Facile preparation of open-cellular porous poly (l-lactic acid) scaffold by supercritical carbon dioxide foaming for potential tissue engineering applications

Abstract

Porous poly (l-lactic acid) (PLLA) scaffold has been widely used as substitutes for tissue engineering. However, PLLA is intrinsically difficult to be produced for low-density and high porosity by physical foaming procedure, due to its weak melt strength, slow crystallization kinetic, and low heterogeneous nucleation efficiency in bulk. For the sake of enhancing the PLLA’s crystallization and heterogeneous nucleation in supercritical CO2 (ScCO2) foaming, a pressure-induced flow (PIF) method was applied on neat PLLA. As a result, the PLLA’s crystallinity and its spherulite size increased from original 15.3% and 5.0nm to 42.1% and 28.5nm, respectively. High-strength and low-density PLLA foams with uniform and controlled cellular morphology were feasibly produced, varying the foaming temperature from 100 to 140°C in a ScCO2 batch foaming process. The closed cellular structure was transformed to high-interconnected porous structure, when reducing the foaming temperature. The open-cellular PLLA scaffolds foams, with a relatively high open pore content of 77.3%, prepared using this approach can achieve a high porosity up to 92.5%, and exhibit excellent compressive stress. To evaluate its tissue engineering application, long-term culture of mouse embryonic fibroblast cells (MEFs) demonstrated that the selected open-cellular PLLA scaffold provided prominent advantages ranging from enhanced cell adhesion and proliferation to facilitated nutrient transport. The combination of PIF and CO2 foaming process can produce a great promising PLLA scaffold for tissue engineering with desirable open-cellular structure, high-strength, low-cost and easy production capacity.