Selection and characterization of structure-switching DNA aptamers for the salivary peptide histatin 3

In this study, single-stranded DNA aptamers that switch structural conformation upon binding to the salivary peptide histatin 3 have been reported for the first time. Histatin 3 is an antimicrobial peptide that possesses the capability of being a therapeutic agent against oral candidiasis and has recently been linked as a novel biomarker for acute stress. The aptamers were identified through a library immobilization version of an iterative in vitro process known as the Systematic Evolution of Ligands by EXponential enrichment (SELEX). Through the SELEX process, four unique aptamer candidates sharing a consensus sequence were identified. These selected sequences exhibited binding affinity and specificity to histatin 3 and in order to further characterize these aptamers, a direct format enzyme-linked aptamer sorbent assay (ELASA) was developed. The best performing candidate demonstrated an equilibrium dissociation constant (K_d) value of 1.97 ± 0.48 μM. These novel aptamers have the potential to lead to the further development of refined sensing assays and platforms for the detection and quantification of histatin 3 in human saliva and other biological media.