대기압 플라즈마의 생물 의학에 응용

Abstract

Plasma research, with success in semiconductor processing at low pressure (~ mTorr), has expanded to include biomedical areas by operating at atmospheric pressure (760 Torr), which eliminates bulky and expensive vacuum systems. Atmospheric pressure plasma has the advantages of high density and rich chemical agents without elevation of the substrate temperature. These non-equilibrium characteristics promise applications in the biomedical field, opening a new research area called “Plasma Medicine” which includes sterilization, coagulation, wound healing, and cancer treatment. This research investigates the effects of atmospheric pressure plasma on cancer cells. Plasma devices operated in the ambient air with 22kHz power supply based on the Dielectric Barrier Discharge. These discharges are rich source of ozone which have been used for ozone generator. Despite much effort over the past five decades, we are still having limited success in the war against cancer. As an alternative to conventional chemical methods, physical methods have been proposed in cancer treatment. This research focused on the induction of apoptosis in cancer cells by non-thermal atmospheric pressure plasma and the mechanism of apoptosis. As well, for the therapeutic purpose, plasma was coupled with antibody conjugated gold nanoparticles. When the cells die, they have two different types of death. One is known necrosis caused by accidental injury. The other is called apoptosis induced by internal and external death signals which looks like programmed cell death. Plasma induced the apoptosis which was indicated by nucleus condensation and fragmentation and verified by TUNEL assay. To investigate the apoptosis mechanism by plasma, western blot method was used. Apoptosis was induced by DNA damages. The advanced mammalian cells have defense systems that respond to DNA damages. p53 tumor suppress gene is representative proteins. At 3 hr later the plasma treatment, p53 was accumulated. But if the damages were severe, damaged cells withdrew the cure and initiated the apoptosis process. After plasma exposure, the proteins related to apoptosis were activated (Bcl-2, Bax, caspase-3). Cytochrome C release into the cytosol from the mitochondria is also involved in intrinsic apoptosis pathway. In the case of plasma treatment, Cytochrome C also released. From these results, the effects of plasma on cells involve genetic signaling cascade from DNA-damage and damage in cellular membrane systems. For the therapeutic purpose, plasma was coupled with antibody conjugated gold nanoparticles. When plasma meets the conjugates, the killing effect was amplified (5 times compared to without conjugates). It also suggests that with abundant antigens in cancer it could be a selective cancer therapy. It is known that various cancer cells overexpress the FAK proteins. We have made conjugates with FAK and 30 nm gold nanoparticles. Even though these conjugates were located within the cancer cells, they do nothing. When the plasma was exposed, the cancer cells died effectively. From these results, it is suggested that plasma treatment coupled with antibody conjugated gold nanoparticles could achieve effective and selective cancer therapy. In summary, plasma induced cell apoptosis caused by DNA damages and mitochondria dysfunction. As well, the effective and selective cancer therapy with plasma was suggested by coupling with antibody conjugated gold nanoparticles.