NEW NANOCOMPOSITE FILMS FOR BIOSENSORS - LAYER-BY-LAYER ADSORBED FILMS OF POLYELECTROLYTES, PROTEINS OR DNA

This report describes the construction of ultrathin multicomponent fil ms with an internal structure on the nanometre scale. In the simplest case, the films are built-up by the subsequent adsorption of polyanion s and polycations. They can be fabricated on inorganic substrates such as glass, quartz or silicon wafers, or on various organic materials. The polymeric interlayers can incorporate materials with desired elect rical or optical properties. The average thickness of the layers can b e fine-tuned with Angstrom precision by the addition of suitable salts . They are temperature stable up to at least 200 degrees C and can be laterally structured using conventional photolithographic techniques. The films provide for a well-defined substrate-independent interface f or the immobilization of biological macromolecules, such as proteins o r DNA, in their active state. The immobilization of streptavidin enabl es the controlled attachment of any biotinylated molecule with no resu lting loss in its biological activity. Area-selective immobilization p rovides the possibility of built-in quality control for the fabricatio n of biosensors with separated reference and sample areas on the same substrate.