DNA Hairpins and Stabilization of Gold Nanoparticles: Effect of Stem Length and Toehold Composition

This study investigates the effect of DNA hairpins on the stabilization of gold nanoparticles (AuNPs) against salt-induced aggregation (SIA) in label-free colorimetric biosensors. AuNPs were incubated with DNA hairpins of varying stem lengths and toehold sequences, followed by the addition of NaCl, before being subjected to ultraviolet-visible (UV-vis) measurement. Results showed that hairpins with longer stems generally provide better stabilization of AuNPs (18-bp >14-bp >10-bp). No improvement was observed for 14- and 18-bp hairpins with a toehold beyond 8A, which may be attributed to saturated adsorption of hairpins on the gold surface. For 14-bp hairpins with an 8-mer homopolymeric toehold, we observed a stabilization trend of A > C > G > T, similar to the reported trend of ssDNA. For variants containing >= 50% adenine as terminal bases, introducing cytosine or guanine as preceding bases could also result in strong stabilization. As the proportion of adenine decreases, variants with guanine or thymine provide less protection against SIA, especially for guanine-rich hairpins (>= 6G) that could form G-quadruplexes. Such findings could serve as guidelines for researchers to design suitable DNA hairpins for label-free AuNP-based biosensors.

Automated summary

This study investigates the effect of DNA hairpins on the stabilization of gold nanoparticles against salt-induced aggregation in label-free colorimetric biosensors. Results showed that longer hairpin stems generally provide better stabilization, and hairpins with toeholds beyond a certain length did not improve stabilization. The stability trend of the hairpins with a homopolymeric toehold was similar to that of ssDNA. Variants with a high proportion of adenine as terminal bases showed stronger stabilization, and the introduction of cytosine or guanine as preceding bases also enhanced stabilization. However, variants with guanine or thymine showed less protection against salt-induced aggregation, especially guanine-rich hairpins that could form G-quadruplexes. These findings can guide researchers in designing suitable DNA hairpins for label-free AuNP-based biosensors.