The stabilization and targeting of surfactant-synthesized gold nanorods

摘要

The strong cetyl trimethylammonium bromide (CTAB) surfactant responsible for the synthesisand stability of gold nanorod solutions complicates their biomedical applications. The criticalparameter to maintain nanorod stability is the ratio of CTAB to nanorod concentration. Theratio is approximately 740 000 as determined by chloroform extraction of the CTAB from ananorod solution. A comparison of nanorod stabilization by thiol-terminal PEG and by anionicpolymers reveals that PEGylation results in higher yields and less aggregation upon removal ofCTAB. A heterobifunctional PEG yields nanorods with exposed carboxyl groups for covalentconjugation to antibodies with the zero-length carbodiimide linker EDC. This conjugationstrategy leads to approximately two functional antibodies per nanorod according to fluorimetryand ELISA assays. The nanorods specifically targeted cells in vitro and were visible with bothtwo-photon and confocal reflectance microscopies. This covalent strategy should be generallyapplicable to other biomedical applications of gold nanorods as well as other gold nanoparticlessynthesized with CTAB.