Chanseok Hong

Porous silicon nanoparticles for cancer photothermotherapy

The in vitro cell tests and in vivo animal tests were performed to investigate the feasibility of the photothermal therapy based on porous silicon (PSi) in combination with near-infrared (NIR) laser. According to the Annexin V- fluorescein isothiocyanate Apoptosis assay test results, the untreated cells and the cells exposed to NIR laser without PSi treatment had a cell viability of 95.6 and 91.3%, respectively. Likewise, the cells treated with PSi but not with NIR irradiation also had a cell viability of 74.4%. Combination of these two techniques, however, showed a cell viability of 6.7%. Also, the cell deaths were mostly due to necrosis but partly due to late apoptosis. The in vivo animal test results showed that the Murine colon carcinoma (CT-26) tumors were completely resorbed without nearly giving damage to surrounding healthy tissue within 5 days of PSi and NIR laser treatment. Tumors have not recurred at all in the PSi/NIR treatment groups thereafter. Both the in vitro cell test and in vivo animal test results suggest that thermotherapy based on PSi in combination with NIR laser irradiation is an efficient technique to selectively destroy cancer cells without damaging the surrounding healthy cells.

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.

Comparison of oxidized porous silicon with bare porous silicon as a photothermal agent for cancer cell destruction based on in vitro cell test results

In the systematic administration of cancer, cancer markers are normally used to help the therapeutic agents access the cancer cells spontaneously. Therefore, it is essential to functionalize the surface of porous silicon (pSi) for cancer markers to attach well to pSi in systematic administration because most cancer markers does not attach easily to pSi. The thermal oxidation of pSi is adopted most widely as a surface functionalization technique for pSi. This study examined the photothermal properties and cancer cell-killing ability of oxidized pSi (pSiO). The temperature measurement and in vitro cell tests including the annexin V-fluorescein isothiocyanate (FITC) apoptosis assay tests, MTT assay tests, and Trypan blue cell death assay tests were performed to compare the photothermal properties and the cytotoxic effect of pSiO with those of pSi in combination with an 808-nm NIR laser. pSiO showed lower photothermal properties and a lower cell-death rate than bare pSi. On the other hand, the pSiO treatment used in combination with an NIR laser treatment showed a cytotoxic effect high enough to kill a considerable portion of the cancer cells.

In-vivo cancer cell destruction using porous silicon nanoparticles.

In-vivo animal tests were performed to investigate the feasibility of photothermal therapy based on porous silicon nanoparticles (PSiNPs) in combination with a near-infrared (NIR) laser. The in-vivo animal test results showed that the murine colon carcinoma (CT-26) tumors were completely resorbed with minimal damage to surrounding healthy tissue within 5 days after PSiNPs and NIR laser treatments. In contrast, tumors in the groups treated only with PSiNPs or NIR and a control group continued to grow until the mice died. All of the mice treated with both PSiNPs and NIR remained healthy and free of tumors even 90 days after the treatment. In-vivo fluorescence imaging and the urine and feces tests revealed that PSiNPs injected intratumorally into mice were cleared mainly through the urine. The in-vivo animal test results suggest that thermotherapy based on porous silicon in combination with NIR laser irradiation can efficiently destroy cancer cells selectively without damaging the surrounding healthy cells.

In-vitro cell tests using doxorubicin-loaded polymeric TiO2 nanotubes used for cancer photothermotherapy.

To determine the appropriate surfactant to be added to TiO2 nanotubes (TNTs) for use in cancer photothermotherapy, this study measured the increase in temperature and examined the size distribution of TNT particles loaded with different surfactants during near-infrared irradiation. In addition, in-vitro cell (fluorescein isothiocyanate and MTT assay) tests were carried out to examine the cytotoxic effect of doxorubicin-loaded and polyvinyl alcohol-added TNTs (pTNTs). The mean particle size of the pTNTs was 151.8 nm with a particle size variation of less than 3 nm, which is low enough to flow through blood vessels without causing a blockage. The temperature of the pTNTs was ∼47°C, which is high enough to destroy cancer cells. Doxorubicin-loaded TNTs and pTNTs in combination with a near-infrared laser showed a cell viability of 4.5% – a sufficiently high cytotoxic effect.

Influence of coating and annealing on the optical properties of ZnSe/CdO core‐shell nanorods

We prepared ZnSe/CdO coaxial nanorods on Si(100) substrates by using a two step process comprising the thermal evaporation of ZnSe powders and the sputter‐deposition of CdO. PL measurements show that the ZnSe‐core/CdO‐shell nanorods have a strong emission band centered at around 605 nm in the orange region. The PL emission of the core‐shell nanrods can be significantly enhanced by CdO coating and subsequent annealing. Annealing in a reducing atmosphere is more efficient in enhancing the PL emission of the core‐shell nanorods than annealing in an oxidative atmosphere owing to the generation of Zn interstitials during annealing.