Purification of DNA oligonucleotides to improve hybridization chain reaction performance

Hybridization Chain Reaction (HCR) is a technique to generate a linear polymerization of oligonucleotide hairpins, used in multiple molecular biology methods. The HCR reaction is dependent on every hairpin being metastable in the absence of a triggering oligonucleotide and that every hairpin can continue the polymerization, which puts a strong demand on oligonucleotide quality. We show how further purification can greatly increase polymerization potential. It was found that a single extra PAGE-purification could greatly enhance hairpin polymerization both in solution and in situ. Purification using a ligation-based method further improved polymerization, yielding in situ immunoHCR stains at least 3.4-times stronger than a non-purified control. This demonstrates the importance of not only good sequence design of the oligonucleotide hairpins, but also the demand for high quality oligonucleotides to accomplish a potent and specific HCR.