Baiting bacteria with polymers

Anyone who has experienced food poisoning while on vacation in warm climates is sure to recognize the importance of safeguarding hygiene - and of microbial food testing.,

Since many types of bacteria, such as salmonella, multiply at an exceptionally fast rate in warm weather on meat or in milk products, relatively lengthy laboratory investigations are hardly an appropriate means of identifying acute risks. This has prompted various manufacturers to offer pocket-size test kits. But how do such tests recognize which microbes are pathogenic? Antigen-antibody reactions provide a high degree of specificity, acting in the same way as the immune defenses of living organisms. In such test kits, the antibody is chemically attached to the surface of a substrate carrier, which is immersed in the test solution. Just as a key only fits in its matching lock, antigens, such as bacteria, viruses or toxic proteins only bind with their corresponding antibody. After the substrate has been rinsed, a color reagent is applied. Color intensity, which is proportional to the bacteria count, can be measured using a small, portable photometer.
The technological crux of the procedure lies above all in fixing antibodies and other large biomolecules to the substrate. The aim is to ensure that as great a number as possible retain their biological activity as Dr. Andreas Holländer of the Fraunhofer Institute for Applied Polymer Research IAP explains: We treat substrates made of polyethylene, polypropylene and even Teflon chemically in such a way that reactive molecular groups form on their surfaces. To them the antibodies are bonded with the proper alignment and particularly firm.
This method has two fundamental advantages by comparison with older testing procedures: Correct spatial orientation of the antibodies on the substrate increases the sensitivity of testing, says Dr. Michael Keusgen of the University of Bonn, who is responsible for biological aspects within the project. Molecules that - figuratively speaking - stick their heads in the substrate, dont contribute to the testing. The strength of the bond prevents the antibodies and their coupled antigens from being washed away by large volumes of solutions being tested. Up until now, bacteria in higher concentrations had to be cultivated in enriched culture media. This time-consuming step can now be ignored in most cases. Biognosis GmbH in Jülich meanwhile markets complete test kits for a variety of applications.,For further information:,Dr. Andreas Hollander,Phone +49 3 31 / 5 68-14 04,Fax +49 3 31 / 5 68-31 48 ,E-mail: [e-mail]
Fraunhofer-Institut fur Angewandte Polymerforschung IAP,Geiselbergstrasse 69,14476 Golm, Germany,http://www.iap.fraunhofer.de/english/index.html
Dr. Michael Keusgen,Phone +49 2 28 / 73-26 76,Fax +49 2 28 / 73-32 50,E-mail: [e-mail]
Institut fur Pharmazeutische Biologie, University of Bonn,http://www.pharmbio.uni-bonn.de/

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