2.4 Fabrication of PLGA/GelMA fibers on PTMC/TPU scaffolds
15 w/v% PLGA, 5 w/v% GelMA and 0.5 w/v% 2-hydroxy-2-methylpropiophenone were dissolved in HFIP solvent to prepare a PLGA/GelMA solution for electrospinning. The solution was then transferred to a 10 ml syringe equipped with a steel needle with an inner diameter of 0.8 mm. The syringe was fixed to a pump (LongerPump, LSP01-3A, UK). The steel needle was connected to a high-voltage power supply (Kou Hing Hong Scientific Supplies Ltd., HK). To determine the optimal parameters for electrospinning of PLGA/GelMA fibers, different applied voltages (10, 15, 20 kV) and feeding rates (0.5, 1.0, 2.0 ml/h) were investigated. The 3D printed PTMC/TPU scaffolds were attached to an aluminum foil. The aluminum foil was connected to the high-voltage power supply and was placed 10 cm away from the needle tip to collect electrospun PLGA/GelMA fibers on the PTMC/TPU scaffolds. The bilayer scaffolds thus formed were exposed to a UV light (365 nm) for 10 min and then incubated in an oven at 50 ℃ overnight. In the current study, these bilayer scaffolds were designated as S+F scaffolds. The fabrication of S+F-PDA scaffolds was similar to the above process but with different concentrations (0.5, 1.0, 2.5 and 5.0%, with the concentration referring to the PDA mass to the total mass of PLGA and GelMA) of PDA particles dispersed in the PLGA/GelMA electrospinning solution.
The surface morphology and diameters of electrospun PLGA/GelMA fibers and PLGA/GelMA-PDA fibers were studied using SEM. The mechanical properties of PLGA/GelMA and PLGA/GelMA-PDA fibers were investigated via tensile tests. Moreover, the surface and cross-sectional morphology of S+F-PDA scaffolds were examined through SEM. The mechanical performance and shape morphing behavior of bilayer scaffolds were also investigated.