A planar, rigid substrate made from a porous, inorganic material coated with cationic
polymer molecules for attachment of an array of biomolecules, such as
DNA,
RNA, oligonucleotides, peptides, and proteins. The substrate has a top surface with about at least 200 to about 200,000 times greater surface area than that of a comparable, non-
porous substrate. The cationic
polymer molecules are anchored on the top surface and in the pores of the porous material. In high-density applications, an array of polynucleotides of a known, predetermined sequence is attached to this cationic
polymer layer, such that each of the
polynucleotide is attached to a different localized area on the top surface. The top surface has a surface area for attaching biomolecules of approximately 387,500 cm2 / cm2 of area (˜7.5 million cm2 / 1×3 inch piece of substrate). Each pore of the plurality of pores in the top surface of the substrate has a pore
radius of between about 40 Å to about 75 Å. Not only does the cationic
coating in and over the pores of the substrate greatly increase the overall positive charge on the
substrate surface, but also given the size of the pores provides binding sites to which biomolecules can better attach.