◈ Title : Low-temperature atmospheric-pressure plasma: Effects on cancer cells and on tooth whitening
◈ Speaker : Prof.  Gyoocheon Kim (college of dentistry, Pusan National University)
◈ Date & Time : Friday, March 4, 2011 (2:00pm ~ 3:30pm)
◈ Place : LG Research Building, Room #101
◈ Host : Prof.  Jae Koo, Lee (Tel. 2083)
◈ Abstract : Non-thermal air plasma was investigated in cell-death of G361 melanoma and SCC25 oral cancer cells, targeted by antibody-conjugated gold nanoparticles. Although plasma alone is effective in killing cancer cells, it also adversely affects normal cells during the treatment process. For enhanced effects, cells were pretreated with gold nanoparticles and cancer-specific antibodies before plasma treatment. The nanoparticles, taken up by the cancer cells, are stimulated by the plasma, resulting  in the observed increase in death rate. The selectivity of this kill-process is achieved by conjugating the gold nanoparticles with anti-focal adhesion kinase (FAK), epidermal growth factor receptor  (EGFR) and -transferrin receptor (TFR) antibodies, conjugates that can bind specifically to cancer cells. The killing efficiency of the plasma treatment in the presence of conjugates was amplified about 18-fold compared to the effect in their absence. Therefore, this technique shows promise as a therapy for treating cancer selectively and effectively. We have also demonstrated that plasma can be used for bleaching of teeth: A low-temperature, atmospheric-pressure helium plasma jet device, in conjunction with hydrogen peroxide (H2O2), was developed for this purpose. All teeth, sectioned sagittally into halves, were assigned randomly to   either an experimental group or a control group. The former was treated with H2O2 (28%, 20 mL  every 30 seconds) plus plasma (5 W) for 10 minutes, while the control group was treated with H2O2 alone for the same duration. Removal of the tooth-surface protein was demonstrated by scanning electron microscopy and by Ponceau staining. The production of hydroxyl radicals (·OH) was measured by spin-trapping, using electron-spin resonance (ESR) spectroscopy. Combining plasma and H2O2 was found to improve the bleaching efficacy 3-fold compared with H2O2 alone,  tooth-surface proteins being noticeably removed in the former case. When a piece of tooth was added as a catalyst to a solution of H2O2, production of ·OH after plasma treatment was ca. twice greater than when using H2O2 alone. We conclude that the improvement of tooth bleaching induced by plasma is due to the removal of the surface proteins and to increased ·OH production.