Nanoscale characterization of DNA binding on gold nanostars via quantitative EELS spectral imaging

Nanoconstructs of organic ligands conjugated onto inorganic nanoparticles are capitalized heavily as drug or biomolecule delivery vehicles. A notable candidate is DNA-conjugated gold nanostar, a complex anisotropic nanoparticle¹. Ligand loading on nanoparticle surface has been shown to be strongly affected by curvature², but conventional characterization techniques lack the spatial resolution to study local dependence of ligand binding on anisotropic nanoparticles³. Here, we directly visualize and quantify local distribution of DNA ligands on gold nanostars with few nm resolution, without any labeling or ligand removal. By combining quantitative scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) spectral mapping, we find a twofold increase in ligand density with respect to increase in surface curvature, indicating corressponding higher DNA binding. Our results elucidate the role of nanoscale steric interactions in molecular binding to metal nanoparticles and can be used to probe nanoscale variations in biomolecule loading on inorganic nanocarriers.

¹K. Lee, et al., Nano Lett. 20, 8 (2020)

²Hiil, H.D., et al., ACS Nano 3, 2 (2009)

³A. Smith, et al., Analyst 142 (2017)