Influence of membrane structure on the preparation of colloidal lipid dispersions by premix membrane emulsification.

Since premix membrane emulsification was developed as alternative technique for the preparation of emulsions and solid lipid particles as carrier systems for lipophilic drugs, many types of membranes have been used in this preparation process. The purpose of this study was to evaluate the influence of different types of membranes on the processability of colloidal lipid dispersions using the premix membrane emulsification technique. Polycarbonate, polyester, nylon, polyvinylidene fluoride, polysulfone and polyethersulfone membranes with a pore size of 200 nm were used in a small- and a large-volume extrusion process to yield dispersions of highly concentrated (20%) nonpolar lipids (medium chain triglycerides, trimyristin) stabilized by sodium dodecyl sulfate (15%) in aqueous solution. The structure of the different membranes was characterized by scanning electron microscopy. Similar mean particle sizes and size distributions were observed for all solid lipid nanoparticles obtained from both extrusion processes after 11 or 21 extrusion cycles. Smaller mean particle sizes were observed for emulsions prepared with track-etched membranes (polycarbonate, polyester). The use of a stack of four polycarbonate membranes in the large-volume extrusion process led to small particle sizes with monomodal size distributions already after one membrane passage.