Maximizing DNA Loading on a Range of Gold Nanoparticle Sizes

TLDR

Stable large gold nanoparticles are attractive for biodiagnostic assays. The study investigates variables influencing DNA coverage on gold nanoparticles. The authors evaluated salt concentration, spacer composition, nanoparticle size, and sonication to determine their effects on DNA loading. Maximum DNA loading was achieved by aging nanoparticles in ~0.7 M NaCl with PEG‑spacer DNA, further enhanced by sonication, and nanoparticles up to 250 nm exhibited roughly two orders of magnitude higher loading than 13–30 nm particles due to their larger surface area.

Abstract

We have investigated the variables that influence DNA coverage on gold nanoparticles. The effects of salt concentration, spacer composition, nanoparticle size, and degree of sonication have been evaluated. Maximum loading was obtained by salt aging the nanoparticles to ∼0.7 M NaCl in the presence of DNA containing a poly(ethylene glycol) spacer. In addition, DNA loading was substantially increased by sonicating the nanoparticles during the surface loading process. Last, nanoparticles up to 250 nm in diameter were found have ∼2 orders of magnitude higher DNA loading than smaller (13−30 nm) nanoparticles, a consequence of their larger surface area. Stable large particles are attractive for a variety of biodiagnostic assays.