Abstract
Fluorocarbons are novel systems in the fast-growing fields of diverse biomedical applications and fluorocarbon-water emulsions. However, characterization of these systems with modern measuring techniques such as drop profile analysis tensiometry is almost impossible because of practically identical refractive indexes and high-density differences. Due to the material properties of the fluorocarbon-water system, the invasive Du Noüy ring is the most appropriate method to measure interfacial tensions over long times. However, the influence of the ring on a fluorocarbon/water interface packed with phospholipids needs careful analysis. For the proof of methodology, the spinning drop tensiometry was used for comparison as a non-invasive technique to measure interfacial tension between water and perfluoroperhydrophenanthrene (PFPH) covered by 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) proving almost identical results. This demonstrates the validity of the invasive measurement technique for the studied system. The Du Noüy ring method was applied for further measurements of phospholipids with different chain lengths (1,2-dmyristoyl-sn-glycero-3-phostphatidylcholine, DMPC; 1,2-distearoyl-sn-glycero-3-phosphatidylcholine, DSPC) which revealed a difference in interfacial adsorption kinetics and equilibrium tensions. The Du Noüy ring tensiometry is appropriate to examine the slow adsorption kinetics of phospholipids emulsifying fluorocarbons. The results enable functional optimization of fluorocarbon emulsions regarding physical emulsification parameters and the selection of lipids.
Highlights
Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Phospholipids (PLs) are widely used in nutrients and pharmaceutical applications because of their natural occurrence in cell membranes
The aim of this work is to show that the Du Noüy ring is an appropriate method to measure interfacial tensions of systems, which are impossible to characterize with other modern techniques such as Profile analysis tensiometry (PAT)
To measure interfacial tensions with the Du Noüy ring method, the determination of the equilibration time is essential to carry out further experiments
Summary
They are safe to be applied in the food and pharma industry and often utilized as natural emulsifiers [1]. Understanding the adsorption kinetics of PLs helps to improve nanoemulsions. From the thermodynamic behaviour of interfacial layers, the optimum area per lipid molecule is derived and can be adduced to determine the PL concentration for the emulsifying process as well as give information about the emulsion stability [2]. Studies of interfacial tensions between PL and an oil or organic phase are of high interest to understand the adsorption kinetics and improve the emulsification process. Organic phase-water or water-air interfaces and the adsorption behaviour of PL used in these systems have been described in a variety of literature [3,4,5].
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