Nanoshell-Mediated Near Infrared Photothermal Tumor Therapy

A novel photothermal therapy of neoplastic tissue is described. The use of near infrared (NIR) absorbing nanoshells permits targeted photothermal ablation of tumor tissue via NIR heating of nanoshell-laden tumors using an extracorporeal near infrared source. Human breast carcinoma cells incubated with nanoshells in vitro were found to undergo photothermally induced morbitity upon exposure to NIR light (820 nm, 44 W/cm²) as determined using a fluorescent viability stain. Cells without nanoshells displayed no loss in viability after the same periods and conditions of near infrared illumination. Likewise, in vivo studies under MR guidance revealed that exposure to low doses of near infrared light (820 nm, 4 W/cm²) in solid tumors treated with metal nanoshells reached average temperatures capable of inducing irreversible tissue damage (δT = 37.4 ± 6.6°C) within 4-6 minutes. Controls treated without nanoshells demonstrated significantly less average temperatures upon exposure to near infrared light (δT< 10°C). These findings demonstrated good correlation with histological findings. Tissues heated above the thermal damage threshold displayed coagulation, cell shrinkage, and loss of nuclear staining - indicators of irreversible thermal damage. Control tissues did not display these indicators and appeared undamaged.