Sterilization of narrow tube inner surface using discharge plasma, ozone, and UV light irradiation

• We developed a method to sterilize the inner surface of a silicone tube.
• Sterilization inside the silicone tube is performed by active oxygen species.
• The surface of a silicone tube is not modified by 30-min plasma treatment.

Sterilization of medical equipment is an important procedure in the field of medicine. However, methods for sterilizing medical equipment such as catheters or endoscopes have yet to be established. We developed novel sterilization methods to sterilize the inner surface of a tube using low-pressure discharge plasma, atmospheric pressure ozone, and ultraviolet (UV) light irradiation. Generation of active oxygen and hydroxyl (OH) radicals were measured by a chemical indicator and a spectrum analysis of light emission from the plasma. A biological indicator with Geobacillus stearothermophilus was used to evaluate the sterilizing ability. A tube 1000 mm long and 4 mm in diameter was successfully sterilized for 30 min using air and water vapor discharge. Furthermore, the atmospheric pressure method sterilized the tube in 1 min. Compared to conventional methods, sterilization using discharge plasma, ozone, and UV light irradiation is safe for the human body and harmless to the environment.