Planar integrated optical waveguide used as a transducer to yield chemical information: Detection of the activity of proteolytic enzymes e.g. serine-proteases

The paper shows the very first results of a feasibility study where the activity of proteolytic enzymes towards dye-labelled artificial substrates immobilized on the surface of planar optical Ta₂O₅ waveguide was investigated. Within this project, a chromophore label was developed, synthesized and attached to the carboxy-terminus of specific tripeptides. The goal was to develop a highly sensitive optical assay in order to monitor the activity of serine-proteases by cleavage of the amide bond between peptide and chromophore. On the one hand, a strategy was developed to immobilize the labeled tripeptide unto integrated planar waveguides. On the other hand, an instrument, the so-called "chip-reader" was developed to detect the biological process on the surface of the integrated planar optical waveguide. Surface characteristics were analyzed by XPS, TOF-SIMS and contact angle measurements. A comparison between the effectivity of ATR-photometry on chip using TE₀ mode and photometry in transmission mode is discussed.