Surface functionalization of gold nanoparticles using hetero-bifunctional poly(ethylene glycol) spacer for intracellular tracking and delivery

Dinesh Shenoy¹, Wei Fu², Jane Li³, Curtis Crasto³, Graham Jones³, Charles DiMarzio⁴, Srinivas Sridhar², Mansoor Amiji¹

Departments of ¹Pharmaceutical, Sciences, ²Physics, ³Chemistry and Chemical Biology, ⁴Electrical and Computer Engineering, and the Nanomedicine Consortium, Northeastern University, Boston, MA, USA 

Abstract: For the development of surface-functionalized gold nanoparticles as cellular probes and delivery agents, we have synthesized hetero-bifunctional poly(ethylene glycol) (PEG, MW 1500) 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 decreased 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 1 hour of incubation. Intracellular particle tracking using a Keck 3-D Fusion Microscope System showed that the functionalized gold nanoparticles were rapidly internalized in the cells and localized in the peri-nuclear region. Using the PEG spacer, the 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 a stimulus at the target site.

Keywords: gold nanoparticles, hetero-bifunctional poly(ethylene glycol) spacer, surface functionalization, cellular trafficking, cytotoxicity