Cationic supramolecules composed of mumple oligoethylenimine-grafted beta-cyclodextrins that are threaded and blocked on a triblock copolymer chain (see figure) are synthesized as gene-delivery vectors. The supramolecules contain many cationic cyclic units threaded on a polymer chain to form an integrated entity, functioning as a macromolecular gene vector with good DNA binding ability, low cytotoxicity, and high gene-transfection efficiency.