Peptide-Based Star Polymers as Potential siRNA Carriers

Abstract

16- and 32-arm star polymers were synthesised using poly(amido amine) (PAMAM) dendrimers as multifunctional initiators for the ring-opening polymerisation (ROP) of ϵ-Z-l-lysine N-carboxyanhydride (Lys NCA) via the core-first approach. The resulting star polymers were subsequently post-functionalised with poly(ethylene glycol) (PEG) via carbodiimide coupling, potentially improving the biodistribution of the stars in vivo. De-protection of the carboxybenzyl (Cbz)-protected star arms yielded water-soluble cationic poly(l-lysine) (PLL) star polymers with hydrodynamic radii ranging from 2.0 to 3.3 nm. Successful complexation of the PLL star polymers with double-stranded oligodeoxynucleotides (ODNs)—a mimic for small interfering RNA (siRNA)—was achieved at a nitrogen-to-phosphate (N/P) ratio of 5. Cell viability studies using HEK293T cells indicated the ‘safe’ concentration for these polymers is within a suitable window for the delivery of siRNA therapeutics.