Small gold nanorods-loaded hybrid albumin nanoparticles with high photothermal efficacy for tumor ablation.

Photothermal therapy using gold nanorods (AuNRs) has gained great attention for cancer therapy because AuNRs emit heat and induce tumor cell death responding to the near infrared light. However, the anticancer efficiency of AuNRs alone is undermined by its poor in vivo stability and potential toxicity. The prime purpose of this study was to send more AuNRs into tumors to more fully ablate them. For this, we fabricated hybrid albumin nanoparticles encapsulating small AuNRs (AuNRs-Alb-NPs), which take advantage of biocompatible albumin as a carrier, with better tumor targetability and high in vivo photothermal activity. The sizes of length/width of AuNRs were approximately 20.5 nm and 4.6 nm, respectively, showing a 4.5 aspect ratio, and the size of the resulting AuNRs-Alb-NPs was ˜130 nm, all of which are favorable for glomerular filtration and passive tumor targeting via extravasation. We chose the best formulation for AuNRs-Alb-NPs by in vitro cytotoxicity based on photothermal conversion efficiency considering the incorporated number of AuNRs. Visualized by a photothermal camera, the local tumor temperature of mice treated with AuNRs-Alb-NPs increased to 57℃, which was sufficient for the hyperthermal effect with 808 nm laser irradiation. Subsequently, AuNRs-Alb-NPs displayed remarkably better tumor ablation vs. naïve formulation of AuNRs (tumor volume: 73.8 ± 105.8 vs. 1455.3 ± 310.4 mm at day 8) in the glioblastoma N2a tumor-bearing mice. Most of all, we demonstrated, using photoacoustic imaging and inductively coupled plasma mass spectrometry, that this much better tumor ablation was due to enhanced tumor targeting with albumin nanoparticles. We believe our AuNRs-Alb-NPs should be considered promising photothermal agents that are safer, have good targetability, and exhibit excellent tumor ablation.