We are isolating CD4+ human primary T-cells from PBMC using immunomagnetic isolation (negative selection). We are transfecting them with our sgRNA using electroporation, but we are getting really low transfection efficiency. We're using the Lonza nucleofector kit.

We transfect the T-cells right after isolating them, then we let them recover for ~18 hours in IL-2 supplemented media before sorting them using flow.

Does anyone have any tips to improve the efficiency?