Enhanced virucidal activity of facet-engineered Cu-doped TiO2 nanorods under visible light illumination.

Crystal facet engineering has emerged as a promising approach to enhance photocatalytic activity of semiconductors by preferentially accumulating charge carriers (electrons and holes) on specific facets. This facilitates efficient electron and hole transfer across the semiconductor/cocatalyst interface, enabling their transport to the cocatalyst surface for redox reactions. In this study, three Cu-doped TiO2 nanorods with small, medium, and large ratios of reductive {110} to oxidative {111} facets were synthesized (namely Cu-TiO2-SR, Cu-TiO2-MR, and Cu-TiO2-LR, respectively). These materials were comparatively evaluated for the inactivation of phiX174 bacteriophage under visible light illumination. Notably, Cu-TiO2-LR demonstrated an outstanding inactivation rate of phiX174 (0.42 log inactivation/min), approximately 11.8 times higher than that of Cu-TiO2-SR. Photo- and electrochemical analyses revealed that Cu-TiO2-LR exhibited superior electron/hole separation efficiency, leading to enhanced Cu redox reactions. Various experiments, encompassing viral inactivation tests with different additives, protein oxidation assays, and DNA damage assessments, indicated that Cu(III) is the major virucidal species responsible for the phiX174 inactivation by illuminated Cu-TiO2-LR. Under visible light illumination, Cu-TiO2-LR also showed excellent reusability and minimal activity loss in the presence of humic acid and inorganic anions, as well as general microbicidal effects on other viral and bacterial species.

Evaluation of inhibitory activity of essential oils and natural extracts on foodborne viruses.

AIMS: Enteric viruses are recognized as a major concern in health care and in the food sector in Canada. Novel clean-label strategies for controlling enteric viruses are sought in the food industry. In this study, we examined the antiviral potential of plant extracts and essential oils on murine norovirus 1 (MNV-1), hepatitis A virus (HAV), and herpes simplex virus 1 (HSV-1). METHODS AND RESULTS: Inactivation of the viruses by grape seed, blueberry, green tea, and cranberry extracts and by rosemary and thyme essential oils was measured using plaque formation assay. Concentrations ranging from 50 to 200 000 ppm with a contact time of 90 min were tested. Grape seed extract at 10 000 ppm was the most effective (P < 0.05) at reducing MNV-1 and HAV infectious titers, respectively, by 2.85 ± 0.44 log10 and 1.94 ± 0.17 log10. HSV-1 titer was reduced by 3.81 ± 0.40 log10 at 1000 ppm grape seed extract. CONCLUSIONS: Among the plant products tested, grape seed extract was found the most effective at reducing the infectious titers of MNV-1, HAV, and HSV.

A Critical Look at Heavy Ion Beam Irradiation for Vaccine Development.

Recent studies offer valuable insights into viral inactivation for vaccine development. Schulze et al. have demonstrated the potential of heavy ion beam irradiation to create effective vaccines, which is particularly relevant in the context of airborne pandemics. Notably, the success in immunizing mice via intranasal administration with the inactivated influenza virus is encouraging, especially given the genetic similarities between influenza and SARS-CoV-2. However, the study raises important considerations. While heavy ion treatment shows advantages, there are concerns about viral inactivation completeness and the potential for surviving viruses, albeit at extremely low levels. Prolonged irradiation times and the risk of selective pressure leading to the evolution of resistant variants are highlighted. Biosafety concerns regarding accidental lab escape of resistant strains are crucial, emphasizing the need for caution during experiments. Moreover, limitations in Monte Carlo simulations of virus irradiation are discussed, pointing out the need for more comprehensive studies to assess the impact of secondary particles on virus inactivation under realistic irradiation conditions. Given these considerations, while the study presents a promising approach for vaccine development, further research is essential to address potential drawbacks and optimize the method for safe and effective application.

Essential oil mediated synthesis and application of highly stable copper nanoparticles as coatings on textiles and surfaces for rapid and sustained disinfection of microorganisms.

Rampant pathogenesis induced by communicable microbes has necessitated development of technologies for rapid and sustained disinfection of surfaces. Copper nanoparticles (CuNPs) have been widely reported for their antimicrobial properties. However, nanostructured copper is prone to oxidative dissolution in the oil phase limiting its sustained use on surfaces and coatings. The current study reports a systematic investigation of a simple synthesis protocol using fatty acid stabilizers (particularly essential oils) for synthesis of copper nanoparticles in the oil phase. Of the various formulations synthesized, rosemary oil stabilized copper nanoparticles (RMO CuNPs) were noted to have the best inactivation kinetics and were also most stable. Upon morphological characterization by TEM and EELS, these were found to be monodispersed (φ5-8 nm) with copper coexisting in all three oxidation states on the surface of the nanoparticles. The nanoparticles were drop cast on woven fabric of around 500 threads per inch and exposed to gram positive bacteria (Staphylococcus aureus), gram negative bacteria (Escherichia coliandPseudomonas aeruginosa), enveloped RNA virus (phi6), non-enveloped RNA virus (MS2) and non-enveloped DNA virus (T4) to encompass the commonly encountered groups of pathogens. It was possible to completely disinfect 107copies of all microorganisms within 40 min of exposure. Further, this formulation was incorporated with polyurethane as thinners and used to coat non-woven fabrics. These also exhibited antimicrobial properties. Sustained disinfection with less than 9% cumulative copper loss for upto 14 washes with soap water was observed while the antioxidant activity was also preserved. Based on the studies conducted, RMO CuNP in oil phase was found to have excellent potential of integration on surface coatings, paints and polymers for rapid and sustained disinfection of microbes on surfaces.

Modeling scalability of impurity precipitation in downstream biomanufacturing.

Precipitation during the viral inactivation, neutralization and depth filtration step of a monoclonal antibody (mAb) purification process can provide quantifiable and potentially significant impurity reduction. However, robust commercial implementation of this unit operation is limited due to the lack of a representative scale-down model to characterize the removal of impurities. The objective of this work is to compare isoelectric impurity precipitation behavior for a monoclonal antibody product across scales, from benchtop to pilot manufacturing. Scaling parameters such as agitation and vessel geometry were investigated, with the precipitate amount and particle size distribution (PSD) characterized via turbidity and flow imaging microscopy. Qualitative analysis of the data shows that maintaining a consistent energy dissipation rate (EDR) could be used for approximate scaling of vessel geometry and agitator speeds in the absence of more detailed simulation. For a more rigorous approach, however, agitation was simulated via computational fluid dynamics (CFD) and these results were applied alongside a population balance model to simulate the trajectory of the size distribution of precipitate. CFD results were analyzed within a framework of a two-compartment mixing model comprising regions of high- and low-energy agitation, with material exchange between the two. Rate terms accounting for particle formation, growth and breakage within each region were defined, accounting for dependence on turbulence. This bifurcated model was successful in capturing the variability in particle sizes over time across scales. Such an approach enhances the mechanistic understanding of impurity precipitation and provides additional tools for model-assisted prediction for process scaling.

GMP implementation of a hybrid continuous manufacturing process for a recombinant non-mAb protein-A case study.

Advances in manufacturing technology coupled with the increased potency of new biotherapeutic modalities have created an external environment where continuous manufacturing (CM) can address a growing need. Amgen has successfully implemented a hybrid CM process for a commercial lifecycle program. In this process, the bioreactor, harvest, capture column, and viral inactivation/depth filtration unit operations were integrated together in an automated, continuous module, while the remaining downstream unit operations took place in stand-alone batch mode. CM operations are particularly suited for so-called "high mix, low volume" manufacturing plants, where a variety of molecules are manufactured in relatively low volumes. The selected molecule fit this mold and was manufactured in a low-capital micro-footprint suite attached to an existing therapeutic production facility. Use of a hybrid process within an already operating facility required less capital and minimized complexity. To enable this hybrid CM process, an established fed-batch process was converted to a perfusion process with continuous harvest. Development efforts included both process changes and the generation of a novel cell line adapted to long-term perfusion. Chromatography resins were updated, and purification processes adapted to handle variable inputs due to the fluctuations in harvest titer from the lengthy production process. A novel automated single-use (SU) viral inactivation (VI) skid was introduced, which entailed the development of a robust pH verification and alarm system, along with procedures for product isolation to allow discard of specific cycles. The CM process demonstrated consistent performance, meaning it met predefined performance criteria (including product quality attributes, or PQAs) when operated within established process parameters and manufactured according to applicable procedures. Using a 75% reduction in scale, it resulted in a five-fold reduction in process media and buffer usage, a fifteen-fold increase in mass per thaw, and an overall process productivity increase of 45-fold (as measured by grams drug substance per liter per day.) The hybrid CM process also enabled increased material demand to be met with no change in cost of goods manufactured or plant capacity, due to the repurposing of existing facility space and the flexible duration of the hybrid CM harvest. Overall, the success of the hybrid CM platform represents an exciting opportunity to reduce costs and increase process efficiency in industry.

Viral inactivation for pH-sensitive antibody formats such as multi-specific antibodies.

Recently developed multi-specific antibody formats enable new therapeutic concepts. Conveniently, formats with an Fc domain allow purification in well-established mAb platform processes. However, due to the structural complexity of the formats, the assembled molecules may be sensitive to extreme pH commonly used for viral inactivation. An alternative to low pH incubation for virus inactivation is the use of a mixture of tri-n-butyl phosphate (TnBP, solvent) and Polysorbate 80 (PS80, detergent). While TnBP is toxic, this combination has a long history of use in the manufacturing of human plasma-derived products that are sensitive to low or high pH incubation. Data are provided demonstrating that the solvent/detergent (S/D) treatment using TnBP and PS80 can be successfully used for pH-sensitive, multi-specific antibody formats in the clarified cell culture fluid (CCCF). A different placement of the S/D within the purification process, namely during the capture by Protein A (PA), has been evaluated. This alternative placement allows effective viral inactivation by S/D while preserving the viral reduction and viral inactivation achieved through the PA step itself, enabling the cumulation of these effects. Furthermore, the process alternative simplifies the liquid handling by reducing the added volumes of the required S/D liquids, thus reducing the amount of toxic TnBP to a minimum. Data are shown demonstrating a complete removal of TnBP and PS80 in the process.

Effect of chemical and physical agents on monkeypox virus infectivity and downstream research applications.

The 2022 global spread of Monkeypox Virus (MPXV) underlined the need to investigate safe-handling procedures of clinical and research samples. Here we evaluated the efficiency in reducing MPXV infectious titer of Triton X-100 (0.1 and 0.2%), UV-C irradiation (15 or 30 min), and heat (56 °C 30 min or 70 °C 5 min). The treatment of MPXV at 70 °C resulted in the strongest decrease of MPXV infectious titer (5.4 Log TCID50/mL), 56 °C and UV-C had a lighter impact (3.9 and 4.3Log), Triton X-100 was less efficient (1.8-2.5Log). Notably, SARS-CoV-2 was much more susceptible to Triton X-100 (4.0 Log decrease). UV-C had the highest impact on MPXV DNA detection by PCR (2.2-4.3 Ct value increase); protein detection by ELISA was dramatically impaired by heating. Overall, UV-C and heating were more effective in lowering MPXV infectious titer but their impact on nucleic acids or protein detection assays must be considered.

Virucidal activity of Cu-doped TiO2 nanoparticles under visible light illumination: Effect of Cu oxidation state.

Copper (Cu) is an effective antimicrobial material; however, its activity is inhibited by oxidation. Titanium dioxide (TiO2) photocatalysis prevents Cu oxidation and improves its antimicrobial activity and stability. In this study, the virucidal efficacy of Cu-doped TiO2 nanoparticles (Cu-TiO2) with three different oxidation states of the Cu dopant (i.e., zero-valent Cu (Cu0), cuprous (CuI), and cupric (CuII) oxides) was evaluated for the phiX174 bacteriophage under visible light illumination (Vis/Cu-TiO2). CuI-TiO2 exhibited superior virucidal activity (5 log inactivation in 30 min) and reusability (only 11 % loss of activity in the fifth cycle) compared to Cu0-TiO2 and CuII-TiO2. Photoluminescence spectroscopy and photocurrent measurements showed that CuI-TiO2 exhibited the highest charge separation efficiency and photocurrent density (approximately 0.24 µA/cm2) among the three materials, resulting in the most active redox reactions of Cu. Viral inactivation tests under different additives and viral particle integrity analyses (i.e., protein oxidation and DNA damage analyses) revealed that different virucidal species played key roles in the three Vis/Cu-TiO2 systems; Cu(III) was responsible for the viral inactivation by Vis/CuI-TiO2. The Vis/CuI-TiO2 system exhibited substantial virucidal performance for different viral species and in different water matrices, demonstrating its potential practical applications. The findings of this study offer valuable insights into the design of effective and sustainable antiviral photocatalysts for disinfection.

Preparing for another Ebola Outbreak: The impact of viral inactivation methods on commonly measured biochemistry analytes in plasma and urine.

INTRODUCTION: Infectious specimens containing viruses like Ebola require sample manipulation to ensure the safety of laboratory staff, which may negatively impact biochemistry test results. We evaluated the impact of viral inactivation methods on 25 biochemistry analytes in plasma, and seven biochemistry analytes in urine. METHODS: Fifteen lithium heparinized plasma specimens with and without gel underwent the following viral inactivation methods: 1) untreated, 2) Triton X-100 treatment, 2) heated for 60 min then Triton X-100 treatment, 3) heated for 60 min, 4) heated for 75 min, and 5) heated for 90 min. Electrolytes, protein, enzymes, glucose, as well as hepatic and renal markers were measured on the Roche Cobas e601, c502 or c702. Urinalysis analytes were measured on the Siemens CLINITEK. Acceptable recovery was based on Institute for Quality Management in Healthcare 2021 guidelines or ± 1 for urinalysis. RESULTS: Potassium and lactate dehydrogenase were impacted by the presence of gel. Viral inactivation with Triton X-100 had minimal impact on the biochemistry results. Heat inactivation resulted in significant negative bias in alanine aminotransferase, alkaline phosphatase, gamma-glutamyl transferase, creatinine, total protein, amylase, lactate dehydrogenase and creatine kinase. Positive bias in phosphate, aspartate transaminase, total bilirubin, and uric acid were observed after heat inactivation. CONCLUSION: Reliable results for commonly measured electrolytes, enzymes and proteins can be obtained after viral inactivation by Triton X-100 treatment at room temperature. However, heat inactivation has significant negative impact on routine biochemistry enzymes and alternative testing processes should be explored.

Effectiveness of TRIzol in Inactivating Animal Pathogens.

Introduction: Safe handling of biological samples sourced from wild ecosystems is a pressing concern for scientists in disparate fields, including ecology and evolution, OneHealth initiatives, bioresources, geography, veterinary medicine, conservation, and many others. This is especially relevant given the growing global research community and collaborative networks that often span international borders. Treatments to inactivate potential pathogens of concern during transportation and analysis of biospecimens while preserving molecular structures of interest are necessary. Objective: We provide a detailed resource on the effectiveness and limitations of TRIzol™ Reagent, a product commonly used in molecular biology to inactivate bacterial and viral pathogens found in wild animals. Methods: By literature review, we evaluate the mode of action of TRIzol Reagent and its main components on bacterial and viral structures. We also synthesize peer-reviewed literature on the effectiveness of TRIzol in inactivating a broad range of infectious bacteria and viruses. Key Findings: TRIzol Reagent inactivation is based on phenol, chaotropic salts, and sodium acetate. We find evidence of widespread efficacy in deactivating bacteria and a broad range of enveloped viruses. The efficacy against a subset of potential pathogens, including some nonenveloped viruses, remains uncertain. Conclusion: Available evidence suggests that TRIzol Reagent is effective in inactivating a broad spectrum of bacteria and viruses from cells, tissues, and liquids in biological samples when the matrices are exposed to at least 10 min at room temperature to the reagent. We highlight areas that require additional research and discuss implications for laboratory protocols.

Evaluating the viral clearance ability of continuous monoclonal antibody purification steps, in order to inactivate and/or remove four model viruses.

Background and Objectives: Viral clearance studies are an essential part of a manufacturer's plan to ensure the safety of an injectable biologic product. In this way, viral safety is a critical quality attribute for biologics such as monoclonal antibodies (Mabs). Evaluation of virus purification by downstream processes is a key component of risk mitigation. In this study, the capability of continuous monoclonal antibody purification steps was evaluated in the process of instant monoclonal antibody purification in different stages of purification, and the amount of reduction or inactivation of each step was determined. Materials and Methods: Four enveloped and non-enveloped viral models VSV, Reovirus, EMCV, and HSV1 were used for spiking in selected samples in the designated tests, to have a comprehensive examination of the ability to clear the virus such as the type of genetic material, chemical resistance, and particle size. A TCID50 and qPCR methods were used to measure viral reduction. Two cell lines, Vero (African green monkey kidney) and L929 (Mouse fibroblast) were used for 4 model viruses propagation. The steps that were evaluated included 4 steps monoclonal antibody purification; cation exchange chromatography, acidic pH treatment, affinity chromatography, and nanofiltration. Results: The nano-filter stage showed the highest viral reduction and cation exchange chromatography showed the lowest reduction. The cumulative decrease using TCID50 is equal to 19.27 [log10] for all steps and for the qPCR method is equal to 12.47 [log10] in three steps of nano-filter, affinity chromatography, and ion exchange chromatography. Conclusion: The overall average reduction coefficient for all four model viruses is significantly high, which indicates the high capacity of the monoclonal antibody production process in inactivating and removing viruses leads to reducing the load of all four model viruses.

Decreasing hydrophobicity or shielding hydrophobic areas of CH2 attenuates low pH-induced IgG4 aggregation.

Protein aggregation is a major challenge in the development of therapeutic monoclonal antibodies (mAbs). Several stressors can cause protein aggregation, including temperature shifts, mechanical forces, freezing-thawing cycles, oxidants, reductants, and extreme pH. When antibodies are exposed to low pH conditions, aggregation increases dramatically. However, low pH treatment is widely used in protein A affinity chromatography and low pH viral inactivation procedures. In the development of an IgG4 subclass antibody, mAb1-IgG4 showed a strong tendency to aggregate when temporarily exposed to low pH conditions. Our findings showed that the aggregation of mAb1-IgG4 under low pH conditions is determined by the stability of the Fc. The CH2 domain is the least stable domain in mAb1-IgG4. The L309E, Q311D, and Q311E mutations in the CH2 domain significantly reduced the aggregation propensity, which could be attributed to a reduction in the hydrophobicity of the CH2 domain. Protein stabilizers, such as sucrose and mannose, could also attenuate low pH-induced mAb1-IgG4 aggregation by shielding hydrophobic areas and increasing protein stability. Our findings provide valuable strategies for managing the aggregation of protein therapeutics with a human IgG4 backbone.

Mega-scale desalination efficacy (Reverse Osmosis, Electrodialysis, Membrane Distillation, MED, MSF) during COVID-19: Evidence from salinity, pretreatment methods, temperature of operation.

The unprecedented situation of the COVID-19 pandemic heavily polluted water bodies whereas the presence of SARS-CoV-2, even in treated wastewater in every corner of the world is reported. The main aim of the present study is to show the effectiveness and feasibility of some well-known desalination technologies which are reverse osmosis (RO), Electrodialysis (ED), Membrane Distillation (MD), multi effect distillation (MED), and multi stage flashing (MSF) during the COVID-19 pandemic. Systems' effectiveness against the novel coronavirus based on three parameters of nasopharynx/nasal saline-irrigation, temperature of operation and pretreatment methods are evaluated. First, based on previous clinical studies, it showed that using saline solution (hypertonic saline >0.9% concentration) for gargling/irrigating of nasal/nasopharynx/throat results in reducing and replication of the viral in patients, subsequently the feed water of desalination plants which has concentration higher than 3.5% (35000ppm) is preventive against the SARS-CoV-2 virus. Second, the temperature operation of thermally-driven desalination; MSF and MED (70-120°C) and MD (55-85°C) is high enough to inhibit the contamination of plant structure and viral survival in feed water. The third factor is utilizing various pretreatment process such as chlorination, filtration, thermal/precipitation softening, ultrafiltration (mostly for RO, but also for MD, MED and MSF), which are powerful treatment methods against biologically-contaminated feed water particularly the SARS-CoV-2. Eventually, it can be concluded that large-scale desalination plants during COVID-19 and similar situation are completely reliable for providing safe drinking water.

Viral Disinfection of Porous Fomites Utilizing a Bacteriophage Model and Chlorine Dioxide Gas.

The pursuit of disinfecting porous materials or fomites to inactivate viral agents has special challenges. To address these challenges, a highly portable chlorine dioxide (ClO2) gas generation system was used to ascertain the ability of a gaseous preparation to inactivate a viral agent, the MS2 bacteriophage, when associated with potentially porous fomites of cloth, paper towel, and wood. The MS2 bacteriophage is increasingly used as a model to identify means of inactivating infectious viral agents of significance to humans. Studies showed that MS2 bacteriophage can be applied to and subsequently recovered from potential porous fomites such as cloth, paper towel, and wood. Paired with viral plaque assays, this provided a means for assessing the ability of gaseous ClO2 to inactivate bacteriophage associated with the porous materials. Notable results include 100% inactivation of 6 log bacteriophage after overnight exposure to 20 parts per million(ppm) ClO2. Reducing exposure time to 90 minutes and gas ppm to lower concentrations proved to remain effective in bacteriophage elimination in association with porous materials. Stepwise reduction in gas concentration from 76 ppm to 5 ppm consistently resulted in greater than 99.99% to 100% reduction of recoverable bacteriophage. This model suggests the potential of ClO2 gas deployment systems for use in the inactivation of viral agents associated with porous potential fomites. The ClO2 gas could prove especially helpful in disinfecting enclosed areas containing viral contaminated surfaces, rather than manually spraying and wiping them.

Glycolytic stress deteriorates 229E virulence to improve host defense response.

Viral infection treatment is a difficult task due to its complex structure and metabolism. Additionally, viruses can alter the metabolism of host cells, mutate, and readily adjust to harsh environments. Coronavirus stimulates glycolysis, weakens mitochondrial activity, and impairs infected cells. In this study, we investigated the efficacy of 2-DG in inhibiting coronavirus-induced metabolic processes and antiviral host defense systems, which have not been explored so far. 2-Deoxy-d-glucose (2-DG), a molecule restricting substrate availability, has recently gained attention as a potential antiviral drug. The results revealed that 229E human coronavirus promoted glycolysis, producing a significant increase in the concentration of fluorescent 2-NBDG, a glucose analog, particularly in the infected host cells. The addition of 2-DG decreased its viral replication and suppressed infection-induced cell death and cytopathic effects, thereby improving the antiviral host defense response. It was also observed that administration of low doses of 2-DG inhibited glucose uptake, indicating that 2-DG consumption in virus-infected host cells was mediated by high-affinity glucose transporters, whose levels were amplified upon coronavirus infection. Our findings indicated that 2-DG could be a potential drug to improve the host defense system in coronavirus-infected cells.

Bacteria and Virus Inactivation: Relative Efficacy and Mechanisms of Peroxyacids and Chlor(am)ine.

Peroxyacids (POAs) are a promising alternative to chlorine for reducing the formation of disinfection byproducts. However, their capacity for microbial inactivation and mechanisms of action require further investigation. We evaluated the efficacy of three POAs (performic acid (PFA), peracetic acid (PAA), and perpropionic acid (PPA)) and chlor(am)ine for inactivation of four representative microorganisms (Escherichia coli (Gram-negative bacteria), Staphylococcus epidermidis (Gram-positive bacteria), MS2 bacteriophage (nonenveloped virus), and Φ6 (enveloped virus)) and for reaction rates with biomolecules (amino acids and nucleotides). Bacterial inactivation efficacy (in anaerobic membrane bioreactor (AnMBR) effluent) followed the order of PFA > chlorine > PAA ≈ PPA. Fluorescence microscopic analysis indicated that free chlorine induced surface damage and cell lysis rapidly, whereas POAs led to intracellular oxidative stress through penetrating the intact cell membrane. However, POAs (50 µM) were less effective than chlorine at inactivating viruses, achieving only ∼1-log PFU removal for MS2 and Φ6 after 30 min of reaction in phosphate buffer without genome damage. Results suggest that POAs' unique interaction with bacteria and ineffective viral inactivation could be attributed to their selectivity toward cysteine and methionine through oxygen-transfer reactions and limited reactivity for other biomolecules. These mechanistic insights could inform the application of POAs in water and wastewater treatment.

Inactivation of SARS-CoV-2 variants by nitrogen-doped titanium dioxide loaded with metals as visible-light photocatalysts.

PURPOSE: We examined the inactivation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by a nitrogen-doped titanium dioxide (N-TiO2) visible-light photocatalyst that was activated via light irradiation in the natural environment and was safe for human use as a coating material. METHODS: The photocatalytic activity of glass slides coated with three types of N-TiO2 without metal or loaded with copper or silver and copper was investigated by measuring acetaldehyde degradation. The titer levels of infectious SARS-CoV-2 were measured using cell culture after exposing photocatalytically active coated glass slides to visible light for up to 60 min. RESULTS: N-TiO2 photoirradiation inactivated the SARS-CoV-2 Wuhan strain and this effect was enhanced by copper loading and further by the addition of silver. Hence, visible-light irradiation using silver and copper-loaded N-TiO2 inactivated the Delta, Omicron, and Wuhan strains. CONCLUSION: N-TiO2 could be used to inactivate SARS-CoV-2 variants, including emerging variants, in the environment.

Development of a charged model of the SARS-CoV-2 viral surface.

A recent study provided experimental evidence of inactivation of viral activity after radio-frequency (RF) exposures in the 6-12 GHz band that was hypothesized to be caused by vibrations of an acoustic dipole mode in the virus that excited the viral membrane to failure. Here, we develop an atomic-scale molecular dynamics (MD) model of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral surface to estimate the electric fields necessary to rupture the viral membrane via dipole shaking of the virus. We computed the absorption spectrum of the system via unbiased MD simulations and found no particular strong absorption in the GHz band. We investigated the mechanical resiliency of the viral membrane by introducing uniaxial strains in the system and observed no pore formation in the membrane for strains up to 50%. Because the computed absorption spectrum was found to be essentially flat, and the strain required to break the viral membrane was >0.5, the field strength associated with rupture of the virus was greater than the dielectric breakdown value of air. Thus, RF disinfection of enveloped viruses would occur only once sufficient heat was transferred to the virus via a thermal mechanism and not by direct action (shaking) of the RF field oscillations on the viral membrane.

Effectiveness of a low-cost UVGI chamber for decontaminating filtering facepiece respirators to extend reuse.

In emergencies like the COVID-19 pandemic, the reuse or reprocessing of filtering facepiece respirators (FFRs) may be required to mitigate exposure risk. Research gap: Only a few studies evaluated decontamination effectiveness against SARS-CoV-2 that are practical for low-resource settings. This study aimed to determine the effectiveness of a relatively inexpensive ultraviolet germicidal irradiation chamber to decontaminate FFRs contaminated with SARS-CoV-2. A custom-designed UVGI chamber was constructed to determine the ability to decontaminate seven FFR models including N95s, KN95, and FFP2s inoculated with SARS-CoV-2. Vflex was excluded due to design folds/pleats and UVGI shadowing inside the chamber. Structural and functional integrity tolerated by each FFR model on repeated decontamination cycles was assessed. Twenty-seven participants were fit-tested over 30 cycles for each model and passed if the fit factor was ≥100. Of the FFR models included for testing, only the KN95 model failed filtration. The 3M™ 3M 1860 and Halyard™ duckbill 46727 (formerly Kimberly Clark) models performed better on fit testing than other models for both pre-and-post decontaminations. Fewer participants (0.3 and 0.7%, respectively) passed fit testing for Makrite 9500 N95 and Greenline 5200 FFP2 and only two for the KN95 model post decontamination. Fit testing appeared to be more affected by donning & doffing, as some passed with adjustment and repeat fit testing. A ≥ 3 log reduction of SARS-CoV-2 was achieved for worn-in FFRs namely Greenline 5200 FFP2. Conclusion: The study showed that not all FFRs tested could withstand 30 cycles of UVGI decontamination without diminishing filtration efficiency or facial fit. In addition, SARS-CoV-2 log reduction varied across the FFRs, implying that the decontamination efficacy largely depends on the decontamination protocol and selection of FFRs. We demonstrated the effectiveness of a low-cost and scalable decontamination method for SARS-CoV-2 and the effect on fit testing using people instead of manikins. It is recognized that extensive experimental evidence for the reuse of decontaminated FFRs is lacking, and thus this study would be relevant and of interest in crisis-capacity settings, particularly in low-resource facilities.