Optimal environmental sampling conditions for electrostatic aerosol-to-hydrosol collection of airborne viruses.

Due to adverse effects of viral outbreaks on human health, accurate detection of airborne pathogens is essential. Among many methods available for bioaerosol sampling, electrostatic precipitation (ESP) has been used to directly collect bioaerosols as hydrosols. The performance of an ESP sampler depends on its design, operational and environmental parameters such as air relative humidity (RH), air temperature, sampling liquid type and liquid temperature. Thus, it is essential to identify and maintain optimal conditions throughout sampling process to operate the sampler at its highest capacity. This study provides crucial insights into parameters that affect the collection efficiency of the aerosol-to-hydrosol ESP sampler and its virus recovery. The results indicate that air temperature does not affect collection efficiency, meanwhile, air RH, sampling liquid temperature, and salt concentration are the main parameters that significantly affect collection efficiency. Likewise, when deionized water is used as sampling liquid, hydrogen peroxide concentration increases proportionally with increasing air RH, resulting in significant decrease of virus viability. Consequently, for ESP samplers similar to our study, the following conditions are recommended: air RH of 55-65%, air and sampling liquid temperature of 37 °C, and a mixture of 10-20 mM ascorbic acid in PBS as sampling liquid.

Determination of airborne influenza virus and coronavirus infectivity using capsid integrity polymerase chain reaction.

Accurate airborne virus monitoring is important for preventing the spread of infectious diseases. Although standard reverse transcription-quantitative polymerase chain reaction (RT-qPCR) can efficiently detect viral ribonucleic acid (RNA), it cannot determine whether the RNA is associated with active (infectious) or inactive (non-infectious) viruses. Plaque assay is the gold standard for determining viral infectivity but is laborious and time-consuming. This study explored the viral infectivity of H1N1 influenza virus and human coronavirus (HCoV-229E) using capsid integrity RT-qPCR, where virus samples were pretreated with reagents penetrating viruses with damaged capsids, impeding amplification by binding to their RNA. Therefore, the amplified signals corresponded solely to active viruses with undamaged capsids. Propidium monoazide (PMA) and platinum (IV) chloride (PtCl4) were used to investigate the effects of reagent concentration. Feasibility tests revealed that PtCl4 was more efficient than PMA, with optimal concentrations of 125-250 µM and 250-500 µM for H1N1 influenza virus and HCoV-229E, respectively. The results of percentage of active virus showed that capsid integrity RT-qPCR provided a trend similar to that of plaque assay, indicating an accurate measure of viral infectivity. Virus sampling in the laboratory and field highlighted the precision of this methodology for determining viral infectivity. Therefore, this methodology enables rapid and accurate detection of infectious airborne H1N1 influenza virus and HCoV-229E, allowing swift response to outbreaks.

Air sampling and simultaneous detection of airborne influenza virus via gold nanorod-based plasmonic PCR.

Reliable and sensitive virus detection is essential to prevent airborne virus transmission. The polymerase chain reaction (PCR) is one of the most compelling and effective diagnostic techniques for detecting airborne pathogens. However, most PCR diagnostics rely on thermocycling, which involves a time-consuming Peltier block heating methodology. Plasmonic PCR is based on light-driven photothermal heating of plasmonic nanostructures to address the key drawbacks of traditional PCR. This study introduces a methodology for plasmonic PCR detection of air-sampled influenza virus (H1N1). An electrostatic air sampler was used to collect the aerosolized virus in a carrier liquid for 10 min. Simultaneously, the viruses collected in the liquid were transferred to a tube containing gold (Au) nanorods (aspect ratio = 3.6). H1N1 viruses were detected in 12 min, which is the total time required for reverse transcription, fast thermocycling via plasmonic heating through gold nanorods, and in situ fluorescence detection. This methodology showed a limit of detection of three RNA copies/µL liquid for H1N1 influenza virus, which is comparable to that of commercially available PCR devices. This methodology can be used for the rapid and precise identification of pathogens on-site, while significantly reducing the time required for monitoring airborne viruses.

Application of a magnetically separable Zr-MOF for fast extraction of palladium before its spectrophotometric detection.

In this research, a novel magnetic zirconium-based metal-organic framework (Fe3O4@SiO2@MIP-202, MMOF), was fabricated, fully characterized, and applied for the batch-mode solid phase extraction of trace amounts of Pd2+ ions from water and wastewater samples before its spectrophotometric detection. Pd2+ ions were desorbed from MMOF by nitric acid and were complexed by treating with KI solution to have a maximum absorbance at 410 nm. The synthesized MMOF composite showed a very large surface area (65 m2.g- 1), good magnetization (1.7 emu.g- 1) and a large pore volume (0.059 cm3.g- 1) with adsorption capacity of 194.5 mg of Pd2+ ions/g of the adsorbent. This nanosorbent boasts chemo-mechanical stability, high adsorption capacity due to its vast active sites, and facile recovery facilitated by its magnetic properties. Parameters affecting the extraction efficiency of the method were optimized as pH of the sample 7.4, volume of the sample 25 mL, 15 mg adsorbent, 1 mL of 0.1 M HNO3 eluent, with 10 and 15 min as the extraction and desorption times, respectively. The calibration curve was found to be linear across the 10.0-1500.0 µg.L- 1 range with a limit of detection of 1.05 µg.L- 1. The obtained extraction efficiency and enrichment were 98% and 245, respectively. The total analysis time was less than 30 min. This MMOF has never been used for the extraction of Pd2+ ions before.

Enhanced enrichment of collected airborne coronavirus and influenza virus samples via a ConA-coated microfluidic chip for PCR detection.

The severe acute respiratory syndrome (SARS-CoV-2) outbreak triggered global concern and emphasized the importance of virus monitoring. During a seasonal influenza A outbreak, relatively low concentrations of 103-104 viral genome copies are available per 1 m3 of air, which makes detection and monitoring very challenging because the limit of detection of most polymerase chain reaction (PCR) devices is approximately 103 viral genome copies/mL. In response to the urgent need for the rapid detection of airborne coronaviruses and influenza viruses, an electrostatic aerosol-to-hydrosol (ATH) sampler was combined with a concanavalin A (ConA)-coated high-throughput microfluidic chip. The samples were then used for PCR detection. The results revealed that the enrichment capacity of the ATH sampler was 30,000-fold for both HCoV-229E and H1N1 influenza virus, whereas the enrichment capacities provided by the ConA-coated microfluidic chip were 8-fold and 16-fold for HCoV-229E and H1N1 virus, respectively. Thus, the total enrichment capacities of our combined ATH sampler and ConA-coated microfluidic chip were 2.4 × 105-fold and 4.8 × 105-fold for HCoV-229E and H1N1 virus, respectively. This methodology significantly improves PCR detection by providing a higher concentration of viable samples.

Aero-manufacture of nanobulges for an in-place anticoronaviral on air filters.

The interest in removing contagious viruses from indoor air using ventilation and filtration systems is increasing rapidly because people spend most of the day indoors. The development of an effective platform to regenerate the antiviral function of air filters during use and safe abrogation of used filters containing infectious viruses is a challenging task, because an on-demand safe-by-design manufacture system is essential for in-place antiviral coatings, but it has been rarely investigated. With these considerations, an electrically operable dispenser was prepared for decorating continuous ultrafine Fe-Zn, Fe-Ag, or Fe-Cu particles (<5 nm) onto SiO2 nanobeads (ca. 130 nm) to form nanobulges (i.e., nanoroughness for engaging coronavirus spikes) in the aerosol state for 3 min direct deposition on the air filter surfaces. The resulting nanobulges were exposed to human coronaviruses (HCoV; surrogates of SARS-CoV-2) to assess antiviral function. The results were compared with similar-sized individual Zn, Ag, and Cu particles. The nanobulges exhibited comparable antiviral activity to Zn, Ag, and Cu particles while retaining biosafety in both in vitro and in vivo models because of the significantly smaller metallic fractions. This suggests that the bimetallic bulge structures generate reactive oxygen species and Fenton-mediated hydroxyl radicals for inactivating HCoV.

Effects of nanosized water droplet generation on number concentration measurement of virus aerosols when using an airblast atomizer.

Development of efficient virus aerosol monitoring and removal devices requires aerosolization of the test virus using atomizers. The number concentration and size measurements of aerosolized virus particles are required to evaluate the performance of the devices. Although diffusion dryers can remove water droplets generated using atomizers, they often fail to remove them entirely from the air stream. Consequently, particle measurement devices, such as scanning mobility particle sizer (SMPS), can falsely identify the remaining nanosized water droplets as virus aerosol particles. This in turn affects the accuracy of the evaluation of devices for sampling or removing virus aerosol particles. In this study, a plaque-forming assay combined with SMPS measurement was used to evaluate sufficient drying conditions. We proposed an empirical equation to determine the total number concentration of aerosolized particles measured using the SMPS as a function of the carrier air flow rate and residence time of the particles in the diffusion dryers. The difference in the total number concentration of particles under sufficient and insufficient diffusion drying conditions was presented as a percentage of error.

Chromium-based metal organic framework for pipette tip micro-solid phase extraction: an effective approach for determination of methyl and propyl parabens in wastewater and shampoo samples.

BACKGROUND: A chromium-based metal organic framework was synthesized and employed as an efficient sorbent for pipette tip micro-solid phase extraction and preconcentration of parabens from wastewater and shampoo samples up to sub-ppb level before their spectrophotometric analysis. RESULTS: Factors affecting preconcentration including volume and type of solvent, amount of sorbent, number of extraction, and volume and pH of samples were optimized employing one-variable-at-a-time and response surface methodology. Obtained analytical characteristics of the method proves its usefulness for analysis of real samples. Linear range of the method for parabens was 1.0-200.0 µg/L. Detection limit of the protocol was 0.24 µg/L for propyl paraben and 0.25 µg/L for methyl paraben. Reproducibility of the protocol defined as % RSD was better than 5.78%. Synthesized adsorbent can be re-used for at least 20 extractions. CONCLUSION: The method showed a good detection limit and precision for determination of methyl- and propyl-paraben in wastewater and shampoo samples.

Increased survivability of coronavirus and H1N1 influenza virus under electrostatic aerosol-to-hydrosol sampling.

Airborne virus susceptibility is an underlying cause of severe respiratory diseases, raising pandemic alerts worldwide. Following the first reports of the novel severe acute respiratory syndrome coronavirus-2 in 2019 and its rapid spread worldwide and the outbreak of a new highly variable strain of influenza A virus (H1N1) in 2009, developing quick, accurate monitoring and diagnostic approaches for emerging infections is considered critical. Efficient air sampling of coronaviruses and the H1N1 virus allows swift, real-time identification, triggering early adjuvant interventions. Electrostatic precipitation is an efficient method for sampling bio-aerosols as hydrosols; however, sampling conditions critically impact this method. Corona discharge ionizes surrounding air, generating reactive oxygen species (ROS), which may impair virus structural components, leading to RNA and/or protein damage and preventing virus detection. Herein, ascorbic acid (AA) dissolved in phosphate-buffered saline (PBS) was used as the sampling solution of an electrostatic sampler to counteract virus particle impairment, increasing virus survivability throughout sampling. The findings of this study indicate that the use of PBS+AA is effective in reducing the ROS damage of viral RNA by 95%, viral protein by 45% and virus yield by 60%.

Determination of Air Filter Anti-Viral Efficiency against an Airborne Infectious Virus.

Recently, various studies have reported the prevention and treatment of respiratory infection outbreaks caused by lethal viruses. Consequently, a variety of air filters coated with antimicrobial agents have been developed to capture and inactivate virus particles in continuous airflow conditions. However, since aerosolized infectious viral-testing is inadvisable due to safety concerns, their anti-viral capability has only been tested by inserting the filters into liquid media, where infectious virus particles disperse. In this study a novel method of determining anti-viral performance of an air filter against airborne infectious viruses is presented. Initially, anti-viral air filter tests were conducted. Firstly, by an air-media test, in which the air filter was placed against an aerosolized non-infectious virus. Secondly, by a liquid-media test, in which the filter was inserted into a liquid medium containing a non-infectious virus. Subsequently, a correlation was established by comparing the susceptibility constants obtained between the two medium tests and an association was found for the air medium test with infectious virus. After ensuring the relationship did not depend on the virus species, the correlation was used to derive the results of the air-medium test from the results of the liquid-medium test.

Prevention of damage caused by corona discharge-generated reactive oxygen species under electrostatic aerosol-to-hydrosol sampling.

Human exposure to airborne pathogens is a major cause of health concerns; therefore, it is imperative to monitor, sample, and detect airborne bio-particles. Among various bio-aerosol sampling methods, electrostatic precipitation (EP) is an efficient technique for capturing bio-aerosols as hydrosols due to a lower pressure drop and less damage to sensitive bio-particles. Corona discharge is the main EP mechanism; however, this inevitably generates reactive oxygen species (ROS), which can be transported and dissolved in the sampling liquid. ROS can modify cellular component structures and damage DNA. Additionally, during the sampling process, the liquid flow rate and sampling liquid type can highly affect sampling efficiency. Here, different liquid types and flow rates are examined and ascorbic acid (AA), known as vitamin C, is added to prevent bio-particle damage. However, a high AA concentration can cause oxidative damage. Therefore, the optimal AA concentration should be chosen to obtain the greatest protective effect.

On the prediction of critical micelle concentration for sugar-based non-ionic surfactants.

Micellization phenomenon occurs in natural and technical processes, necessitating the need to develop predictive models capable of predicting self-assembly behavior of surfactants. A least squares support vector machine (LSSVM) based quantitative structure property relationships (QSPR) model is developed in order to predict critical micelle concentration (CMC) for sugar-based surfactants. Model development is based on training and validating a predictive LSSVM strategy using a comprehensive data base consisting of 83 sugar-based surfactants. Model's reliability and robustness has been evaluated using different visual and statistical parameters, revealing its great predictive capabilities. Results are also compared to previously reported best multi-linear regression (BMLR) based QSPR and group contribution based models, showing better performance of the proposed LSSVM-based QSPR model regarding lower RMSE value of 0.023 compared to the group contribution based and the best results from BMLR-based QSPR.