TF and neoplasm: For example, targeting ligands such as B6 [109,143], cRGD [143], folic acid (FolA) [109,113], methotrexate (MTX) [144], c-Met-binding peptide (cMBP2) [114,115], transferrin (Tf), AP-1, EGF receptor-binding peptide (GE11) [143] and IL-6 receptor binding I6P7 peptide [145] were attached to precise PEG shielding domains and then introduced to the surface of polyplexes by pre- or post-modification for active receptor-mediated accumulation in target tumor cells.