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From Nanosensors to Cytotoxicity Test: ”We can reduce the number of animal experiments“
Doctor Jennifer Schmidt;
Animal experiments are a part of everyday life in medical research, yet they have been the subject of criticism for decades. Even though scientists all over the world are searching for alternative methods, the complexity of physical processes in the human body however makes this very difficult.
But nothing is ever impossible, as scientists at the Fraunhofer Research Institution for Modular Solid State Technologies (EMFT) in Regensburg demonstrate with their nanosensors, which make it possible to reduce the number of animal experiments. MEDICA.de spoke with project manager Doctor Jennifer Schmidt about the kind of technology that is required for this and what nanosensors can already test.
MEDICA.de: Doctor Schmidt, first allow us to ask this question: how many animals die each year for research in German laboratories?
Jennifer Schmidt: According to reports by the German Department of Agriculture, in 2005 the number was approximately 2.41 million animals and in 2009 this number had increased to 2.79 million. The department lists two primary reasons for this: on the one hand German research is being expanded and on the other hand increasingly transgenic – this being gene-modified- animals are being used which are specifically bred for experimental research.
MEDICA.de: Now you have developed nanosensors that can reduce the number of animal experiments. What are nanosensors and how can they save the lives of animals in research laboratories?
Schmidt: Nanosensors are very small particles to which sensor dyes are permanently attached. These dyes have the ability to change their optical properties in the presence of certain molecules that you would like to detect for research purposes- for instance in pharmaceutical testing. We can measure this and also make it visible with fluorescent dyes that we can observe under a fluorescence microscope.
In accordance with the EU Regulation on Chemicals for instance, all chemicals that are put in circulation, have to be tested and undergo a risk assessment. Our method makes it possible to exclude cytotoxic substances at the front end, to where they no longer need to be tested on animals. We only expose living cells that were isolated from either human or animal tissue and cultured in cell cultures, to risky substances and continuously monitor their “well-being”.
We work with adenosine triphosphate-sensitive nanoparticles. Adenosine triphosphate, ATP in short, depicts the energy store of the cell and acts as a vitality marker. If the cell is very active, it produces a lot of ATP. If it is damaged or its metabolism is severely impaired it can no longer produce ATP. We can measure this with our nanosensors and thus assess cellular health.
During the experiment, we first give the nanoparticles two fluorescent dyes: one green indicator dye that is sensitive to ATP, and a red reference dye that does not change its properties. The particles then are being introduced to cultivated cells. We observe under a fluorescence microscope how the substances influence the ATP level. The degree to which the particles light up depends on the amount of ATP present: the more yellow the signal in the overlay image of the indicator and reference appears, the more active the cells are. A red overlay image on the other hand indicates an impaired state. We can add substances at the same time and observe live how they affect cell viability.
Nanosensors show by the yellow signal on the overlay image (on the right) that the cells are active. If they were in bad condition they would be significantly redder. Centre photo: signal from the indicator dye. Left photo: signal from the reference dye; © Fraunhofer EMFT
The cells are cultivated under a specific gas atmosphere, temperature and certain degree of moisture, adjusted to the body temperature and fed with a medium that contains properties that can also be found in blood. Of course it is vitally important that you always carry untreated control cells along, since the procedure is incredibly complex and each cell line also reacts a little differently.
Unfortunately you cannot always predict whether and to what extent a substance is poisonous. Though with our cell culture experiment, 80 out of 100 substances can be detected as being poisonous, to where only the remaining 20 have to be tested on animals. However, for these remaining 20 substances we cannot get by without animal experiments.
MEDICA.de: Which drugs can you test for example with the nanosensors you developed?
Schmidt: You can primarily test chemicals for risk assessments with our nanosensors, but you can also potentially test new pharmaceuticals or “drug prototypes“. The question behind all this is: do these substances have cytotoxic, meaning cell-damaging effects or not? You can also question which concentration makes them cytotoxic? That is to say, how much can a cell tolerate without being affected and starting at what amount is it significantly being impaired or dies off?
There are also drugs available that are intended to interfere with the metabolism of fast dividing cells – this pertains to chemotherapeutic and cytostatic drugs for example. By using these drugs, the desired effect is to destroy the metabolism of cells to the point of getting them to die off. That’s why it is also interesting to see whether you can achieve the effect or not with the substances or molecules that are meant to be used there – we can test for this as well.
MEDICA.de: In your opinion, will it eventually be possible to completely do without animal experiments?
Schmidt: That is very difficult since the physiological processes- whether in the human body or in animals – are very complex. When we conduct our test series in cell culture experiments, it is only a simulation of what is really going on in the body. You mustn’t forget that this is merely a model system.
In the case of our cytotoxicity studies certain transferability is given – so when substances have an extremely poisonous effect on cells in the laboratory, it is very likely that they also have a poisonous effect on animals or human beings.
You probably also won’t be able to do without animal experiments with this method. The goal of our research however, is to reduce the number of experiments as much as possible.
The interview was conducted by Michalina Chrzanowska and translated by Elena O'Meara.