CPP-modified redox-responsive polymer: GALA or CREKA conjugated to MAL-PEG-SS-PEI (PEG2k–SS–PEI25k). Disulfide bond enables GSH-triggered release. Peptide coupling: maleimide-terminated PEG-SS-PEI reacted with thiol-terminated peptide (1:1) then dialyzed/lyophilized.