Semifluorinated Alkanes as Stabilizing Agents of Fluorocarbon Emulsions

Abstract

We obtained highly stable, small-sized, and narrowly dispersed perfluorooctyl bromide (PFOB) emulsions using combinations of phospho-lipids and semifluorinated alkanes C n F 2n+1 C m H 2m+1 (FnHm diblocks) as the emulsifying system. For example, after 6 months at 25°C the average droplet diameter of an emulsion stabilized by F6H10 was only ~80 nm, compared to ~180 nm for the reference emulsion stabilized by phospholipids alone. In parallel, a co-surfactant effect has been demonstrated for F8H16 at the water–PFOB interface using pendant drop interfacial activity measurements, which supports the hypothesis that a fraction of the diblocks is located at the phospholipid interfacial film. We also established that the length of the hydro-carbon segment, Hm, must be comparable to that of the phospholipid's fatty chains to obtain the stabilization effect; a strong mismatch leads to rapid coa-lescence of droplets in the emulsion. For fluorocarbon emulsions, small droplet sizes translate into prolonged intravascular persistence and reduced side effects. FnHm diblocks thus provide a useful, versatile tool to improve the characteristics and stability of injectable fluorocarbon emulsions.