Surface plasmonic gold nanorods for enhanced two-photon microscopic imaging and apoptosis induction of cancer cells.

Two-photon microscopy powered by a femtosecond laser is a promising tool for luminescence imaging and localized microsurgery of cancers. However, the high energy required to destruct cells limits its medical applications. In this work, gold nanorods were conjugated with transferrin for efficient targeting, two-photon luminescence imaging and enhanced microsurgery of cancer cells. Due to the large two-photon excitation cross section of gold nanorods, gold nanorods are a hundred times more efficient than Fluorescein isothiocyanate (FITC), a common molecular dye, in three-dimensional imaging of cancer cells. The enhanced light absorption and energy conversion by gold nanorods enable treatment of cells with energy fluences two orders of magnitude below that in the absence of gold nanorods. By manipulating the energy fluence, apoptosis of cancer cells has been achieved. At a same power density, the energy fluence for apoptosis induction is less than 20% of that for necrosis. Gold nanorods-enhanced luminescence imaging coupled with apoptosis induction of cancer cells provides a medically safe femtosecond laser-based imaging and microsurgery system for cancer diagnosis and treatment.