SERS Detecton Of Low Levels Of Virus

The sensitivity and dynamic range of the SERS technique for virus detection has been investigated by analyzing dilutions of a respiratory syncytial virus (RSV) mutant lacking the G (attachment) gene (ΔG). The SERS peak areas of the main band at 1045 cm^-1 (C–N stretching mode) are plotted against the ΔG RSV concentration in fig 6. The concentrations of the diluted solutions are calculated from the volume of water used for the dilutions. The SERS intensity increases with concentration of the viral solution, reaching a plateau at concentrations above 10 PFU/ml (PFU = plaque-forming unit). This behavior is not uncommon and similar findings of decreasing signal with increasing concentration have been reported for SERS substrates with an adsorbate coverage ≤ 0.01 monolayer. Although at this stage little emphasis have been placed on determining the lowest detectable titer, values as low as 100 PFU/mL are readily detectable. These data suggest a limit of virus detection ranging from 1–10 PFU of virus in this assay format.

Fig. 6. The SERS calibration curve for ΔG RSV constructed with the peak area or the C–N stretching band at 1045 cm-1.