How can I detach preosteoblast cells from corning tissue culture flask as these cells are not detaching from flask with 0.2% trypsin edta?

i am culturing calverial cells from 3day old rat pups ,i seeded in 25cm corning culture flask. when i gave 0.25%  trypsin treatment they are not at all detaching from flask even after 20 min....so...

12 December 2014 2,837 10 View