Aptamers dimerization inspired biomimetic clamp assay towards impedimetric SARS-CoV-2 antigen detection.

Antigen-detecting rapid diagnostic testing (Ag-RDT) has contributed to containing the spread of SARS-CoV-2 variants of concern (VOCs). In this study, we proposed a biomimetic clamp assay for impedimetric SARS-CoV-2 nucleocapsid protein (Np) detection. The DNA biomimetic clamp (DNA-BC) is formed by a pair of Np aptamers connected via a T20 spacer. The 5'- terminal of the DNA-BC is phosphate-modified and then anchored on the surface of the screen-printed gold electrode, which has been pre-coated with Au@UiO-66-NH2. The integrated DNA-material sensing biochip is fabricated through the strong Zr-O-P bonds to form a clamp-type impedimetric aptasensor. It is demonstrated that the aptasensor could achieve Np detection in one step within 11 min and shows pronounced sensitivity with a detection limit of 0.31 pg mL-1. Above all, the aptasensor displays great specificity and stability under physiological conditions as well as various water environments. It is a potentially promising strategy to exploit reliable Ag-RDT products to confront the ongoing epidemic.

Customization of aptamer to develop CRISPR/Cas12a-derived ultrasensitive biosensor.

The CRISPR/Cas systems have provided wide biosensing applications. Particularly, the aptamer-involved CRISPR/Cas sensor system powerfully expanded to non-nucleic-acid targets. However, tailoring the sequence of the aptamer to explore the relationship between affinity and the activation of CRISPR/Cas12a trans-cleavage activity has not been reported yet. Herein, we developed a series of new aptamers toward the spike protein 1(S1) of SARS-CoV-2. Surface plasmon resonance measurements showed that the affinity of these aptamers to S1 was at the nM level. Subsequently, a "SET" effect (Sequence Essential Trans-cleavage activity) is discovered for the activation of CRISPR/Cas12a trans-cleavage activity. That is, an aptamer, as the activator, sequence needs to be tailored to activate CRISPR/Cas12a efficiently. A balance should be reached between affinity and activation ability. On the one hand, high affinity ensures target recognition performance, and on the other hand, activation can achieve adequate amplification and output of recognition signals. The optimized sequence (with 27 nucleotides, for short 27-nt) not only recognizes the target with a high affinity and specificity but also can trigger the CRISPR/Cas12a trans-cleavage activity efficiently, showing an excellent detection performance in electrochemical biosensors. The detection limit for SARS-CoV-2 S1 can be low at 1.5 pg mL-1. The new CRISPR/Cas12a-derived aptasensor also displays a remarkable ability to detect Beta, Delta, and Omicron variants but is selective toward other kinds of proteins. Above all, it is robust for point-of-care testing (POCT) in complex biological fluids, such as saliva, urine, and serum, and provides a universal and scalable detecting platform. Our results provide new insights into aptamer development and a different strategy for COVID-19 antigen detection and biosensor development.

Psychological Impact and Workload of COVID-19 on Healthcare Workers in China During the Early Time of the Pandemic: A Cross-sectional Study.

OBJECTIVE: This study aimed to investigate the organization, workload, and psychological impact of COVID-19 on healthcare workers from the domestic Medical Aid Teams (MATs) sent to Wuhan in China. METHODS: Leaders and members of MATs involved in the care for COVID-19 patients were invited to participate in a study by completing 2 separate self-report questionnaires from April 1 to 24, 2020. RESULTS: A total of 9 MAT leaders were involved and 464 valid questionnaires were collected from 140 doctors and 324 nurses. Mean age of the doctors and nurses were 39.34 ± 6.70 (26∼58 years old) and 31.88 ± 5.29 (21∼52 years old), with 72 (15.5%) being males. Nurses were identified as an independent risk factor (HR 1.898; P = 0.001) for a day working time in the multivariate analysis. The proportions of psychological consulting received among nurses were higher than those among doctors (49.7 vs 30.0%, P < 0.001). More than 50% of the anesthetists and emergency doctors who have received psychological consulting thought that it was effective according to self-evaluation. CONCLUSIONS: This study focused on healthcare workers' situation during the early period of the pandemic. Nurses worked longer than doctors. The effectiveness of psychological consulting depends on the physicians' specialties and the working conditions of the nurses and psychological consulting targeting different specialties need to be improved.