Sensitivity-improved SERS detection of SARS-CoV-2 spike protein by Au NPs/COFs integrated with catalytic-hairpin-assembly amplification technology.

BACKGROUND: The COVID-19 pandemic, caused by the novel coronavirus, has had a profound impact on global health and economies worldwide. This unprecedented crisis has affected individuals, communities, and nations in diverse manners. Developing simple and accurate diagnostic methods is an imperative task for frequent testing to mitigate the spread of the virus. Among these methods, SARS-CoV-2 antigen tests in clinical specimens have emerged as a promising diagnostic method for COVID-19 due to their sensitive and accurate detection of spike (S) protein, which plays a crucial role in viral infection initiation. RESULTS: In this work, a dual-signal amplification surface enhanced Raman scattering (SERS)-based S protein biosensor was constructed based on Au NPs/COFs and enzyme-free catalytic hairpin assembly (CHA) amplification method. The approach relies on a released free DNA sequence (T), which is generated from the competition reaction between Aptamer/T and Aptamer/S protein, to trigger a CHA reaction. Due to the high binding affinity and selectivity between the S protein and its aptamer, CHA process was triggered with the maximum SERS tags (H2-conjugated Au@4-mercaptobenzonitrile@Ag) anchored onto Au NPs/COFs substrate surface. This SERS platform could detect the S protein at concentrations with high sensitivity (limit of detection = 3.0 × 10-16 g/mL), wide detection range (1 × 10-16 to 1 × 10-11 g/mL), acceptable reproducibility (relative standard deviation = 7.01 %) and excellent specificity. The biosensor was also employed to detect S protein in artificial human salivas. SIGNIFICANCE: Thus, this study not only developed a novel Au NPs/COFs substrate exhibiting strong SERS enhancement ability and high reproducibility, but also proposed a promising dual-signal amplification SERS-based diagnostic method for COVID-19, holding immense potential for the detection of a wide range of antigens and infectious diseases in future applications.

Dual-mode SERS/colorimetric sensing of nitrite in meat products based on multifunctional au NPs@COF composite.

The presence of nitrite in food products has generated significant public concern. A simple and rapid dual-mode surface-enhanced Raman spectroscopy (SERS)/colorimetric detection of nitrite is proposed based on a diazo reaction and multifunctional gold nanoparticle-doped covalent organic framework (Au@COF) composite. Under acidic conditions, the reaction between toluidine blue and nitrite yielded a colorless diazo salt, simultaneously attenuating its characteristic absorption peak and Raman signal. The multifunctional Au@COF materials enhanced the Raman signal and ensured good reproducibility. Additionally, the reaction rates improved, and the sensitivity was enhanced due to the excellent adsorption capacity of the COF. The proposed method demonstrated high sensitivity and excellent recovery rates for nitrite detection in food samples. This approach shows potential for precisely detecting nitrite content in real-world food samples by integrating the simplicity of colorimetric analysis with the enhanced sensitivity of SERS.