Hohyeong Kim

Porous silicon as an agent for cancer thermotherapy based on near-infrared light irradiation†

In recent years, new thermotherapies based on nanoshells and more recently single-wall carbon nanotubes (SWCNTs) in combination with near-infrared (NIR) light irradiation have received significant attention as efficient techniques to destroy cancer cells selectively. Very recently we have reported that porous silicon (PSi) can also be utilized as a therapeutic agent that generates heat sufficient to kill cancer cells without toxicity upon exposure to NIR light. In this paper, we report the heat generation abilities of a PSi suspension, a PSi/NaCl suspension and a PSi/phosphate-buffered saline (PBS) suspension during continuous irradiation with NIR light and the in vitrocell test results obtained by using thermotherapy based on PSi and NIR light irradiation. The PSi/NaCl suspension showed heat generation ability superior to those of the PSi suspension and PSi/PBS suspension. The temperature of the PSi/NaCl suspension was elevated to 55 and 76 °C after 3 and 20 min NIR irradiation at 300 mW cm−2, respectively, while that of the control was elevated to 31 and 39 °C after 3 and 20 min, respectively. In vitrocell test results suggest that thermotherapy based on PSi in combination with NIR light irradiation is an efficient technique to destroy cancer cells selectively without damaging the surrounding healthy cells and that heterochromatic NIR radiation can also be utilized successfully for this purpose.

TiO2 Nanotubes as a Therapeutic Agent for Cancer Thermotherapy

We report the photothermal properties as well as the in vitro cell test results of titanium oxide nanotubes (TiO2 NTs) as a potential therapeutic agent for cancer thermotherapy in combination with near‐infrared (NIR) light. TiO2 NTs are found to have a higher photothermal effect upon exposure to NIR laser than Au nanoparticles and single‐wall carbon nanotubes, which have also attracted considerable interest as therapeutic agents for cancer thermotherapy. The temperature increase of a TiO2 NT/NaCl suspension during NIR laser exposure is larger than that of a TiO2 NT/D.I. water suspension due to the heat generated by the formation of Na2TiF6. According to the in vitro cell test results the cells exposed to NIR laser without TiO2 NT treatment have a cell viability of 96.4%. Likewise, the cells treated with TiO2 NTs but not with NIR irradiation also have a cell viability of 98.2%. Combination of these two techniques, however, shows a cell viability of 1.35%. Also, the cell deaths are mostly due to necrosis but partly due to late apoptosis. These results suggest that TiO2 NTs can be used effectively as therapeutic agents for cancer thermotherapy due to their excellent photothermal properties and high biocompatibility.