“…0.15 g PLLA and 1 g PLGA were added to 1.25 mL and 5 mL 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP, Macklin, Shanghai, China) so as to make the PLLA core solution and PLGA sheath solution, respectively. After stirring overnight, BMP-2 in phosphate buffered saline (PBS, 0.01 M, HyClone, Logan, USA) (1 μg, 0.125 mL) was added into the core solution by stirring and sonicating, while bFGF in PBS (500 ng, 0.5 mL) was slowly added into the sheath solution in the same way according to our previous study [ 20 ]. In addition, the control group selected PBS as the water phase, which was prepared under similar parameters.…”