ITS: to filter or not to filter - (Apr/18/2008 )
I've been using ITS+1 (from Sigma) for serum-free cell culture for years. I had always mixed the medium and then filtered it through 22 micron sterile filter before adding it to the cells. Recently I started wondering weather it is good practice, considering that ITS contains proteins (insulin and transferrin), which can stick to the filter. Or does the 0.5 mg/ml BSA prevent them from sticking? No info on this in the product manual.
I always filter medium I use that do not contain antibiotics, because some of my reagents are powdered so I have to measure it outside. I mix all the growth factors and other components before filtering. If the compound dissolves into the media and is fully mixed, it should be fine. The membrane of the filtercup you use should not be adherent to proteins and should be designed not to adhere to proteins; I use 0.22um PES membrane from Millipore.