Surface Functionalization of Gold Nanoparticles using Hetero-Bifunctional Poly (Ethylene Glycol) Spacer for Intracellular Tracking and Delivery

D. Shenoy, Wei Fu, J. Li, C. Crasto, G. Jones, C. DiMarzio, S. Sridhar, M. Amiji
International Journal of Nanomedicine (2005)

For development of surface functionalized gold nanoparticles as cellular probes and delivery agents, we have synthesized hetero-bifunctional poly(ethylene glycol) (PEG, MW 1,500) having a thiol group on one terminus and a reactive functional group on the other for use as a flexible spacer. Coumarin, a model fluorescent dye, was conjugated to one end of the PEG spacer and gold nanoparticles were modified with coumarin-PEG-thiol. Surface attachment of coumarin through the PEG spacer decreases the fluorescence quenching effect of gold nanoparticles. The results of cellular cytotoxicity and fluorescence confocal analyses showed that the PEG spacer modified nanoparticles were essentially non-toxic and could be efficiently internalized in the cells within one hour of incubation. Intracellular particle tracking using Keck 3-D Fusion Microscope System shows that the functionalized gold nanoparticles were rapidly internalized in the cells and localized in the peri-nuclear region. Using the PEG spacer, gold nano-platform can be conjugated with a variety of biologically-relevant ligands such as fluorescent dyes, antibodies, etc in order to target, probe, and induce stimulus at the target site.