title: Detection and localization of gold nanoshells inside cells: near-field approximation.
abstract: The optical properties of metal nanoparticles play a fundamental role for their use in a wide range of applications. In hyperthermia treatment, for example, gold nanoshells (NSs, dielectric core+gold shell) pre-embedded in a cancer cell absorb energy when exposed to appropriate wavelengths of a laser beam and heat up, thereby destroying the cancer cell. In this process, nevertheless, healthy tissues (not targeted by the NSs) along the laser path are not affected; this is because most biological soft tissues have a relatively low light absorption coefficient in the near-infrared (NIR) regions-a characteristic known as the tissue optical window. Over such a window, NIR light transmits through the tissues with scattering-limited attenuation and minimal heating, thereby avoiding damage to healthy tissues. As a consequence, the identification of NSs assumed a fundamental role for the further development of such cancer treatment. Recently, we have demonstrated the possibility to identify 100-150 nm diameter gold NSs inside mouse cells using a scanning near-optical microscope (SNOM). In this paper, we provide a numerical demonstration that the SNOM is able to locate NSs inside the cell with a particle-aperture distance of about 100 nm. This result was obtained by developing an analytical approach based on the calculation of the dyadic Green function in the near-field approximation. The implications of our findings will remarkably affect further investigations on the interaction between NSs and biological systems.
authors.forename: Mario
authors.initials: M
authors.lastname: D'Acunto
authors.forename: Antonio
authors.initials: A
authors.lastname: Cricenti
authors.forename: Serena
authors.initials: S
authors.lastname: Danti
authors.forename: Simone
authors.initials: S
authors.lastname: Dinarelli
authors.forename: Marco
authors.initials: M
authors.lastname: Luce
authors.forename: Davide
authors.initials: D
authors.lastname: Moroni
authors.forename: Ovidio
authors.initials: O
authors.lastname: Salvetti
mesh_terms: D000818:Animals; D006046:Gold; D006979:Hyperthermia, Induced; D053768:Metal Nanoparticles; D051379:Mice; D057145:Nanoshells; D009369:Neoplasms / Q000628:therapy*; D012542:Scattering, Radiation
chemical_list: D006046:Gold