Highlights From The Latest Articles in Gold Nanoparticles for Theranostics

Abstract

2014 Cancer theranostics using gold-nanorods: photoacoustic imaging & photothermal therapy Evaluation of: Kim S, Chen YS, Luke GP, Emelianov SY. In-vivo ultrasound and photoacoustic image guided photothermal cancer therapy using silica-coated gold nanorods. IEEE Trans. Ultrasonics Ferroelectrics Freq. Control 5, 891–897 (2014). Gold nanoparticles have been intensively explored as photothermal transducers based on excessive optical absorption for cancer diagnosis and treatment [1,2]. By controlling the shape and size of gold nanoparticles, their localized plasmon resonance peaks can be tuned to a near-infrared spectral region in which optical light can penetrate deeper into biological tissues. Photoacoustic imaging is a hybrid biomedical imaging tool that can sensitively map the distribution of optical absorbers and local temperatures in biological tissues. Therefore, plasmonic gold nanoparticles have been widely utilized in order to maximize the photoacoustic detection sensitivity in cancer physiopathologic studies. In a recent issue of IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Kim et al. demonstrated photoacoustic and ultrasound image-guided photothermal cancer therapy using silica-coated plasmonic gold nanorods in small animals in vivo. The silica-coated gold nanorods with an average length and width of 63 ± 7 nm and 35 ± 5 nm, respectively, were synthesized from cetyltrimethylammonium bromidestabilized gold nanorods [3]. Then, the biocompatibility was enhanced by switching cetyltrimethylammonium bromide with mPEG-thiol, and the mPEG polymers were used for silica coating. The plasmonic peak of the silica-coated gold nanorods was at 805 nm within the near-infrared spectral window. A xenograft tumor model was induced by subcutaneous injection of human epithelial cancer cells to the right flank of a nude mouse. A total of 200 μl of silica-coated gold nanorod solution (40 μg of gold) was intravenously injected via the tail vein. The concentrations of oxygenated hemoglobin, deoxygenated hemoglobin and silica-coated gold nanorods within the tumor site were measured by a spectroscopic photoacoustic imaging scanner. Then, photothermal therapy was performed by irradiating with continuous-wave laser beams with an average laser power of 1 W at 808 nm, and the temperature elevation was monitored by the photoacoustic imaging scanner. The temperature reached up to 16°C above the body temperature. Therefore, this paper clearly proves that silica-coated gold nanorods can be used as theranostic photoacoustic and photothermal agents for cancer studies.