A method for coimmobilizing two or more biomolecules on a substrate in a
defined ratio is disclosed. The method uses a copolymer conjugated to a
number, N, of different types of oligonucleotides. The copolymer can be
adsorbed to the surface of the substrate. N types of oligonucleotides
complementary to the copolymer-bound oligonucleotides can be conjugated
to N types of biomolecules. The types of the copolymer-bound
oligonucleotides can be mixed in a defined ratio then adsorbed to the
surface. The biomolecule-bound complementary oligonucletides can be
conjugated to the copolymer-oligonucleotides to create a substrate with
the biomolecules coimmobilized in a defined ratio. The invention also
relates to a substrate prepared by the method of the invention.