Adsorption process for phospholipids of different chain lengths at a fluorocarbon/water interface studied by Du Noüy ring and spinning drop

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-3phostphatidylcholine, 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.

Water‐in‐Fluorocarbon Nanoemulsions Stabilized by Phospholipids and Characterized for Pharmaceutical Applications

“…This finding is in accordance with data gained from previous tensiometry experiments (see Ref. [ 17 ] ) specifically performed between the used fluorocarbon and a phospholipid suspension. SAXS measurements reveal the small enlargement of liposomes the longer the chain lengths (from DMPC to DPPC).…”

“…The concentration of phospholipids needed for stabilization of water droplets and being able to form a bilayer from phospholipids in excess came from previous tensiometry experiments (see Ref. [ 17 ] ) and was found to be at least 150 m m . For the most part, experiments were carried out with 150 m m of phospholipids in the stock suspension.…”

“…Preliminary work in our research group addressed the mentioned problems systematically from measurements of interfacial tensions to characterization of nanoemulsions as well as the selection of a suitable hydrophobic phase. [ 17 ] For the latter, a fluorocarbon, perfluoroperhydrophenanthrene (PFPH), was selected as the biocompatibility and inert characteristics make fluorocarbons unique in biomedical use. [ 18,19 ] While there are short‐chain‐ and long‐chain‐ fluorocarbons commercially available, it was decided to use a cyclic molecule with long chains and an exceptional high density while having a low viscosity (ρ = 2.03 g cm −3 ; η = 28.4 mPa s).…”

“…According to the Gibbs approach, a concentration of 150 m m is necessary to stabilize nanoemulsions that are used for further processing of liposomes. [ 17 ]…”

The Phospholipid Research Center: Current Research in Phospholipids and Their Use in Drug Delivery

“…Here, the group of Hermann Nirschl (Karlsruhe Institute for Technology, Karlsruhe, Germany) developed a novel process using centrifugation of water-in-oil (w/o) emulsions, based on the use of phospholipids as emulsifiers, avoiding the use of aggressive treatments and allowing asymmetric membrane functionalities. While the previous project addressed the characterization of the applied substances to produce liposomes [ 55 , 117 , 118 , 119 , 120 , 121 ], the follow-up study focuses on the optimization of liposome production process [ 122 , 123 ]. The proof-of-concept of the flotation of aqueous droplets from a w/o nano-emulsion to an aqueous phase by centrifugation shows advantages when compared to known liposome production methods; the use of solvents is redundant, and the encapsulation efficiency of hydrophilic model substances is higher than anything described in the literature so far.…”