Hydrogen Peroxide Gas Plasma Sterilizer Combined with Dielectric Barrier Discharge and Corona Discharge Inactivates Prions

Abstract

Prions are highly resistant to physical or chemical damage, although previous studies have shown that STERRAD®, a hydrogen gas plasma sterilizer using radiofrequency (RF) discharge, has an inactivation effect. Here, the effect of hydrogen peroxide gas combined with dielectric barrier discharge (DBD) plasma and corona discharge plasma using a RENO-S130 sterilizer on scrapie prions was examined. Scrapie prion-infected mouse brain homogenate was air-dried on a cover glass, sealed in a Tyvek pouch, and subjected to RENO-S130 treatment using either non-lumen mode (28 min) or Eco mode (45 min) with hydrogen peroxide gas derived from 50% hydrogen peroxide. Control (untreated) samples were prepared on a cover glass using the same procedure but without exposure to RENO-S130. PrPres (proteinase K (PK)-resistant prion protein), an index of the conformational variant of prion protein (PrPSc), was decreased by treatment with RENO-S130 under both modes of operation. Specifically, PrPres was identified after the 1st and 2nd cycles of protein misfolding cyclic amplification (PMCA) in control samples but was below the detection limit in RENO-S130-treated samples. A bioassay showed that treatment of prions with RENO-S130 (non-lumen or Eco mode) significantly prolonged mouse survival time. Taken together, these findings show hydrogen peroxide gas combined with DBD/corona discharge plasma can inactivate prions by reducing prion propagation and prion infectivity. This treatment is potentially applicable to the sterilization of prion-contaminated heat-sensitive medical devices.

Recent Advances in Prion Inactivation by Plasma Sterilizer

“…Survival rates of animals were 83% (both non-lumen and Eco mode) after injection with plasma-treated prions. Survival of untreated controls was 0% [ 65 ] RF: radio frequency; DBD: dielectric barrier discharge. …”

“…As mentioned above, STERRAD ® generates plasma using RF discharge. Recently, the authors examined other hydrogen peroxide gas plasma instruments to evaluate prion inactivation [ 65 ]. RENO-S130 (Renosem Co., Ltd., Bucheon-si, Korea) utilizes hydrogen peroxide gas plasma similar to STERRAD ® but does not use RF plasma [ 66 ].…”

“…The authors succeeded in prion inactivation using hydrogen peroxide gas plasma and RENO-S130 against scrapie prions [ 65 ]. RENO-S130 is composed of a DBD plasma region for sterilization and a corona plasma region for the removal of residual hydrogen peroxide.…”

“…Furthermore, a mouse bioassay showed that treatment of prions with RENO-S130 (both non-lumen and Eco modes) increased the survival rates of mice ( Table 2 ) and prolonged mouse survival time ( Table 3 ). Significant differences in survival curves analyzed using log-rank tests were observed between the RENO-S130 (non-lumen or Eco mode)-treated and untreated groups in the mouse bioassay [ 65 ]. Results of protein misfolding cyclic amplification (PMCA) also supported the evidence of prion inactivation using the non-lumen or Eco mode RENO-S130 treatment.…”

“…The sterilization activity of RENO-S130 appears to be related to the co-generation of chemicals other than hydrogen peroxide gas. Ozone generated by DBD plasma enters the sterilization chamber region, and 10–50 ppm of ozone gas was detected using an ozone analyzer UV-100 (Eco Sensors Division of KWJ Engineering Inc., Santa Fe, NM, USA) in the RENO-S130 sterilization chamber box during operation [ 65 ]. Ozone synergistically enhances the prion inactivation efficiency of hydrogen peroxide gas [ 67 ].…”