Abstract: A new method was presented for controllable preparation of nanoscale drug carriers based on the phase behaviors of microemulsions. The pseudoternary phase diagrams for the system polyoxyethylene (40)stearate (S-40)/polyoxyethylene-polyoxypropylene (F-68)/Glycerol monostearate (GMS)/water were obtained at 60 ℃ using home-made apparatus with temperature control.Different structures of microemulsion (W/O,B.C.and O/W) were distinguished by the conductivity measurement, and liquid crystal region was found to be in existence. The mass ratio of S-40 and F-68 was selected to be 7 ∶3. It was concluded that the introduce of retinoic acid (RA) has little influence on the phase behavior of drug-loading microemulsions. Solid lipid nanoparticle (SLN) of retinoic acid was prepared based on the phase behavior results. The mean particle size of RA-SLN determined by PCS is about 10 nm, and TEM images indicate that particles of RA-SLN are spherical with a size about 10 nm. The study on the phase behaviors of drug-loading microemulsions has been proved to be very significative for the controllable preparation of SLN.

Key words: Microemulsions, Phase behavior, Solid lipid nanoparticle, Retinoic acid