Sensors for bioanalytes by imprinting--polymers mimicking both biological receptors and the corresponding bioparticles.

Structuring of thin polymer layers by soft lithography with template bioparticles results in the formation of selective surface cavities, leading to highly effective sensor systems when combined with mass-sensitive transducers, especially QCM. These sensors allow selective differentiation of various stages of development of yeast cells. In order to achieve a higher degree of standardisation, we fabricated plastic yeast cells and utilised them for the stamp imprinting procedures. These sensitive layers are capable of the differentiation between Saccharomyces cerevisiae and Saccharomyces bayanus. Aside from achieving the same sensitivity compared to the polymers that were structured using native cells, we realised further enhancement of selectivity exceeding a factor of three regarding the two cell strains. These ideas could also be transferred to develop a recognition system for the more flexible erythrocytes and therefore MIP-layers of polyvinylpyrrolidone were combined with QCMs. These devices provide sensor-based ABO blood group typing. Additionally, the differentiation of the subgroups A(1) and A(2) is shown with the generated MIP-layers that are decorated by high selectivity, namely the threefold frequency effect for the imprinted template, and negligible unspecific effects. Application of soft lithographic methods furthermore allows the design of artificial erythrocytes. These "plastic" blood cells possess an increased robustness compared to the native cells, thus opening up multiple novel strategies of surface patterning.

Surface imprinting strategies for the detection of trypsin.

Self-organized receptor layers are synthesized by molecular imprinting methods directly on pre-coated 10 MHz quartz-crystal microbalances (QCMs). The surface-imprinting is performed by three methods using amorphous, crystalline and solubilized trypsin, respectively, as templates. These attempts allowed us to compare imprinting results obtained with templating proteins in the dry state as well as in aqueous solution. All methods are generally applicable for surface imprinting of thin films. The biomimetic sensor layers allow selective enzyme enrichment on the imprinted electrode with detection limits as low as 100 ng ml(-1) and response times of a few minutes. Solution-based polymer imprinting with native trypsin as template resulted in the highest specific enzyme recognition, which even allowed us to distinguish denatured trypsin from the native form.