Aptamers are small, highly structured DNA/RNA molecules, isolated from combinatorial libraries by SELEX. They have affinities for their target molecules similar to how antibodies work. Aptamers have demonstrated great potential to replace antibodies in biosensors, point-of-care diagnostics, therapeutics, and all areas currently dominated by antibodies. Once aptamers are identified, they can be produced for less than 10% of the cost for producing antibodies. Oak BioSciences provides a broad range of unique aptamer screening services for custom aptamer development assays.
maybe you can also find interesting "aptamers" at SOMAlogic (http://www.somalogic.com/). They are selling small binders, which are a hybride between DNA and Protein.