Comparison of the Photothermal Efficiency of Different Types of Plasmonic Nanoparticles in vitro and in vivo

Abstract

Due to their unique optical properties and biocompatibility gold nanoparticles irradiated with near-infra red (NIR) light are promising candidates for photothermal cancer therapy [Hirsch et al., PNAS 2003, 23, 13549-13554]. In particular, the NIR region is preferable for cancer therapies since it has the lowest absorption and highest penetration depth in biological material. When irradiated, gold nanoparticles efficiently absorb the light and convert it into extremely local and well-controlled heating with temperature increases that easily exceeds 100°C [Bendix et al., ACS Nano 2010, 4, 2256-2262]. We report a comparison study of the capability of NIR-resonant 150 nm silica gold nanoshells as photothermal transducers to that of NIR-off resonant 80 and 150 nm spherical gold nanoparticles in vitro and in vivo. Using a NIR optical trap coupled into a Leica SP5 confocal microscope we investigate the temperature profile as a function of laser power of single irradiated nanoshells and spherical nanoparticles in vitro; this is done using an assay with phospholipid vesicles with a well-characterized phase transition and phase sensitive fluorescent molecules that returns directly the temperature profile of the 3D optically trapped nanoshell or spherical nanoparticle [Kyrsting et al., Nano Letters 2011, 11, 888-892]. The photothermal relationship between laser power and the composition/size of a single particle in vitro are compared to the photothermal efficiency in vivo where the particles were delivered in a mouse tumor model. Nanoparticles were injected directly into the tumor of tumor-bearing mice that were subsequent irradiated with a NIR diode laser. The photothermal efficiency of the nanoshells and spherical nanoparticles in vivo is evaluated by 18F-flourodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT)-based imaging and caliper-based tumor volume shrinkage [Munk Jensen et al., PloS one 2013, 8, e85126].