In a method for analysis biomolecules (3) attached to a solid surface of a substrate (1) are used for detecting the presence of analytes (4) in a sample by binding of the analytes to the biomolecules. The biomolecules (3) are attached directly to the surface of the substrate together with biomolecule-repellent molecules (5), which cover the surface between the biomolecules (3) to prevent nonspecific binding of analytes (4) and other biomolecules. The invention relates also to a biosensor where biomolecules (3) are attached directly to the substrate (1) together with biomolecule-repellent molecules (5), which cover the surface between the biomolecules (3) to prevent non-specific binding of analytes (4) and other biomolecules. The biomolecules (5) can be self-assembled hydrophilic polymers. One example of using the invention is immunological analysis using surface plasmon resonance (SPR).