Functional Doubly Porous Materials Based on Polymer Networks

摘要

Over the last decade, the preparation of doubly porous materials has particularly attracted the focus of researchers for the design of biocompatible scaffolds meant for biomedical applications. A hierarchical double porosity may constitute a real benefit in the area of tissue engineering as the first porosity with pore sizes higher than 100 μm may enable the seeding and development of suitable cell lines within the material, while the second porosity with pore diameters lower than 1 μm should permit to improve the nutrient and waste flow though the material when the macropores are clogged at the last stage of the cell culture. In this context, different methodologies have hitherto been developed for the design and synthesis of such materials displaying a double porosity. Temperature-induced phase separation (TIPS) in combination with particle leaching has recently been reported for the design of poly(L-lactic acid) (PLLA), gelatin or PLGA scaffolds. In these studies, poly(ethyl methacrylate), paraffin, and sucrose spheres (with different diameter ranges) were used as the macroporogens, while dioxane, ethanol/water or chloroform allowed for the formation of small pores during the TIPS process. Gas foaming combined with particle leaching also seems to be appropriate for the preparation of doubly porous PLLA- and PLGA-based frameworks when using dioxane/water as a porogenic solvent mixture and sodium bicarbonate particles. The design of doubly porous materials was also investigated by a double porogen approach. In this case, PLLA scaffolds were prepared by using a macromolecular porogen, i.e. poly(ethylene glycol), in combination with NaCl particles. On the other hand, superporous PHEMA scaffolds were produced through the use of NaCl or (NH4)2SO4 macroporogens in conjunction with cyclohexanol/dodecan-1-ol as a porogenic solvent mixture. In addition, High Internal Phase Emulsion (HIPE) templating has allowed for the generation of PHEMA-based materials presenting a hierarchically-structured porosity.