Efficacy of photothermal ablation using intravenously delivered NIR-absorbing nanorods in colon cancer

The use of near-infrared absorbing nanoparticles recently has been proposed for the minimally invasive photothermal ablation of solid tumors, and this approach currently is being investigated in the clinic. One class of nanoparticles, gold nanorods, has been investigated for the ablation of various cancer types using both direct injection and systemic delivery. Here we investigate the photothermal ablation of colon cancer in an animal model using intravenously delivered gold nanorods. Nanorods with an aspect ratio of similar to 3.2 and an extinction peak of 774 nm were PEGylated, suspended in an isotonic solution, and infused into the tail vein of BALB/c mice bearing subcutaneous CT26.wt murine colon cancer tumors. After 24 hrs, an isotropic laser fiber was inserted through a small incision in the skin to a point proximate to and beneath the tumor. The area was illuminated with 3.5 W average power for 3 minutes. Control groups consisted of laser-only, nanorod-only and untreated tumored animals. The survival of the animals receiving nanorod-based photothermal ablation was statistically longer than the control groups with >44% complete response. This work demonstrates the promise of systemically delivering nanoparticles to tumors for thermal ablation