Depends on the charge of the plastic used to make the tissue culture plates, either positive, negative, or neutral. And companies will change plastic formulations based on design and ease of manufacture rather than maintain the same plastic formulation throughout all their tissue culture plates. One can ask the tech reps, but they usually do not know. We culture using Falcon flasks, Costar 96-well plates, and Corning 48-well, 24-well, and 6-well plates. Best to empirically determine what is best for your system and reagents.

Also, be careful of the FBS being used. All FBS that we have tested, > 300 lots, have contained various concentrations of bioactive factors (inductive, proliferative, inhibitory). Unfortunately there is so much lot to lot variation that one either has to purchase entire lot of serum that works for their system OR purchase heart-inactivated serum. After dealing with the former for many years, we have gone to the later with much success. We purchase our heat-inactivated serum from Atlas Biologicals (Fort Collins, CO).

Thanks Henry. Looks like we will just compare 3 brands that say 'tissue culture treated' and see what happens. Have you tried different densities of monocytes specifically? We have 2 brands of FBS and test for endotoxin but that is another thing that changes over time as you said with different lots. Guess we will also explore if the FBS lot could be affecting our monocytes or other cells compared to a couple years ago when we didn't have this issue.

Dear Deanna. How do you store your serum? If you store via manufacturer's recommendation, i.e., -20C, the serum will deteriorate after about a year's time frame. In contrast, if you store the serum at -80C it will enter a "suspended animation" phase and remain in stasis. When you are ready for use, aliquot amount needed for experiment and freeze at -20C (for use within six months). The activity should remain constant. Also, do NOT use a frost-free freezer. To maintain a frost-free state the freezer basically thaws everything out, repeatedly. Multiple freeze-thaws is not good for any biological reagent, serum included.

Lastly, my lab has discovered that if we use heat-inactivated serum, we can control activities in culture by adding what we want to the serum. For example if you want your cells to proliferate, add PDGF-BB. Works wonders on any cell type with a nucleus. We purchase from Atlas Biologicals, Fort Collins, CO.

Keep in touch.

Hi Deanna. We use Costar 96-, 6- and 24-well plates. We have observed best results using 2x105 cells/well (96-w plate), 5-10x 105 cells/well (24-w plates) and 3-5x106 cells/well (6-w plates). If you use fewer cells in each case the cell loss would be great. Consider that monocytes do not proliferate and cell density is important for monolayer formation. Monocytes adhere firmly. If you only need 24h stimulation and would like to recover the cells, it is going to be a difficult task if you culture them in adherence. Adherence is Ok for cell lysates and supernatant collection. 

Good luck