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

Abstract

Fluorocarbons are one of the most promising hydrophobic phases for future pharmaceutical production processes and various biomedical applications. Yet, because of their specific characteristics such as high density and refractive index similar to water, analysis of water‐in‐fluorocarbon (w/fc) nanoemulsions remains a challenge. The present work examines w/fc nanoemulsions stabilized with phospholipids as natural emulsifiers and tackles the measuring problems of photon correlation spectroscopy (PCS) when used for investigation of fluorocarbon nanoemulsions. These emulsions are suitable to form liposomes via centrifugation and thus, are required to meet certain criteria such as stability and size. The results imply a stability of up to 4 weeks with an average size of 180 nm. The intensity mean diameter gained from PCS measurements shows large scattering directly after sonication which is due to gas bubbles from sonication. The number mean is not influenced by gas bubbles and gives a more accurate depiction of the produced nanoemulsions. These findings are supported by small‐angle X‐ray scattering data, which are additionally applied for liposome analysis measuring a size of approximately 60 nm.

Transparent and Highly Flexible Hierarchically Structured Polydimethylsiloxane Surfaces Suppress Bacterial Attachment and Thrombosis Under Static and Dynamic Conditions

“…Next, interactions between hierarchically structured‐TPFS PDMS substrates and perfluoroperhydrophenanthrene (PFPP)—a biocompatible lubricant commonly used for clinical applications, were explored. [ 47 ] Ultraviolet–visible spectroscopy was used to quantify optical transparency (Figure 2b). Planar PDMS exhibited 95–97% transmittance.…”

How to Achieve High Encapsulation Efficiencies for Macromolecular and Sensitive APIs in Liposomes

“…A concentration of only 50 mM was found to be too low for an adequate stabilization of w/fc nano-emulsions (cf. Ullmann et al [18]). The phospholipid DMPC shows a similar low RR FS of 45%, even at 150 mM.…”

“…The hydrophobic phase consisted of the fluorocarbon perfluoro-perhydro-phenanthrene (C 14 F 24 ), if not stated otherwise. The droplet size averaged around 180 nm and was found to be suitable for liposome production [18].…”

“…Zeta potential of liposomes was measured at a constant voltage of 50 mV with the Zetasizer Nano ZS (Malvern Instruments, Worcestershire, UK). For a detailed description of nano-emulsion and liposome preparation, as well as results of droplet and liposome size, please refer to Ullmann et al [18]. Thus, the lipid-coated aqueous cores of the nano-emulsion became surrounded by outer lipid leaflets, incorporating the API.…”

“…Organogel formation is no longer detectable. Nano-emulsion droplets are stable for several weeks and liposome production is successful [18]. Because of the heavier hydrophobic phase, the aqueous droplets float up instead of sedimenting during centrifugation, which enables easy removal of the liposomal suspension from the top.…”