Ambions transfection reagents are not good for most "challenging" cell lines. I love their siRNAs, but for transfection I use RNAiMax (Invitrogen) or Lipofectamine 2000- for pDNA delivery

for the transfection of siRNA and mRNA biontex transfection reagent works great. I tried their test samples for free then I am using the products. check this link https://www.biontex-usa.com/index.php?id=2&subID=18

Does anyone have suggestions for a good transfection reagent for primary cells? I'm trying to transfect primary monocytes.

RNAiMax works well for most cell lines!