How to achieve a uniform monolayer with HepG2 cells, seeded in 24 welll plate fo - (Apr/10/2015 )

I tried plating HepG2 (passage 9) in 24 well plate format with cell seeding density of 4 X 10^5 cells /mL and added 500 uL in each well. But I always notice cells pool in the center. 

This is a typical problem actually. To improve, don't swirl the plate when you seed. Instead you rotate the plate north to south, east to west , like a cross few times, and gently put in incubator. We find cells accumulate less in the center.