Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
Volume 1838, Issue 10, Pages 2716-2727Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbamem.2014.05.007
Keywords
Tear fluid lipid layer; Langmuir film balance; Epi-fluorescence microscopy; Atomic force microscopy; Ectoine; Dry eye syndrome
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Funding
- NRW International Graduate School of Chemistry
- Ursapharm Arzneimittel GmbH, Saarbrucken
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The tear fluid lipid layer is present at the outermost part of the tear film which lines the ocular surface and functions to maintain the corneal surface moist by retarding evaporation. Instability in the structure of the tear fluid lipid layer can cause an increased rate of evaporation and thus dry eye syndrome. Ectoine has been previously shown to fluidize lipid monolayers and alter the phase behavior. In the current study we have investigated the effect of ectoine on the artificial tear fluid lipid layer composed of binary and ternary lipid mixtures of dipalmitoyl phosphatidylcholine (DPPC), cholesteryl esters and tri-acyl-glycerols. The focus of our study was mainly the structural and the biophysical aspects of the artificial tear fluid lipid layer using surface activity studies and topology analysis. The presence of ectoine consistently causes an expansion of the pressure-area isotherm indicating increased intermolecular sparing. The topology studies showed the formation of droplet-like structures due to the addition of ectoine only when tri-acyl-glycerol is present in the mixture of DPPC and chol-palmitate, similar to the natural meibomian lipids. Consequently, the hypothesis of an exclusion of tri/di-acyl-glycerol from the meibomian lipid film in the presence of ectoine in the subphase is confirmed. A model describing the effect of ectoine on meibomian lipid films is further presented which may have an application for the use of ectoines in eye drops as a treatment for the dry eye syndrome. (C) 2014 Elsevier B.V. All rights reserved.
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