Conjugation of multivalent ligands to gold nanoshells and designing a dual modality imaging probe

Design and synthesis of branched tetraethylene glycol (TEG) based ligands for subsequent conjugation to gold nanoshells are reported. TEG enhances the aqueous solubility of hollow gold nanoshells (HAuNShs), and the branched architecture provides stability. An examination of the supernatant of the surface displacement reaction shows that the structure of the ligand plays an important role in the functionalization of HAuNShs. The binding of multivalent ligands leads to rupturing of the gold nanoshell architecture; most probably due to the large dendron not compensating the replacement of small citrate capping agents. The construction of a probe with dual imaging capabilities is demonstrated by covalent linking of a dendron containing Cy5.5(A) dye to gold nanoshells. It leads to fluorescence quenching of Cy5.5(A) by the gold nanoshells, as evidenced in solution and in cellular internalization studies with J774 and bEnd.3 cells.