This protocol describes a stepwise procedure to prepare nucleic acids encapsulated in a polyethylene glycol (PEG)-shielded nanolipoparticle (NLP) that contain a bioresponsive lipid and ligand. This process provides several advantages for systemic gene delivery. The in vivo circulation time is extended. Also, low pH-sensitive lipids enhance DNA unpacking and endosomal escape. Finally, ligands inserted into the NLP surface can target gene delivery to specific tissues or cells in vivo.