Methods relying on either Raman scattering or infrared (IR) absorption offer intrinsic chemical selectivity at a single virus level by using spectroscopic signatures of chemical bonds 24, 25. ![]() Vibrational spectroscopic detection of viruses is valuable for analyzing the chemical components of virus strains 21, 22, 23. However, these methods lack molecular information about the viruses while the chemical contents are critical to viral structure and function 20. Towards translation into the clinic, interferometric sensing methods have also demonstrated the visualization of single viruses in undiluted fetal bovine serum 18 and the rapid detection of a single intact virion in human saliva 19. With the enhanced signal contrasts, interferometric imaging has been used for single virus tracking and viral infection study 15, 16, 17. Although the scattering from a single virion is weak, it can be enhanced by interfering with a strong reference field in an interferometric light microscope 14. Thus, in addition to detecting viral fragments, new complement assays are required to identify the intact virions with preserved structures in order to confirm viral infection and reduce false diagnoses.Īccelerated efforts have been devoted to developing label-free technologies, in which optical detection and morphological characterization of single viruses have shown to be promising for clinical diagnosis 12, 13. It is noteworthy that residual viral RNA from patient specimens remains detectable even though patients have recovered or without culturable viruses 9, 10, 11. Although nucleic acid amplification tests 4, 5, 6 and antigen rapid diagnostic tests 7, 8 can provide accurate testing results, they usually require pre-treatments of a large number of virions, extraction, or tagging that add time to any assay 5. Detecting viral nucleic acids is challenging without signal amplification techniques such as polymerase chain reaction. Generally, the amount of viral nucleic acid in a single virion is lower than the amount of viral protein. Diagnostic tests on the viruses commonly rely on the detection of nucleic acids or surface proteins. With the spread of virus-based infectious diseases, rapid and accurate testing is crucial for mitigating the impact of current and future pandemics 4. The emergence of the monkeypox outbreak in early 2022 has posed a new global health threat during the coronavirus-19 (COVID-19) pandemic 1, 2, 3. ![]() Together, these advances open a new avenue for compositional analysis of viral vectors and elucidating protein function in an assembled virion. WIDE-MIP imaging further reveals an enriched β sheet components in DNA varicella-zoster virus proteins. Different nucleic acid signatures of thymine and uracil residue vibrations are obtained to differentiate DNA and RNA viruses. ![]() With the identification of feature absorption peaks, WIDE-MIP reveals the contents of viral proteins and nucleic acids in single DNA vaccinia viruses and RNA vesicular stomatitis viruses. Here, we report a widefield interferometric defocus-enhanced mid-infrared photothermal (WIDE-MIP) microscope for high-throughput fingerprinting of single viruses. Yet, amplification-based and antigen-based methods are not able to provide precise compositional information of individual virions due to small particle size and low-abundance chemical contents (e.g., ~ 5000 proteins in a vesicular stomatitis virus). Clinical identification and fundamental study of viruses rely on the detection of viral proteins or viral nucleic acids.
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