Photocatalytic degradation of prions using the photo-Fenton reagent

Inactivation of Template-Directed Misfolding of Infectious Prion Protein by Ozone

“…Hydrogen peroxide inactivation (1.5 mol/liter) in the presence of Fe 2ϩ (15.7 mmol/liter) and heating at 50°C for 22 h was able to produce an approximately 6 log 10 reduction of prion infectivity (35). PrP Sc could also be degraded by Ն2.4 log 10 by photo-Fenton treatment (147 mmol/liter H 2 O 2 , 8.9 mmol/liter Fe 3ϩ ) after 5 h of UV-A exposure (25) and be degraded by Ն2 log 10 by titanium dioxide photocatalysis (25 mmol/liter titanium dioxide, 118 mmol/liter H 2 O 2 ) after 12 h of UV-A exposure (26). Due to the low sensitivity of the PrP Sc detection methods used in the last two studies cited above, inactivation of more than 2.4 log 10 was not achieved.…”

“…However, the UV-ozone system studied by Johnson et al (14) produced limited ozone, thus generating limited hydroxyl radicals, requiring exposure times up to several weeks, and questioning the practicality of using UV-generated ozone as a decontamination/sterilizing approach to prion inactivation. Prion inactivation has also been studied with other advanced oxidation methods, such as the use of copper and hydrogen peroxide (17,34), iron and hydrogen peroxide (35), photo-Fenton treatment (25), and titanium dioxide photocatalysis (26). Hydrogen peroxide inactivation (100 mmol/liter) in the presence of copper (0.5 mmol/liter) was reported to achieve Ն5.2 log 10 inactivation of 263K scrapie prion with a contact time of 2 h at room temperature (34).…”

“…Although certain advanced oxidation processes have been shown to inactivate infectious prions (14,25,26,34,35), several major knowledge gaps exist; in particular, knowledge concerning how interactions between oxidant reaction conditions (e.g., temperature, pH, duration of exposure, ozone dose, and organic load) affect inactivation levels of prions is lacking. Consequently, the derivation of a concentration-time (CT) disinfection value for prions has never been reported.…”

Kinetics of Ozone Inactivation of Infectious Prion Protein

“…Ozone inactivation of Giardia lamblia at pH 7 (45), Naegleria gruberi at pH 7 (45), Cryptosporidium at pH 6 to 8 (41,42), and Bacillus subtilis spores at pH 7 (48) was higher as temperature increased toward 25°C, which is consistent with ozone inactivation of PrP Sc observed in this study. Inactivation of prions by other oxidants has also been examined in various studies (23,(54)(55)(56)(57)(58)(59)(60)(61). Chlorine and hydroxyl radicals are the primary oxidants in these studies.…”

“…Although more than a 5-log 10 inactivation was achieved, the exposure time was up to 2 weeks. Other studies also demonstrated that hydroxyl radicals inactivated infectious prions, more or less, with exposure times from 30 min to several hours (23,56,57,59,60,62). However, none of these studies investigated the reaction kinetics.…”