Duration 5min, Q&A 3min
A Novel Tear Film Analytical Method Based on Surface Enhanced Raman Spectroscopy
Surface-enhanced Raman spectroscopy (SERS) has been suggested as a quick, noninvasive and sensitive analytical tool. This study was to investigate the utility of SERS in tear film analysis.
A minimum of 1.5μL tears was collected from each healthy volunteer. Silver nanoparticles (Ag NPs) and gold nanoparticles (Au NPs) with a size of 55 nm were used in the study. According to tear physiological compositions, Lysozyme (2mg/ml), lactoferrin (2mg/ml) and albumin (0.1mg/ml) were dissolved in double distilled water.
A comparative manner is used to establish an optimal tear SERS analytical method in this study. The enhanced effects and spectra reproducibility were tested by Raman spectroscopy, and the signals based on Ag NPs and Au NPs were compared. SERS spectra variation of tear-Ag NP mixture during evaporation were also evaluated. Spectra of different crystal zone was observed and photographed after the mixture deposit and crystallized. The optimal effect of above established methods were further confirmed by testing spectra of three main tear proteins: lysozyme, lactoferrin and albumin.
Results and Conclusion
Compared with the Au NPs enhanced SERS, stable and reproducible spectra could be obtained in the Ag NPs enhanced SERS. In addition, better signal to noise (SNR) and more peaks are shown in the SERS spectra; The raman shift intensity increases gradually as the tear-nanoparticles mixture evaporation and reaches the maximum at transitional phase, and there was little variation in intensity and highly reproducible spectra were obtained; The reproducibility, relatively intensity and the SNR of SERS spectra observed at central none crystal zone are superlative than central square-dendritic crystal zone and edge zone; The three main tear proteins, i.e. lysozyme, lactoferrin and albumin were detected with the same method and shows its specific peaks which are related to those in tears. Among the three proteins, lysozyme has the most resemblance of tears with respect to its SERS spectrum. lactoferrin and albumin also have some correspondence to those of tears.
Conclusion: Surface enhanced raman spectroscopy can be a quick, noninvasive and sensitive tool to analyze tear flim and this optimum detection method was shown the high signal-to-noise ratio spectra and good reproducibility
[ Keyword ]
Tear film / Surfaced enhanced raman spectroscopy / nanoparticles
[ Conflict of Interest ]