Development and Application of an SPR Nanobiosensor Based on AuNPs for the Detection of SARS-CoV-2 on Food Surfaces.

A new transmission route of SARS-CoV-2 through food was recently considered by the World Health Organization (WHO), and, given the pandemic scenario, the search for fast, sensitive, and low-cost methods is necessary. Biosensors have become a viable alternative for large-scale testing because they overcome the limitations of standard techniques. Herein, we investigated the ability of gold spherical nanoparticles (AuNPs) functionalized with oligonucleotides to detect SARS-CoV-2 and demonstrated their potential to be used as plasmonic nanobiosensors. The loop-mediated isothermal amplification (LAMP) technique was used to amplify the viral genetic material from the raw virus-containing solution without any preparation. The detection of virus presence or absence was performed by ultraviolet-visible (UV-Vis) absorption spectroscopy, by monitoring the absorption band of the surface plasmonic resonance (SPR) of the AuNPs. The displacement of the peak by 525 nm from the functionalized AuNPs indicated the absence of the virus (particular region of gold). On the other hand, the region ~300 nm indicated the presence of the virus when RNA bound to the functionalized AuNPs. The nanobiosensor system was designed to detect a region of the N gene in a dynamic concentration range from 0.1 to 50 × 103 ng·mL-1 with a limit of detection (LOD) of 1 ng·mL-1 (2.7 × 103 copy per µL), indicating excellent sensitivity. The nanobiosensor was applied to detect the SARS-CoV-2 virus on the surfaces of vegetables and showed 100% accuracy compared to the standard quantitative reverse transcription polymerase chain reaction (RT-qPCR) technique. Therefore, the nanobiosensor is sensitive, selective, and simple, providing a viable alternative for the rapid detection of SARS-CoV-2 in ready-to-eat vegetables.

ATR-FTIR spectroscopy and chemometrics as a quick and simple alternative for discrimination of SARS-CoV-2 infected food of animal origin.

Alternative routes such as virus transmission or cross-contamination by food have been suggested, due to reported cases of SARS-CoV-2 in frozen chicken wings and fish or seafood. Delay in routine testing due to the dependence on the PCR technique as the standard method leads to greater virus dissemination. Therefore, alternative detection methods such as FTIR spectroscopy emerge as an option. Here, we demonstrate a fast (3 min), simple and reagent-free methodology using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy for discrimination of food (chicken, beef and fish) contaminated with the SARS-CoV-2 virus. From the IR spectra of the samples, the "bio-fingerprint" (800 - 1900 cm-1) was selected to investigate the distinctions caused by the virus contamination. Exploratory analysis of the spectra, using Principal Component of Analysis (PCA), indicated the differentiation in the data due to the presence of single bands, marked as contamination from nucleic acids including viral RNA. Furthermore, the partial least squares discriminant analysis (PLS-DA) classification model allowed for discrimination of each matrix in its pure form and its contaminated counterpart with sensitivity, specificity and accuracy of 100 %. Therefore, this study indicates that the use of ATR-FTIR can offer a fast and low cost and not require chemical reagents and with minimal sample preparation to detect the SARS-CoV-2 virus in food matrices, ensuring food safety and non-dissemination by consumers.