Highly concentrated 1,2-bis(perfluoroalkyl) iodoethene emulsions for use as contrast agents for diagnosis

Abstract

New 1,2-bis( F-alkyl)-1-iodoethenes, C n F 2 n+1 CH=CIC n′ F 2 n′+1 (F nn′IE), have been evaluated a to their emulsifying ability for use as contrast agents. Highly concentrated (up to 90% w/v), heat-sterilizable emulsions were obtained with egg yolk phospholipids (EYP) as surfactant, with both small average particle sizes and narrow size distributions. The emulsions prepared from F nn′IE with n + n′ = 10 were more stable at 40 °C than those with n + n′ = 8. The latter were stabilized by replacing a small amount (~ 3% w/v) of F nn′IE by an iodinated mixed hydrocarbon/fluorocarbon molecule C n F 2 n+1 CH=CIC m H 2 m+1 (F n H m IE) acting as a molecular dowel, without any adverse consequence on the radiopacity. Phase separation occurred, however, in all cases after about two months at 40 °C. The in vitro radiopacity of these emulsions is, for the same concentration, three-to four-times larger than that of perfluoro-octyl bromide. However, a decrease in pH during heat-sterilization and upon ageing, which compromised their use in vivo, was observed.