NRP1 and central nervous system cancer: 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].