Amplification-Free Detection of SARS-CoV-2 Down to Single Virus Level by Portable Carbon Nanotube Biosensors.

The rapid and sensitive detection of trace-level viruses in a simple and reliable way is of great importance for epidemic prevention and control. Here, a multi-functionalized floating gate carbon nanotube field effect transistor (FG-CNT FET) based biosensor is reported for the single virus level detection of SARS-CoV-2 virus antigen and RNA rapidly with a portable sensing platform. The aptamers functionalized sensors can detect SARS-CoV-2 antigens from unprocessed nasopharyngeal swab samples within 1 min. Meanwhile, enhanced by a multi-probe strategy, the FG-CNT FET-based biosensor can detect the long chain RNA directly without amplification down to single virus level within 1 min. The device, constructed with packaged sensor chips and a portable sensing terminal, can distinguish 10 COVID-19 patients from 10 healthy individuals in clinical tests both by the RNAs and antigens by a combination detection strategy with an combined overall percent agreement (OPA) close to 100%. The results provide a general and simple method to enhance the sensitivity of FET-based biochemical sensors for the detection of nucleic acid molecules and demonstrate that the CNT FG FET biosensor is a versatile and reliable integrated platform for ultrasensitive multibiomarker detection without amplification and has great potential for point-of-care (POC) clinical tests.

Characterization and protein engineering of glycosyltransferases for the biosynthesis of diverse hepatoprotective cycloartane-type saponins in Astragalus membranaceus.

Although plant secondary metabolites are important source of new drugs, obtaining these compounds is challenging due to their high structural diversity and low abundance. The roots of Astragalus membranaceus are a popular herbal medicine worldwide. It contains a series of cycloartane-type saponins (astragalosides) as hepatoprotective and antivirus components. However, astragalosides exhibit complex sugar substitution patterns which hindered their purification and bioactivity investigation. In this work, glycosyltransferases (GT) from A. membranaceus were studied to synthesize structurally diverse astragalosides. Three new GTs, AmGT1/5 and AmGT9, were characterized as 3-O-glycosyltransferase and 25-O-glycosyltransferase of cycloastragenol respectively. AmGT1G146V/I variants were obtained as specific 3-O-xylosyltransferases by sequence alignment, molecular modelling and site-directed mutagenesis. A combinatorial synthesis system was established using AmGT1/5/9, AmGT1G146V/S and the reported AmGT8 and AmGT8A394F . The system allowed the synthesis of 13 astragalosides in Astragalus root with conversion rates from 22.6% to 98.7%, covering most of the sugar-substitution patterns for astragalosides. In addition, AmGT1 exhibited remarkable sugar donor promiscuity to use 10 different donors, and was used to synthesize three novel astragalosides and ginsenosides. Glycosylation remarkably improved the hepatoprotective and SARS-CoV-2 inhibition activities for triterpenoids. This is one of the first attempts to produce a series of herbal constituents via combinatorial synthesis. The results provided new biocatalytic tools for saponin biosynthesis.

Estimating the restraint of SARS-CoV-2 spread using a conventional medical air-cleaning device: Based on an experiment in a typical dental clinical setting.

OBJECTIVES: Droplets or aerosols loaded with SARS-CoV-2 can be released during breathing, coughing, or sneezing from COVID-19-infected persons. To investigate whether the most commonly applied air-cleaning device in dental clinics, the oral spray suction machine (OSSM), can provide protection to healthcare providers working in clinics against exposure to bioaerosols during dental treatment. METHOD: In this study, we measured and characterized the temporal and spatial variations in bioaerosol concentration and deposition with and without the use of the OSSM using an experimental design in a dental clinic setting. Serratia marcescens (a bacterium) and ΦX174 phage (a virus) were used as tracers. The air sampling points were sampled using an Anderson six-stage sampler, and the surface-deposition sampling points were sampled using the natural sedimentation method. The Computational Fluid Dynamics method was adopted to simulate and visualize the effect of the OSSM on the concentration spatial distribution. RESULTS: During dental treatment, the peak exposure concentration increased by up to 2-3 orders of magnitude (PFU/m3) for healthcare workers. Meanwhile, OSSM could lower the mean bioaerosol exposure concentration from 58.84 PFU/m3 to 4.10 PFU/m3 for a healthcare worker, thereby inhibiting droplet and airborne transmission. In terms of deposition, OSSM significantly reduced the bioaerosol surface concentration from 28.1 PFU/m3 to 2.5 PFU/m3 for a surface, effectively preventing fomite transmission. CONCLUSION: The use of OSSM showed the potential to restraint the spread of bioaerosols in clinical settings. Our study demonstrates that OSSM use in dental clinics can reduce the exposure concentrations of bioaerosols for healthcare workers during dental treatment and is beneficial for minimizing the risk of infectious diseases such as COVID-19.

Distribution of droplets/droplet nuclei from coughing and breathing of patients with different postures in a hospital isolation ward.

Suspected and confirmed cases of infectious diseases such as COVID-19 are diagnosed and treated in specific hospital isolation wards, posing a challenge to preventing cross-infection between patients and healthcare workers. In this study, the Euler-Lagrange method was used to simulate the evaporation and dispersion of droplets with full-size distribution produced by fluctuating coughing and breathing activities in an isolation ward. The effects of supply air temperature and relative humidity, ventilation rates and patient postures on droplet distribution were investigated. The numerical models were validated by an aerosol experiment with an artificial saliva solution containing E. coli bacteria conducted in a typical isolation ward. The results showed that the small size group of droplets (initial size ≤87.5 µm) exhibited airborne transmission in the isolation ward, while the large size group (initial size ≥112.5 µm) were rapidly deposited by gravitational effects. The ventilation rate had a greater effect on the diffusion of droplet nuclei than the supply air temperature and relative humidity. As the air changes per hour (ACH) increased from 8 to 16, the number fraction of suspended droplet nuclei reduced by 14.2% and 6.4% in the lying and sitting cases, respectively, while the number fraction of escaped droplet nuclei increased by 16.2% and 14.6%. Regardless of whether the patient was lying or sitting, the amount of droplet nuclei deposited on the ceiling was highest at lower ventilation rates. These results may provide some guidance for routine disinfection and ventilation strategies in hospital isolation wards.

Bioaerosol distribution characteristics and potential SARS-CoV-2 infection risk in a multi-compartment dental clinic.

Dental clinics have a potential risk of infection, particularly during the COVID-19 pandemic. Multi-compartment dental clinics are widely used in general hospitals and independent clinics. This study utilised computational fluid dynamics to investigate the bioaerosol distribution characteristics in a multi-compartment dental clinic through spatiotemporal distribution, working area time-varying concentrations, and key surface deposition. The infection probability of SARS-CoV-2 for the dental staff and patients was calculated using the Wells-Riley model. In addition, the accuracy of the numerical model was verified by field measurements of aerosol concentrations performed during a clinical ultrasonic scaling procedure. The results showed that bioaerosols were mainly distributed in the compartments where the patients were treated. The average infection probability was 3.8% for dental staff. The average deposition number per unit area of the treatment chair and table are 28729 pcs/m2 and 7945 pcs/m2, respectively, which creates a possible contact transmission risk. Moreover, there was a certain cross-infection risk in adjacent compartments, and the average infection probability for patients was 0.84%. The bioaerosol concentrations of the working area in each compartment 30 min post-treatment were reduced to 0.07% of those during treatment, and the infection probability was <0.05%. The results will contribute to an in-depth understanding of the infection risk in multi-compartment dental clinics, forming feasible suggestions for management to efficiently support epidemic prevention and control in dental clinics.

Influence of air supply velocity and room temperature conditions on bioaerosols distribution in a class I operating room

Surgical site infections (SSIs) have gained increasing prominence in recent decades. Bioaerosols are an important factor causing such intraoperative infections. Their distribution can be affected by environmental parameters in the operating room (OR), such as the air supply velocity and room temperature. The research object of this study was a Class I operating room, which has the strictest cleanliness requirements. Four different air supply velocities (0.16, 0.24, 0.29, and 0.33 m/s) and four different room temperatures (18 °C, 20 °C, 22 °C, and 24 °C) formed seven orthogonal experiment cases. The bioaerosols release experiments conducted in an environmental chamber to simulate a full-scale operating room. The experiments could well verify the computational fluid dynamics-based numerical simulation using the renormalization group (RNG) k-ε model as a turbulence model. The experimental and numerical results confirmed that an increase in the air supply velocity would increase the dispersion of bioaerosols particles. An air supply velocity greater than 0.24 m/s can ensure greater cleanliness in the surgical area. Whereas, when the air supply velocity continues to increase (0.33 m/s), it will increase the bioaerosols deposition in the surgical area. In terms of controlling the concentration of bioaerosols in a certain area, 0.24 m/s-0.29 m/s is the optimal range of air supply velocity. However, the distribution of bioaerosols particles is not sensitive to the response of OR room temperature changes.

Droplet aerosols transportation and deposition for three respiratory behaviors in a typical negative pressure isolation ward.

Negative pressure isolation wards could provide safety for health care workers (HCWs) and patients infected with SARS-CoV-2. However, respiratory behavior releases aerosols containing pathogens, resulting in a potential risk of infection for HCWs. In this study, the spatiotemporal distribution of droplet aerosols in a typical negative pressure isolation ward was investigated using a full-scale experiment. In this experiment, artificial saliva was used to simulate the breathing behavior, which can reflect the effect of evaporation on droplet aerosols. Moreover, numerical simulations were used to compare the transport of droplet aerosols released by the three respiratory behaviors (breathing, speaking, and coughing). The results showed that droplet aerosols generated by coughing and speaking can be removed and deposited more quickly. Because reduction in the suspension proportion per unit time was much higher than that in the case of breathing. Under the air supply inlets, there was significant aerosol deposition on the floor, while the breathing area possessed higher aerosol concentrations. The risk of aerosol resuspension and potential infection increased significantly when HCWs moved frequently to these areas. Finally, more than 20% of the droplet aerosols escaped from the ward when the number of suspended aerosols in the aerosol space was 1%.

The influence of air supply inlet location on the spatial-temporal distribution of bioaerosol in isolation ward under three mixed ventilation modes

The outbreak of COVID-19 and the spread of infectious pathogens through bioaerosols have once again aroused widespread concern worldwide. Isolation ward is an important place to prevent the spread of infectious bioaerosols. However, infection of health care workers (HCWs) in the isolation ward often occurs, so it is urgent to carry out relevant research to reduce the cross-infection between HCWs and patients. In this paper, the temporal and spatial distribution characteristics of bioaerosols under three mixed ventilation modes in a single ward were studied, namely, upper supply side return air of Case 1 and side supply and side return ventilation are Case 2 and Case 3 respectively. The results show that the removal efficiency of bioaerosol in the ventilation mode of Case 3, in which directional airflow is formed from the air supply inlet to the release source and then to the exhaust outlet, is 46.6% and 67.7% higher than that of Case 1 and Case 2, respectively. In addition, ventilation methods based on mixed theory do not guarantee good air quality in the breathing zone (1.3m to 1.7m) of HCWs, which may increase the inhalation risk for HCWs. It is hoped that our results can provide some useful suggestions for optimizing the airflow layout of the isolation ward, reducing the risk of cross-infection, and virus elimination.

AmAT19, an acetyltransferase from Astragalus membranaceus, catalyses specific 6α-OH acetylation for tetracyclic triterpenes and steroids.

Tetracyclic triterpenes and steroids are pharmacologically important molecules, and acetylation could improve their bioactivities. In this study, a highly regio- and stereo-specific acetyltransferase, AmAT19, was discovered from Astragalus membranaceus. AmAT19 could selectively catalyze the 6α-OH acetylation of four tetracyclic triterpenes and steroids. The strict selectivity is associated with different orientations of the 6α/ß-OH as indicated by molecular docking. Acetylated products 1a, 3a and 4a remarkably increased the inhibitory activity against the 3-chymotrypsin-like protease (3CLpro) of SARS-CoV-2, compared to 1, 3, and 4. AmAT19 could be a promising catalyst for specific 6α-OH acetylation to expand the molecular diversity of triterpenes and steroids.

Post-traumatic Growth and Related Influencing Factors in Discharged COVID-19 Patients: A Cross-Sectional Study.

The purpose of this study is to investigate the current state of post-traumatic growth (PTG) and identify its influencing factors in discharged COVID-19 patients. PTG refers to individual experiences of significant positive change arising from the struggle with a major life crisis. This descriptive cross-sectional study used the convenient sampling method to recruit 140 discharged COVID-19 patients in Hunan, China. The results show that the PTG of the discharged COVID-19 patients was positively correlated with self-esteem, post-traumatic stress disorder, coping style tendency, and social support, but negatively correlated with the time from onset to diagnosis. Our findings could provide guidance on improving the psychological state and well-being of discharged COVID-19 patients.

Clinical features and prognostic factors of patients with COVID-19 in Henan Province, China.

Since December 2019, the novel coronavirus SARS-CoV-2 pandemic (COVID-19) outbroke in Wuhan and spread in China. Here we aimed to investigate the clinical and radiological characteristics of COVID-19 cases. We collected and analyzed the clinical data of 172 hospitalized cases of COVID-19 who were diagnosed via qRT-PCR of nasopharyngeal swabs during January 2020 and February 2020. The chest images were reviewed by radiologists and respirologists. The older patients with COVID-19 in Henan Province had more severe disease and worse prognosis. The male sex, smoking history and Wuhan exposure of patients are not related to the severity or prognosis of COVID-19. Family gatherings were showed among 26.7% of patients. A greater proportion of patients in the severe group suffer from combined chronic diseases. CT results showed that most patients had bilateral lung lesions and multiple lung lobes. The lungs of severe patients are more damaged. Both the infection range and inflammatory factor levels are related to the poor prognosis. Antiviral drugs, immunoglobulin and traditional Chinese medicine are mainly used for the treatment of COVID-19 patients. The discharge rate of COVID-19 patients was 93.0%, and the mortality rate was 2.3%. Case type, lymphocyte ratio grade, and respiratory failure at admission are risk factors for poor prognosis, except for the number of infiltrating lung lobes. The results showed that severe disease process, lymphopenia and respiratory failure are risk factors for the COVID-19.

Changes in Neuroanesthesia Practice During the Early Stages of the COVID-19 Pandemic: Experiences From a Single Center in China.

BACKGROUND: Coronavirus disease 2019 (COVID-19), caused by a novel coronavirus, is highly contagious. Global medical systems have been heavily impacted by the COVID-19 pandemic. Although the majority of patients with intracranial disease require time-sensitive surgery, how to conduct neurosurgery and prevent and control nosocomial infection during a pandemic is challenging. MATERIALS AND METHODS: We retrospectively reviewed the clinical data of patients undergoing neurosurgical and neurointerventional procedures at Beijing Tiantan Hospital, China during the early stages of the COVID-19 pandemic between January 21 and July 31, 2020. A 3-level system of COVID-19 risk was established based on medical conditions, epidemiologic, and symptom inquiry and the results of triage. A transitional unit was established for patients in whom COVID-19 had not been ruled out on admission to hospital. RESULTS: A total of 4025 patients underwent neurosurgery during the study period, including 768 emergent and 3257 nonemergent procedures. Of these patients, 3722 were low-risk for COVID-19, 303 were moderate-risk, and none were high-risk. In addition, 1419 patients underwent neurointerventional procedures, including 114 emergent and 1305 nonemergent interventions, of which 1339 were low-risk patients, 80 were moderate-risk and none were high-risk. A total of 895 patients (neurosurgical and neurointerventional) were admitted to the transitional unit. Forty-five patients were diagnosed with COVID-19 and transferred to the COVID-19 designated hospital. There were no cases of COVID-19 nosocomial infections among surgical patients or health care workers. CONCLUSION: On the basis of our single-center experience, developing a full screening protocol for COVID-19, establishing a risk level, and using a transitional unit for those with unknown COVID-19 status are effective measures to provide a safe environment for patients and health care workers.