Substrate influence in viral and bacteria UV-C disinfection

Germicidal ultraviolet (UV-C) has been reported for the disinfection of water, air, and surfaces without textures, mainly in hospital environments. With the hit of the SARS-CoV-2 pandemic and its broad dissemination ability, hospital facilities were at full capacity and personal protective equipment, such as protective masks and protective gowns, was scarce due to the high demand and abusive prices. In this scenario, the reuse of disposable personal protective equipment (PPE) became necessary in Brazil, requiring the search for quick and effective disinfection methods. Then, we tested UV-C, due to its substrate penetration nature, as a disinfection method against virus (Murine Hepatitis Coronavirus, MHV-3) and bacteria (Escherichia coli ATCC 25922) on different surfaces, including microscope slide glass and synthetic fabric, to mimic PPE material. Different UV-C time-dose exposures were tested, in order to observe the influences of substrate and UV-C parameters in the possible use of this disinfection method. We observed different virus inactivation behavior when different substrates were used, glass slides and synthetic fabric, and two different inactivation doses for each substrate inactivation curve. For bacteria, no viable E. coli ATCC 25922 cells were recovered after 2400 s, under 65 µW/cm² UV-C irradiance. Overall, our findings indicate that UV-C disinfection of bacteria and viruses present in glass and fabric surfaces were observed, considering that there are differences in the microorganism, the substrate properties, and population log inactivation that affect the UV-C inactivation doses. It is highlighted that each substrate must be tested prior to the use of UV-C effective disinfection.