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Int. J. Mol. Sci. 2015, 16(9), 21813-21831; doi:10.3390/ijms160921813

Surface Properties of Squalene/Meibum Films and NMR Confirmation of Squalene in Tears

Department of Biochemistry, Faculty of Biology, St. Kliment Ohridski University of Sofia, 1164 Sofia, Bulgaria
Institute of Physical Chemistry "R. Kaischew"-BAS, Phase Formation, Crystals and Amorphous Materials Department, 1113 Sofia, Bulgaria
Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto 602-0841, Japan
Department of Chemistry, University of Louisville, Louisville, KY 40202, USA
Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40202, USA
Biointerfaces and Biomaterials Laboratory, Department of Optics and Spectroscopy, Faculty of Physics, St. Kliment Ohridski University of Sofia, 1164 Sofia, Bulgaria
These authors contributed equally to this work.
Author to whom correspondence should be addressed.
Academic Editor: Jeffrey H. Boatright
Received: 3 August 2015 / Revised: 28 August 2015 / Accepted: 31 August 2015 / Published: 9 September 2015
(This article belongs to the Section Biochemistry, Molecular and Cellular Biology)
View Full-Text   |   Download PDF [4089 KB, uploaded 9 September 2015]   |  


Squalene (SQ) possesses a wide range of pharmacological activities (antioxidant, drug carrier, detoxifier, hydrating, emollient) that can be of benefit to the ocular surface. It can come in contact with human meibum (hMGS; the most abundant component of the tear film lipid layer) as an endogenous tear lipid or from exogenous sources as eyelid sebum or pharmaceuticals. The aims of this study were to determine (i) if SQ is in tear lipids and (ii) its influence on the surface properties of hMGS films. Heteronuclear single quantum correlation NMR confirmed 7 mol % SQ in Schirmer’s strips extracts. The properties of SQ/hMGS pseudo-binary films at the air/water interface were studied with Langmuir surface balance, stress-relaxation dilatational rheology and Brewster angle microscopy. SQ does not possess surfactant properties. When mixed with hMGS squalene (i) localized over the layers’ thinner regions and (ii) did not affect the film pressure at high compression. Therefore, tear SQ is unlikely to instigate dry eye, and SQ can be used as a safe and “inert” ingredient in formulations to protect against dry eye. The layering of SQ over the thinner film regions in addition to its pharmacological properties could contribute to the protection of the ocular surface. View Full-Text
Keywords: Langmuir trough; meibum; NMR; sebum; squalene; tear film Langmuir trough; meibum; NMR; sebum; squalene; tear film

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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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Ivanova, S.; Tonchev, V.; Yokoi, N.; Yappert, M.C.; Borchman, D.; Georgiev, G.A. Surface Properties of Squalene/Meibum Films and NMR Confirmation of Squalene in Tears. Int. J. Mol. Sci. 2015, 16, 21813-21831.

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