Hygiene quality management systems (QM) are of great importance in hygienically demanding areas because hygiene requirements are constantly increasing. For analysing quality of cleaning and disinfection measures determined by QM-systems, random-check like controls are carried out routinely. Currently, contact plates are used for sampling of surfaces. After sampling, contact plates must be incubated and analysed by external microbiological laboratories. This requires at least 3 days (determination of total germ count and hygienically relevant microorganisms) and results in high costs. Therefore, there is a strong need of innovative methods for contemporary determination of both hygienically relevant microorganisms and total germ count on surfaces within a self-control.

Aim of the project was the development of a method for sampling surfaces on the basis of lectin functionalized thermosensitive polymer brushes and subsequent visualization of bound microorganisms with lectin-functionalized (determination of total germ count) and antibody-functionalized (determination of hygienically relevant microorganisms) quantum dots. The development of the biochemical synchronous determination was based on the selection of appropriate lectins. The lectins concanavalin A (ConA) and wheat germ agglutinin (WGA) showed appropriate binding affinity against the tested microorganisms.

A commercially available polysiloxan was chosen as substrate for the thermosensitive polymer brushes. Due to stepwise modification of the polysiloxan with amino groups, functionalization with initiator molecules and a final radical copolymerisation with acrylate monomers, surface bound polymer chains (polymer brushes) with a lower critical solution temperature (LCST) of 32 °C were generated.

The chain ends of the polymer chains were functionalized with the lectins ConA and WGA. The visualization of the developed sampling system was carried out with lectin- and antibody-functionalized quantum dots. Therefore, a two-step dying procedure was developed due to using antibody-functionalized quantum dots during the first step and ConA- or WGA-functionalized quantum dots during the second step.

Within the scope of practical investigations of disinfected and non-disinfected surfaces was shown that same results were obtained using contact plates and the new sampling system.
Therefore, the new biochemical synchronous determination allows both determination of total germ count and hygienically relevant microorganisms on the same sample within approximately 3 hours.

The re­search re­port is avail­able on re­quest from FRT.