Efficient polycation non-viral gene delivery system with high buffering capacity and low molecular weight for primary cells: Branched poly(β-aminoester) containing primary, secondary and tertiary amine groups

•Transfection efficiency of PBAE on primary cells was realized for the first time.•Nanoparticles prepared with DMSO have more stable than those prepared with ethanol.•More pEGFN1 were loaded into the nanoparticle with the encapsulation method.•Nanoparticles loaded pEGFN1 by encapsulation increased the transfection efficiency.•The presence of three amine structures on PBAE increased transfection efficiency.