Gold nanostars functionalized with amine-terminated PEG for X-ray/CT imaging and photothermal therapy

Multifunctional gold nanostructures effective at photothermal therapy (PTT) and high-quality X-ray/computed tomography (CT) imaging have drawn much attention in recent research. In particular, the development of improved PTT against cancer has been a particularly focused area of research for which the clinical need is great. Since the intracellular concentration of gold nanostructures is critical for their therapeutic photothermal efficacy, we decorated gold nanostructures with positively charged polyethylene glycol (PEG) to boost their degree of uptake by the cell. Herein gold nanostars (GNSs) were decorated with amine-terminated PEG (GNS-PEG-NH₂) and methoxy-terminated PEG (GNS-mPEG). PEGylated GNSs showed good dispersivity, high stability and low cytotoxicity. Moreover, compared with GNS-mPEG, GNS-PEG-NH₂ exhibited superior thermal therapeutic efficacy against breast tumor cells due to their higher cellular uptake. Measurement of the X-ray absorption coefficient revealed that the attenuation of GNS-PEG-NH₂ was about 3.6-fold higher than that of the commercial CT contrast agent iodixanol at the concentration of 25 mg L^-1. Importantly, GNS-PEG-NH₂ also exhibited effective tumor therapeutic efficacy in vivo, and the tumor sites injected with GNS-PEG-NH₂ showed high contrast X-ray/CT imaging. And most of the injected GNS-PEG-NH₂ was cleared from tumors 15 days post-injection, indicating rapid clearance and minimal toxicity of GNS-PEG-NH₂. Such PEGylated GNSs, when used for producing high-contrast images to guide enhanced PTT therapy, may thus provide new opportunities for the development of cancer theranostics.