Editing Tissue engineering (section)

====Emulsification freeze-drying====
This technique does not require the use of a solid porogen like SCPL. First, a synthetic polymer is dissolved into a suitable solvent (e.g. polylactic acid in dichloromethane) then water is added to the polymeric solution and the two liquids are mixed in order to obtain an [[emulsion]]. Before the two phases can separate, the emulsion is cast into a mold and quickly frozen by means of immersion into [[liquid nitrogen]]. The frozen emulsion is subsequently [[Freeze drying|freeze-dried]] to remove the dispersed water and the solvent, thus leaving a solidified, porous polymeric structure. While emulsification and freeze-drying allow for a faster preparation when compared to SCPL (since it does not require a time-consuming leaching step), it still requires the use of solvents. Moreover, pore size is relatively small and porosity is often irregular. Freeze-drying by itself is also a commonly employed technique for the fabrication of scaffolds. In particular, it is used to prepare collagen sponges: collagen is dissolved into acidic solutions of [[acetic acid]] or [[hydrochloric acid]] that are cast into a mold, frozen with liquid nitrogen and then [[lyophilized]].