Synthesis of sulfhydryl cross-linking poly(ethylene glycol)-peptides and glycopeptides as carriers for gene delivery.

Sulfhydryl cross-linking poly(ethylene glycol) (PEG)-peptides and glycopeptides were prepared and tested for spontaneous polymerization by disulfide bond formation when bound to plasmid DNA, resulting in stable PEG-peptide and glycopeptide DNA condensates. A 20 amino acid synthetic peptide possessing a single sulfhydryl group on the N-terminal cysteine, with two or five internal acetamidomethyl (Acm)-protected cysteine residues, was reacted with either PEG vinyl sulfone or iodoacetamide tyrosinamide triantennary N-glycan. Following RP-HPLC purification, Acm groups were removed by silver tetrafluoroborate to generate sulfhydryl cross-linking PEG-peptides and glycopeptide that were characterized by either (1)H NMR or LC-MS. Sulfhydryl cross-linking PEG-peptides and glycopeptides were found to bind to plasmid DNA and undergo disulfide cross-linking resulting in stable DNA condensates with potential utility for in vivo gene delivery.