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The coronavirus disease 2019 (COVID-19) pandemic has highlighted the need for rapid and accurate nucleic acid detection at the point of care. Here, we report an amplification-free nucleic acid immunoassay, implemented on a lateral flow strip, for the fluorescence detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in less than one hour. The assay uses DNA probes that are designed to bind to the conserved open reading frame 1ab (ORF1ab), envelope protein (E) and the nucleocapsid (N) regions of the SARS-CoV-2 genome, and a fluorescent-nanoparticle-labelled monoclonal antibody that binds to double-stranded DNA-RNA hybrids. In a multi-hospital randomized double-blind trial involving 734 samples (593 throat swabs and 141 sputum) provided by 670 individuals, the assay achieved sensitivities of 100% and specificities of 99% for both types of sample (ground truth was determined using quantitative PCR with reverse transcription). The inexpensive amplification-free detection of SARS-CoV-2 RNA should facilitate the rapid diagnosis of COVID-19 at the point of care.

Herein we presented a novel, rapid and amplification-free SARS-CoV-2 nucleic acid detection system based on hybrid capture fluorescence immunoassay (HC-FIA) technology. The usage of the monoclonal antibody S9.6 in recognizing DNA-RNA double-stranded hybrids enabled the conversion of nucleic acid testing into immunofluorescence carrying on a simple lateral flow dipstick. The established HC-FIA also exhibited satisfactory sensitivity, specificity and great robustness. The clinical evaluation of HC-FIA kit and fluorescence reading device are further processed in three hospitals independently. The results of 734 samples from 670 subjects indicated high consistency between our HC-FIA and quantitative polymerase chain reaction based commercially available kit or clinical diagnosis according to Kappa statistics. Altogether, HC-FIA related method and commercial test kit show unparalleled advantages as time saving, amplification-free, high throughput and portable POCT molecular diagnosis, which facilitates its application as on-site Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid detection in epidemic prevention and control worldwide, especially during the outbreak.

The coronavirus disease 2019 (COVID-19) pandemic has highlighted the need for rapid and accurate nucleic acid detection at the point of care. Here, we report an amplification-free nucleic acid immunoassay, implemented on a lateral flow strip, for the fluorescence detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in less than one hour. The assay uses DNA probes that are designed to bind to the conserved open reading frame 1ab (ORF1ab), envelope protein (E) and the nucleocapsid (N) regions of the SARS-CoV-2 genome, and a fluorescent-nanoparticle-labelled monoclonal antibody that binds to double-stranded DNA-RNA hybrids. In a multi-hospital randomized double-blind trial involving 734 samples (593 throat swabs and 141 sputum) provided by 670 individuals, the assay achieved sensitivities of 100% and specificities of 99% for both types of sample (ground truth was determined using quantitative PCR with reverse transcription). The inexpensive amplification-free detection of SARS-CoV-2 RNA should facilitate the rapid diagnosis of COVID-19 at the point of care.

Perovskite nanocrystals (NCs), which have emerged as a new class of phosphors with superb luminescence properties and bandgaps that can be easily tuned using chemical methods, have generated tremendous interest for a wide variety of applications where colloidal quantum dots have been very successful as carrier sources. In this study, self-assembled films of CsPbBr3 NCs were produced via drop casting of colloidal NCs onto glassy carbon electrodes (GCEs) to form an NC film-modified electrode. The possible fabrication process of the CsPbBr3 NCs films was discussed. We further studied the anodic electrochemiluminescence (ECL) behavior of the perovskite CsPbBr3 NCs film using cyclic voltammetry with tripropylamine (TPA) as a coreactant, and a possible ECL mechanism was proposed. Briefly, TPA was oxidized to produce strongly reducing radical species, which can react with electrochemically oxidized CsPbBr3 NCs to generate excited CsPbBr3 NCs* capable of light emission. The relative stability of the ECL emission of the CsPbBr3 NC films under aqueous conditions was also investigated, and it was found that they showed operational stability over the first three hours, indicating suitable reliability for application as sensing materials. The results suggested that semiconducting perovskite NCs have great potential for application in the ECL field.

Fluorescent boron nitride quantum dots (BNQDs) were synthesized from boric acid and ammonium hydroxide by a hydrothermal method. Under 305 nm excitation, the BNQDs emit blue fluorescence with a peak at 400 nm and a quantum yield of 32%. The BNQDs are highly photostable and resistant to ionic strength. A rapid fluorometric method for the determination of Ni2+ was developed using the heavy-metal free BNQDs via photo-induced electron transfer. Under optimal conditions, fluorescence varies linearly with the logarithm of the Ni2+ concentration in the range from 0.1 to 100 μmol·L−1. The detection limit is 0.1 μmol·L−1.

In the present work, a direct “touch” method was developed for attaching AuNPs with clean surface on the graphene-ionic liquid modified glassy carbon electrode (G-IL GCE). The morphology and composition of the thus-prepared AuNPs on G-IL GCE were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The results showed that AuNPs with interesting flower-like shapes are well dispersed on the G-IL film. Significantly, as it is a surfactant-free synthesis, the AuNPs are very clean and can be directly modified on a G-IL GCE without any pre-treatments. Comparing with the bare or even various AuNPs-G-IL mixtures modified GCEs, the proposed sensor exhibit better electrochemical activity with a higher peak current and a lower overpotential towards bisphenol A (BPA) oxidation. After optimization, a good linear relationship between current response and the concentration of BPA in the range of 0.01–1 and 1–60 μM were obtained, and the detection limit was as low as 4.8 nM. To testify the reliability, the thus-prepared AuNPs/G-IL GCE was used for determining the concentration of BPA in disposable paper cups, plastic bottles and noodles cups.