Gold Nanoroses for Optical Biomedical Imaging and Photothermal Therapy In Atherosclerosis and Cancer

Novel nanoscaled composites of iron oxide and gold, coated with hydrophilic polymers, have been designed to absorb light in the near infrared (NIR) spectral region for optical imaging in atherosclerosis and cancer. These “nanoroses” form a stable colloidal dispersion in aqueous media. The geometry of the gold domains in the nanorose particle leads to a red-shift in absorbance into the NIR region, where light scattering of blood is less. The hydrophilic coatings are designed to control the synthesis of the nanoroses and to enhance the circulation time in the bloodstream. The nanoroses are compared with four previously reported types of NIR contrast enhancement agents: nanospheres, nanorods, nanoshells, and nanocages. The nanoroses have high optical sensitivity (absorption and scattering) in the NIR and visible region (500 nm -1100 nm), and thus provide high contrast enhancement for various optical biomedical imaging techniques including optical coherence tomography (OCT), photoacoustic imaging, and optical microscopy. The nanoroses are coated with dextran to target the macrophage cells. Uptake of nanoroses into macrophage cells associated with atherosclerotic plaque is investigated with dark field and phase contrast microscopy, and the nanoroses optical properties within the cells are measured with hyperspectral microscopy. Experiments were carried out ex-vivo on animal tissue injected with the broadly absorbing gold nanocomposites. Photoacoustic imaging identified the presence of gold nanocomposites in tissue. In addition, a localized temperature increase, obtained during therapy, was monitored using photoacoustic and ultrasound imaging.