Polarizability of DNA Block Copolymer Nanoparticles Observed by Electrostatic Force Microscopy

Abstract

In this study, DNA block copolymer (DBC) micelles with a polystyrene (PS) core and a single-stranded (ss) DNA shell were doped with ferrocene (Fc) molecules. Tapping mode atomic force microscopy (AFM) was used to study the morphology of the doped and undoped block copolymer aggregates. We show that introducing Fc molecules into the hydrophobic core does not affect the structural properties such as shape or size. In contrast, doping with Fc significantly changes the micelles' electrical properties, namely their polarizability. Electrostatic force microscopy (EFM) measurements reveal that the undoped micelles show no significant polarization signal, while the Fc-doped aggregates exhibit strongly enhanced polarizability. Furthermore, the nucleic acid moieties were utilized in combination with complementary ssDNA strands to assemble single particles into linear arrays of DBC nanoobjects. The ability to tune the electrostatic properties of the polymer core and the presence of nucleic acids might open the way for using these bioorganic nanoparticles as building blocks for nanoelectronic or biosensing devices.