In recent studies, a polyethyleneimine (PEI) nanocomplex conjugated with neuropilin-1 (NRP-1) targeting peptide and vascular endothelial growth factor receptor 2 (VEGFR-2) binding peptide demonstrated significant efficiency in crossing the blood–brain barrier (BBB) and targeting glioma tissue in vivo [195]. The gene discussed is KDR; the disease is glioma.