Research Article Issue
Ratiometric fluorescent Si-FITC nanoprobe for immunoassay of SARS-CoV-2 nucleocapsid protein
Nano Research 2023, 16 (2): 2859-2865
Published: 30 September 2022
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Coronavirus disease 2019 (COVID-19) highlights the importance of rapid and reliable diagnostic assays for the management of virus transmission. Here, we developed a one-pot hydrothermal method to prepare Si-FITC nanoparticles (NPs) for the fluorescent immunoassay of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid protein (N protein). The synthesis of Si-FITC NPs did not need post-modification, which addressed the issue of quantum yield reduction during the coupling reaction. Si-FITC NPs showed two distinct peaks, Si fluorescence at λem = 385 nm and FITC fluorescence at λem = 490 nm. In the presence of KMnO4, Si fluorescence was decreased and FITC fluorescence was enhanced. Briefly, in the presence of N protein, catalase (CAT)-linked secondary antibody/reporter antibody/N protein/capture antibody immunocomplexes were formed on microplates. Subsequently, hydrogen peroxide (H2O2) and Si-FITC NPs/KMnO4 were injected into the microplate together. The decomposition of H2O2 by CAT resulted in remaining of KMnO4, which changed the fluorescence intensity ratio of Si-FITC NPs. The fluorescence intensity ratio correlated significantly with the N protein concentration ranging from 0.02 to 50.00 ng/mL, and the detection limit was 0.003 ng/mL, which was more sensitive than the commercial ELISA kit with a detection limit of 0.057 ng/mL. The N protein concentration can be accurately determined in human serum. Furthermore, the COVID-19 and non-COVID-19 patients were distinguishable by this method. Therefore, the ratiometric fluorescent immunoassay can be used for SARS-CoV-2 infection diagnosis with a high sensitivity and selectivity.

Research Article Issue
A novel method for the synthesis of carbon dots assisted by free radicals
Nano Research 2022, 15 (10): 9470-9478
Published: 28 June 2022
Abstract PDF (12.7 MB) Collect

Carbon dots (CDs) have gradually become a widely favored type of fluorescent nanomaterials with unlimited and promising applications. This work reports a means of breaking the shackle of method to develop new red and white CDs by introducing free radicals. The resulting white emissive CDs in this strategy are employed to demonstrate electroluminescent white-light-emitting diodes (WLEDs) and achieve a record-high external quantum efficiency (0.95%) of one-step-produced white CDs (WCD)-LEDs, which dramatically simplifies the whole fabrication processes of WLEDs. With additional passivation treatment, the red CDs (RCD2) with excellent properties such as N and S co-doping, bright (quantum yield = 49%) and stable photoluminescence (PL), large positive zeta potential (+20.5 mV), and two-photon fluorescence are obtained. Such RCD2 are used for rapid staining (5 min) of yeast cells. The two CDs synthesized via this method have outstanding performance in different aspects, which provides new promise of CDs for further functionalization and applications.

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