AquaBioTox – Detection of toxic substances by fluorescence change

Drinking water is the most important foodstuff for humans. Water pipes are exposed to constant danger from possible contamination. In addition, the drinking water supply is a potential target for terrorist attacks, so that dangers to public health must be identified in good time.

The Drinking Water Ordinance therefore provides for routine tests for certain pathogens and chemical substances. For this purpose, random samples are taken and examined in the laboratory. However, the standard analysis methods used here are lengthy and limited to selected parameters: Unknown or unexpected toxic substances are not detected promptly. These procedures are therefore not suitable as warning systems that can promptly indicate an entry of chemical or biological substances.

Objective: Online monitoring with biosensor

In the present project "AquaBioTox", we at Fraunhofer IGB are therefore working together with the project partners Berliner Wasserbetriebe, bbe Moldaenke and Fraunhofer IOSB to develop solutions for the continuous online monitoring of drinking water pipes. The aim is to establish a biological broadband sensor that reacts immediately and reliably to hazardous substances in the water and makes this visible by means of automatic image evaluation.

Results

Figure 1: Measuring cell with microbial test organisms and probe for measuring the fluorescence intensity
Figure 2: Fixed-bed reactor covered with E. coli RFP before (left) and after addition of glutardialdehyde (right).

Fraunhofer IGB's contribution to the AquaBioTox project is to provide microbiological and mammalian cell systems that react quickly to the entry of toxic compounds by decreasing fluorescence and can thus be used as biological sensors. The fluorescence is currently being recorded using a measuring probe from bbe Moldaenke.

After extensive screening, two bacterial strains (Caulobacter crescentus, Escherichia coli) and two mammalian cell lines (HEK 293, CHO) were selected. The test organisms are immobilized on carrier material in small bioreactors in the measuring cell and test fluid flows around them (Figure 1). In addition, these biological sensors are used in combination with a Daphnia toximeter from bbe Moldaenke in order to increase the broad band of the detection system. Table 1 summarises the reactions detected in the biological systems used in AquaBioTox at the current project stage. The diagram on the right shows the stability of the biosensor under normal or permissible conditions in drinking water and illustrates the influence of a toxic compound on the test organisms. Figure 2 shows a clear colour change of the microbial system when a toxic substance is added.

Outlook

After completion of the current research project it is planned to transfer and adapt the measuring principle to other fields of application. In the environmental field, the Fraunhofer IGB is engaged in research on semidecentralized infrastructure systems for water supply and disposal. For the expected increasing spread of such solutions, for example the use of treated rainwater, techniques of online monitoring with similar functional principles as those developed in AquaBioTox are suitable. With appropriate adaptation to the area of application, they could replace the currently usual complex and very expensive chemical analysis, which to a large extent only provides summary parameters.