T.J. Cho, J.M. Gorham, J.M. Pettibone, V.A. Hackley
National Institute of Standards and Technology,
Keywords: gold nanoparticles, positively charged gold nanoparticles, polyethyleneimine, stability
Summary:PEI functionalized gold nanoparticles (Au-PEIs) are positively charged gold nanoparticles (AuNPs) with potential for nano-medicinal applications due to their cationic surfaces that promote cellular uptake and gene transfection. Au-PEIs can generally be prepared by two methods: (1) ligand modification (exchange or co-attachment) of AuNPs and PEI, and (2) reduction of AuIII ions in the presence of PEI. Herein, the ligand exchanged Au-PEIs (Au-PEI[LE]s) and the materials by reduction (Au-PEI[Red]s) were prepared from citrate-stabilized AuNPs (10 nm, nominal) and HAuCl4, respectively. We demonstrated differentiated product formation via each synthetic route and their discriminated physico-chemical properties by systematic examination considering reaction condition and the dependency of relative molar mass/backbone structure of PEIs. The physico-chemical properties and the conjugation mechanisms of Au-PEI[LE] and Au-PEI[Red] were characterized by orthogonal analyses including dynamic light scattering, UV-Vis, atomic force microscope, transmission electron microscope, attenuated total reflectance FT-IR, and X-ray photoelectron spectroscopy measurements. Furthermore, the colloidal stabilities of all produced Au-PEIs were investigated under various physiologically relevant conditions, including: shelf-life (least 6 months period), temperature variation, wide range of pH values, stability in biological level media. We found that some of Au-PEIs showed outstanding stability under physiological conditions which is a critical property for applications in drug delivery.