Distinguishing Between Different Virus Types

Using the direct intrinsic SERS configuration as shown in fig 1a, we have shown that it is possible to rapidly and sensitively distinguish different viruses by their SERS spectra (fig 3). For example, the baseline-corrected SERS spectra of the DNA virus, adenovirus (adeno), and RNA viruses, i.e., rhinovirus (rhino) and human immunodeficiency (HIV) viruses, which can readily be detected and distinguished as shown in fig 3. The adeno SERS spectrum is characterized by strong bands due to nucleic acid bases at 650 cm^-1 (guanine), 731 cm^-1 (adenine), 1325 cm^-1 (adenine), and 1248 cm^-1 (guanine). The 650 cm^-1 band may also have contributions due to Tyr. The Raman lines at 1003 cm^-1 and 1033 cm^-1 have been assigned to the symmetric ring breathing mode and the in-plane C-H bending mode of Phe (phenylalanine), respectively while the bands at 1457 cm^-1, 1576 cm^-1 and 1655 cm^-1 can be attributed to the CH₂ deformation mode of proteins, the carboxylate stretching vibration (v_a COO^-) of Trp (Tryptophan) and the amide I vibration of peptide groups, respectively. A notable characteristic of the adeno SERS spectrum is the relative intensity of the bands associated with the nucleic acids, indicating direct binding to the Ag substrate. The strong band at 731 cm^-1 has been assigned to denatured DNA, caused by its interaction with the Ag SERS substrate. A similar band analysis can identify the prominent SERS bands for the other viruses in fig 3. Thus, the uniqueness of the SERS spectrum provides a molecular fingerprint for detection of specific viruses and provides the foundation for SERS-based biosensing

Fig. 3. SERS spectra of different virus types obtained using Ag nanorod substrates.