Chargeability study of disinfectants and the optimization of design parameters of a handheld electrostatic disinfection device for small scale applications.

Apart from aerosols, contaminated surfaces with SARS-CoV-2 virus are the significant carriers of virus transmission. The disinfection and sanitization of the indoor and outdoor places are one among the powerful and effective strategies to avoid the surface-to-human transmission of SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) through frequent touch and physical contact. Electrostatic spraying is one of the effective and efficient methods to apply the liquid-based sprays on surfaces to be disinfected or sanitized. This technique covers the directly exposed and obscured surfaces uniformly and reaches to hidden areas of the target. In this paper, the design and performance parameters of a motorized pressure-nozzle based handheld electrostatic disinfection device were optimized and the chargeability of ethanol (C2H5OH), formaldehyde (CH2O), glutaraldehyde (C5H8O2), hydrogen peroxide (H2O2), phenol (C6H5OH) and sodium hypochlorite (NaClO) has been critically investigated. The chargeability indicator for disinfectants was presented in terms of the charge-to-mass ratio. The significant value of the charge-to-mass ratio of 1.82 mC/kg was achieved at an applied voltage of 2.0 kV, the liquid flow rate and pressure of 28 ml/min and 5 MPa, respectively. The experimental results are well aligned to the proposed theoretical context.

The Impact of Serum Levels of Reactive Oxygen and Nitrogen Species on the Disease Severity of COVID-19.

Elucidation of the redox pathways in severe coronavirus disease 2019 (COVID-19) might aid in the treatment and management of the disease. However, the roles of individual reactive oxygen species (ROS) and individual reactive nitrogen species (RNS) in COVID-19 severity have not been studied to date. The main objective of this research was to assess the levels of individual ROS and RNS in the sera of COVID-19 patients. The roles of individual ROS and RNS in COVID-19 severity and their usefulness as potential disease severity biomarkers were also clarified for the first time. The current case-control study enrolled 110 COVID-19-positive patients and 50 healthy controls of both genders. The serum levels of three individual RNS (nitric oxide (NO•), nitrogen dioxide (ONO-), and peroxynitrite (ONOO-)) and four ROS (superoxide anion (O2•-), hydroxyl radical (•OH), singlet oxygen (1O2), and hydrogen peroxide (H2O2)) were measured. All subjects underwent thorough clinical and routine laboratory evaluations. The main biochemical markers for disease severity were measured and correlated with the ROS and RNS levels, and they included tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), the neutrophil-to-lymphocyte ratio (NLR), and angiotensin-converting enzyme 2 (ACE2). The results indicated that the serum levels of individual ROS and RNS were significantly higher in COVID-19 patients than in healthy subjects. The correlations between the serum levels of ROS and RNS and the biochemical markers ranged from moderate to very strongly positive. Moreover, significantly elevated serum levels of ROS and RNS were observed in intensive care unit (ICU) patients compared with non-ICU patients. Thus, ROS and RNS concentrations in serum can be used as biomarkers to track the prognosis of COVID-19. This investigation demonstrated that oxidative and nitrative stress play a role in the etiology of COVID-19 and contribute to disease severity; thus, ROS and RNS are probable innovative targets in COVID-19 therapeutics.

Paper-based colorimetric detection of COVID-19 using aptasenor based on biomimetic peroxidase like activity of ChF/ZnO/CNT nano-hybrid.

Corona Virus Disease 2019 (COVID-19) as the infectious disease caused the pandemic disease around the world through infection by SARS-CoV-2 virus. The common diagnosis approach is Quantitative RT-PCR (qRT-PCR) which is time consuming and labor intensive. In the present study a novel colorimetric aptasensor was developed based on intrinsic catalytic activity of chitosan film embedded with ZnO/CNT (ChF/ZnO/CNT) on 3,3',5,5'-tetramethylbenzidine (TMB) substrate. The main nanocomposite platform was constructed and functionalized with specific COVID-19 aptamer. The construction subjected with TMB substrate and H2O2 in the presence of different concentration of COVID-19 virus. Separation of aptamer after binding with virus particles declined the nanozyme activity. Upon addition of virus concentration, the peroxidase like activity of developed platform and colorimetric signals of oxidized TMB decreased gradually. Under optimal conditions the nanozyme could detect the virus in the linear range of 1-500 pg mL and LOD of 0.05 pg mL. Also, a paper-based platform was used for set up the strategy on applicable device. The paper-based strategy showed a linear range between 50 and 500 pg mL with LOD of 8 pg mL. The applied paper based colorimetric strategy showed reliable results for sensitive and selective detection of COVID-19 virus with the cost-effective approach.

Endothelial dysfunction, oxidative stress and low-grade endotoxemia in COVID-19 patients hospitalised in medical wards.

BACKGROUND: Endothelial dysfunction, assessed by flow-mediated dilation (FMD), is related to poor prognosis in patients with COVID-19 pneumonia (CP). In this study, we explored the interplay among FMD, NADPH oxidase type 2 (NOX-2) and lipopolysaccharides (LPS) in hospitalised patients with CP, community acquired pneumonia (CAP) and controls (CT). METHODS: We enrolled 20 consecutive patients with CP, 20 hospitalised patients with CAP and 20 CT matched for sex, age, and main cardiovascular risk factors. In all subjects we performed FMD and collected blood samples to analyse markers of oxidative stress (soluble Nox2-derived peptide (sNOX2-dp), hydrogen peroxide breakdown activity (HBA), nitric oxide (NO), hydrogen peroxide (H2O2)), inflammation (TNF-α and IL-6), LPS and zonulin levels. RESULTS: Compared with controls, CP had significant higher values of LPS, sNOX-2-dp, H2O2,TNF-α, IL-6 and zonulin; conversely FMD, HBA and NO bioavailability were significantly lower in CP. Compared to CAP patients, CP had significantly higher levels of sNOX2-dp, H2O2, TNF-α, IL-6, LPS, zonulin and lower HBA. Simple linear regression analysis showed that FMD inversely correlated with sNOX2-dp, H2O2, TNF-α, IL-6, LPS and zonulin; conversely FMD was directly correlated with NO bioavailability and HBA. Multiple linear regression analysis highlighted LPS as the only predictor of FMD. CONCLUSION: This study shows that patients with COVID-19 have low-grade endotoxemia that could activate NOX-2, generating increased oxidative stress and endothelial dysfunction.

Evaluating the effect of gargling with hydrogen peroxide and povidone-iodine on salivary viral load of SARS-CoV-2: A pilot randomized clinical trial.

Background and Aim: This study evaluates the salivary viral load of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in hospitalized patients and outpatients before and after gargling with 1% hydrogen peroxide and 0.25% povidone-iodine in comparison with normal saline. Patients and Methods: This clinical trial was conducted on 120 participants with laboratory-confirmed coronavirus disease 2019 (COVID-19) in two groups: outpatients (n = 60) and hospitalized patients (n = 60). In each group, the patients were randomly divided into three subgroups of 20 based on their given mouthwash for gargling (hydrogen peroxide, povidone-iodine, or normal saline). Two saliva samples were taken from each patient: the first one before gargling and the second one 10 minutes after gargling 10 ml of the respected mouthwashes for 30 seconds. The TaqMan real-time polymerase chain reaction (PCR) amplification of SARS-CoV-2 was used to measure the viral load. Results: Saliva samples from 46% of patients were positive for coronavirus before gargling the mouthwashes. The percentage of patients with an initial positive saliva sample was significantly higher in the outpatient group (83.3%) than in the hospitalized group (5.4%) (P = 0.01). According to the findings, gargling any mouthwash similar to saline did not reduce the viral load (P > 0.05). Conclusion: The saliva of COVID-19 patients in the initial stage of the disease was more likely to contain SARS-CoV-2 than the saliva of the hospitalized patients. Gargling hydrogen peroxide or povidone-iodine did not reduce the salivary SARS-CoV-2 viral load.

Efficacy of mouthrinses in reducing oral SARS-COV-2 load: a review.

Accumulated evidence has shown that the oral cavity may be an important reservoir for SARS-CoV-2. Some authors have suggested that the use of mouthrinses could reduce SARS-CoV-2 viral load in the saliva. Thus, the aim of this review was to synthesize evidence about the efficacy of mouthrinses in reducing the salivary viral load of SARS-CoV-2. 2. Nine randomized controlled trials (RCTs) have investigated the efficacy of different mouthrinses in reducing salivary SARS-CoV-2 loads. Various active ingredients have been tested in these trials: 0.5%,1% and 2% povidone-iodine, 0.2% and 0.12% chlorhexidine (CHX), 0.075% cetylpyridinium chloride (CPC), 0.075% CPC with Zinc lactate, 1% and 1.5% hydrogen peroxide (HP), 1.5% HP + 0.12% CHX and ß-cyclodextrin and citrox. The studies reported an intra-group reduction in the salivary levels of the virus, when compared with the baseline. However, the majority of these trials failed to demonstrate a significant inter-group difference between active groups and the control group relative to the decrease in salivary SARS-CoV-2 loads. Although promising, these results should be confirmed by larger trials.

PdPtRu trimetallic nanozymes and application to electrochemical immunosensor for sensitive SARS-COV-2 antigen detection.

Herein, a ternary PdPtRu nanodendrite as novel trimetallic nanozyme was reported, which possessed excellent peroxidase-like activity as well as electro-catalytic activity on account of the synergistic effect between the three metals. Based on the excellent electro-catalytic activity of trimetallic PdPtRu nanozyme toward the reduction of H2O2, the trimetallic nanozyme was applied to construct a brief electrochemical immunosensor for SARS-COV-2 antigen detection. Concretely, trimetallic PdPtRu nanodendrite was used to modify electrode surface, which not only generated high reduction current of H2O2 for signal amplification, but also provided massive active sites for capture antibody (Ab1) immobilization to construct immunosensor. In the presence of target SARS-COV-2 antigen, SiO2 nanosphere labeled detection antibody (Ab2) composites were introduced on the electrode surface according sandwich immuno-reaction. Due to the inhibitory effect of SiO2 nanosphere on the current signal, the current signal was decreased with the increasing target SARS-COV-2 antigen concentration. As a result, the proposed electrochemical immunosensor presented sensitive detection of SARS-COV-2 antigen with linear range from 1.0 pg/mL to 1.0 µg/mL and limit of detection down to 51.74 fg/mL. The proposed immunosensor provide a brief but sensitive antigen detection tool for rapid diagnosis of COVID-19.

Electrochemical sensing of dual biomolecules in live cells and whole blood samples: A flexible gold wire-modified copper-organic framework-based hybrid composite.

For clinical research, the precise measurement of hydrogen peroxide (H2O2) and glucose (Glu) is of paramount importance, due to their imbalanced concentrations in blood glucose, and reactive oxygen species (ROS) play a huge role in COVID-19 viral disease. It is critical to construct and develop a simple, rapid, flexible, long-term, and sensitive detection of H2O2 and glucose. In this paper, we have developed a unique morphological structure of MOF(Cu) on a single-walled carbon nanotube-modified gold wire (swnt@gw). Highly designed frameworks with nanotube composites enhance electron rate-transfer behavior while extending conductance and electroactive surface area.The composite sensing system delivers wide linear-range concentrations, low detection limit, and interference-free performance in co-existence with other biomolecules and metal ions. Endogenous quantitative tracking of H2O2 was performed in macrophage live-cells with the help of a strong stimulator lipopolysaccharide.The composite device was effectively utilized for the measurement of H2O2 and glucose in turbid samples of whole blood and milk samples without a pretreatment process. The practical results of biofluids showed favorable voltammetric results and acceptance recovery percentage levels between 97.49 and 98.88%. Finally, a flexible MOF-based hybrid system may provide a suitable detection platform in the construction of electro-biosensors and hold potential promise for clinical-sensory applications.

A Direct Catalytic Ethanol Fuel Cell (DCEFC) Modified by LDHs, or by Catalase-LDHs, and Improvement in Its Kinetic Performance: Applications for Human Saliva and Disinfectant Products for COVID-19.

In this work, it has been experimentally proven that the kinetic performance of a common Direct Catalytic Ethanol Fuel Cell (DCEFC) can be increased by introducing nanostructured (ZnII,AlIII(OH)2)+NO3-·H2O Layered Double Hydroxides (LDHs) into the anode compartment. Carrying out the measurements with the open-circuit voltage method and using a kinetic format, it has been shown that the introduction of LDHs in the anodic compartment implies a 1.3-fold increase in the calibration sensitivity of the method. This improvement becomes even greater in the presence of hydrogen peroxide in a solution. Furthermore, we show that the calibration sensitivity increased by 8-times, when the fuel cell is modified by the enzyme catalase, crosslinked on LDHs and in the presence of hydrogen peroxide. The fuel cell, thus modified (with or without enzyme), has been used for analytical applications on real samples, such as biological (human saliva) and hand disinfectant samples, commonly used for the prevention of COVID-19, obtaining very positive results from both analytical and kinetic points of view on ethanol detection. Moreover, if the increase in the calibration sensitivity is of great importance from the point of view of analytical applications, it must be remarked that the increase in the speed of the ethanol oxidation process in the fuel cell can also be extremely useful for the purposes of improving the energy performance of a DCEFC.

Effects of 5α-dihydrotestosterone on the modulation of monocyte/macrophage response to Staphylococcus aureus: an in vitro study.

BACKGROUND: Staphylococcus aureus (S. aureus) is a pathogen responsible for a wide range of clinical manifestations and potentially fatal conditions. There is a paucity of information on the influence of androgens in the immune response to S. aureus infection. In this study, we evaluated the influence of the hormone 5α-dihydrotestosterone (DHT) on mouse peritoneal macrophages (MPMs) and human peripheral blood monocytes (HPBMs) induced by S. aureus. METHODS: An in vitro model of MPMs from BALB/c sham males, orchiectomised (OQX) males, and females was used. Cells were inoculated with 10 µL of S. aureus, phage-type 80 or sterile saline (control) for 6 h. The MPMs of OQX males and females were pre-treated with 100 µL of 10-2 M DHT for 24 h before inoculation with S. aureus. The concentration of the cytokines TNF-α, IL-1α, IL-6, IL-8, and IL-10; total nitrites (NO-2); and hydrogen peroxide (H2O2) were measured in the supernatant of MPM cultures. In addition, the toll-like receptor 2 (TLR2) and nuclear factor kappa B (NF-kB) genes that are involved in immune responses were analysed. For the in vitro model of HPBMs, nine men and nine women of childbearing age were selected and HPBMs were isolated from samples of the volunteers' peripheral blood. In women, blood was collected during the periovulatory period. The HPBMs were inoculated with S. aureus for 6 h and the supernatant was collected for the analysis of cytokines TNF-α, IL-6, IL-12; and GM-CSF, NO-2, and H2O2. The HPBMs were then removed for the analysis of 84 genes involved in the host's response to bacterial infections by RT-PCR array. GraphPad was used for statistical analysis with a p value < 0.05. RESULTS: Our data demonstrated that MPMs from sham males inoculated with S. aureus displayed higher concentrations of inflammatory cytokines and lower concentrations of IL-10, NO-2, and H2O2 when compared with MPMs from OQX males and females. A similar result was observed in the HPBMs of men when compared with those of women. Previous treatment with DHT in women HPBMs increased the production of pro-inflammatory cytokines and decreased the levels of IL-10, NO-2, and H2O2. The analysis of gene expression showed that DHT increased the activity of the TLR2 and NF-kB pathways in both MPMs and HPBMs. CONCLUSIONS: We found that DHT acts as an inflammatory modulator in the monocyte/macrophage response induced by S. aureus and females exhibit a better immune defence response against this pathogen.

Detection of SARS-CoV-2 receptor binding domain using fluorescence probe and DNA flowers enabled by rolling circle amplification.

Using rolling circle amplification (RCA) and two different ways of signal readout, we developed analytical methods to detect the receptor-binding domain (RBD) of SARS-CoV-2 spike protein (S protein). We modified streptavidin-coated magnetic beads with an aptamer of RBD through a biotin-tagged complementary DNA strand (biotin-cDNA). Binding of RBD caused the aptamer to dissociate from the biotin-cDNA, making the cDNA available to initiate RCA on the magnetic beads. Detection of RBD was achieved using a dual signal output. For fluorescence signaling, the RCA products were mixed with a dsDNA probe labeled with fluorophore and quencher. Hybridization of the RCA products caused the dsDNA to separate and to emit fluorescence (λex = 488 nm, λem = 520 nm). To generate easily detectable UV-vis absorbance signal, the RCA amplification was extended to produce DNA flower to encapsulate horseradish peroxidase (HRP). The HRP-encapsulated DNA flower catalyzed a colorimetric reaction between H2O2 and 3,3',5,5'-tetramethylbenzidine (TMB) to generate an optical signal (λabs = 450 nm). The fluorescence and colorimetric assays for RBD have low detection limits (0.11 pg mL-1 and 0.904 pg mL-1) and a wide linear range (0.001-100 ng mL-1). For detection of RBD in human saliva, the recovery was 93.0-100% for the fluorescence assay and 87.2-107% for the colorimetric assay. By combining fluorescence and colorimetric detection with RCA, detection of the target RBD in human saliva was achieved with high sensitivity and selectivity.

The effects of acute hydrogen peroxide exposure on respiratory cilia motility and viability.

COVID-19 has seen the propagation of alternative remedies to treat respiratory disease, such as nebulization of hydrogen peroxide (H2O2). As H2O2 has known cytotoxicity, it was hypothesised that H2O2 inhalation would negatively impact respiratory cilia function. To test this hypothesis, mouse tracheal samples were incubated with different H2O2 concentrations (0.1-1%) then cilia motility, cilia generated flow, and cell death was assessed 0-120 min following H2O2 treatment. 0.1-0.2% H2O2 caused immediate depression of cilia motility and complete cessation of cilia generated flow. Higher H2O2 concentrations (≥0.5%) caused immediate complete cessation of cilia motility and cilia generated flow. Cilia motility and flow was restored 30 min after 0.1% H2O2 treatment. Cilia motility and flow remained depressed 120 min after 0.2-0.5% H2O2 treatment. No recovery was seen 120 min after treatment with ≥1% H2O2. Live/dead staining revealed that H2O2 treatment caused preferential cell death of ciliated respiratory epithelia over non-ciliated epithelia, with 1% H2O2 causing 35.3 ± 7.0% of the ciliated epithelia cells to die 120 min following initial treatment. This study shows that H2O2 treatment significantly impacts respiratory cilia motility and cilia generated flow, characterised by a significant impairment in cilia motility even at low concentrations, the complete cessation of cilia motility at higher doses, and a significant cytotoxic effect on ciliated respiratory epithelial cells by promoting cell death. While this data needs further study using in vivo models, it suggests that extreme care should be taken when considering treating respiratory diseases with nebulised H2O2.

Susceptibility of SARS COV-2 nucleocapsid and spike proteins to reactive oxygen species and role in inflammation.

Chemiluminescence was used to test the susceptibility of the SARS-CoV-2 N and S proteins to oxidation by reactive oxygen species (ROS) at pH 7.4 and pH 8.5. The Fenton's system generates various ROS (H2O2, OH, -OH, OOH). All proteins were found to significantly suppress oxidation (the viral proteins exhibited 25-60% effect compared to albumin). In the second system, H2O2 was used both as a strong oxidant and as a ROS. A similar effect was observed (30-70%); N protein approached the effect of albumin at physiological pH (∼45%). In the O2.--generation system, albumin was most effective in the suppression of generated radicals (75%, pH 7.4). The viral proteins were more susceptible to oxidation (inhibition effect no more than 20%, compared to albumin). The standard antioxidant assay confirmed the strong antioxidant capacity of both viral proteins (1.5-1.7 fold higher than albumin). These results demonstrate the effective and significant inhibition of ROS-induced oxidation by the proteins. Obviously, the viral proteins could not be involved in the oxidative stress reactions during the course of the infection. They even suppress the metabolites involved in its progression. These results can be explained by their structure. Probably, an evolutionary self-defense mechanism of the virus has been developed.

Hydrogen peroxide emissions from surface cleaning in a single-family residence.

High levels of reactive chemicals may be emitted to the indoor air during household surface cleaning, leading to poorer air quality and potential health hazards. Hydrogen peroxide (H2O2)-based cleaners have gained popularity in recent years, especially in times of COVID-19. Still, little is known regarding the effects of H2O2 cleaning on indoor air composition. In this work we monitored time-resolved H2O2 concentrations during a cleaning campaign in an occupied single-family residence using a cavity ring-down spectroscopy (CRDS) H2O2 analyzer. During the cleaning experiments, we investigated how unconstrained (i.e., "real-life") surface cleaning with a hydrogen peroxide solution influenced the indoor air quality of the house, and performed controlled experiments to investigate factors that could influence H2O2 levels including surface area and surface material, ventilation, and dwell time of the cleaning solution. Mean peak H2O2 concentrations observed following all surface cleaning events were 135 ppbv. The factors with the greatest effect on H2O2 levels were distance of the cleaned surface from the detector inlet, type of surface cleaned, and solution dwell time.

Safety Assessment of the Modified Lactoperoxidase System-In Vitro Studies on Human Gingival Fibroblasts.

One strategy in caries prevention is to inhibit the formation of cariogenic biofilms. Attempts are being made to develop oral hygiene products enriched with various antimicrobial agents. One of them is lactoperoxidase-an enzyme that can oxidise (pseudo)halide ions to reactive products with antimicrobial activity. Currently, commercially available products utilise thiocyanate as a substrate; however, several alternatives that are oxidised to products with greater antimicrobial potential have been found. In this study, toxicity against human gingival fibroblasts of the lactoperoxidase system was evaluated using four different (pseudo)halide substrate systems-thiocyanate, iodide, selenocyanate, and a mixture of thiocyanate and iodide. For this purpose, cells were treated with the systems and then apoptosis, cell cycle, intracellular glutathione concentration, and mitochondrial superoxide production were assessed. The results showed that each system, after generating 250 µM of the product, inhibited cell divisions, increased apoptosis, and increased the percentage of dead cells. It was concluded that the mechanism of the observed phenomena was not related to increased superoxide production or the depletion of glutathione concentration. These findings emphasised the need for the further in vitro and in vivo toxicity investigation of the modified lactoperoxidase system to assess its safety and the possibility of use in oral hygiene products.

Decreased plasma H2O2 levels are associated with the pathogenesis leading to COVID-19 worsening and mortality.

Oxidative Stress (OS) is involved in the pathogenesis of COVID-19 and in the mechanisms by which SARS-CoV-2 causes injuries to tissues, leading to cytopathic hypoxia and ultimately multiple organ failure. The measurement of blood glutathione (GSH), H2O2, and catalase activity may help clarify the pathophysiology pathways of this disease. We developed and standardized a sensitive and specific chemiluminescence technique for H2O2 and GSH measurement in plasma and red blood cells of COVID-19 patients admitted to the intensive care unit (ICU). Contrary to what was expected, the plasma concentration of H2O2 was substantially reduced (10-fold) in COVID-19 patients compared to the healthy control group. From the cohort of patients discharged from the hospital and those who were deceased, the former showed a 3.6-fold and the later 16-fold H2O2 reduction compared to the healthy control. There was a 4.4 reduction of H2O2 concentration in the deceased group compared to the discharged group. Interestingly, there was no variation in GSH levels between groups, and reduced catalase activity was found in discharged and deceased patients compared to control. These data represent strong evidence that H2O2 is converted into highly reactive oxygen species (ROS), leading to the worst prognosis and death outcome in COVID-19 patients admitted to ICU. Considering the difference in the levels of H2O2 between the control group and the deceased patients, it is proposed the quantification of plasma H2O2 as a marker of disease progression and the induction of the synthesis of antioxidant enzymes as a strategy to reduce the production of oxidative stress during severe COVID-19.HighlightsH2O2 plasma levels is dramatically reduced in patients who deceased compared to those discharged and to the control group.Plasmatic quantification of H2O2 can be possibly used as a predictor of disease progression.Catalase activity is reduced in COVID-19.GSH levels remain unchanged in COVID-19 compared to the control group.

An ESIPT-based ratiometric fluorescent probe for detecting H2O2 in water environment and biosystems.

The outbreak of the COVID-19 has resulted in a great increase in the use of H2O2 disinfectant, which is listed as one of the commonly used disinfectants for COVID-19 by the U.S. Environmental Protection Agency. However, excessive use of H2O2 disinfectant can threaten human health and damage the water environment. Therefore, it's of great importance to detect H2O2 in aquatic environments and biological systems. Herein, we proposed a novel ESIPT ratio fluorescent probe (named probe 1) for detecting H2O2 in water environment and biosystems. Probe 1 emits blue fluorescence as the introduction of the phenylboronic acid disrupts the ESIPT process. After reacting with H2O2, the phenylboronic acid is oxidatively removed, and the ESIPT process is restored, which makes the fluorescence emission wavelength red-shifted. Probe 1 exhibited a short response time, high sensitivity, and a large Stokes shift to H2O2. Importantly, it has been successfully used to detect H2O2 not only in actual water samples, but also endogenous and exogenous H2O2 in living cells. The characteristics of probe 1 have a wide range of applications in environmental and biological systems.

Fingerprinting trimeric SARS-CoV-2 RBD by capillary isoelectric focusing with whole-column imaging detection.

Because the spike (S) protein of the severe acute respiratory syndrome coronavirus (SARS-CoV) is the immunodominant antigen, the S protein and its receptor-binding domain (RBD) are both targets currently to be genetically engineered for designing the broad-spectrum vaccine. In theory, the expressed protein exists as a set of variants that are roughly the same but slightly different, which depends on the protein expression system. The variants can be phenotypically manifested as charge heterogeneity. Here, we attempted to depict the charge heterogeneity of the trimeric SARS-CoV-2 RBD by using capillary isoelectric focusing with whole-column imaging detection (cIEF-WCID). In its nature form, the electropherogram fingerprints of the trimeric RBD were presented under optimized experimental conditions. The peaks of matrix buffers can be fully distinguishable from peaks of trimeric RBD. The isoelectric point (pI) was determined to be within a range of 6.67-9.54 covering the theoretical pI of 9.02. The fingerprints of three batches of trimeric RBDs are completely the same, with the intra-batch and batch-to-batch relative standard deviations (RSDs) of both pI values and area percentage of each peak no more than 1.0%, indicating that the production process is stable and this method can be used to surveillance the batch-to-batch consistency. The fingerprint remained unchanged after incubating at 37 °C for 7 d and oxidizing by 0.015% H2O2. In addition, the fingerprint was destroyed when adjusting the pH value to higher than 10.0 but still stable when the pH was lower than 4.0. In summary, the cIEF-WCID fingerprint can be used for the identification, batch-to-batch consistency evaluation, and stability study of the trimeric SARS-CoV-2 RBD, as part of a quality control strategy during the potential vaccine production.

Dual-Gene-Controlled Rolling Circle Amplification Strategy for SARS-CoV-2 Analysis.

The development of sensitive, accurate, and conveniently operated methods for the simultaneous assay of two nucleic acids is promising while still challenging. In this work, by using two genes (the N gene and RdRp gene) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as examples, we have designed an ingenious dual-gene-controlled rolling circle amplification (RCA) strategy to propose an accurate and sensitive electrochemical method. Specifically, the coexistence of the two target genes can trigger the RCA reaction to generate a number of repeated G-quadruplex (G4)-forming sequences. These sequences then switch into G4/hemin complexes with redox activity after the incubation of hemin, which can catalyze the TMB/H2O2 substrates to produce significantly enhanced current responses. Experimental results reveal that the proposed method exhibits satisfying feasibility and analytical performance, enabling the sensitive detection of SARS-CoV-2 in the range of 0.1-5000 pM, with the detection limit of 57 fM. Meanwhile, because only the simultaneous existence of the two target genes can effectively trigger the downstream amplification reaction, this method can effectively avoid false-positives and ensure specificity as well as accuracy. Furthermore, our method can distinguish the COVID-19 samples from healthy people, and the outcomes show a satisfying agreement with the results of RT-PCR, manifesting that our label-free dual-gene-controlled RCA strategy exhibits great possibility in clinical application.

Filtration performance, fit test and side effects of respiratory personal protective equipment following decontamination: Observations for user safety and comfort.

OBJECTIVE: While facing personal protective equipment (PPE) shortages during the COVID-19 pandemic, several institutions looked to PPE decontamination and reuse options. This study documents the effect of two hydrogen peroxide treatments on filtration efficiency and fit tests as well as the side effects for volunteers after the decontamination of N95 filtering facepiece respirators (FFRs). We also propose an efficient and large-scale treatment protocol that allows for the traceability of this protective equipment in hospitals during PPE shortages. METHODS: The effects of low-temperature hydrogen peroxide sterilization and hydrogen peroxide vapor (HPV) on two FFR models (filtration, decontamination level, residual emanation) were evaluated. Ten volunteers reported comfort issues and side effects after wearing 1h FFRs worn and decontaminated up to five times. RESULTS: The decontamination process does not negatively affect FFR efficiency, but repeated use and handling tend to lead to damage, limiting the number of times FFRs can be reused. Moreover, the recommended 24-h post-treatment aeration does not sufficiently eliminate residual hydrogen peroxide. Prolonged aeration time increased user comfort when using decontaminated FFRs. CONCLUSIONS: HPV and low-temperature hydrogen peroxide sterilization seem to be appropriate treatments for FFR decontamination when the PPE is reused by the same user. PPE decontamination and reuse methods should be carefully considered as they are critical for the comfort and safety of healthcare workers.