Department of Chemistry , University of Helsinki , P.O. Box 55, FI-00014 Helsinki , Finland.
Ophthalmology , University of Helsinki and Helsinki University Hospital , Haartmaninkatu 8 , FI-00290 Helsinki , Finland.
Langmuir. 2019 Mar 5;35(9):3545-3552. doi: 10.1021/acs.langmuir.8b04182. Epub 2019 Feb 23.
Dry eye syndrome (DES) is a prevalent disease in which the tear film homeostasis is compromised. One of the main causes of DES is thought to be an alteration in the composition of the outermost layer of the tear film, the tear film lipid layer (TFLL), resulting in an increased evaporation of water from the tear film and subsequent drying of the ocular surface. Recent studies have suggested that the specific TFLL lipids, namely, O-acyl-ω-hydroxy fatty acids (OAHFAs) and diesters (DiEs), may play a role in the development of DES. However, their specific connection to DES has remained largely unknown until now because of the lack of information on their biophysical properties and their role in the TFLL. Herein, we have addressed this issue by studying the biophysical properties and evaporation resistance of a library containing 10 synthetic analogues of TFLL OAHFAs and DiEs. Our results show how the variations of chain length and polar groups affect the phase behavior of these lipids at the tear film surface. In addition, the results revealed that the OAHFAs exhibiting a liquid-expanded to solid phase transition formed films with high evaporation resistance, whereas the DiEs were found to have no evaporation resistance. Altogether, our results shed new light on the role of the OAHFAs and DiEs in the TFLL and their connection to DES, suggesting that OAHFAs are likely a key lipid class in maintaining the TFLL evaporation resistance.
干眼症（DES）是一种常见疾病，其泪膜的动态平衡受到损害。DES 的主要原因之一被认为是泪膜最外层——泪膜脂质层（TFLL）的组成发生改变，导致泪膜中的水分蒸发增加，随后眼表面干燥。最近的研究表明，TFLL 中的特定脂质，即 O-酰基-ω-羟基脂肪酸（OAHFAs）和二酯（DiEs），可能在 DES 的发展中起作用。然而，由于缺乏有关其物理性质及其在 TFLL 中作用的信息，它们与 DES 的具体联系在很大程度上仍不清楚。在此，我们通过研究包含 10 种 TFLL OAHFAs 和 DiEs 合成类似物的文库的物理性质和抗蒸发性来解决这个问题。我们的研究结果表明，链长和极性基团的变化如何影响这些脂质在泪膜表面的相行为。此外，结果表明，表现出液体扩展到固体相转变的 OAHFAs 形成具有高抗蒸发性的薄膜，而 DiEs 则没有抗蒸发性。总的来说，我们的研究结果揭示了 OAHFAs 和 DiEs 在 TFLL 中的作用及其与 DES 的联系，表明 OAHFAs 可能是维持 TFLL 抗蒸发性的关键脂质类。
