The World Health Organization has declared the outbreak of a novel coronavirus (SARS-CoV-2 or 2019-nCoV) as a global pandemic. However, the mechanisms behind the coronavirus infection are not yet fully understood, nor are there any targeted treatments or vaccines. In this study, we identified high-binding-affinity aptamers targeting SARS-CoV-2 RBD, using an ACE2 competition-based aptamer selection strategy and a machine learning screening algorithm. The K d values of the optimized CoV2-RBD-1C and CoV2-RBD-4C aptamers against RBD were 5.8 nM and 19.9 nM, respectively. Simulated interaction modeling, along with competitive experiments, suggests that two aptamers may have partially identical binding sites at ACE2 on SARS-CoV-2 RBD. These aptamers present an opportunity for generating new probes for recognition of SARS-CoV-2 and could provide assistance in the diagnosis and treatment of SARS-CoV-2 while providing a new tool for in-depth study of the mechanisms behind the coronavirus infection.

The COVID-19 pandemic, caused by SARS-CoV-2, currently poses an urgent global medical crisis for which there remains a lack of affordable point-of-care testing (POCT). In particular, resource-limited areas need simple...

The World Health Organization has declared the outbreak of a novel coronavirus (SARS-CoV-2 or 2019-nCoV) as a global pandemic. However, the mechanisms behind the coronavirus infection are not yet fully understand, nor are there any targeted treatments or vaccines. In this study, we identified high-binding-affinity aptamers targeting SARS-CoV-2 RBD, using an ACE2 competition-based aptamer selection strategy and a machine learning screening algorithm. The K_d values of the optimized CoV2-RBD-1C and <a>CoV2-RBD-</a>4C aptamers against RBD were 5.8 nM and 19.9 nM, respectively. Simulated interaction modeling, along with competitive with experiments, suggests that two aptamers may have partially identical binding sites at ACE2 on SARS-CoV-2 RBD. These aptamers present an opportunity for generating new probes for recognition of SARS-CoV-2, and could provide assistance in the diagnosis and treatment of SARS-CoV-2 while providing a new tool for in-depth study of the mechanisms behind the coronavirus infection.

The World Health Organization has declared the outbreak of a novel coronavirus (SARS-CoV-2 or 2019-nCoV) as a global pandemic. However, the mechanisms behind the coronavirus infection are not yet fully understood, nor are there any targeted treatments or vaccines. In this study, we identified high-binding-affinity aptamers targeting SARS-CoV-2 RBD, using an ACE2 competition-based aptamer selection strategy and a machine learning screening algorithm. The K_d values of the optimized CoV2-RBD-1C and <a>CoV2-RBD-</a>4C aptamers against RBD were 5.8 nM and 19.9 nM, respectively. Simulated interaction modeling, along with competitive with experiments, suggests that two aptamers may have partially identical binding sites at ACE2 on SARS-CoV-2 RBD. These aptamers present an opportunity for generating new probes for recognition of SARS-CoV-2, and could provide assistance in the diagnosis and treatment of SARS-CoV-2 while providing a new tool for in-depth study of the mechanisms behind the coronavirus infection.

The detection of environmental mercury (Hg) contamination requires complex and expensive instruments and professional technicians. We present a simple, sensitive, and portable Hg2+ detection system based on a smartphone and colorimetric aptamer nanosensor. A smartphone equipped with a light meter app was used to detect, record, and process signals from a smartphone-based microwell reader (MR S-phone), which is composed of a simple light source and a miniaturized assay platform. The colorimetric readout of the aptamer nanosensor is based on a specific interaction between the selected aptamer and Hg2+, which leads to a color change in the reaction solution due to an aggregation of gold nanoparticles (AuNPs). The MR S-phone-based AuNPs-aptamer colorimetric sensor system could reliably detect Hg2+ in both tap water and Pearl River water samples and produced a linear colorimetric readout of Hg2+ concentration in the range of 1 ng/mL–32 ng/mL with a correlation of 0.991, and a limit of detection (LOD) of 0.28 ng/mL for Hg2+. The detection could be quickly completed in only 20 min. Our novel mercury detection assay is simple, rapid, and sensitive, and it provides new strategies for the on-site detection of mercury contamination in any environment.

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Divalent mercury ion (Hg) is one of the most common and stable forms of mercury pollution. In this study, a skillfully designed lateral flow strip (LFS) was developed for sensitive detection of Hg in river water samples. Aptamer, a specific oligonucleotide probe, was used to selectively identify and target Hg instead of antibody in traditional immunechromatographic strips; and the fluorescence-quenching system was used to generate positive and low background florescence signals in the competitive-likely LFS. The linear detection range of the LFS for Hg was 0.13 ng mL to 4 ng mL and the limit of detection (LOD) was 0.13 ng mL. This test provided results in 15 min and demonstrated high specificity. For detection of Hg in river water, the results were consistent with inductively coupled plasma-mass spectrometry measurements. The aptamer-based fluorescence-quenching LFS was shown to provide a reliable, accurate method for rapid detection of mercury contamination. Graphical Abstract The principle of the aptamer-based fluorescence-quenching LFS.

Tetrodotoxin (TTX) is a potent, low molecular weight analyte that can lead to fatal poisoning and requires a sensitive, rapid detection method. Here, we have developed a competitive, lateral-flow immunochromatographic strip combined with quantum dot nanobeads (QDNBs) and gold nanoflowers (AuNFs). This approach is called turn-on C-LFICS and it meets all testing requirements. Subsequent analysis revealed that this turn-on C-LFICS was rapid (8 min), sensitive (LOD = 0.2 ng mL), and quantitative (DLR = 1.56-100 ng mL), and had a positive signal readout (based on fluorescence quenching effects) for TTX detection. Moreover, it had superior signal brightness and a low background interference signal when compared with previous methods. Finally, it can function free of interference from the sample matrix and has a demonstrated recovery range of 85.5% to 119.7% in spiked samples. Taken together, these results show that our turn-on C-LFICS is an effective detection tool for TTX or other small molecules.