Two-photon luminescence imaging of cancer cells using molecularly targeted gold nanorods

We demonstrate the use of gold nanorods as bright contrast agents for two-photon luminescence (TPL) imaging of cancer cells in a three-dimensional tissue phantom down to 75 mu m deep. The TPL intensity from gold-nanorod-labeled cancer cells is 3 orders of magnitude brighter than the two-photon autofluorescence (TPAF) emission intensity from unlabeled cancer cells at 760 nm excitation light. Their strong signal, resistance to photobleaching, chemical stability, ease of synthesis, simplicity of conjugation chemistry, and biocompatibility make gold nanorods an attractive contrast agent for two-photon imaging of epithelial cancer.