To evaluate whether UV-visible spectroscopy could be
used to determine the number of DNA strands per AuNP, we
prepared AuNPs functionalized with DNA1(5’-AGA GAA
CCT GGG GGA GTA TTG CGG AGG AAG GT-3’), determined
the DNA-NP concentration from A520 and used Equation
1 to determine A260 of DNA1, where dDNA-NPs denotes
decomposed DNA-NPs and dAuNPs are decomposed citratestabilized
nanoparticles. DNA1 was chosen as a representative
sequence for this study because its length (32 bases) is comparable
to recognition sequences typically used to functionalize
AuNPs. Using DNA1’s extinction coefficient (Table 1) and
Beer’s law, we determined that there were 58±7 DNA strands
per 12 nm AuNP (n = 9).
A260 DNA1 = A260 dDNA-NPs - A260 dAuNPs (Equation 1)
If A260 of the decomposed AuNPs was not subtracted
from A260 of the solution prior to calculating the DNA concentration,
it would cause 28±4% determinate error.