Nucleic acid-directed self-assembly of multifunctional gold nanoparticle imaging agents

Gold nanoparticles have attracted much interest as a platform for development of multifunctional imaging and therapeutic agents. Multifunctionalized gold nanoparticles are generally constructed by covalent assembly of a gold core with thiolated ligands. In this study, we have assembled multifunctionalized gold nanoparticles in one step by nucleic acid hybridization of ODN (oligodeoxynucleotide)-derivatized gold nanoparticles with a library of pre-functionalized complementary PNAs (peptide nucleic acids). The PNAs were functionalized by conjugation with DOTA (1,4,7,10- tetraazacyclododecane-1,4,7,10-tetraacetic acid) for chelating ⁶⁴Cu for PET imaging, PEG (polyethylene glycol) for conferring stealth properties, and Cy5 for fluorescent imaging. The resulting nanoparticles showed good stability in vitro by melting temperature studies, and in vivo by showing biodistribution behavior in a mouse that would be expected for a PEGylated gold nanoparticle rather than that for the radiolabelled PNA used in its assembly.