Surface functionalized gold nanorods: tracking and observing live cell via three optical signals.

Surface functionalized gold nanorods (GNRs) with three optical signals and the ability to track and observe live cells was investigated. The Cetyltrimethyl Ammonium Bromide (CTAB) was used as the shape-directing agent to develop GNRs with uniform size and aspect ratio. The as-synthesized GNRs can strongly enhance the Raman signal of the attached MGITC on the GNRs. Polyethylene glycol (SH-PEG-COOH) and SH-PEG-FITC were attached with GNRs through ligand exchange with CTAB. They can stabilize the GNRs, reduce the cytotoxicity and provide fluorescence signal. A cell-penetrating peptide was covalently conjugated with SH-PEG-COOH to assist the GNRs to enter living cell. After cultured with the MCF-7 cells, the surfaced functionalized Au nanorods can enter the MCF-7 cells and be tracking with enhanced MGITC Raman signal, FITC fluorescence, and Rayleigh scatter signal.