Novel biosensoric devices based on molecular protein hetero-multilayer films.

We have developed a novel concept for the modification of technical surfaces with molecularly well-organized layers of bioorganic components. A molecular construction set has been used to implement this concept which is based on molecularly stratified polyelectrolyte films as a structure decoupling protein layers from solid substrates. Utilizing this technology, one can start from a number of different substrates to obtain the same surface structures, on which protein hetero-multilayer films can be prepared to functionalize the interface for (potentially very different) purposes. We have demonstrated the viability of this concept by constructing a biosensor surface that was characterized by x-ray, spectroscopic, and immunological techniques. For the preparation of this functionalized interface, a cascade of biospecific recognition processes has been used, in which a layer of SpA was supplanted on a dense SA monolayer (binding stoichiometry, approximately 0.2 SpA/SA). On the SpA, IgG has been immobilized (binding stoichiometry, approximately 0.5 IgG/ SpA). The resultant biosensor displays extremely low unspecific background reactivity, high sensitivity, and good response linearity over more than 3 orders of magnitude in antigen concentration.