Hi,

OCI are acute myeloid leukemia cells and can be considered as difficult to transfect. As they are in suspension, a classic transfection reagent should not be really efficient.

Nucleofection should work better but will induce toxicity and cell death.

Considering only these two options, you'll have to chose between low efficiency/high viability and low viability/efficiency.

Actually, the best way to genetically modify such cells is the transduction method, using a virus. In the case you can use a viral vector, I'd like to let you know that there are some technics to dramatically enhance viral infection/transduction such as magnetofection (http://www.ozbiosciences.com/virus-infection-2.html).

I hope this will help, good luck with your experiments