The aim was a Snap Sensitizing sensor for the control of the microbiological water quality, e.g. according to drinking water regulations. The sensor consists of 5 magnetostrictive sensor sections. The surfaces of the sensor sections 1-5 are functionalized with specific aptamers that bind E. coli, coliform germs, enterococci, P. aeruginosa and legionella.

On the sensor section surfaces there are movably anchored gold microparticles (GMP), which are functionalized with the respective aptamers. The bacteria are bound by a snap sensitizing mechanism: a complex of GMP and bacteria is inelastically bound to the sensor section surface. This leads to a strong shift in the resonance frequency of the magnetostrictive sensor section, which can easily be measured.

Therefore, a single cell can be detected for the first time with a magnetostrictive sensor section. The determination of the total bacterial count on sensor section 6 is carried out without snap sensitizing mechanism due to the lower necessary detection sensitivity. The sensor can be thermally regenerated at least a hundred times and can be integrated into the water-bearing system as a bypass.

Aptamers with specificity towards E. coli or legionella were identified for the binding of target microorganisms on the respective sensor sections. An aptamer for the binding of phylogenetically different bacteria (total bacterial count) was identified and characterized.

Aptamer binding was successful in water with different qualities. The binding of aptamers was reversible by thermal treatment and therefore the sensor section would be regenerable.
The immobilization of aptamers on gold-plated sensor surfaces was successfully established. Subsequently, sensor sections could be generated for the binding of E. coli and legionella or for the binding of total bacteria.

It was possible to measure the resonance frequency of the magnetostrictive sensor sections using a simple network analyzer. This measurement setup was suitable to detect contactless minimal changes of the mass on the sensor section, which were able to be built in a water bearing system.

The research report is available on request from FRT.