氬氣常壓電漿束之特性及滅除細菌與內孢子效率之研究

Abstract

本實驗主要為探討以氬氣為主要氣體之非熱平衡低溫常壓電漿束在生物醫學中之殺菌與殺內孢子效率的研究，藉由處理E. coli與B. subtilis細菌與B. subtilis內孢子來改善處理傷口或手術過程中殺菌的效率，以降低院內感染(HAI)的機會。此電漿束包含一石英管為介電材料，並有兩個外包銅管為高電位與接地電位，內部包含一銅管為浮動電位。在每分鐘五公升的氬氣體積流速下，通以7.5千伏特與20千赫茲之正弦波交流電場來產生常壓低溫電漿。本實驗用酒精溫度計測得電漿之溫度低於人體的攝氏三十七度，利用高壓探棒與Rogowski電流線圈來量測輸入電壓與輸出電流。另外，因活性氧化物質(ROS)在生物醫學與殺菌效果有重要的影響，本實驗藉由放光光譜儀(OES)量測到本電漿束中含有相對豐富的OH粒子。OH的相對強度在加入少量氧氣時會獲得少許的提升，然而在超過0.04%時會急遽下降。D-value代表殺死90%細菌所需之時間。在本論文的殺菌實驗中，在前九秒的純氬氣電漿處理中，E.coli與B. subtilis細菌之D-value分別為5.5與2.7秒，然而在處理時間超過九秒後，D-value分別上升至16.1與7.8秒。殺菌效率的差異或許與兩種細菌細胞壁結構不同或細菌本身大小有關係。而至於B. subtilis內孢子，在前一分鐘電漿處理內之D-value為 49.7秒，超過一分鐘後則上升至111.6秒。另外，加入少許的氧氣能為三種細菌增加在培養基上的殺菌面積，然而超過0.02%之氧氣濃度後，殺菌面積則會減少。最後，利用掃描式電子顯微鏡(SEM)觀測則會發現三種細菌的表面形貌接受到電漿的破壞。

In this study, we developed a round argon-based non-thermal atmospheric pressure plasma jet (APPJ), which was carefully characterized by alcohol thermometer, optical emission spectra (OES), high-voltage probe, and Rogowski type current coil. The temperature of our APPJ is lower than 37°C, which will not induce damage to living tissue. Furthermore, while studies suggest that reactive oxygen species (ROS) play important roles in microorganism sterilization, OES measurements indicate that there are relative high amount of hydroxyl (OH) radicals in our APPJ, while the OH intensity increases with the addition of oxygen. However, OH intensity decreases dramatically after the oxygen percentage becomes higher than 0.04% due to quenching effects. D-value is the time required at a given temperature to kill 90% of the exposed microorganisms. For sterilizing experiment, our argon APPJ has a D-value of 5.5 and 2.7 seconds for E. coli and B. subtilis bacteria within the first 9 seconds of pure argon plasma treatment respectively. For plasma treatment time longer than 9 seconds, the D-value will increase to 16.1 and 7.8 seconds respectively. The sterilizing efficacy of B. subtilis is slightly better than E. coli which is maybe due to the difference of cell wall structure or cell size. For endospores, it takes 49.7 seconds to inactivate 90% of Bacillus subtilis endospore in the first 60 seconds of plasma treatment, while the efficacy will reduce to 111.6 seconds for longer treatment. Addition of oxygen will increase the inactivation area on agar dishes for all 3 microorganisms until the percentage of 0.02. More than 0.02% of oxygen will decrease the sterilization efficacy. At last, observation on scanning electron microscope (SEM) shows morphological rupture on all 3 microorganisms after plasma treatment.