Preparation of biodegradable polymeric scaffolds with porosity gradients and interconnected structures using a sub critical carbon dioxide foaming process

The use of CO2 at sub-critical states and formation of porous structures with porosity gradients and interconnectivities from biodegradable polymers and their blends were investigated. Porous structures with well-defined pore sizes ranging from very large (i.e. d>100mum) to very small pores (i.e. d<10mum) were prepared by foaming multilayered films of poly (dl-lactic-co-glycolic acid) (PLGA 50/50), poly &egr;-caprolactone (PCL), poly (dl-lactic-co-caprolactone) (PLCL) and their blends. In order to improve the interconnectivity, a ternary system comprised of poly (lactic-co-glycolic acid) (PLGA 50/50)/poly (ethylene glycol) (PEG)/ethanol (C2H5OH)/CO2 was foamed by CO2 under sub-critical conditions. By varying the PEG concentration in the mixture, and subsequently foaming the samples by either pressure quench or temperature quench, an interconnected porous structure was generated. Investigations demonstrated that the (PLGA 50/50)/PEG blend in ratios of 95/5, 90/10, 75/25, 50/50 and 33/67 wt% can be foamed into a wide range of pore sizes from 10 to 500 mum and opening sizes from 5 to 250 mum. The generated scaffolds geometry in the investigated systems ranged from partially open to completely open, well interconnected, homogeneous or heterogeneous big pore structures. The scaffolds could find potential applications in tissue engineering