Enhancement of gold nanorods-assisted photothermal treatment on cancer with laser power in stepwise modulation

Objectives Photothermal therapy (PTT) is a minimally invasive or noninvasive method by destructing cancer cells through selective thermal decomposition. However, a long period of laser irradiation to achieve coagulative necrosis often causes unfavorable thermal damage to the surrounding healthy tissue. The current study aims to evaluate the feasibility of temporal power modulation to improve the treatment efficacy of gold nanorods-assisted PTT against tumor tissue. Materials and Methods A total of 25 mu g/ml of PEGylated gold nanorods (PEG-GNR) was used as an absorbing agent during 1064 nm laser irradiation for PTT. Temperature monitoring was conducted on the aqueous solution of PEG-GNR for dosimetry comparison. For in vivo tests, CT-26 tumor-bearing murine models with PEG-GNR injected were treated with three irradiation conditions: 3 W/cm(2) for 90 s, 1.5 W/cm(2) for 180 s, and 3 W/cm(2) for 60 s followed by 1.5 W/cm(2) for 60 s (modulated). Ten days after the treatments, histology analysis was performed to assess the extent of coagulation necrosis in the treated tissues. Results The temporal power modulation maintained the tissue temperature of around 50 degrees C for a longer period during the irradiation. Histology analysis confirmed that the modulated group entailed a larger coagulative necrosis area with less thermal damage to the peripheral tissue, compared to the other irradiation conditions. Conclusion Therefore, the power-modulated PTT could improve treatment efficacy with reduced injury by maintaining the constant tissue temperature. Further studies will examine the feasibility of the proposed technique in large animal models in terms of acute and chronic tissue responses and treatment margin for clinical translations.