Biophysical properties of tear film lipid layer I. Surface tension and surface rheology

Xu, Xin­guang; Li, Guangle; Zuo, Yi Y.

doi:10.1016/j.bpj.2021.12.033

Cited by 12 publications

(12 citation statements)

References 78 publications

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“…Nevertheless, our previous studies have demonstrated that this model TFLL represents the biophysical and rheological properties of the natural TFLL to a certain degree. 38 , 39 …”

Section: Resultsmentioning

confidence: 99%

“…Surface pressure 47 mN/m corresponds to a surface tension approximately 23 mN/m, which is significantly lower than the surface tension of whole tears but corresponds to the lowest surface tension of a highly compressed TFLL. 38 …”

Section: Resultsmentioning

confidence: 99%

“…Physicochemical properties of these lipids can be found elsewhere. 38 Individual lipids were dissolved in chloroform as 1 mM stock solutions. Water used was Milli-Q ultrapure water with a resistivity greater than 18 MΩ⋅cm at room temperature.…”

Section: Methodsmentioning

confidence: 99%

“…The surface tension of whole tears of healthy individuals was reported to be around 43 to 46 mN/m, 36 , 37 which most likely represents the surface tension of major proteins in tears, such as lysozyme. 38 Upon film compression during the blinking process, the TFLL can reduce the surface tension to approximately 20 mN/m, corresponding to a surface pressure as high as 50 mN/m. 38 , 39 However, most existing in vitro evaporation studies only covered the surface pressure range between 5 and 30 mN/m, because the TFLL rapidly collapses at higher surface pressures in a Langmuir trough.…”

mentioning

confidence: 99%

“… 38 Upon film compression during the blinking process, the TFLL can reduce the surface tension to approximately 20 mN/m, corresponding to a surface pressure as high as 50 mN/m. 38 , 39 However, most existing in vitro evaporation studies only covered the surface pressure range between 5 and 30 mN/m, because the TFLL rapidly collapses at higher surface pressures in a Langmuir trough. Hence, there is an urgent need for alternative biophysical models to evaluate the effect of TFLL on water evaporation under physiologically relevant conditions.…”

mentioning

confidence: 99%

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Effect of Model Tear Film Lipid Layer on Water Evaporation

Zuo

2023

Invest. Ophthalmol. Vis. Sci.

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Purpose A majority of in vitro models were incapable of reproducing the evaporation resistance of tear film lipid layer (TFLL) in vivo. The purpose of this research is to develop a novel in vitro model to study the effect of TFLL on water evaporation. Methods A ventilated, closed-chamber, droplet evaporimeter with a constant surface area has been invented to study the evaporation resistance of TFLL. This evaporimeter ensures a rigorous control of environmental conditions, including the temperature, relative humidity, airflow rate, surface area, and surface pressure, thus allowing for reproducible water evaporation measurements over a time period of only 5 minutes. The volumetric evaporation rate of this droplet evaporimeter is less than 2.7 µL/min, comparable to the basal tear production of healthy adults. Together with direct film imaging using atomic force microscopy (AFM), we have studied the effect of a model TFLL on water evaporation, as a function of the lipid composition and surface pressure. Results A model TFLL composed of 40% wax esters, 40% cholesteryl esters, and 20% polar lipids was capable of reducing the water evaporation rate by 11% at surface pressure 47 mN/m. AFM revealed that the model TFLL at high surface pressures consists of discrete droplets/aggregates of the nonpolar lipids residing atop a polar lipid monolayer with phase separation. Conclusions The TFLL may resist water evaporation with a combined mechanism by increasing film compactness of the polar lipid film at the air-water surface, and, to a lesser extent, by increasing film thickness of the nonpolar lipid film.

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“…Nevertheless, our previous studies have demonstrated that this model TFLL represents the biophysical and rheological properties of the natural TFLL to a certain degree. 38 , 39 …”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%