Biophysical investigations of the structure and function of the tear fluid lipid layer and the effect of ectoine. Part A: Natural meibomian lipid films

Abstract

The tear fluid lipid layer is the outermost part of the tear film on the ocular surface which protects the eye from inflammations and injuries. We investigated the influence of ectoine on the structural organization of natural meibomian lipid films using surface activity analysis and topographical studies. These films exhibit a continuous pressure-area isotherm without any phase transition. With the addition of ectoine, the isotherm is expanded towards higher area per molecule values suggesting an increased area occupied by the interfacial lipid molecules. The AFM topology scans of natural meibomian lipid films reveal a presence of fiber-like structures. The addition of ectoine causes an appearance of droplet-like structures which are hypothesized to be tri-acyl-glycerols and other hydrophobic components excluded from the lipid film. Further the material properties of the droplet-like structure with respect to the surrounding were determined by using the quantitative imaging mode of the AFM technique. The droplet-like structures were found to be comparatively softer than the surrounding. Based on the observations a preliminary hypothesis is proposed explaining the mechanism of action of ectoine leading to the fluidization of meibomian lipid films. This suggests the possibility of ectoine as a treatment for the dry eye syndrome.

Prospective randomized study to evaluate the efficacy and tolerability of Ectoin® containing Eye Spray (EES09) and comparison to the liposomal Eye Spray Tears Again® (TA) in the treatment of dry eye disease

“…Drozhzhyna and Troychenko also reported an improvement in dry eye symptoms (OSDI) and with respect to TBUT with use of 0.5 % Ectoin® eye drops on 21 subjects with moderately dry eyes. [27] Dwivedi and colleagues showed that ectoine is able to stabilize the meibomian lipid film against shear stress as occurs with blinking of the eye lids [30]. Based on these literature findings, a general improvement of the DED symptoms after use of an Ectoin® eye spray was expected.…”

Meet the IUPAB Councilor—Hans-Joachim Galla

“…Besides the organization of bilayer structures, we investigated lipid and lipid-peptide monolayers by film balance experiments including fluorescence and Brewster angle microscopy and transfer techniques to allow atomic force microscopic investigations of the monolayer structure. The biological relevant systems under biophysical investigation were lung surfactants (Post et al 1995 ; Krol et al 2000 ) and tear films (Dwivedi et al, 2014a , b ) including the effect of nanoparticles on the structure of these monolayer films (Harishchandra et al 2010 , Sachan et al 2012 ). For the first time, TOF–SIMS analysis was used to image the structure and the chemical composition of the domains formed within the monolayer (Breitenstein et al 2006 ).…”

Ocular Surface as Barrier of Innate Immunity

“…It forms a thin film layer of 8 μm thick; Although is typically said that is formed of three layers; the external or lipid layer, the central or aqueous layer and the inner or mucin layer, It is now recognized that the tear film is more a lipid boundary layer with aqueous phases incorporating differing concentrations of mucins throughout. Meibomian and Moll glands produce the lipid component [ 34 ], mainly wax esters, triglycerides, free fatty acids, as well as neutral diesters [ 35 ]. Lacrimal glands produce the aqueous component and goblet cells which are located in the conjunctiva, secrets the mucin and contains membrane associated glycoproteins [ 36 ].…”