Implication of cell culture methods and biases on UV inactivation of viruses.

Inactivation of human respiratory viruses in air and on surfaces is important to control their spread. Exposure to germicidal ultraviolet (UV-C) light damages viral nucleic acid rendering them non-infectious. Most of the recent viral inactivation studies have not considered potential artifacts caused by interactions between UV-C light and culture media used to suspend and deposit virus on surfaces. We show that the reactive oxygen and nitrogen species (ROS and RNS) form when commonly used virus culture media is exposed to 265 nm irradiation from light emitting diodes (LEDs) at UV-C doses (4 or 40 mJ/cm2) commonly considered to achieve multiple log-inactivation of virus. Surface viral inactivation values were enhanced from 0.49 to 2.92 log10 of viruses in DMEM, EMEM or EMEM-F as compared to absence of culture media (only suspended in Tris-buffer). The mechanisms responsible for the enhanced surface inactivate is hypothesized to involve photo-activation of vitamins and dyes present in the culture media, deposited with the virus on surfaces to be disinfected, which produce ROS and RNS. Given the rapidly growing research and commercial markets for UV-C disinfecting devices, there is a need to establish surface disinfecting protocols that avoid viral inactivation enhancement artifacts associated with selection and use of common cell culture media in the presence of UV-C light. This study addresses this weak link in the literature and highlights that inadequate selection of virus suspension media may cause a bias (i.e., over-estimation) for the UV-C dosages required for virus inactivation on surfaces.

A UV-LED module that is highly effective at inactivating human coronaviruses and HIV-1.

Ultraviolet (UV) light has previously been established as useful method of disinfection, with demonstrated efficacy to inactivate a broad range of microorganisms. The advent of ultraviolet light-emitting diodes provides advantages in ease of disinfection, in that there can be delivery of germicidal UV with the same light unit that delivers standard white light to illuminate a room. Herein we demonstrate the efficacy and feasibility of ultraviolet light-emitting diodes as a means of decontamination by inactivating two distinct virus models, human coronavirus 229E and human immunodeficiency virus. Importantly, the same dose of ultraviolet light that inactivated human viruses also elicited complete inactivation of ultraviolet-resistant bacterial spores (Bacillus pumilus), a gold standard for demonstrating ultraviolet-mediated disinfection. This work demonstrates that seconds of ultraviolet light-emitting diodes (UV-LED) exposure can inactivate viruses and bacteria, highlighting that UV-LED could be a useful and practical tool for broad sanitization of public spaces.