COMPAMED.de: Should both methods be used separately or jointly?
Fritzsche: I would say they should be done in sequence. The Raman method allows a very quick identification of organisms once it is established. When a sample is on the glass slide, it can most likely be identified within a half hour – but this is still very complex at the moment, since the equipment is very large. In addition, identification requires great expertise, whereas the approach with the biochip is a different one. This procedure is already farther along and more established. That is why we hope that later on the staff can be more easily educated. It should be easy for the user and quickly provide a clear decision.
COMPAMED.de: Biochips are already being used in different medical areas. In your case, will it also be possible for the user to only place a drop of the testable solution, in this case water, onto the chip and a reader afterwards shows the result? Were you perhaps even able to build on an existing system?
Fritzsche: Actually, the approach is similar to some biochips and you could build on that. However, our focus at first is on the sample preparation. The sample preparation always depends on the particular case and requires the collaboration with the expert in the respective department. After all, as technology developers we of course could develop a general solution and then make it available. However, that does not make sense because a general solution is not comprehensive enough. We have to factor in the sample preparation, that is, the specifics of a particular sample preparation. Problems always do not show up until after specification of a problem, which only the expert recognizes however. This is why we then have to solve the problem in collaboration.
The bio chip card reader © IPHT
COMPAMED.de: Does nanotechnology create new leeway in the process?
Fritzsche: In the case of the chip, nanotechnology allows us to work in a relatively small space. The reader technology itself can benefit from metallic nanoparticles by being able to take an electrical measurement instead of the hard to differentiate optical limit. Aside from a more precise response, the required readers can also be simplified as well as made smaller and thus become more cost-effective. This way, nanotechnology can provide solutions for a broader use of bioanalytical measuring technology.
The interview was conducted by Simone Ernst and translated by Elena O'Meara.