A novel meibum analytical method based on surface enhanced raman spectroscopy

Abstract

Purpose : We applied the surface enhanced Raman spectroscopy (SERS) to analyze the composition of proteins, saturated fats, unsaturated fatty acids and their interaction in Meibomian gland secretion, i.e., meibum, and evaluate the pathological changes of Meibomian gland dysfunction.

Methods : Human meibum from healthy individuals and Meibomian gland dysfunction patients was expressed from eyelids and collected for direct spectroscopic study. The meibum was immediately spread onto the silicon slice coated by gold surface or preserved in glass tube. All samples were frozen under liquid nitrogen for analysis using a Raman spectrometer within two hours.

Results : Human meibum was enrich with lipid. We used the Raman band intensity ratio, I1659/I1438cm⁻¹ and I3013/I2860cm⁻¹, to calculate a saturation level CH2/=CH of meibum; used the Raman band intensity ratio, I1659/I1161cm⁻¹, to calculate the relative amount of lipid and protein; and used the Raman band intensity ratio, I2860/I2934cm⁻¹, to calculate the conformation of lipid. We found that there was significant difference (P<0.01) at I1659/I1438cm⁻¹, I3013/I2860cm⁻¹, and I1659/I1161cm⁻¹ between liquid-like, granular and paste-like meibum. However, there was no significant difference (P>0.05) at I1659/I1438cm⁻¹. Raman mapping was used for relative quantity analysis and the results showed similar as that of the Raman spectra.

Conclusions : Compared with liquid-like meibum, the unsaturated fatty acid of granular and paste-like meibum was decreased; while the protein was increased; the conformation of lipid was similar. We predict that Meibomian gland dysfunction may be accompanied by decrease of non-saturated fatty acid and increase of protein in meibum. SERS may be used as a method to analyze the meibum and determine the pathological changes of MGD.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.