Aptamers are single-stranded nucleic acids (DNA or RNA) selected by a molecular selection process called Systematic Evolution of Ligands by Exponential Enrichment (SELEX). Numerous high-affinity and highly specific aptamers have been selected against a wide variety of target molecules including small organics, peptides, proteins, and even supramolecular complexes such as viruses or cells.  Aptamers are alternative candidates to antibodies in respect to their sensitivities and affinities.

Low abundant proteins in blood, tissue or saliva can be detected using mass spectrometry following the enrichment with aptamer attached surfaces. Thus, highly sensitive and selective protein enrichment can be carried out using an aptamer attached surface and bioanalytical method prior to mass spectrometric analysis. Mass spectrometry is one of the most powerful tool for the detection of biomolecules with very high sensitivity and selectivity even at very low concentrations.