Light-based technologies for management of COVID-19 pandemic crisis

The virucidal potential effects of violet-blue light on influenza D virus

Influenza D virus (IDV) is a novel influenza virus, first isolated from swine with influenza-like symptoms in the USA in 2011. To date, IDV circulation has been reported in various animal species such as cattle, pigs, horses with the ability to expand its range of hosts. UV radiation has been widely used for the disinfection of various sources such as water, air, and surfaces, especially in places at greater risk of contamination by viruses and bacteria, such as hospitals and health facilities. The aim of this study was to evaluate the potential virucidal effect of a violet-blue light against IDV. Viral suspension of IDV was exposed to a violet-blue light (405 nm) for different times (radiant exposures): 22 min and 30 s (5.4 J/cm2), 45 min (10.8 J/cm2), 90 min (21.6 J/cm2), 180 min (43.2 J/cm2), and 360 min (86.4 J/cm2), and different temperatures (room temperature, 4 and 37 °C). At the end of exposure, virus titration was performed on MDCK cells. After violet-blue light exposure, a viral titre reduction proportional to exposure time was observed: 0.228 log10 after 22 min and 30 s, 0.668 log10 after 45 min, 0.940 log10 after 90 min, 1.375 log10 after 180 min and 2.293 log10 after 360 min. Differences were observed among temperatures of exposure, with the greatest virucidal effect observed at room temperature. As reported for other respiratory viruses, this violet-blue light can potentially be used to reduce IDV spread in potentially hotspot areas for animals and humans.

Circadian re-set repairs long-COVID in a prodromal Parkinson's parallel: a case series

BACKGROUND

In this case series, results from daily visual exposure to intense polychromatic light of 2000 to 4000 LUX is presented. Bright light treatment is a standard procedure for treating seasonal affective disorder and prodromal Parkinson's disease with high success. With the post-encephalitic symptoms of long-COVID closely approximating those of prodromal Parkinson's disease, we treated insomnia and sleep-related parameters in these patients, including total sleep, number of awakenings, tendency to fall back to sleep, and fatigue, to determine whether mending sleep could improve quality of life.

CASE PRESENTATION

We present three female and two male Caucasian patients aged 42-70 years with long-COVID that persisted from 12 weeks to 139 weeks after contracting coronavirus disease.

CONCLUSION

A light presentation protocol was adapted for long-COVID that not only restored sleep in all patients, but also unexpectedly repaired the depression, anxiety, and cognitive changes (brain fog) as well. A robust pattern of recovery commencing 4-5 days after treatment and was maintained for weeks to months without relapse. These preliminary findings represent a novel, minimally invasive approach for managing the most debilitating symptoms of long-COVID, making it an ideal candidate for the drug hypersensitive, post-encephalitic brain. That a compromised circadian mechanism seen in Parkinson's disease may also underlie post-encephalitic long-COVID implicates a compromised role of the circadian system in these disorders.

In vitro photoinactivation effectiveness of a portable LED device aimed for intranasal photodisinfection and a photosensitizer formulation comprising methylene blue and potassium iodide against bacterial, fungal, and viral respiratory pathogens

Antimicrobial photodynamic therapy (aPDT) can be a viable option for management of intranasal infections. However, there are light delivery, fluence, and photosensitizer-related challenges. We report in vitro effectiveness of an easily fabricated, low-cost, portable, LED device and a formulation comprising methylene blue (MB) and potassium iodide (KI) for photoinactivation of pathogens of the nasal cavity, namely, methicillin-resistant Staphylococcus aureus, antibiotic-resistant Klebsiella pneumoniae, multi-antibiotic-resistant Pseudomonas aeruginosa, Candida spp., and SARS-CoV-2.In a 96-well plate, microbial suspensions incubated with 0.005% MB alone or MB and KI formulation were exposed to different red light (~ 660 ± 25 nm) fluence using the LED device fitted to each well. Survival loss in bacteria and fungi was quantified using colony-forming unit assay, and SARS-CoV-2 photodamage was assessed by RT-PCR.The results suggest that KI addition to MB leads to KI concentration-dependent potentiation (up to ~ 5 log10) of photoinactivation in bacteria and fungi. aPDT in the presence of 25 or 50 mM KI shows the following photoinactivation trend; Gm + ve bacteria  > Gm - ve bacteria > fungi  > virus. aPDT in the presence of 100 mM KI, using 3- or 5-min red light exposure, results in complete eradication of bacteria or fungi, respectively. For SARS-CoV-2, aPDT using MB-KI leads to a ~ 6.5 increase in cycle threshold value.The results demonstrate the photoinactivation effectiveness of the device and MB-KI formulation, which may be helpful in designing of an optimized protocol for future intranasal photoinactivation studies in clinical settings.

Photophysical properties of Radachlorin photosensitizer in solutions of different pH, viscosity and polarity

We present a thorough experimental investigation of fluorescence properties of Radachlorin photosensitizer in solutions of different acidity, viscosity and polarity. Experiments were performed using time-resolved fluorescence lifetime imaging and time-resolved analysis of polarized fluorescence. Variations of solution acidity resulted in considerable changes of Radachlorin fluorescence quantum yield and lifetime in the pH range from 4 to 7, but did not affect the rotational diffusion time, and almost did not change the quantum yield and characteristic times of singlet oxygen phosphorescence. Variations of solution polarity and viscosity were achieved by changing ethanol or methanol fraction in aqueous solution. The decrease of solution polarity resulted in nonlinear rise of Radachlorin fluorescence quantum yield and lifetime up to alcohol concentration of 50%-65%, as well as in considerable rise of singlet oxygen quantum yield and significant changes in characteristic times of its phosphorescence. Variations of solution viscosity resulted in changes of rotational diffusion time of Radachlorin molecules, which appeared to be in perfect correlation with methanol solution viscosity. Good correspondence with ethanol solution viscosity was observed only up to 50% alcohol fraction. Deviations of rotational diffusion time of Radachlorin molecules from direct proportionality with solution viscosity at higher ethanol concentrations were suggested to be due to different solvation conditions. The data obtained can give important reference points for analysis of microenvironment of Radachlorin molecules, their intracellular localization and performance in singlet oxygen generation.

An Approach to Improve Energy Efficiency during Antimicrobial Blue Light Inactivation: Application of Pulse-Width Modulation Dimming to Balance Irradiance and Irradiation Time

Antimicrobial blue light (aBL) is an effective non-destructive inactivation technique and has received increasing attention. Despite its significance, the existing research has not thoroughly delved into the impacts of irradiance and irradiation time on enhancing energy efficiency during aBL inactivation and the explanation of the enhancement effect of pulse exposure. In this paper, a series of Escherichia coli inactivation experiments with different duty cycles, pulse frequencies, and irradiation times were conducted, and the relative concentrations of reactive oxygen species (ROS) were measured under corresponding conditions. A two-dimensional (2-D) Hom model was proposed to evaluate the effect of irradiance and irradiation time. The results show that, compared to continuous exposure, pulsed aBL (duty cycle = 25%) can save ~37% of the energy to achieve the same inactivation effect and generate a 1.95 times higher ROS concentration. The 2-D Hom model obtains the optimal combination of average irradiance and time according to the desired reduction and shows that the irradiation time has a higher weight than the irradiance (1.677 and 1.083, respectively). Therefore, using pulse exposure with a lower average irradiance for a longer period of time can achieve a better inactivation effect when consuming equivalent energy. The proposed pulse-width modulation dimming approach helps promote the application of the aBL technique.

Endogenous Photosensitizers in Human Skin

Endogenous photosensitizers play a critical role in both beneficial and harmful light-induced transformations in biological systems. Understanding their mode of action is essential for advancing fields such as photomedicine, photoredox catalysis, environmental science, and the development of sun care products. This review offers a comprehensive analysis of endogenous photosensitizers in human skin, investigating the connections between their electronic excitation and the subsequent activation or damage of organic biomolecules. We gather the physicochemical and photochemical properties of key endogenous photosensitizers and examine the relationships between their chemical reactivity, location within the skin, and the primary biochemical events following solar radiation exposure, along with their influence on skin physiology and pathology. An important take-home message of this review is that photosensitization allows visible light and UV-A radiation to have large effects on skin. The analysis presented here unveils potential causes for the continuous increase in global skin cancer cases and emphasizes the limitations of current sun protection approaches.

Infections associated with SARS-CoV-2 exploited via nanoformulated photodynamic therapy

Background and purpose

The pandemic of COVID-19 has highlighted the need for managing infectious diseases, which spreads by airborne transmission leading to serious health, social, and economic issues. SARS-CoV-2 is an enveloped virus with a 60-140 nm diameter and particle-like features, which majorly accounts for this disease. Expanding diagnostic capabilities, developing safe vaccinations with long-lasting immunity, and formulating effective medications are the strategies to be investigated.

Experimental approach

For the literature search, electronic databases such as Scopus, Google Scholar, MEDLINE, Embase, PubMed, and Web of Science were used as the source. Search terms like 'Nano-mediated PDT,' 'PDT for SARS-CoV-2', and 'Nanotechnology in treatment for SARS-CoV-2' were used. Out of 275 initially selected articles, 198 were chosen after the abstract screening. During the full-text screening, 80 papers were excluded, and 18 were eliminated during data extraction. Preference was given to articles published from 2018 onwards, but a few older references were cited for their valuable information.

Key results

Synthetic nanoparticles (NPs) have a close structural resemblance to viruses and interact greatly with their proteins due to their similarities in the configurations. NPs had previously been reported to be effective against a variety of viruses. In this way, with nanoparticles, photodynamic therapy (PDT) can be a viable alternative to antibiotics in fighting against microbial infections. The protocol of PDT includes the activation of photosensitizers using specific light to destroy microorganisms in the presence of oxygen, treating several respiratory diseases.

Conclusion

The use of PDT in treating COVID-19 requires intensive investigations, which has been reviewed in this manuscript, including a computational approach to formulating effective photosensitizers.

Topological Avenue for Efficient Decontamination of Large Volumes of Fluids via UVC Irradiation of Packed Metamaterials

Nowadays, metamaterials application enjoys notoriety in fluid decontamination and pathogen annihilation, which are frequently present in polluted fluids (e.g., water, blood, blood plasma, air or other gases). The depollution effect is largely enhanced by UVC irradiation. The novelty of this contribution comes from the significant increase by packing of the total surface of metamaterials in contact with contaminated fluids. Packed metamaterial samples are subjected to UVC irradiation, with expected advantages for implant sterilization and long-term prevention of nosocomial infections over large clinical areas. The novel aspect of the investigation consists of a combination of big and small elements of the metamaterial to optimize the above effects connected with fluids and irradiation. The big elements allow the radiation to penetrate deep inside the fluid, and the small elements optimally disperse this radiation toward deeper regions of the metamaterial. A packing scheme of smaller, in-between large metamaterial spheres and fibres is proposed for promoting enhanced depollution against pathogen agents. It is demonstrated that the total surface of metamaterials in contact with contaminated fluids/surface is significantly increased as a result of packing. This opens, in our opinion, new auspicious perspectives in the construction of novel equipment with high sensibility in the detection and decontamination of microorganisms.

A review on indoor environmental quality in sports facilities: Indoor air quality and ventilation during a pandemic

Because of COVID-19, the indoor environmental quality (IEQ) in sports facilities has been a concern to environmental health practitioners. To develop an overall understanding of the available guidelines and standards and studies performed on IEQ in sports facilities, an extensive literature study was conducted, with the aim of identifying: (1) indicators that are being used to assess IEQ in different sports facilities; (2) indicators that are potentially interesting to be used to assess indoor air, in particular; (3) gaps in knowledge to determine whether sports facilities are safe, healthy and comfortable for people to stay and perform their activities. The outcome indicates that most current standards and previous investigations on IEQ in sports facilities mainly focused on dose-related indicators (such as ventilation rate), while building-related indicators (such as ventilation regime) and occupant-related indicators (such as IEQ preferences) were rarely considered. Little attention is given to the fact that ventilation systems may play an important role in the air quality of the location, and few investigations have been performed on the transmission of SARS-CoV-2. This study recommends more research into both occupant and building-related indicators as well as cross-modal effects between various IEQ factors for developing future standards on sports facilities.

Evaluation of Viral Inactivation on Dry Surface by High Peak Power Microwave (HPPM) Exposure

Previous research has shown that virus infectivity can be dramatically reduced by radio frequency exposure in the gigahertz (GHz) frequency range. Given the worldwide SARS-CoV-2 pandemic, which has caused over 1 million deaths and has had a profound global economic impact, there is a need for a noninvasive technology that can reduce the transmission of virus among humans. RF is a potential wide area-of-effect viral decontamination technology that could be used in hospital rooms where patients are expelling virus, in grocery and convenience stores where local populations mix, and in first responder settings where rapid medical response spans many potentially infected locations within hours. In this study, we used bovine coronavirus (BCoV) as a surrogate of SARS-CoV-2 and exposed it to high peak power microwave (HPPM) pulses at four narrowband frequencies: 2.8, 5.6, 8.5, and 9.3 GHz. Exposures consisted of 2 µs pulses delivered at 500 Hz, with pulse counts varied by decades between 1 and 10,000. The peak field intensities (i.e. the instantaneous power density of each pulse) ranged between 0.6 and 6.5 MW/m² , depending on the microwave frequency. The HPPM exposures were delivered to plastic coverslips containing BCoV dried on the surface. Hemagglutination (HA) and cytopathic effect analyses were performed 6 days after inoculation of host cells to assess viral infectivity. No change in viral infectivity was seen with increasing dose (pulse number) across the tested frequencies. Under all conditions tested, exposure did not reduce infectivity more than 1.0 log_10. For the conditions studied, high peak power pulsed RF exposures in the 2-10 GHz range appear ineffective as a virucidal approach for hard surface decontamination. © 2023 Bioelectromagnetics Society.

A singlet state oxygen generation model based on the Monte Carlo method of visible antibacterial blue light inactivation

Visible antibacterial blue light (VABL) has received much attention recently as a nondestructive inactivation approach. However, due to the sparse distribution of bacteria, the light energy evaluation method used in existing studies is inaccurate. Thus, the sensitivity of microorganisms to VABL in different experiments cannot be compared. In this paper, a Monte Carlo-based photon transport model with the optimized scattering phase function was constructed. The model calculated the spatial light energy distribution and the temporal distribution of cumulative singlet state oxygen (CSO) under various cell and medium parameters. The simulation results show that when the cells are sparsely distributed, <30% of light energy from the light source is absorbed by microbes and participates in photochemical reactions. The CSO produced increases with cell density and cell size. Little light energy is available, and thus, the concentration of CSO produced is insufficient to inactivate microbes at deeper depths. As the light intensity and inactivation time increased, the production of singlet state oxygen tended to level off. The model proposed here can quantify the generation of singlet state oxygen and provide a more accurate light energy guide for the VABL inactivation process.

Photodynamic nasal SARS-CoV-2 decolonization shortens infectivity and influences specific T-Cell responses

Background

The main objective was to evaluate the efficacy of intranasal photodynamic therapy (PDT) in SARS-CoV-2 mildly symptomatic carriers on decreasing the infectivity period. SARS-CoV-2-specific immune-stimulating effects and safety were also analysed.

Methods

We performed a randomized, placebo-controlled, clinical trial in a tertiary hospital (NCT05184205). Patients with a positive SARS-CoV-2 PCR in the last 48 hours were recruited and aleatorily assigned to PDT or placebo. Patients with pneumonia were excluded. Participants and investigators were masked to group assignment. The primary outcome was the reduction in in vitro infectivity of nasopharyngeal samples at days 3 and 7. Additional outcomes included safety assessment and quantification of humoral and T-cell immune-responses.

Findings

Patients were recruited between December 2021 and February 2022. Most were previously healthy adults vaccinated against COVID-19 and most carried Omicron variant. 38 patients were assigned to placebo and 37 to PDT. Intranasal PDT reduced infectivity at day 3 post-treatment when compared to placebo with a β-coefficient of -812.2 (CI95%= -478660 - -1.3, p<0.05) infectivity arbitrary units. The probability of becoming PCR negative (ct>34) at day 7 was higher on the PDT-group, with an OR of 0.15 (CI95%=0.04-0.58). There was a decay in anti-Spike titre and specific SARS-CoV-2 T cell immunity in the placebo group 10 and 20 weeks after infection, but not in the PDT-group. No serious adverse events were reported.

Interpretation

Intranasal-PDT is safe in pauci-symptomatic COVID-19 patients, it reduces SARS-CoV-2 infectivity and decelerates the decline SARS-CoV-2 specific immune-responses.

Licht und Covid-19 — Ein Update

Licht, Laser und Akupunktur haben auch in der aktuellen Pandemie wichtige Beiträge zur Medizin geleistet. Hauptziel einer vor kurzem veröffentlichten Übersichtsarbeit war es zu untersuchen, wie Licht als therapeutische Methode während der durch COVID-19 ausgelösten Krise bislang eingesetzt wurde. Ein weiteres Ziel ist es, Wissenschaftlerinnen und Wissenschaftler sowie die Industrie zu ermutigen, schnell neue einfache Verfahren der Photobiomodulationstherapie (PBMT) und/oder photodynamischen Therapie (PDT) für zu Hause zu entwickeln. Die bisherigen Ergebnisse zeigten, dass PBMT teilweise erfolgreich bei SARSCoV-2-Infektionen angewendet werden kann und signifikante Verbesserungen bei Atemwegsentzündungen und dem allgemeinen klinischen Zustand der Patientinnen und Patienten ermöglichte. Die Anwendung nur in einer begrenzten Anzahl von Fällen impliziert die Notwendigkeit zukünftiger randomisierter, placebokontrollierter klinischer Studien, um die Wirkung von PBMT und PDT bei COVID-19 tatsächlich zu objektivieren. Bei dieser anhaltenden und herausfordernden Suche nach dem scheinbar nicht greifbaren Ende dieser Pandemie scheinen die PBMT und PDT nicht-invasive, leicht zugängliche, sichere und nebenwirkungsfreie Methoden zu sein.

Cardiopulmonary and hematological effects of infrared LED photobiomodulation in the treatment of SARS-COV2

BACKGROUND

COVID-19 disease is caused by SARS-CoV-2 which can trigger acute respiratory syndrome, which presents with dense alveolar and interstitial infiltrates and pulmonary edema, causing severe hypoxemia and significant alteration to pulmonary mechanics with reduced pulmonary compliance. The photobiomodulation technique alters cellular and molecular metabolism, showing promising results regarding the reduction of acute pulmonary inflammation.

OBJECTIVE

To compare the photomodulation technique using near-infrared LED to conventional respiratory physiotherapy treatment in patients with COVID-19 in reversing acute conditions, reducing hospitalization time, and decreasing the need for oxygen therapy.

METHODOLOGY

The cohort was comprised of 30 patients undergoing COVID-19 treatment who were divided and allocated into two equal groups randomly: the LED group (LED), treated with infrared LED at 940 nm and conventional therapy, and the control group (CON), who received conventional treatment (antibiotic therapy for preventing superimposed bacterial infections, and physiotherapy) with LED irradiation off. Phototherapy used a vest with an array of 300 LEDs (940 nm) mounted on a 36 cm × 58 cm area and positioned in the patient's anterior thoracic and abdominal regions. The total power was 6 W, with 15 min irradiation time. Cardiopulmonary functions and blood count were monitored before and after treatment. The patients were treated daily for 7 days. Statistical analysis was conducted using a two-tailed unpaired Student's t-test at a significance level of α = 0.05.

RESULTS

Post-treatment, the LED group showed a reduction in hospital discharge time and a statistically significant improvement for the following cardiopulmonary functions: Partial Oxygen Saturation, Tidal Volume, Maximum Inspiratory, and Expiratory Pressures, Respiratory Frequency, Heart Rate, and Systolic Blood Pressure (p < 0.05). Regarding blood count, it was observed that post-treatment, the LED group presented with significant differences in the count of leukocytes, neutrophils, and lymphocytes.

CONCLUSION

Photobiomodulation therapy can be used as a complement to conventional treatment of COVID-19, promoting the improvement of cardiopulmonary functions, and minimization of respiratory symptoms.

Unfolding of the SARS-CoV-2 spike protein through infrared and ultraviolet-C radiation based disinfection

The spreading of coronavirus from contacting surfaces and aerosols created a pandemic around the world. To prevent the transmission of SARS-CoV-2 virus and other contagious microbes, disinfection of contacting surfaces is necessary. In this study, a disinfection box equipped with infrared (IR) radiation heating and ultraviolet-C (UV-C) radiation is designed and tested for its disinfection ability against pathogenic bacteria and SARS-CoV-2 spike protein. The killing of a Gram-positive, namely, S. aureus and a Gram-negative namely, S. typhi bacteria was studied followed by the inactivation of the spike protein. The experimental parameters were optimized using a statistical tool. For the broad-spectrum antibacterial activity, the optimum condition was holding at 65.61 °C for 13.54 min. The killing of the bacterial pathogen occurred via rupturing the cell walls as depicted by electron microscopy. Further, the unfolding of SARS-CoV-2 spike protein and RNase A was studied under IR and UV-C irradiations at the aforesaid optimized condition. The unfolding of both the proteins was confirmed by changes in the secondary structure, particularly an increase in β-sheets and a decrease in α-helixes. Remarkably, the higher penetration depth of IR waves up to subcutaneous tissue resulted in lower optimum disinfection temperature, <70 °C in vogue. Thus, the combined UV-C and IR radiation is effective in killing the pathogenic bacteria and denaturing the glycoproteins.

Potent Virucidal Activity In Vitro of Photodynamic Therapy with Hypericum Extract as Photosensitizer and White Light against Human Coronavirus HCoV-229E

The emergent human coronavirus SARS-CoV-2 and its high infectivity rate has highlighted the strong need for new virucidal treatments. In this sense, the use of photodynamic therapy (PDT) with white light, to take advantage of the sunlight, is a potent strategy for decreasing the virulence and pathogenicity of the virus. Here, we report the virucidal effect of PDT based on Hypericum extract (HE) in combination with white light, which exhibits an inhibitory activity of the human coronavirus HCoV-229E on hepatocarcinoma Huh-7 cells. Moreover, despite continuous exposure to white light, HE has long durability, being able to maintain the prevention of viral infection. Given its potent in vitro virucidal capacity, we propose HE in combination with white light as a promising candidate to fight against SARS-CoV-2 as a virucidal compound.

COVID-19 pandemic lesson learned- critical parameters and research needs for UVC inactivation of viral aerosols

The COVID-19 pandemic highlighted public awareness of airborne disease transmission in indoor settings and emphasized the need for reliable air disinfection technologies. This increased awareness will carry in the post-pandemic era along with the ever-emerging SARS-CoV variants, necessitating effective and well-defined protocols, methods, and devices for air disinfection. Ultraviolet (UV)-based air disinfection demonstrated promising results in inactivating viral bioaerosols. However, the reported data diversity on the required UVC doses has hindered determining the best UVC practices and led to confusion among the public and regulators. This article reviews available information on critical parameters influencing the efficacy of a UVC air disinfection system and, consequently, the required dose including the system's components as well as operational and environmental factors. There is a consensus in the literature that the interrelation of humidity and air temperature has a significant impact on the UVC susceptibility, which translate to changing the UVC efficacy of commercialized devices in indoor settings under varying conditions. Sampling and aerosolization techniques reported to have major influence on the result interpretation and it is recommended to use several sampling methods simultaneously to generate comparable and conclusive data. We also considered the safety concerns and the potential safe alternative of UVC, far-UVC. Finally, the gaps in each critical parameter and the future research needs of the field are represented. This paper is the first step to consolidating literature towards developing a standard validation protocol for UVC air disinfection devices which is determined as the one of the research needs.

Pulsed-Xenon Ultraviolet Light Highly Inactivates Human Coronaviruses on Solid Surfaces, Particularly SARS-CoV-2

In the context of ongoing and future pandemics, non-pharmaceutical interventions are critical in reducing viral infections and the emergence of new antigenic variants while the population reaches immunity to limit viral transmission. This study provides information on efficient and fast methods of disinfecting surfaces contaminated with different human coronaviruses (CoVs) in healthcare settings. The ability to disinfect three different human coronaviruses (HCoV-229E, MERS-CoV, and SARS-CoV-2) on dried surfaces with light was determined for a fully characterized pulsed-xenon ultraviolet (PX-UV) source. Thereafter, the effectiveness of this treatment to inactivate SARS-CoV-2 was compared to that of conventional low-pressure mercury UVC lamps by using equivalent irradiances of UVC wavelengths. Under the experimental conditions of this research, PX-UV light completely inactivated the CoVs tested on solid surfaces since the infectivity of the three CoVs was reduced up to 4 orders of magnitude by PX-UV irradiation, with a cumulated dose of as much as 21.162 mJ/cm² when considering all UV wavelengths (5.402 mJ/cm² of just UVC light). Furthermore, continuous irradiation with UVC light was less efficient in inactivating SARS-CoV-2 than treatment with PX-UV light. Therefore, PX-UV light postulates as a promising decontamination measure to tackle the propagation of future outbreaks of CoVs.

A meta-analysis result: Uneven influences of season, geo-spatial scale and latitude on relationship between meteorological factors and the COVID-19 transmission

Meteorological factors have been confirmed to affect the COVID-19 transmission, but current studied conclusions varied greatly. The underlying causes of the variance remain unclear. Here, we proposed two scientific questions: (1) whether meteorological factors have a consistent influence on virus transmission after combining all the data from the studies; (2) whether the impact of meteorological factors on the COVID-19 transmission can be influenced by season, geospatial scale and latitude. We employed a meta-analysis to address these two questions using results from 2813 published articles. Our results showed that, the influence of meteorological factors on the newly-confirmed COVID-19 cases varied greatly among existing studies, and no consistent conclusion can be drawn. After grouping outbreak time into cold and warm seasons, we found daily maximum and daily minimum temperatures have significant positive influences on the newly-confirmed COVID-19 cases in cold season, while significant negative influences in warm season. After dividing the scope of the outbreak into national and urban scales, relative humidity significantly inhibited the COVID-19 transmission at the national scale, but no effect on the urban scale. The negative impact of relative humidity, and the positive impacts of maximum temperatures and wind speed on the newly-confirmed COVID-19 cases increased with latitude. The relationship of maximum and minimum temperatures with the newly-confirmed COVID-19 cases were more susceptible to season, while relative humidity's relationship was more affected by latitude and geospatial scale. Our results suggested that relationship between meteorological factors and the COVID-19 transmission can be affected by season, geospatial scale and latitude. A rise in temperature would promote virus transmission in cold seasons. We suggested that the formulation and implementation of epidemic prevention and control should mainly refer to studies at the urban scale. The control measures should be developed according to local meteorological properties for individual city.

Ultrafast-UV laser integrating cavity device for inactivation of SARS-CoV-2 and other viruses

Ultraviolet (UV) irradiation-based methods used for viral inactivation have provided an important avenue targeting severe acute respiratory-syndrome coronavirus-2 (SARS-CoV-2) virus. A major problem with state-of-the-art UV inactivation technology is that it is based on UV lamps, which have limited efficiency, require high power, large doses, and long irradiation times. These drawbacks limit the use of UV lamps in air filtering systems and other applications. To address these limitations, herein we report on the fabrication of a device comprising a pulsed nanosecond 266 nm UV laser coupled to an integrating cavity (LIC) composed of a UV reflective material, polytetrafluoroethylene. Previous UV lamp inactivation cavities were based on polished walls with specular reflections, but the diffuse reflective UV ICs were not thoroughly explored for virus inactivation. Our results show that LIC device can inactivate several respiratory viruses including SARS-CoV-2, at ~ 1 ms effective irradiation time, with > 2 orders of magnitude higher efficiency compared to UV lamps. The demonstrated 3 orders of magnitude cavity enhancement relative to direct exposure is crucial for the development of efficient real-time UV air and water purification systems. To the best of our knowledge this is the first demonstration of LIC application for broad viral inactivation with high efficiency.

Photodynamic Inactivation of SARS-CoV-2 Infectivity and Antiviral Treatment Effects In Vitro

Despite available vaccines, antibodies and antiviral agents, the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic still continues to cause severe disease and death. Current treatment options are limited, and emerging new mutations are a challenge. Thus, novel treatments and measures for prevention of viral infections are urgently required. Photodynamic inactivation (PDI) is a potential treatment for infections by a broad variety of critical pathogens, including viruses. We explored the infectiousness of clinical SARS-CoV-2 isolates in Vero cell cultures after PDI-treatment, using the photosensitizer Tetrahydroporphyrin-tetratosylate (THPTS) and near-infrared light. Replication of viral RNA (qPCR), viral cytopathic effects (microscopy) and mitochondrial activity were assessed. PDI of virus suspension with 1 µM THPTS before infection resulted in a reduction of detectable viral RNA by 3 log levels at day 3 and 6 after infection to similar levels as in previously heat-inactivated virions (<99.9%; p < 0.05). Mitochondrial activity, which was significantly reduced by viral infection, was markedly increased by PDI to levels similar to uninfected cell cultures. When applying THPTS-based PDI after infection, a single treatment had a virus load-reducing effect only at a higher concentration (3 µM) and reduced cell viability in terms of PDI-induced toxicity. Repeated PDI with 0.3 µM THPTS every 4 h for 3 d after infection reduced the viral load by more than 99.9% (p < 0.05), while cell viability was maintained. Our data demonstrate that THPTS-based antiviral PDI might constitute a promising approach for inactivation of SARS-CoV-2. Further testing will demonstrate if THPTS is also suitable to reduce the viral load in vivo.

Infectivity and Morphology of Bovine Coronavirus Inactivated In Vitro by Cationic Photosensitizers

Bovine coronaviruses (BCoVs), which cause gastrointestinal and respiratory diseases in cattle, and are genetically related to the human coronavirus HCoV-OC43, which is responsible for up to 10% of common colds, attract increased attention. We applied the method of photodynamic inactivation with cationic photosensitizers (PSs) to reduce the titers of BCoV and studied the morphological structure of viral particles under various modes of photodynamic exposure. The samples of virus containing liquid with an initial virus titer of 5 Log₁₀ TCID50/mL were incubated with methylene blue (MB) or octakis(cholinyl)zinc phthalocyanine (Zn-PcChol₈₊) at concentrations of 1–5 μM for 10 min in the dark at room temperature. After incubation, samples were irradiated with LED (emission with maximum at 663 nm for MB or at 686 nm for Zn-PcChol₈₊) with light doses of 1.5 or 4 J/cm². Next, the irradiation titrated virus containing liquid was studied using negative staining transmission electron microscopy. MB and Zn-PcChol₈₊ at concentrations of 1–5 μM, in combination with red light from LED sources in the low doses of 1.5–4.0 J/cm², led to a decrease in BCoV titers by at least four orders of magnitude from the initial titer 5 Log₁₀ TCID50/mL. Morphological changes in photodamaged BCoVs with increasing PS concentrations were loss of spikes, change in shape, decreased size of virus particles, destruction of the envelope, and complete disintegration of viruses. BCoV has been found to be sensitive to MB, which is the well-known approved drug, even in the absence of light.

Rationale for 1068 nm Photobiomodulation Therapy (PBMT) as a Novel, Non-Invasive Treatment for COVID-19 and Other Coronaviruses: Roles of NO and Hsp70

Researchers from across the world are seeking to develop effective treatments for the ongoing coronavirus disease 2019 (COVID-19) outbreak, which arose as a major public health issue in 2019, and was declared a pandemic in early 2020. The pro-inflammatory cytokine storm, acute respiratory distress syndrome (ARDS), multiple-organ failure, neurological problems, and thrombosis have all been linked to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) fatalities. The purpose of this review is to explore the rationale for using photobiomodulation therapy (PBMT) of the particular wavelength 1068 nm as a therapy for COVID-19, investigating the cellular and molecular mechanisms involved. Our findings illustrate the efficacy of PBMT 1068 nm for cytoprotection, nitric oxide (NO) release, inflammation changes, improved blood flow, and the regulation of heat shock proteins (Hsp70). We propose, therefore, that PBMT 1068 is a potentially effective and innovative approach for avoiding severe and critical illness in COVID-19 patients, although further clinical evidence is required.

Tuning riboflavin derivatives for photodynamic inactivation of pathogens

The development of effective pathogen reduction strategies is required due to the rise in antibiotic-resistant bacteria and zoonotic viral pandemics. Photodynamic inactivation (PDI) of bacteria and viruses is a potent reduction strategy that bypasses typical resistance mechanisms. Naturally occurring riboflavin has been widely used in PDI applications due to efficient light-induced reactive oxygen species (ROS) release. By rational design of its core structure to alter (photo)physical properties, we obtained derivatives capable of outperforming riboflavin's visible light-induced PDI against E. coli and a SARS-CoV-2 surrogate, revealing functional group dependency for each pathogen. Bacterial PDI was influenced mainly by guanidino substitution, whereas viral PDI increased through bromination of the flavin. These observations were related to enhanced uptake and ROS-specific nucleic acid cleavage mechanisms. Trends in the derivatives' toxicity towards human fibroblast cells were also investigated to assess viable therapeutic derivatives and help guide further design of PDI agents to combat pathogenic organisms.

Development of an Ultraviolet-C Irradiation Room in a Public Portuguese Hospital for Safe Re-Utilization of Personal Protective Respirators

Almost two years have passed since COVID-19 was officially declared a pandemic by the World Health Organization. However, it still holds a tight grasp on the entire human population. Several variants of concern, one after another, have spread throughout the world. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) omicron variant may become the fastest spreading virus in history. Therefore, it is more than evident that the use of personal protective equipment (PPE) will continue to play a pivotal role during the current pandemic. This work depicts an integrative approach attesting to the effectiveness of ultra-violet-C (UV-C) energy density for the sterilization of personal protective equipment, in particular FFP2 respirators used by the health care staff in intensive care units. It is increasingly clear that this approach should not be limited to health care units. Due to the record-breaking spreading rates of SARS-CoV-2, it is apparent that the use of PPE, in particular masks and respirators, will remain a critical tool to mitigate future pandemics. Therefore, similar UV-C disinfecting rooms should be considered for use within institutions and companies and even incorporated within household devices to avoid PPE shortages and, most importantly, to reduce environmental burdens.

Photodynamic disinfection of SARS-CoV-2 clinical samples using a methylene blue formulation

Abstract

The amplitude of the coronavirus disease 2019 (COVID-19) pandemic motivated global efforts to find therapeutics that avert severe forms of this illness. The urgency of the medical needs privileged repositioning of approved medicines. Methylene blue (MB) has been in clinical use for a century and proved especially useful as a photosensitizer for photodynamic disinfection (PDI). We describe the use of MB to photo-inactivate SARS-CoV-2 in samples collected from COVID-19 patients. One minute of treatment can reduce the percentage inhibition of amplification by 99.99% under conditions of low cytotoxicity. We employed a pseudotyped lentiviral vector (LVs) encoding the luciferase reporter gene and exhibiting the S protein of SARS-CoV-2 at its surface, to infect human ACE2-expressing HEK293T cells. Pre-treatment of LVs with MB-PDI prevented infection at low micromolar MB concentrations and 1 min of illumination. These results reveal the potential of MB-PDI to reduce viral loads in the nasal cavity and oropharynx in the early stages of COVID-19, which may be employed to curb the transmission and severity of the disease.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s43630-022-00202-6.

Singlet oxygen generation in aerosol jet and on biological surfaces

The paper presents steady-state and time-resolved experiments on photophysical processes associated with photodynamic inactivation of infections provided by nebulization of Radachlorin photosensitizer solution. As models of surfaces subjected to photodynamic inactivation we used glass, plant leaf, mushroom cap peel and superficial fascia of chicken and salmon skin flaps. The oxygen content in the photosensitizer solution was varied by blowing with atmospheric air and with pure oxygen. It was shown that singlet oxygen was generated efficiently in the aerosol jet and that its amount increased noticeably at higher oxygen concentrations. The kinetics of photosensitizer photobleaching on different surfaces were found to be significantly different with characteristic decay times varying from seconds for leaf and glass to minutes for fascial flaps. This observation was attributed to much faster oxygen depletion on rough crumbly surfaces of biological samples due to effective oxidation reactions occurred. The singlet oxygen generation and degradation times, and the relative quantum yield were determined on different surfaces by recording time-resolved phosphorescence at about 1270 nm under normoxic and hyperoxic conditions and analyzed on the basis of the set of master equations. The results obtained provide reference marks for choosing optimal irradiation durations for photodynamic inactivation of pathogenic infectious agents (bacteria, mycobacteria, fungi, viruses) on mucous membranes, including the tracheobronchial tree.

Whole-organ transdermal photobiomodulation (PBM) of COVID-19: A 50-patient case study

A nonrandomized 50-person case study of COVID-19-positive patients was conducted employing (for the first time) a regimen of whole-organ deep-tissue transdermal dynamic photobiomodulation (PBM) as a primary (or exclusive) therapeutic modality in the treatment of coronavirus. Therapy sessions comprised algorithmically alternating red (650 nm) and near-infrared (NIR; 850 nm) LEDs with an average irradiance of 11 mW/cm² dynamically sequenced at multiple pulse frequencies. Delivered via 3D bendable polymeric pads maintaining orthogonal optical incidence to body contours over 1,000 cm² , a single 84-minute session concurrently delivered 20 kJ to the sinuses and 15 kJ to each lung at skin temperatures below 42°C. Therapeutic outcomes observed include significant reductions in the duration and severity of disease symptoms. Acute conditions including fever, body aches (BA) and respiratory distress comprising paroxysmal coughing; lung congestion, dyspnea and hypoxia; sinus congestion; acute eye inflammation; and extreme malaise were eliminated in 41/50 patients within 4 days of commencing PBM treatments with 50/50 patients fully recovering within 3 weeks with no supplemental oxygen requirements. SpO₂ concentrations improved as much as 9 points (average 2.5 points) across the entire study population. The PBM sessions required to completely resolve COVID-19 conditions appears monotonically correlated to the time-to-treatment (TTTx)-the delay between the onset of a patient's symptoms and commencing PBM therapy. In contrast, acute inflammatory symptoms were resolved within 4 days irrespective of TTTx.

Taking leads out of nature, can nano deliver us from COVID-like pandemics?

The COVID-19 crisis has alerted the research community to re-purpose scientific tools that can effectively manage emergency pandemic situations. Researchers were never so desperate to discover a 'magic bullet' that has significant clinical benefits with minimal or no side effects. At the beginning of the pandemic, due to restricted access to traditional laboratory techniques, many research groups delved into computational screening of thousands of lead molecules that could inhibit SARS-CoV-2 at one or more stages of its infectious cycle. Several in silico studies on natural derivatives point out their potency against SARS-CoV-2 proteins. However, theoretical predictions and existing knowledge on related molecules reflect their poor oral bioavailability due to biotransformation in the gut and liver. Nanotechnology has evolved into a key field for precise and controlled delivery of various drugs that lack aqueous solubility, have low oral bioavailability and possess pronounced toxicity in their native form. In this review, we discuss various nanoformulations of natural products with favorable ADME properties, and also briefly explore nano-drug delivery to lungs, the primary site of SARS-CoV-2 infection. Natural products are also envisioned to augment nanotechnology-based 1) personnel protective equipment for ex vivo viral inactivation and 2) wearable sensors that perform rapid and non-invasive analysis of volatile organic compounds in exhaled breath of the infected person after therapeutic food consumption.

Magnetic Resonance Imaging During a Pandemic: Recommendations by the ISMRM Safety Committee

The COVID-19 pandemic highlighted the challenges delivering face-to-face patient care across healthcare systems. In particular the COVID-19 pandemic challenged the imaging community to provide timely access to essential diagnostic imaging modalities while ensuring appropriate safeguards were in place for both patients and personnel. With increasing vaccine availability and greater prevalence of vaccination in communities worldwide we are finally emerging on the other side of the COVID-19 pandemic. As we learned from our institutional and healthcare system responses to the pandemic, maintaining timely access to MR imaging is essential. Radiologists and other imaging providers partnered with their referring providers to ensure that timely access to advanced MR imaging was maintained. On behalf of the International Magnetic Resonance in Medicine (ISMRM) Safety Committee, this white paper is intended to serve as a guide for radiology departments, imaging centers, and other imaging specialists who perform MR imaging to refer to as we prepare for the next pandemic. Lessons learned including strategies to triage and prioritize MR imaging research during a pandemic are discussed. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY: Stage 5.

Anti-infective dyes in the time of COVID

The phenomenal global upheaval caused by SARS-CoV-2 has produced amazing responses from science and healthcare, particularly in the rapid realisation and production of vaccines. However, until early 2020 global infection control research was highly focused on rapidly increasing rates of conventional antimicrobial resistance (AMR) and the supply of drugs to counter this. Antimicrobial dyes have been suggested by various authors for inclusion in this effort, usually with little return from responsible authorities, and normally on the basis of post-treatment staining or potential toxicity, but this does not deny the fact that such dyes, particularly with photoactivation, are the only class of agents with pan-microbial activity - i.e. against each of bacteria, viruses, fungi and protozoa - regardless of the organism's drug resistance status. Conventional antibacterials, antivirals etc. usually demonstrate activity against one particular section of pathogens only, and disinfectants such as chlorhexidine or benzalkonium salts are too toxic for internal use. This perspective reflects both the background utility of antimicrobial dyes and ways forward for their inclusion in 21st Century infection control protocols.

A systematic scoping review of ultraviolet C (UVC) light systems for SARS-CoV-2 inactivation

A significant amount of epidemiological evidence has underlined that human-to-human transmission due to close contacts is considered the main pathway of transmission, however since the SARS-CoV-2 can also survive in aerosols, water, and surfaces, the development and implementation of effective decontamination strategies are urgently required. In this regard, ultraviolet germicidal irradiation (UVGI) using ultraviolet C (UVC) has been proposed to disinfect different environments and surfaces contaminated by SARS-CoV-2. Herein, we performed a systematic scoping review strictly focused on peer-reviewed studies published in English that reported experimental results of UVC-based technologies against the SARS-CoV-2 virus. Studies were retrieved from PubMed and the Web of Science database. After our criterious screening, we identified 13 eligible articles that used UVC-based systems to inactivate SARS-CoV-2. We noticed the use of different UVC wavelengths, technologies, and light doses. The initial viral titer was also heterogeneous among studies. Most studies reported virus inactivation in well plates, even though virus persistence on N95 respirators and different surfaces were also evaluated. SARS-CoV-2 inactivation reached from 90% to 100% depending on experimental conditions. We concluded that there is sufficient evidence to support the use of UVC-based technologies against SARS-CoV-2. However, appropriate implementation is required to guarantee the efficacy and safety of UVC strategies to control the COVID-19 pandemic.

Application of TD-DFT Theory to Studying Porphyrinoid-Based Photosensitizers for Photodynamic Therapy: A Review

An important focus for innovation in photodynamic therapy (PDT) is theoretical investigations. They employ mostly methods based on Time-Dependent Density Functional Theory (TD-DFT) to study the photochemical properties of photosensitizers. In the current article we review the existing state-of-the-art TD-DFT methods (and beyond) which are employed to study the properties of porphyrinoid-based systems. The review is organized in such a way that each paragraph is devoted to a separate aspect of the PDT mechanism, e.g., correct prediction of the absorption spectra, determination of the singlet-triplet intersystem crossing, and interaction with molecular oxygen. Aspects of the calculation schemes are discussed, such as the choice of the most suitable functional and inclusion of a solvent. Finally, quantitative structure-activity relationship (QSAR) methods used to explore the photochemistry of porphyrinoid-based systems are discussed.

A photoactivable natural product with broad antiviral activity against enveloped viruses including highly pathogenic coronaviruses

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak has highlighted the need for broad-spectrum antivirals against coronaviruses (CoVs). Here, pheophorbide a (Pba) was identified as a highly active antiviral molecule against human CoV-229E after bioguided fractionation of plant extracts. The antiviral activity of Pba was subsequently shown for SARS-CoV-2 and Middle East respiratory syndrome coronavirus (MERS-CoV), and its mechanism of action was further assessed, showing that Pba is an inhibitor of coronavirus entry by directly targeting the viral particle. Interestingly, the antiviral activity of Pba depends on light exposure, and Pba was shown to inhibit virus-cell fusion by stiffening the viral membrane, as demonstrated by cryoelectron microscopy. Moreover, Pba was shown to be broadly active against several other enveloped viruses and reduced SARS-CoV-2 and MERS-CoV replication in primary human bronchial epithelial cells. Pba is the first described natural antiviral against SARS-CoV-2 with direct photosensitive virucidal activity that holds potential for COVID-19 therapy or disinfection of SARS-CoV-2-contaminated surfaces.

UVC LED and Conducting Yarn-Based Heater for a Smart Germicidal Face Mask to Protect against Airborne Viruses

"Wear a mask. Save lives" is the slogan of WHO and all the government agencies over the world to the public. One of the most adopted prevention measures that can limit the spread of the airborne virus in the form of respiratory viral diseases, including the new strain of COVID-19, is wearing a proper mask. If the mask surface is heated to 65 to 70 °C, it could help potentially diminish any viruses or bacteria accumulated. The FAR-Ultraviolet -C (FAR-UV-C) dose for the influenza limit to 254 nm light is ~3 mJ/cm2/hour exposure is not harmful to the human skin and eyes. Here, we propose an intelligent mask served by FAR-UV-C and conducting a yarn-based heater that could potentially be activated in a controlled manner to kill the virus. The effective irradiation intensity for skin application would be under 0.1 µW/cm2. The exposure risk of UV-C is technically prevented by fabricating multi-layered fabrics with multiple functionalities. Along with experimental validation on bacterial filtration efficiency (BFE), tinker cad simulation for circuit design, and comsol multiphysics for temperature profile study, we probed Moisture Management Test (MMT) in addition with cytotoxicity risk by MTT Assay for survivability to ensure safer application potential. This novel proposed design with the germicidal combination of heating and FAR-UV-C models, described here, is promising in retaliating and combating any airborne viruses.

Solar simulated ultraviolet radiation inactivates HCoV-NL63 and SARS-CoV-2 coronaviruses at environmentally relevant doses

The germicidal properties of short wavelength ultraviolet C (UVC) light are well established and used to inactivate many viruses and other microbes. However, much less is known about germicidal effects of terrestrial solar UV light, confined exclusively to wavelengths in the UVA and UVB regions. Here, we have explored the sensitivity of the human coronaviruses HCoV-NL63 and SARS-CoV-2 to solar-simulated full spectrum ultraviolet light (sUV) delivered at environmentally relevant doses. First, HCoV-NL63 coronavirus inactivation by sUV-exposure was confirmed employing (i) viral plaque assays, (ii) RT-qPCR detection of viral genome replication, and (iii) infection-induced stress response gene expression array analysis. Next, a detailed dose-response relationship of SARS-CoV-2 coronavirus inactivation by sUV was elucidated, suggesting a half maximal suppression of viral infectivity at low sUV doses. Likewise, extended sUV exposure of SARS-CoV-2 blocked cellular infection as revealed by plaque assay and stress response gene expression array analysis. Moreover, comparative (HCoV-NL63 versus SARS-CoV-2) single gene expression analysis by RT-qPCR confirmed that sUV exposure blocks coronavirus-induced redox, inflammatory, and proteotoxic stress responses. Based on our findings, we estimate that solar ground level full spectrum UV light impairs coronavirus infectivity at environmentally relevant doses. Given the urgency and global scale of the unfolding SARS-CoV-2 pandemic, these prototype data suggest feasibility of solar UV-induced viral inactivation, an observation deserving further molecular exploration in more relevant exposure models.

Photodynamic disinfection and its role in controlling infectious diseases

Photodynamic therapy is witnessing a revival of its origins as a response to the rise of multi-drug resistant infections and the shortage of new classes of antibiotics. Photodynamic disinfection (PDDI) of microorganisms is making progresses in preclinical models and in clinical cases, and the perception of its role in the clinical armamentarium for the management of infectious diseases is changing. We review the positioning of PDDI from the perspective of its ability to respond to clinical needs. Emphasis is placed on the pipeline of photosensitizers that proved effective to inactivate biofilms, showed efficacy in animal models of infectious diseases or reached clinical trials. Novel opportunities resulting from the COVID-19 pandemic are briefly discussed. The molecular features of promising photosensitizers are emphasized and contrasted with those of photosensitizers used in the treatment of solid tumors. The development of photosensitizers has been accompanied by the fabrication of a variety of affordable and customizable light sources. We critically discuss the combination between photosensitizer and light source properties that may leverage PDDI and expand its applications to wider markets. The success of PDDI in the management of infectious diseases will ultimately depend on the efficacy of photosensitizers, affordability of the light sources, simplicity of the procedures, and availability of fast and efficient treatments.

Mapping of UV-C dose and SARS-CoV-2 viral inactivation across N95 respirators during decontamination

During public health crises like the COVID-19 pandemic, ultraviolet-C (UV-C) decontamination of N95 respirators for emergency reuse has been implemented to mitigate shortages. Pathogen photoinactivation efficacy depends critically on UV-C dose, which is distance- and angle-dependent and thus varies substantially across N95 surfaces within a decontamination system. Due to nonuniform and system-dependent UV-C dose distributions, characterizing UV-C dose and resulting pathogen inactivation with sufficient spatial resolution on-N95 is key to designing and validating UV-C decontamination protocols. However, robust quantification of UV-C dose across N95 facepieces presents challenges, as few UV-C measurement tools have sufficient (1) small, flexible form factor, and (2) angular response. To address this gap, we combine optical modeling and quantitative photochromic indicator (PCI) dosimetry with viral inactivation assays to generate high-resolution maps of "on-N95" UV-C dose and concomitant SARS-CoV-2 viral inactivation across N95 facepieces within a commercial decontamination chamber. Using modeling to rapidly identify on-N95 locations of interest, in-situ measurements report a 17.4 ± 5.0-fold dose difference across N95 facepieces in the chamber, yielding 2.9 ± 0.2-log variation in SARS-CoV-2 inactivation. UV-C dose at several on-N95 locations was lower than the lowest-dose locations on the chamber floor, highlighting the importance of on-N95 dose validation. Overall, we integrate optical simulation with in-situ PCI dosimetry to relate UV-C dose and viral inactivation at specific on-N95 locations, establishing a versatile approach to characterize UV-C photoinactivation of pathogens contaminating complex substrates such as N95s.

Design of optical cavity for air sanification through ultraviolet germicidal irradiation

The transmission of airborne pathogens represents a major threat to worldwide public health. Ultraviolet light irradiation can contribute to the sanification of air to reduce the pathogen transmission. We have designed a compact filter for airborne pathogen inactivation by means of UVC LED sources, whose effective irradiance is enhanced thanks to high reflective surfaces. We used ray-tracing and computational fluid dynamic simulations to model the device and to maximize the performance inside the filter volume. Simulations also show the inhibition of SARS-Cov-2 in the case of high air fluxes. This study demonstrates that current available LED technology is effective for air sanification purposes.

COVID-19 and sunlight: Impact on SARS-CoV-2 transmissibility, morbidity, and mortality

Coronavirus disease 2019 (COVID-19) has already affected millions of people worldwide. There are reports of SARS-CoV-2 transmission as a consequence of environmental contamination. The SARS-CoV-2 laden infective droplets can actively persist on the surface of different materials for several hours to days. Sunlight can affect the stability of SARS-CoV-2 in these aerosols and thereby have an impact on the decay rate of the virus. Solar radiation might play an important role in inactivating SARS-CoV-2 that persists in different surfaces and the environment. Among the different climatological factors, ultraviolet radiation was found to have an important role in determining the spread of SARS-CoV-2. Although ultraviolet radiation C (UVC), UVB, UVA, visible light, and infrared radiation possess germicidal properties, human CoVs including the recently emerged SARS-CoV-2 are inherently sensitive to UVC. However, the successful decontamination using other wavebands requires higher dosages and longer administration times. Furthermore, studies have also identified association between COVID-19 fatalities and the latitude. The intensity of sunlight is highest near the equator, and therefore populations in these regions with more regular exposure to sunlight are less susceptible to vitamin D deficiency. This article has analyzed the potential impact of sunlight in reducing SARS-CoV-2 transmissibility, morbidity, and mortality. It is evident that there exists an interesting link between sunlight exposure, latitude, and vitamin D status with COVID-19 incidence, fatality and recovery rates that requires further investigation.

SARS-CoV-2, hemoglobin and protoporphyrin IX: Interactions and perspectives

Background

SARS-CoV-2 attacks hemoglobin through its structural protein ORF3a, dissociating the iron from the heme, as iron is necessary by cell machinery for virus replication. In this process protoporphyrin (PpIX) is released.

Methods

The decrease in the hemoglobin levels observed in patients with Covid-19 is frequently accompanied by an increase in PpIX levels. This evidence was confirmed by the quantification of PpIX by high-performance liquid chromatography (HPLC). PpIX emission is observed in its two characteristic bands at approximately 635 nm and 705 nm.

Results

This paper searches to understand the role of heme and PpIX inside the cells. Perspectives on the use of PpIX fluorescence as a sensor to monitor the presence of SARS-CoV-2 in the tissue, blood, urine, or feces to map the evolution and severity of the disease or to monitor the response of the Covid-19 treatment modalities were described.

Conclusion

Fluorescence spectroscopy could be adopted as an excellent diagnostic technique for Covid-19, of low cost and high sensitivity. This method can potentially be used as a marker to monitor the response to the treatments. Photodynamic and sonodynamic therapies using the endogenous PpIX increased in the acute phase of the disease, could be employed for Covid-19 treatment.

Guidelines for Reopening a Nation in a SARS-CoV-2 Pandemic: A Path Forward

Background and Objectives: Action, not fear, is the path forward in the coronavirus infectious disease 2019 (COVID-19) pandemic. Since early 2020, the world's nations have faced conundrums over severe acute respiratory syndrome corona virus type 2 (SARS-CoV-2) infections resulting in COVID-19 resulting in national closures, and thus, a clear understandable plan that nations can implement is required to reopen. The healthcare benefits of reopening a nation more likely than not exceed the benefits of continued pandemic-related closure. Pandemic-related closures have resulted in countless delayed or avoided urgent care evaluations. Furthermore, routine care of acute and chronic illnesses, including evaluations, diagnoses, and treatments, has also been delayed. Isolation, loss of income, and fear have resulted in mental health conditions or exacerbated existing conditions. The magnitude of untoward ramifications is unknown and may ultimately represent an inestimable degree of danger and morbidity, and even death. The pandemic of SARS-CoV-2 has created an atmosphere of fear of COVID-19 that has directly and indirectly injured the world's population. Since this has resulted in increasing morbidity and mortality, creating economic chaos, and near systemic collapse of educational systems with no well described plan forward, it is the purpose of this study to provide guidelines that provide a path forward to safely open a nation. Physicians often equipped by their education, training, and experiences across disciplines are uniquely positioned to comprehend, coordinate, and teach other physicians, business owners, and municipal and government leaders from guidelines. As such, physicians may take the lead in a path forward to reopening a nation, including opening businesses, educational facilities, and religious establishments, while minimizing the risk of SARS-CoV-2 infection. Materials and Methods: Reviews of the literature among the disciplines of environmental air, sanitation, social interaction, medical testing, vaccination, protection, and disease prevention and safety allowed for the conceptualization and eventual genesis of identifiable interventions which either reduce the viral load in the environment or inactivate the virus from replication. Each of the guidelines was selected based on the principle that it involved the elimination or inactivation of the viral particle. With a reduction in viral load or inactivation of replication, the implementation of these guidelines is expected to allow for reopening a nation with an increased level of safety. Results: The guidelines identified, including air exchange (ventilation), air filtration, personal protective filtering devices (masks), hand hygiene, social distancing, screening and testing, vaccines, high-risk patient protection, medical management, and adjunctive therapies, are described and referenced. Conclusions: In that the pandemic is primarily a public health issue, the path forward is best coordinated by local, regional, and national physicians. Many physicians with a breadth of experiences are uniquely positioned to coordinate the implementation of these interdisciplinary guidelines. Using these guidelines as a planned, coordinated action, not fear, is a path forward. Nations have a decision to make: closuring versus opening.

The Photosensitizer Octakis(cholinyl)zinc Phthalocyanine with Ability to Bind to a Model Spike Protein Leads to a Loss of SARS-CoV-2 Infectivity In Vitro When Exposed to Far-Red LED

Photodynamic inactivation of pathogenic microorganisms can be successfully used to eradicate pathogens in localized lesions, infected liquid media, and on various surfaces. This technique utilizes the photosensitizer (PS), light, and molecular oxygen to produce reactive oxygen species that kill pathogens. Here, we used the PS, water soluble octakis(cholinyl)zinc phthalocyanine (Zn-PcChol8+), to inactivate an initial 4.75-5.00 IgTCID50/mL titer of SARS-CoV-2, thereby preventing viral infection when tested in Vero E6 cell cultures. Zn-PcChol8+ in a minimally studied concentration, 1 µM and LED 3.75 J/cm2, completely destroyed the infectivity of SARS-CoV-2. To detect possible PS binding sites on the envelope of SARS-CoV-2, we analyzed electrostatic potential and simulated binding of Zn-PcChol8+ to the spike protein of this coronavirus by means of Brownian dynamics software, ProKSim (Protein Kinetics Simulator). Most of the Zn-PcChol8+ molecules formed clusters at the upper half of the stalk within a vast area of negative electrostatic potential. Positioning of the PS on the surface of the spike protein at a distance of no more than 10 nm from the viral membrane may be favorable for the oxidative damage. The high sensitivity of SARS-CoV-2 to photodynamic inactivation by Zn-PcChol8+ is discussed with respect to the application of this PS to control the spread of COVID-19.

Photobiomodulation und COVID-19

Die Zahl hochrangiger Publikationen zur Photobiomodulation steigt weltweit überproportional an und es ist daher auch leicht nachvollziehbar, dass die Therapieoption auch bei der Behandlung von COVID-19 als komplementäres Verfahren zur Pandemiebekämpfung methodisch erweitert und getestet werden soll. Um den gegenwärtigen Stand des Wissens zur Thematik zu erheben, wurde eine aktuelle Recherche zu klinischen laufenden Forschungsprojekten und den ersten vorliegenden Ergebnissen initiiert. Seitens der gewählten Methode wurde dabei die Variante einer möglichen selbst durchführbaren „Heim-Behandlung“ in den Fokus der Recherche gestellt. Drei aktuelle Studiendesigns sollen in diesem Übersichtsreport näher beschrieben und diskutiert werden. Die drei beschriebenen Studienvorhaben entsprechen zwar nicht alle den seitens einer „good scientific practice“ notwendigen Anforderungen, sollen aber dennoch aufgrund der Aktualität hier kurz vorgestellt werden. Wenngleich die Designs durchaus wissenschaftlich beurteilbare Ergebnisse erwarten lassen, kann derzeit (noch) kein wissenschaftlicher Schluss gezogen werden, dass sich die drei Verfahren zur Behandlung von COVID-19 als geeignet erweisen. Gründe dafür sind, dass bei zwei der drei Studien noch keine Ergebnisse vorliegen und eine Pilotstudie grobe formale wissenschaftliche Mängel aufweist, die es gilt, in Folgeuntersuchungen zu vermeiden.

Investigating the Potential for Ultraviolet Light to Modulate Morbidity and Mortality From COVID-19: A Narrative Review and Update

During the COVID-19 (coronavirus disease of 2019) pandemic, researchers have been seeking low-cost and accessible means of providing protection from its harms, particularly for at-risk individuals such as those with cardiovascular disease, diabetes and obesity. One possible way is via safe sun exposure, and/or dietary supplementation with induced beneficial mediators (e.g., vitamin D). In this narrative review, we provide rationale and updated evidence on the potential benefits and harms of sun exposure and ultraviolet (UV) light that may impact COVID-19. We review recent studies that provide new evidence for any benefits (or otherwise) of UV light, sun exposure, and the induced mediators, vitamin D and nitric oxide, and their potential to modulate morbidity and mortality induced by infection with SARS-CoV-2 (severe acute respiratory disease coronavirus-2). We identified substantial interest in this research area, with many commentaries and reviews already published; however, most of these have focused on vitamin D, with less consideration of UV light (or sun exposure) or other mediators such as nitric oxide. Data collected to-date suggest that ambient levels of both UVA and UVB may be beneficial for reducing severity or mortality due to COVID-19, with some inconsistent findings. Currently unresolved are the nature of the associations between blood 25-hydroxyvitamin D and COVID-19 measures, with more prospective data needed that better consider lifestyle factors, such as physical activity and personal sun exposure levels. Another short-coming has been a lack of measurement of sun exposure, and its potential to influence COVID-19 outcomes. We also discuss possible mechanisms by which sun exposure, UV light and induced mediators could affect COVID-19 morbidity and mortality, by focusing on likely effects on viral pathogenesis, immunity and inflammation, and potential cardiometabolic protective mechanisms. Finally, we explore potential issues including the impacts of exposure to high dose UV radiation on COVID-19 and vaccination, and effective and safe doses for vitamin D supplementation.

Antimicrobial blue light and photodynamic therapy inhibit clinically relevant β-lactamases with extended-spectrum (ESBL) and carbapenemase activity

INTRODUCTION

The production of β-lactamases by Gram-negative bacteria is among the most important factors of resistance to antibiotics, which has contributed to therapeutic failures that currently threaten human and veterinary medicine worldwide. Antimicrobial photodynamic therapy and antimicrobial blue light have a broad-spectrum antibacterial activity against multidrug-resistant and hypervirulent pathogens.

OBJECTIVE

To investigate the ability of antimicrobial blue light to inhibit the hydrolytic activity of clinically relevant β-lactamase enzymes (i.e., KPC, IMP, OXA, CTX-M, and SHV), with further comparison of the inhibitory effects of antimicrobial blue light with methylene blue-mediated antimicrobial photodynamic therapy.

METHODS

Blue LED light (λ = 410 ± 10 nm) alone or red LED light (λ = 660 ± 10 nm) in combination with methylene blue were used to inactivate, in vitro, suspensions of Klebsiella pneumoniae strains producing clinically important β-lactamase enzymes assigned to the A, B and D Ambler molecular classes. Furthermore, β-lactamase activity inhibition mediated by antimicrobial blue light and methylene blue-mediated antimicrobial photodynamic therapy was measured by using the chromogenic β-lactam substrate nitrocefin.

RESULTS

β-lactamase activities were effectively inactivated by both visible light-based approaches. In this regard, antimicrobial blue light and methylene blue-antimicrobial photodynamic therapy led to a significant reduction in the hydrolysis of nitrocefin (81-98 %).

CONCLUSION

Sublethal doses of antimicrobial blue light and methylene blue-mediated antimicrobial photodynamic therapy are equally effective to inhibit clinically significant β-lactamases, including extended-spectrum β-lactamases and carbapenemases.