Effect of salt leaching process parameters on the morphology and properties of 3D porous PLA and PEG/PLA scaffolds

Abstract

In this study, porous PLA structures were prepared using the porogen leaching technique, specifically with sodium chloride (NaCl) of particle sizes 200-300 µm and 400-500 µm, and polyethylene glycol (PEG) with molecular weights of 3,000, 6,000, or 10,000 g/mol. Scanning electron microscopy (SEM) characterization of the cross-sections revealed that larger NaCl particle sizes contributed to an increased degree of pore connectivity, while PEG with the lowest molecular weight accelerated the leaching process. As the concentration of NaCl in the polymeric matrix increased, its removal became more effective, as indicated by lower residual percentages during thermogravimetric analysis (TGA). Additionally, lower residual percentages were recorded for the systems containing PEG prior to leaching. Although the average diameter of the resulting pores decreased in systems that used PEG, the porous structure achieved was more uniform, with both micro- and macro-porosity observed on the surfaces of the scaffold cross-sections. This variation in pore geometry is desirable and can be tailored for specific applications in scaffold construction for tissue engineering. Water exposure altered the inherent properties of PLA, affecting its suitability for short-term, soft-tissue compatible scaffolds. Solution viscometry revealed a molecular weight drop to contribute to accelerated biodegradation. Differential Scanning Calorimetry (DSC) showed a decrease in the glass transition temperature (T_g), and in cold crystallization temperature (T_cc). In addition, the thermal degradation resistance of PLA decreased, as determined by TGA experiments. The aforementioned changes were significantly amplified in PLA specimens subjected to dual leaching of both PEG and NaCl.