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Lipid Saturation and the Rheology of Human Tear Lipids

1
Biomaterials and Biointerfaces Laboratory, Department of Optics and Spectroscopy, Faculty of Physics, St. Kliment Ohridski University of Sofia, Sofia 1164, Bulgaria
2
Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA
3
Department of Cytology, Histology and Embryology, Faculty of Biology, St. Kliment Ohridski University of Sofia, Sofia 1164, Bulgaria
4
Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2019, 20(14), 3431; https://doi.org/10.3390/ijms20143431
Received: 17 May 2019 / Revised: 24 June 2019 / Accepted: 4 July 2019 / Published: 12 July 2019
(This article belongs to the Section Molecular Pathology, Diagnostics, and Therapeutics)
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Abstract

Elevated levels of acyl chain saturation of meibomian lipids are associated with enhanced tear film (TF) stability in infants to shortened TF breakup time with meibomian gland dysfunction. Thus, the effect of saturation on the surface properties of human TF lipids (TFLs) using a Langmuir surface balance and Brewster angle microscopy was studied. Lipid phase transitions were measured using infrared spectroscopy. The raise in the % of saturation resulted in thicker, and more elastic films at π = 12 mN/m, with the effects being proportional to the saturation level. At the same time, at lower (≤10 mN/m) π, the raise in saturation resulted in an altered spreading and modified structure of TFL layers. The strong impact of saturation on TFL surface properties correlated with a saturation induced increase of the TFL acyl chain order, phase transition temperature, and lipid–lipid interactions. The native TFL order and πmax were significantly greater, compared with native meibum collected from the same individual. Aggregation of lipids on the tear surface due to saturation was not as significant as it was for meibum. Although the surface pressure/area isotherms for TFL were similar for meibum, differences in rheology and phase transition parameters warrant the study of both. View Full-Text
Keywords: human meibum; acyl chain saturation; Langmuir films; tear film stability; surface properties human meibum; acyl chain saturation; Langmuir films; tear film stability; surface properties
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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MDPI and ACS Style

Georgiev, G.A.; Borchman, D.; Eftimov, P.; Yokoi, N. Lipid Saturation and the Rheology of Human Tear Lipids. Int. J. Mol. Sci. 2019, 20, 3431.

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