2.2. Fabrication method of the PCL-micropatterned nanofibrous microwells

PCL-micropatternd nanofibrous microwells were incorporated into hydrogel micropatterns via photolithography as described in previous study [24]. polycaprolactone (PCL) fibers were initially generated through the electrospinning method. Initially, a 20 wt% PCL solution (Molecular Weight: 80,000 g/mol, Sigma Aldrich) and 2-hydroxy-2-methylpropiophenone(HOMPP) (2 % v/v) as a photoinitiator in dissolved in 2,2,2-trifluoroethanol was extruded via a syringe pump from a 7.5 kV positive voltage-applied 18G metal needle at a consistent rate (0.8 mL/h) for a duration of 1 h. After 200 μL of precursor solution was dropped onto the electrospun fibers, a photomask containing square microarray patterns was placed on the scaffold and exposed to ultraviolet (UV) light (365 nm, EFOS Ultracure 100 ss Plus, UV spot lamp, Mississauga, ON, Canada) for 1 s to generate crosslinked hydrogel. After crosslinking, residual unreacted precursor solution was washed away with water. For cell studies, scaffolds were sterilized in 70%v/v ethanol solution for 10 min, then washed twice in phosphate buffer saline (PBS) to remove ethanol.