the contribution of decomposed AuNPs from the A260
of the DNA-NP decomposition reaction solution. The concentration
of DNA in each sample was determined based on its
extinction coefficient and DNA A260.
To validate our method, Quant-It’s ssDNA Oligreen
quantification assay30 was used to determine the DNA in the
decomposed AuNP solutions, using the supplier’s instructions.
Briefly: a series of standard DNA solutions (80 nM, 40
nM, 20 nM and 8 nM) were prepared. The decomposed DNANP
A260 was used to determine how much to dilute the decomposed
DNA-NP samples for the Oligreen assay. Buffer
(pH 7.5, 10 mM Tris-HCl 1 mM EDTA) and water were added
to each sample, then Oligreen dye. They were incubated 5-
10 minutes before measuring the final fluorescent emission of
the dye. The decomposed AuNPs did not affect the assay results.
To determine the ligand shell composition of the 5 nm
DNA-NPs, the same procedure was followed, except 2.5
moles KCN (1.25 equivalents) were added for every mole of
Au atoms (typically 2-3 mM)