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.

Engineered LwaCas13a with enhanced collateral activity for nucleic acid detection.

Clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 13 (Cas13) has been rapidly developed for nucleic-acid-based diagnostics by using its characteristic collateral activity. Despite the recent progress in optimizing the Cas13 system for the detection of nucleic acids, engineering Cas13 protein with enhanced collateral activity has been challenging, mostly because of its complex structural dynamics. Here we successfully employed a novel strategy to engineer the Leptotrichia wadei (Lwa)Cas13a by inserting different RNA-binding domains into a unique active-site-proximal loop within its higher eukaryotes and prokaryotes nucleotide-binding domain. Two LwaCas13a variants showed enhanced collateral activity and improved sensitivity over the wild type in various buffer conditions. By combining with an electrochemical method, our variants detected the SARS-CoV-2 genome at attomolar concentrations from both inactive viral and unextracted clinical samples, without target preamplification. Our engineered LwaCas13a enzymes with enhanced collateral activity are ready to be integrated into other Cas13a-based platforms for ultrasensitive detection of nucleic acids.

Dynamic response landscape of immune cells identified immune dysfunction which predicts disease progression in COVID-19 infected patients.

During the development of COVID-19 caused by SARS-CoV-2 infection from mild disease to severe disease, it can trigger a series of complications and stimulate a strong cellular and humoral immune response. However, the precise identification of blood immune cell response dynamics and the relevance to disease progression in COVID-19 patients remains unclear. We propose for the first time to use changes in cell numbers to establish new subgroups, which were divided into four groups: first from high to low cell number (H_L_Group), first from low to high (L_H_Group), continuously high (H_Group), and continuously low (L_Group). It was found that in the course of disease development. In the T cell subgroup, the immune response is mainly concentrated in the H_L_Group cell type, and the complications are mainly in the L_H_Group cell type. In the NK cell subgroup, the moderate patients are mainly related to cellular immunity, and the severe patients are mainly caused by the disease, while severe patients are mainly related to complications caused by diseases. Our study provides a dynamic response of immune cells in human blood during SARS-CoV-2 infection and the first subgroup analysis using dynamic changes in cell numbers, providing a new reference for clinical treatment of COVID-19.

Clarifying real receptor binding site between coronavirus HCoV-HKU1 and 9-O-Ac-Sia based on molecular docking.

HCoV-HKU1 is a [Formula: see text]-coronavirus with low pathogenicity, which usually leads to respiratory diseases. At present, a controversial issue is that whether the receptor binding site (RBS) of HCoV-HKU1 is located in the N-terminal domain (NTD) or the C-terminal domain (CTD) in the HCoV-HKU1 S protein. To address this issue, we used molecular docking technology to dock the NTD and CTD with 9-oxoacetylated sialic acid (9-O-Ac-Sia), respectively, with the results showing that the RBS of HCoV-HKU1 is located in the NTD (amino acid residues 80-95, 25-32). Our findings clarified the structural basis and molecular mechanism of the HCoV-HKU1 infection, providing important information for the development of therapeutic antibody drugs and the design of vaccines.