Reverse water-in-fluorocarbon emulsions and microemulsions obtained with a fluorinated surfactant

Neat fluorocarbons (FCs) are being investigated for pulmonary delivery of drugs and genes, triggering interest on reverse water-in-fluorocarbon emulsions as delivery systems for hydrophilic bioactive materials to the lung. In this paper we examine the ability of a series of perfluoroalkylated amphiphiles with a dimorpholinophosphate polar head group, CnF2n+1(CH2)mOP(O)[N(CH2CH2)2O]2 (FnHmDMP, n = 4, 6, 8, 10 and m = 2, 5, 11) to emulsify water in fluorocarbons. F8H11DMP was found to allow the obtaining of both stable water-in-FC emulsions and of microemulsions. For a given formulation (5% (v/v) water, 95% (v/v) perfluorooctyl bromide) stable, narrowly dispersed miniemulsions (mean diameter: 120–150 nm after 1 year at 25 °C) were obtained with F8H11DMP concentrations ranging from 1.5% to 5% (w/v). Molecular diffusion (Ostwald ripening) was determined to be the predominant mechanism of droplet growth in these miniemulsions. For F8H11DMP concentrations higher than 5% (w/v), water-in-FC microemulsions, 12 nm in diameter, were obtained.