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The assessment of the risk of virus transmission through papers, such as postcards, is important. However, the stability of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza A virus (IAV) on different types of papers is currently unknown. Investigation of the survival time of these viruses on different types of papers will provide insights into their risk of long-distance transport by postal items. We evaluated the stability of SARS-CoV-2 and IAV, mixed with a culture medium, on the surface of postcards with various coatings, including plain paper (PP), inkjet paper (IP), and inkjet photo paper (IPP). The surface structure of each paper was microscopically assessed. The surface structures of PP, IP, and IPP varied greatly depending on the presence or absence, and type, of coat layer, regardless of the base material. IP and IPP surfaces were less conducive to virus survival than PP surfaces, because of the difference in surface shapes. The survival times of SARS-CoV-2 on each paper were approximately 59.8 (PP), 6.5 (IP), and 9.8 h (IPP), and significantly longer than those of IAV (10.3, 1.8, and 3.3 h, respectively). The risk of SARS-CoV-2 transmission via paper, such as postcards, is significantly higher than that of IAV transmission. While PP, IP, and IPP have the same base material, their surface structures differ, which affects viral stability. The IP and IPP surfaces are less suitable for virus survival. This study provides novel insights into the risks of viral transmission via paper. [ABSTRACT FROM AUTHOR]

[Display omitted] • Facile, Flexible, and Fast sensing of spike protein with SERS paper sensor. • Low-cost / Ecofriendly green assisted production of spherical silver nanoparticles. • Paper sensor detectability is 2.4 pg/ul of spike protein of SARS-CoV-2 virus. • Spike protein sensing in saliva is achieved with SERS paper sensor. • Lab on paper ensures environment sustainability by its safe disposal. Rapid investigation on the detection of spike protein with paper sensor is projected with Surface Enhanced Raman Spectroscopy (SERS). SERS sensor with lab on paper is preceded with facile, cost-effective strategy. Silver nanoparticles with average size of 20–30 nm were produced by green chemistry approaches, followed by loading the nanoparticles on hydrophobic paper surfaces. The very low %RSD (∼1.5) with mapping scan ensembles high reproducibility. Spike protein detection analysis derived the prominent finger print regions of amide bands as well abundant amnio acids (Phenylalanine-1003 cm−1, Tryptophan- 680 cm−1, Tyrosine-1473 cm−1) respectively. The detectability of sensor is gauged to be 2.4 pg / µL. Real time analysis on human saliva spiked with spike protein exhibited diagnosis within 2 min. Developed paper sensor provide us the scope of SERS technique to bring state of art in early detection of covid infections and safe disposal after its use. [ABSTRACT FROM AUTHOR]

COVID-19 is a highly diffuse respiratory infection caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). Currently, quantitative real-time polymerase chain reaction (qRT-PCR) technology is commonly used in clinical diagnosis of COVID-19. However, this method is time-consuming and labor-intensive, which is limited in clinical application. Here, we propose a new method for the ultrasensitive and visual detection of SARS-CoV-2 viral nucleic acid. The assay integrates with a paper device and highly efficient isothermal amplification technology - Netlike rolling circle amplification (NRCA), which can reach a limit of detection of 4.12 aM. The paper-based NRCA owns advantages of specificity, portability, visualization and low-cost. Therefore, this method can effectively meet the requirements of point-of-care testing, providing a novel molecular detection technology for clinical diagnosis of COVID-19 and promoting the development of NRCA devices. [Display omitted] ● A paper biosensor was used for ultrasensitive and visual detection of SARS-CoV-2. ● Amplified analysis has been achieved by netlike rolling circle amplification. ● The paper-based NRCA owns advantages of portability, visualization and low-cost. ● The assay can effectively meet the requirements of point-of-care diagnosis of COVID-19. [ABSTRACT FROM AUTHOR]