Polylactide biodegradable scaffolds for tissue engineering applications phase separation-based techniques

Abstract

One of the most reliable techniques for the preparation of biodegradable scaffoldssuitable for tissue engineering applications (e.g. regeneration of wounded/damagedtissues) is based on liquid/liquid phase separation of ternary solvent/antisolvent/polymersolutions. In particular, two phase separation protocols are examined here: ThermallyInduced Phase Separation (TIPS) and Diffusion Induces Phase Separation (DIPS). According to the former protocol, a thermodynamically stable polymeric ternarysolution is brought below its metastability/instability point (spinodal/binodal curve) byquench in a cooling medium: under opportune conditions, a foam-like structure is formedby nucleation and 3-D growth of the polymer lean phase, which, after solvent removal byrinsing and drying, will constitute the voids of the as-generated "open-pore" architecture. Two ternary polymeric solutions were examined in detail: Poly-L-Lactic Acid(PLLA)/Dioxane (solvent)/TetrahydroFurane (THF, antisolvent) andPLLA/Dioxane/Water (antisolvent). For both systems (PLLA/Dioxane/THF andPLLA/Dioxane/Water) the solvent (dioxane) to antisolvent (THF or water) ratio and thepolymer concentration were varied; moreover, different cooling paths from the stableternary solution down to the instable zone were examined.In order to tune the biodegradation kinetics of the foams, PLLA/PLA blends invarious proportions were dissolved in the dioxane/water system. As for the latter phase separation protocol, vessel-shape PLLA (and PLLA/PLAblends) scaffolds for vascular tissue engineering applications were produced byperforming a dip-coating around a nylon fibre, followed by a Diffusion Induced PhaseSeparation (DIPS) step, where samples were pool immersed in a bath containing solventand antisolvent in different proportions, thus inducing phase separation by changing thesolvent power.Structure and morphology of the resulting foams were characterized by apparentporosity, Scanning Electron Microscopy (SEM), gas/liquid porometry, calorimetricanalysis (Differential Scanning Calorimetry, DSC), Wide Angle X-ray Diffractometry(WAXD), Optical Microscopy (OM), Confocal Laser Microscopy. Biodegradationkinetics was studied by monitoring weight loss on a dry basis with time under differentenvironmental conditions. © 2011 by Nova Science Publishers, Inc.