Surface enhanced Raman scattering of herpes simplex virus in tear film.

Conjunctivitis is currently diagnosed using white light microscopy of corneal or conjunctival cells in culture. This takes time and is subjective. An ideal test would be sensitive, specific, near-patient and quick. Raman spectroscopy is the measurement of inelastic light scatter that produces unique molecular spectra. Infected human tear film can be analysed for viral and bacterial particles. However, the concentration of these and the constituents of the tear are very low. Surface enhanced Raman scattering can be used to amplify the Raman signal. For this experiment two different SERS substrates were used: silver mirror reaction glass and gold thin film. Heat denatured herpes simplex virus in transport medium culture and transport medium only were added to different ratios of a synthetic tear. The synthetic tear was modelled on the aqueous layer of the human tear film. Linear discriminant analysis was performed on each spectral dataset for each ratio of mixture on both substrates. From the classification tables, the sensitivity and specificity for silver mirror reaction glass were 75.5+/-13.8%, 77.3+/-8.3%, and for gold thin film 75.5+/-5.9% and 78.3+/-6.2% respectively. The results show proof of principle that SERS could potentially be used to detect the presence of herpes simplex viral particles in an aqueous solution such as the tear film.