Moreover, they offer the advantage of being a contrast agent as natural or synthetic isotope for MRI and PET.
To summarize, fluorocarbons are inert, very stable, and biocompatible excipients in pharmaceutical emulsions. Amongst the required contrast agents are fluorocarbons ( 18F). An additional imaging mode is the positron emission tomography (PET). , who took advantage of the fluorination effect of fluoroamphiphiles for a more efficient protein delivery. Fluor-containing compositions of drug or protein delivery systems were examined by Zhang et al. added PLs in various compositions to enhance the contrast and examine lipid layer behaviour. They are utilized for magnetic resonance imaging (MRI) as a contrast agent ( 19F) to detect tissue artefacts such as venous thrombosis at an early stage and various other applications in the field of MRI. The application of fluorocarbon and perfluorocarbon nanoemulsions expanded over the last couple of years. Most fluorocarbons are inert, very stable, biocompatible and a possible alternative in biomedical use. Fluorocarbons have been found to be good for the use of pharmaceutical emulsions. In addition, emulsions from natural oils are less stable and unsaturated oils tend to quickly oxidize. Commonly used oils show a high miscibility with PL and, hence, favour the formation of gel phases at interfaces. However, not many experimental data exist about interfacial tensions with the organic phase being a fluorocarbon including PL as surfactants. 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. Thus, 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. 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. Understanding the adsorption kinetics of PLs helps to improve nanoemulsions. As an endogenous substance, they are safe to be applied in the food and pharma industry and often utilized as natural emulsifiers. Phospholipids (PLs) are widely used in nutrients and pharmaceutical applications because of their natural occurrence in cell membranes.
The results enable functional optimization of fluorocarbon emulsions regarding physical emulsification parameters and the selection of lipids. The Du Noüy ring tensiometry is appropriate to examine the slow adsorption kinetics of phospholipids emulsifying fluorocarbons. 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. This demonstrates the validity of the invasive measurement technique for the studied system. 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. However, the influence of the ring on a fluorocarbon/water interface packed with phospholipids needs careful analysis. 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, 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. Fluorocarbons are novel systems in the fast-growing fields of diverse biomedical applications and fluorocarbon-water emulsions.