Mixed monolayers made from dipalmitoyl phosphatidylcholine and a fluorinated amphiphile

We have recently reported that water-in-fluorocarbon (FC) reverse emulsions and microemulsions could be used as delivery systems of bioactive materials to the lung, in particular for local administration using pressurized metered-dose inhalers. The surfactant involved in these reverse emulsions is a perfluoroalkylated amphiphile derived from the dimorpholinophosphate polar head group C8F17(CH2)11OP(O)[N(CH2CH2)2O]2 (F8H11DMP). The interaction of F8H11DMP with the lung surfactant is unknown, as well as that of reverse FC microemulsions. In this study, based on film balance measurements and fluorescence microscopy, we report on the mixed monolayer behavior of F8H11DMP and dipalmitoylphosphatidylcholine (DPPC) used as a lung surfactant model at the air/water interface. F8H11DMP/DPPC mixtures formed miscible, liquid expanded (LE) mixed monolayers in the whole range of F8H11DMP molar fractions investigated (XF8H11DMP≥0.33). Repulsive interactions were observed for high surface pressures. Miscible monolayers in LE state were also formed when DPPC/F8H11DMP mixtures were put in contact with perfluorooctyl bromide (PFOB). In this case, however, attractive interactions were observed (for XF8H11DMP=0.33 and 0.5) in the all range of surface pressures investigated. In addition, it was found that spreading a water-in-PFOB microemulsion formulated with F8H11DMP on a DPPC monolayer led to the adsorption of F8H11DMP at the interface and formation of a mixed DPPC/F8H11DMP monolayer.