Sung-O Kim

Apoptosis of lung carcinoma cells induced by a flexible optical fiber-based cold microplasma.

Atmospheric pressure plasmas have been used as a therapy for cancer. However, the fairly large size and rigidity of present plasma-delivery systems obstructs the precise treatment of tumors in harder-to-reach internal organs such as the lungs, pancreas, and duodenum. In order to improve the targeted delivery of plasmas a highly flexible microplasma jet device is fabricated using a hollow-core optical fiber with an inner diameter of either 15 μm, 55 μm, or 200 μm. Described herein, based on this device, are results on lung carcinoma therapy using a microplasma cancer endoscope. Despite the small inner diameter and the low gas flow rate, the generated plasma jets are shown to be sufficiently effective to induce apoptosis, but not necrosis, in both cultured mouse lung carcinoma and fibroblast cells. Further, the lung carcinoma cells were found to be more sensitive to plasma treatment than the fibroblast cells based on the overall plasma dose conditions. This work enables directed cancer therapies using on highly flexible and precise hollow optical fiber-based plasma device and offers enhancements to microplasma cancer endoscopy using an improved method of plasma targeting and delivery.

A flexible cold microplasma jet using biocompatible dielectric tubes for cancer therapy

This paper describes a flexible microplasma jet device using a Tygon® S-54-HL tube as a biocompatible tube and its potential in developing cancer therapies. The optical and physical properties of the plasma jets and preliminary apoptosis data of cultured murine tumor cells and nontumor fibroblast cells treated with these plasma jets are presented. Microplasma jets were observed to induce apoptosis in cultured murine cells in a dose-dependent manner. The murine melanoma tumor cells were more sensitive to plasma treatment than fibroblast cells. These features allow the direct and precise application of this microplasma jet device to tumor cells.

Single‐Cell‐Level Microplasma Cancer Therapy

A flexible microplasma endoscope based on a 15 μm hollow-core glass optical fiber is fabricated, and tumor cell apoptotic analysis supports its potential use in targeted cancer therapies. The optical-fiber microplasma jet reveals antitumor activity at a certain plasma dose in animal studies.

15-μm-sized single-cellular-level and cell-manipulatable microplasma jet in cancer therapies

The authors describe a proposed 15-μm-sized, single-cellular-level, and cell-manipulatable microplasma jet device with a microcapillary glass tip and its potential in the development of cancer treatment therapies. The electrical and optical properties of the plasma jets and preliminary apoptosis results of cultured murine tumor cells and non-tumor fibroblast cells treated with the plasma jets are presented. The generated plasma jet was stable and enabled the treatment of cultured cells in cell culture plates regardless of the small inner diameter and low gas flow rate. The microplasma jet was observed inducing apoptosis in cultured murine melanoma tumor cells in a dose-dependent manner. Furthermore, the percentage of apoptotic cells of murine melanoma tumor cells induced by this plasma device was approximately 2.5 times bigger than that of murine fibroblast cells as indicated by an Annex V apoptosis assay. The apoptosis in cultured murine tumor cells by the 15-μm-sized single-cellular-level and cell-manipulatable microplasma jet device was also observed using an in situ apoptosis assay. We report on a novel microplasma jet device with the advantages of single-cellular-level and single cell-manipulatable plasma treatment with precise and solid stimuli. This highly precise plasma medicine, which enables new directed cancer therapies can be combined with current cell manipulation and cell culturing technologies without much difficulty.

Single-cell-level cancer therapy using a hollow optical fiber-based microplasma.

Atmospheric-pressure plasmas have been used in cancer therapies, but the size of the delivery systems precludes single-cell treatments. Plasmas are gaseous collections of ionized particles that include free electrons and radicals that are short-lived but strongly reactive species. Cancer therapies based on plasmas that operate at atmospheric pressure have been developed, which expose these free radicals to tumor cells causing their subsequent apoptosis at a rapid pace. To define the mechanism of plasma-induced tumor cell apoptosis, it would be preferred to have a plasma device that can treat tumor cells at the single-cell level. Thus, the challenge is to generate and deliver plasmas to a single cell. A microplasma jet device consisting of a tube with electrodes has been demonstrated as a source for creating nonthermal atmospheric-pressure plasmas with dimensions on the order of several hundred micrometers. There are two principal methods for reducing the size of the plasma. The first method utilizes a glass capillary tube with a small inner diameter. The second approach employs a thin metal wire as an electrode. Because microplasma jets were originally developed for superficial work (i.e., treating only the surface of objects),

Reactive oxygen species controllable non-thermal helium plasmas for evaluation of plasmid DNA strand breaks

Non-thermal, oxygen-rich helium plasmas were investigated to achieve an enhanced reactive oxygen species concentration at low voltage driving conditions. A non-thermal plasma device was fabricated based on a theta-shaped tube, and its potential was investigated for use in topological alteration of plasmid DNA. The optical emission spectra of the plasma showed that the oxygen flow affected the plasma properties, even though an oxygen plasma was not produced. The plasmid DNA strand breaks became more significant with the addition of oxygen flow to the helium in a single hollow, theta-shaped tube with other experimental conditions being unchanged.

Effects of annealing atmosphere and temperature on properties of ZnO thin films on porous silicon grown by plasma-assisted molecular beam epitaxy

Zinc oxide (ZnO) thin films were grown on porous silicon (PS) by plasma-assisted molecular beam epitaxy (PA-MBE). The thin films were annealed in various atmospheres such as argon, nitrogen, and vacuum, and their structural and optical properties were investigated by scanning electron microscopy, X-ray diffraction, and photoluminescence. The ZnO thin films grown on PS showed a mountain-range-like surface morphology, whereas those grown on Si showed a typical 3D island surface structure. The thin films grown on PS exhibited only one diffraction peak at 34°, whereas those grown on Si showed shoulders of the ZnO (002) diffraction peaks at around 33°; this implies an excellent c-axis preferred orientation and a better crystal quality when PS was used. Large crystals were partially formed at an annealing temperature of 700°C. The films annealed in a vacuum showed nanorod-like ZnO crystals, whereas those annealed in nitrogen and oxygen showed irregularly shaped crystals. It was confirmed that the structural and optical properties of the thin films were enhanced by the annealing process. In particular, relatively large changes in the full width at half maximum of the ZnO (002) diffraction peaks and UV emission peaks, indicating enhanced structural and optical properties, respectively, were observed when the thin films were annealed in argon.

Low-temperature growth of multiple-stack high-density ZnO nanoflowers/nanorods on plastic substrates

Reported here is the low-temperature growth of multiple-stack high-density ZnO nanoflower/nanorod structures on polyethylene naphthalate (PEN) substrates derived from the surface modification of ZnO seed layers using an atmospheric-pressure plasma jet (APPJ) treatment. The plasma treatment could provide several advantages to the growth of multiple-stack ZnO nanoflower/nanorod structures: (i) the surface wettability of the seed layers changes from hydrophobic to hydrophilic, resulting in higher surface energies for the growth of high-density ZnO nanoflowers, (ii) the nucleation sites increase due to the increased surface roughness caused by the plasma etching, and (iii) there is no thermal damage to the plastic substrate from the plasma treatment due to its low-temperature weakly ionized discharge. It was also confirmed that multiple stacks of ZnO nanoflowers were obtained without degradation of the crystal quality or modification to the crystal shape or phase. The ZnO nanoflower/nanorod structures grew by lengths up to 4 μm due to an increased surface roughness of 10% and surface energy 5.5 times that of the seed layers. As shown, the APPJ is a very good method to obtain high-density ZnO nanostructures on plastic substrates below 150 °C, as is critical for flexible electronics.

Growth and characterization of seed layer-free ZnO thin films deposited on porous silicon by hydrothermal method

Catalyst- and seed layer-free zinc oxide (ZnO) thin films were grown on porous silicon (PS) by a hydrothermal method. Atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL) were carried out to investigate the structural and optical properties of the PS and the ZnO thin films. The ZnO thin films have an extraordinary tendency to grow along the a-axis with a hexagonal wurtzite structure. The growth rate of the ZnO thin films was increased with the increase in the precursor concentration. The crystal quality of the ZnO thin films was improved, and the residual stress was decreased as their thickness increased. Monochromatic indigo and red light emission peaks were observed from the ZnO thin films and the PS, respectively. At an excessively high precursor concentration, a green light emission peak was also observed in the ZnO thin films. The luminescent efficiency of the indigo light emission peak was enhanced with the increase in the precursor concentration.

Intense plasma emission induced by jet-to-jet coupling in atmospheric pressure plasma arrays

Intense plasma emissions were achieved via jet-to-jet coupling in a multi-tube array-based plasma device in ambient air. The plasma array device consisted of a central glass tube encircled by an array of hollow glass tubes. A single plasma jet was induced via jet-to-jet coupling and enabled significantly increased plasma emission despite a negligible change in power consumption. An increase in the number of outer tubes yielded a greater number of charged particles involved in the plasma process and resulting in the achievement of higher plasma emission in the coupled system.