UVC inactivation of pathogenic samples suitable for cryo-EM analysis

Cryo-electron microscopy has become an essential tool to understand structure and function of biological samples. Especially for pathogens, such as disease-causing bacteria and viruses, insights gained by cryo-EM can aid in developing cures. However, due to the biosafety restrictions of pathogens, samples are often treated by chemical fixation to render the pathogen inert, affecting the ultrastructure of the sample. Alternatively, researchers use in vitro or ex vivo models, which are non-pathogenic but lack the complexity of the pathogen of interest. Here we show that ultraviolet-C (UVC) radiation applied at cryogenic temperatures can be used to eliminate or dramatically reduce the infectivity of Vibrio cholerae and the bacterial virus, the ICP1 bacteriophage. We show no discernable structural impact of this treatment of either sample using two cryo-EM methods: cryo-electron tomography followed by sub-tomogram averaging, and single particle analysis (SPA). Additionally, we applied the UVC irradiation to the protein apoferritin (ApoF), which is a widely used test sample for high-resolution SPA studies. The UVC-treated ApoF sample resulted in a 2.1 Å structure indistinguishable from an untreated published map. This research demonstrates that UVC treatment is an effective and inexpensive addition to the cryo-EM sample preparation toolbox.

Valorization of Carrot Pomace: UVC Induced Accumulation of Antioxidant Phenolic Compounds

Carrot pomace is the main waste residue obtained during carrot juice extraction. Plant tissues respond to abiotic stresses (i.e., wounding stress and ultraviolet C (UVC) radiation) by accumulating bioactive compounds. Due to the mechanical damage occurring during juice extraction, carrot pomace undergoes extreme wounding stress. In this study, the effects of UVC light (11.8 W m−2, 0–120 min) and storage time (48 h, 25 °C) on the accumulation of phenolics compounds and the antioxidant activity (AOX) of carrot pomace were evaluated. Carrot pomace that was non-treated with UVC (control) showed a 709.5% increase in total phenolics at 48 h. A high correlation of AOX values against total phenolics (R2 = 0.87) was observed, indicating that phenolics were the main contributors to the AOX of the tissue. After UVC treatment, the pomace that was radiated for 120 min with UVC showed an increase (40.4%) in chlorogenic acid (CHA) content. At 24 h, protocatechuic acid and 3,5-dicaffeoylquinic acid, which were not detected before storage, showed accumulation by 166.5 mg/kg and 169.4 mg/kg, respectively, in UVC treated pomace. Chlorogenic acid showed the highest increase (143.6%) at 48 h in the control. Valorization of carrot pomace was achieved by increasing its concentration of antioxidant phenolics through UVC radiation.

The Effectiveness of Far-Ultraviolet (UVC) Light Prototype Devices with Different Wavelengths on Disinfecting SARS-CoV-2

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged as a serious threat to human health worldwide. The inactivation of SARS-CoV-2 on object surfaces and in the indoor air might help to halt the COVID-19 pandemic. Far-ultraviolet light (UVC) disinfection has been proven to be highly effective against viruses and bacteria. To understand the wavelength and duration of UVC radiation required for SARS-CoV-2 inactivation, we examined the efficacy of UVC light prototype devices with the wavelengths of 275, 254, and 222 nm. The disinfection effectiveness was determined by cell-based assays including the median tissue culture infectious dose (TCID50) and an immunofluorescent assay on African green monkey kidney epithelial Vero E6 cells. Among the three prototypes, the UVC LED (275 nm) had the best virucidal activity with a log-reduction value (LRV) >6 after 10 s of exposure. The mercury lamp (254 nm) reached similar virucidal activity after 20 s of exposure. However, the excimer lamp (222 nm) showed limited anti-SARS-CoV-2 activity with a LRV < 2 after 40 s of exposure. Overall, in comparison, the UVC LED (275 nm) exhibited superior SARS-CoV-2 disinfection activity than the mercury lamp (254 nm) and the excimer lamp (222 nm).

222 nm ultraviolet radiation C causes more severe damage to guard cells and epidermal cells of Arabidopsis plants than does 254 nm ultraviolet radiation

Lamps that emit 222 nm short-wavelength ultraviolet (UV) radiation can be safely used for sterilization without harming human health. However, there are few studies on the effects of 222 nm UVC (222-UVC) radiation exposure on plants compared with the effects of germicidal lamps emitting primarily 254 nm UVC (254-UVC) radiation. We investigated the growth inhibition and cell damage caused by 222-UVC exposure to Arabidopsis plants, especially mitochondrial dynamics, which is an index of damage caused by UVB radiation. Growth inhibition resulted from 254-UVC or 222-UVC exposure depending on the dose of UVC radiation. However, with respect to the phenotype of 222-UVC-irradiated plants, the leaves curled under 1 kJ m−2 and were markedly bleached under 10 kJ m−2 compared with those of plants irradiated with 254-UVC. The cellular state, especially the mitochondrial dynamics, of epidermal and mesophyll cells of Arabidopsis leaves exposed to 254-UVC or 222-UVC radiation was investigated using Arabidopsis plants expressing mitochondrial matrix-targeted yellow fluorescent protein (MT-YFP) under the control of Pro35S to visualize the mitochondria. 222-UVC (1 or 5 kJ m−2) severely damaged the guard cells within the epidermis, and YFP signals and chloroplast autofluorescence in guard cells within the epidermis exposed to 222-UVC (1 or 5 kJ m−2) were not detected compared with those in cells exposed to 254-UVC radiation. In addition, 222-UVC irradiation led to mitochondrial fragmentation in mesophyll cells, similar to the effects of 254-UVC exposure. These results suggest that 222-UVC severely damages guard cells and epidermal cells and that such damage might have resulted in growth inhibition.

Not all wavelengths are created equal: disinfection of SARS-CoV-2 using UVC radiation is wavelength-dependent

SARS-CoV-2 is mostly transmitted through close contact with infected people by infected aerosols and fomites. Ultraviolet subtype C (UVC) lamps and light-emitting diodes can be used to disrupt the transmission chain by disinfecting fomites, thus managing the disease outbreak progression. Here, we assess the ultraviolet wavelengths that are most effective in inactivation of SARS-CoV-2 on fomites. Variations in UVC wavelengths impact the dose required for disinfection of SARS-CoV-2 and alter how rapidly and effectively disruption of the virus transmission chain can be achieved. This study reveals that shorter wavelengths (254–268 nm) take a maximum of 6.25 mJ/cm2 over 5 s to obtain a target SARS-CoV-2 reduction of 99.9%. Longer wavelengths, like 280 nm, take longer irradiation time and higher dose to inactivate SARS-CoV-2. These observations emphasize that SARS-CoV-2 inactivation is wavelength-dependent.

Spectral quality as an eliciting agent in the production of phenolic compounds in the callus of Hyptis marrubioides Epling

Hyptis marrubioides Epling is a species of the Brazilian cerrado traditionally used to treat gastrointestinal and cutaneous infections, pain, and cramps. The use of visible and ultraviolet C (UVC) radiation is a promising strategy to optimize the production of the bioactive metabolites. Therefore, the effect of the spectral quality of light on the production of metabolites was evaluated in H. marrubioides callus. The callus was inoculated on MS medium with 50% of the salt concentration containing 2 mg L-1 naphthaleneacetic acid (NAA) and 1 mg L-1 benzylaminopurine (BAP). The callus cultures were exposed for 20 days to the spectral qualities of white light, blue, red, and blue + red as well as to darkness. In addition, the callus cultivated under white light were exposed to UVC on the 21st day for 0, 30, 60, 120, and 240 seconds. The exposure of H. marrubioides callus to blue light negatively affects the synthesis of phenolic compounds. Red light stimulates the synthesis of caffeic acid and luteolin. Darkness was the best condition among those studied because it was associated with the increased accumulation of caffeic acid, chlorogenic acid, rosmarinic acid, and luteolin. The exposure of H. marrubioides callus cultivated under white light to UVC radiation promoted an increase in the synthesis of chlorogenic acid, ferulic acid, rosmarinic acid, and luteolin.

Accidental Exposure to Ultraviolet-C (UVC) Germicidal Lights: A Case Report and Recommendations in Orthodontic Clinical Settings

An emergent health crisis, coronavirus disease 2019 (COVID-19), has demanded strict disinfection and sterilization protocols to limit the spread. One such approach is the use of ultravioletC (UVC) radiation for surface decontamination in hospital settings. UVC is the most powerful of the UV wavelengths and, therefore, the most damaging. The radiation is used for sterilization of workplaces and objects, and although there is no current evidence, perhaps it may eradicate airborne coronavirus. Humans should not be subjected to this form of irradiation. This form of radiation comes with a health warning, and humans should not be in the vicinity when UVC sterilization is occurring. This case report deals with the unfortunate incidence of an operator affected by UVC radiation while working on a patient in an orthodontic clinic. The article will serve as a timely warning to clinicians that awareness of the safety protocols should be observed. Besides, we present some recommendations for the use of UVC depuration of dental operatories.

Degradation of Electrical Wire Sheaths By UV Radiation

The objective of this manuscript is to report experimental results concerning the effect of accelerated UV-C ageing on the properties of samples of halogen-free sheaths of power cables. Two samples of halogen free sheaths of power cables of Vuki a.s. CHKE-V E30 and Nexans 273-K3 HERP/CWB/2SZH were studied after exposition on the UV-C radiation in a closed chamber. Degradation was monitored by the change in infrared spectra of the samples, their hardness and colour. Based on the observed changes, it can be argued that exposure to the UVC radiation affects the observed properties on the surface of the studied samples. All the observed changes were due to the rupture of the bonds towing to the absorption of UV-C radiation.