Reversible two-photon photoswitching and two-photon imaging of immunofunctionalized nanoparticles targeted to cancer cells

J Am Chem Soc. 2011 Jan 19;133(2):365-72. doi: 10.1021/ja106895k. Epub 2010 Dec 15.

Abstract

Both photoswitchable fluorescent nanoparticles and photoactivatable fluorescent proteins have been used for super-resolution far-field imaging on the nanometer scale, but the photoactivating wavelength for such photochemical events generally falls in the near-UV (NUV) region (<420 nm), which is not preferred in cellular imaging. However, using two near-IR (NIR) photons that are lower in energy, we can circumvent such problems and replace NUV single-photon excitations (e.g., 390 nm) with NIR two-photon excitations (e.g., 780 nm). Thus, we have demonstrated that alternating 780 nm NIR two-photon and 488 nm single-photon excitations induces reversible on-off fluorescence switching of immunotargeted nanoparticles in the human breast cancer cell line SK-BR-3. Herein, two-photon absorption not only caused spiropyran-merocyanine photoisomerization within the particles but also imparted red fluorescence. In comparison with single-photon NUV excitations, two-photon NIR laser excitations can potentially reduce absorption-related photodamage to living systems because cellular systems absorb much more weakly in the NIR.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Benzopyrans* / chemistry
  • Cell Line, Tumor
  • Fluorescence
  • Humans
  • Indoles* / chemistry
  • Nanoparticles* / chemistry
  • Neoplasms / pathology*
  • Nitro Compounds* / chemistry
  • Photochemical Processes
  • Photons*

Substances

  • Benzopyrans
  • Indoles
  • Nitro Compounds
  • merocyanine
  • spiropyran