US Patent 7163677 Cationic polymers having degradable crosslinks

A synthetic polymer comprises a cationic recurring unit and a crosslinking unit, wherein the crosslinking unit comprises at least a first degradable unit (preferably acid-labile) and at least a second degradable unit (preferably hydrolyzable). A carrier composition comprising the synthetic polymer and a bioactive agent is useful for the delivery of the bioactive agent into the nuclei of the cells.