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Liying Zhang, Dulei Zou, Juan Li, Shangkun Ou, Yangluowa Qu, Tingting Liu, Sanming Li, Bin Ren, Zuguo Liu, Wei Li; A novel tear analytical method based on surface enhanced raman spectroscopy. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2497.
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© ARVO (1962-2015); The Authors (2016-present)
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 analysis.
A minimum of 1.5μL tear was collected from each healthy volunteer. A comparative manner was used to establish an optimal tear SERS analytical method. The enhanced effects and spectra reproducibility were tested by raman spectroscopy, and the signals based on silver nanoparticles (Ag NPs) and gold nanoparticles (Au NPs) were compared. SERS spectra variation of tear-Ag NP mixture during evaporation was 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 detecting three main tear proteins lysozyme, lactoferrin and albumin and infectious pyocanine tear.
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 were shown in the SERS spectra. The Raman shift intensity increased gradually during the evaporation of tear-nanoparticles mixture and reaches the maximum at transitional phase, and highly reproducible spectra were obtained; The reproducibility, relative intensity and the SNR of SERS spectra observed at central none crystal zone were higher than those of 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 showed their specific raman shift. Among the three proteins, lysozyme showed major contribution to normal tear SERS spectrum. Pyocyanine tear showed specific peaks compared with that of healthy tear.
Surface enhanced raman spectroscopy of human tear exhibits specific raman spectra, SERS may be applied in tear analysis for the diagnosis of ocular surface diseases.
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