Growth media (5 mL) was added to the flask to neutralize the trypsin, and the contents of the flask were transferred to a 15 mL conical tube and centrifuged for 5 min @ 2,000 rpm (SCL456, Southwest Science, Trenton, NJ, USA). The supernatant was decanted, and the cell pellet was resuspended in 5-7 mL of growth medium by gentle pipetting. The cells were counted using the EVE automated cell counter (NanoEntek, Seoul, South Korea), and the cell suspension was diluted to 500,000 cells / mL. For the flat culture condition, the cell suspension was pipetted into four wells of a 12-well plate (1 mL into each well).