Biosensors are used for a variety of applications in medicine and biology. A critical step during the development of such devices is the coordination of biological and technical requirements. The design of the device, as well as of the sample chamber and its functionalized surface is of great importance. Depending on the surface, the method of coupling of the desired receptor has to be adapted to guarantee functionality and biological activity during the measuring process. By using the SNAP-tag technology, a site-specific coupling of molecules with unaltered activity to a variety of O6-benzylguanine functionalized surfaces is possible, making it a versatile tool for the setup of biomedical devices.