I would not recommend electroporation if you just want to preserve cell viability. I have a year working this cell line, but in my transfections I use Lipofectamine LTX with Plus Reagent after diferenciation to macrophagues from THP-1 cells with PMA. In my experience, THP-1 transfection differentiates to type 2 macrophages induced by LTX, but I recommend it too. I can help if says about you need make in transfection.