Jungkeun Lee

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.

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.

Structure and photoluminescence properties of ZnS‐core/In2O3‐shell one‐dimensional nanowires

ZnS‐core/In2O3‐shell nanowires have been prepared by using a two‐step process: the thermal evaporation of ZnS powders on Si(100) substrates coated with Au thin films and the sputter‐deposition of In2O3. The ZnS nanowires were a few tens to a few hundreds of nanometers in diameter and up to a few hundreds of micrometers in length. ZnS nanowires have an emission band centered at around 570 nm in the yellow region. The yellow emission has been enhanced in intensity by coating the ZnS nanowires with In2O3 and further enhanced by annealing in a reducing atmosphere, but it is degraded by annealing in an oxidative atmosphere.

ANNEALING BEHAVIORS OF TiO2-SHEATHED SnO2 NANORODS

We report the preparation and thermal annealing of SnO2-core/TiO2-shell nanorods using a two-step process comprising the thermal evaporation of Snpowders and the sputter-deposition of TiO2. X-ray diffraction analysis revealed that the shells were crystallized by annealing. Photoluminescence measurements showed that the major yellow emission of the SnO2 nanorods was enhanced in intensity by sheathing them with TiO2 and was further enhanced by annealing. A reducing atmosphere was found to be more efficient in enhancing the yellow emission by annealing than an oxidative atmosphere. The origin of the emission enhancement by coating and annealing is also discussed.