Electrostatics of Dna-Wrapped Cationically Stabilized Gold Nanospheres

Abstract

Gold nanoparticles have a unique set of properties that allow them to be utilized in a wide array of research and medical applications. The interface of positively stabilized gold nanoparticles with DNA is of particular interest for a variety of applications such as the study of artificial forms of DNA packing and the design of new vectors for therapeutic gene delivery. DNA wraps electrostatically around gold nanoparticles that are stabilized or layered with cationic molecules. Depending on the size of the gold nanoparticles, the length of the DNA, and the ionic content of the solution, these complexes can vary in stability, morphology, and mechanism of formation. To investigate these complexes, we incubated small cetrimonium bromide (CTAB) stabilized gold nanospheres in solutions of sheared calf thymus DNA. We removed unwrapped DNA and introduced a background concentration of sodium chloride using equilibrium dialysis by serial centrifugation. We characterized the gold nanospheres at all stages of the process using UV spectroscopy, dynamic light scattering (DLS), and zeta potential measurements. Following centrifugation, we analyzed the purified solutions of DNA wrapped gold nanospheres using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The goal of these measurements is to elucidate the electrostatics of these complexes by analyzing the effect of DNA wrapping on the properties of the gold nanospheres within the complex, the incorporation of stabilizing sodium cations into the complex, and the ratio of DNA to nanoparticles utilized in each complex.