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2013|14 Annual Report Fraunhofer IGB

116 DETECTION OF HAZARDOUS SUBSTANCES USING A COMBINATION OF PHYSICAL AND BIOLOGICAL SENSOR TECHNOLOGY Dr. rer. nat. Iris Trick Threat to drinking water networks from toxic substances Contamination from industrial accidents, targeted poison attacks and pollution through the leaching of pesticides from farmland are unforeseeable events. For the population they constitute risks that should be taken seriously, as toxic substances may enter the drinking water supply systems via the groundwater or watercourses. Motivated by the need to improve the treatment and distribution of drinking water com- pared to the status quo by using suitable inline measurement technology, employees of the Fraunhofer IAF and Fraunhofer IGB have teamed up to pool their expertises. Physical and bio- logical methods come together in the “TOXIKOMB” project in order to offer an innovative solution with improved, but – above all – rapid detection of hazardous substances in the field of drinking water. Approach The aim of the project is to detect toxic substances certainly and rapidly by combining electrochemical methods and infra- red spectroscopy with biological systems. The priority is not to detect the presence of specific substances but detecting their toxic impact. Whilst chemical methods of analysis are capable of identifying specific substances, live cell sensors can show toxic influences with the aid of their reaction patterns. The first intended model application for the detection system de- veloped in the project is monitoring of drinking water. Biological sensors reveal toxic effects In order to determine the toxic effects of substances, we use mammalian cells and microorganisms as biological sensors. The two cell types differ in respect of their sensitivity to a variety of substances. Caulobacter crescentus was selected as a bacterial sensor while human embryonic kidney cells were established as a mammalian cell system for the studies. Impedance measurement of biological signals The response of the biosensors to different substances is re- corded using impedance measurement and evaluated. Here, the alternating current resistance of a cell-coated electrode is measured as a function of time. The basis for this method is the fact that the way biological systems respond to different molecules depends on their molecular structure. The associ- ated interactions can influence both structural components of the cell and metabolic reactions. The activity of the cell is thus impaired, depending on the species-specific properties, by cytotoxic substances. This either affects the interactions at interfaces (neighboring cells, material surfaces), or results in a measurable change to cellular components. These responses can be tracked by means of impedance measurement, since they have an influence both on the charges at the surfaces and on the spectrum of cell wall components and reaction products. The first aim was to check which electrodes are suitable for carrying out impedance measurements on immobilized micro- bial and mammalian cells. Fig. 1 shows Caulobacter crescentus grown onto diamond electrodes developed at the Fraunhofer ENVIRONMENT 1 2 impedance[Ω] time [min] 3600 tap water tap water bacteria on dia- mond electrode bacteria on dia- mond electrode 60 s in 1 mM Ni2+ 60 s in 1 mM Ni2+ no variation increase 3300 3000 2850 2900 2950 3000 0 50 100 150 2 μm

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