Hello Dr. Bailey Bonet

A standard method to increase the attachment of semi-adherent cells is the pre-coating of cell culture plates with the cationic polymer poly-L/D-lysine (PLL/PDL). As a standard pre-coating procedure, pre-incubation of the plates with 100 μg/ml PDL for at least 5 min at room temperature can be applied.

In the article which I have attached below, the investigators used a novel approach by adding a particular concentration of PDL directly to the culture medium that would not affect cell growth. Quite interestingly, they noticed that with some concentrations of PDL added to the culture medium, the HEK 293 cells not only still grew well but also strongly attached to the culture plates.

So, according to the investigators in this paper, this novel approach could help replace any pre-coating protocol by direct addition of the cationic polymer (2μg/ml PDL) to the cell suspension before seeding. They have found that the cells with standard polymer addition behave identically to cells on pre-coated substratum. However, with PDL added to the medium, fetal bovine serum will also be required as otherwise the cationic polymers are not tolerated well by the cells.

Go through this paper and try this novel approach on HEK293 cells yourself as the investigators claim that there are no harmful side effects on the growth or appearance of HEK293 cells.

Article Direct addition of poly-lysine or poly-ethylenimine to the m...

Good Luck!

I use a final working conc of 10 ug/mL poly D lysine (I usually coat the plates and leave in fridge overnight, with several PBS rinses to remove excess PDL before adding cells). It works very well.