Detecting Viruses In Biological Media

For most diagnostic situations, the detection of pathogens occurs in a heterogeneous biological medium. Therefore, it is of practical importance that SERS can distinguish between viruses in the presence of a complex background. This capability has been demonstrated by comparing the SERS spectra of uninfected Vero cell lysate, respiratory syncytial virus (RSV) infected cell lysate, and purified RSV (fig 4). As shown in fig 4, although there are common SERS peaks for the three samples, both the SERS spectra of RSV-infected cell lysate and purified RSV have SERS bands at 1000–1100 cm^-1 and 500–600 cm^-1, while the SERS spectrum of Vero cell lysate does not have these two signature peaks. The bands at 527 cm^-1 and 546 cm^-1 can be assigned to a disulfide stretching mode, while the strong band at 1044 cm^-1 has been assigned to the C–N stretching vibration in previous SERS studies. The results show that major Raman bands can be assigned to different constituents of the cell lysate and the virus, such as nucleic acids, proteins, protein secondary structure units and amino acid residues present in the side chains and the backbone. However, our most significant result is the observation that vibrational modes due to the virus can be unambiguously identified in the SERS spectrum of the Vero cell lysate after infection.

Fig. 4. SERS spectra of Vero cell lysate before and after infection with RSV, top and middle spectra, respectively. The SERS spectrum of purified RSV is shown at the bottom for comparison.

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