Non-Invasive, Reliable, and Fast Quantification of DNA Loading on Gold Nanoparticles by a One-Step Optical Measurement

An exquisite, versatile, and reproducible quantification
of DNA
loading on gold nanoparticles (Au NPs) has long been pursued because
this loading influences the analytical, therapeutic, and self-assembly
behaviors of DNA-Au NPs. Nevertheless, the existing methods used thus
far rely solely on the invasive detachment and subsequent spectroscopic
quantification of DNA, which are error-prone and highly dependent
on trained personnel. Here, we present a non-invasive optical framework
that can determine the number of DNA strands on Au NPs by versatile
one-step measurement of the visible absorption spectra of DNA-Au NP
solutions without any invasive modifications or downstream processes.
Using effective medium theory in conjunction with electromagnetic
numerical calculation, the change in DNA loading density, resulting
from varying the ion concentration, Au NP size, DNA strand length,
and surrounding temperature, can be tracked in situ merely by the one-step measurement of visible absorption spectra,
which is otherwise impossible to achieve. Moreover, the simplicity
and robustness of this method promote reproducible DNA loading quantification
regardless of experimental adeptness, which is in stark contrast with
existing invasive and multistep methods. Overall, the optical framework
outlined in this work can contribute to democratizing research on
DNA-Au NPs and facilitating their rapid adoption in transformative
applications.