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Job Title: Research scientist
Cells, including VERO, work hard to make an environment for themselves allowing good viability and growth. When we discard the so-called spent or conditioned media, we are also discarding the growth and other factors the cells have produced for their survival. With primary neurons if you discard all of the spent medium they will go into apoptosis. The best procedure for neurons and many of the stem cells is to remove only about half the volume of medium at each feed and replace with an equal volume of fresh media. With hemoatopioetic stem cells I plate the cells in a minimum amount of medium and just add fresh media at days 3 and 6 and harvest on day 7. If you ever have a cell that is growing poorly, try retaining half the conditioned medium and adding an equal volume of fresh at each feeduntil they are growing well, instead of completely changing the medium. This same conditioned medium can also be used to adapt a cell to growth in a new medium. Save the conditioned medium from cells in log phase growth (day 2 or 3) prior to transfer and at P1 plate them in 50% the medium you wish to adapt them to and 50% of the conditioned medium. At the next passage instead of discarding the spent or conditioned medium collect it prior to trypsinization and plate the new cells in 50% of this medium and 50% of the medium you want to adapt them to. Continue doing this until the cells are growing well and then just use the selected medium. This usually takes about 5 subcultures. If the cultures slow down at let’s say P4, plate the cells in the conditioned medium from P3 with 50% of the desired medium and continue.