Finally, the phospholipids, such as 1,2-dioleoyl-sn-glycerol-3-phosphoethanolamine (DOPE) and 1,2-dioleoyl-3-trimethylammonium propane (DOTAP), were dissolved in an aqueous solution and the PET sheets were coated with this solution to form a phospholipid shell on the polymeric core structure of the hybrid system. After freeze-drying, core-shell hybrid systems were obtained in the form of acicular powder with a size of 200 nm . From spray drying to PRINT, considerable efforts have been made to reduce particle size. Unfortunately, some technical complications, including mechanical problems and low process efficiency, have hindered the further development of this technology .