A case study on biological activity in a surface-bound multicomponent system: the biotin-streptavidin-peroxidase system.

The adsorption of multiple protein layers on biotinylated organic surfaces has been characterized using surface plasmon resonance (SPR) and atomic force microscopy (AFM). Diffusion-limited loading of the biotinylated self-assembled monolayers (SAMs) ensures a precise control of the streptavidin surface density. For the subsequent interaction with biotinylated peroxidase, SPR data hint at a streptavidin density dependent orientation during peroxidase adsorption. Microcontact printed well-defined two-dimensional patterned surfaces of biotinylated organothiols and protein-resistant OEG-thiols allow an in-situ differentiation of specific and nonspecific adsorption (e.g., mono- vs multilayer adsorption). Additionally, the very important issue of biological activity of surface-bound enzymes is addressed by comparing the enzyme activities in solution with that for surface-bound species.