pH-Responsive diblock copolymers made of ω-pentadecalactone and ionically charged α-amino acids.

• Ionic macrolactone-amino acid diblock copolymers were prepared from neutral precursors. • The two copolymer blocks were able to adopt ordered structures separately. • The copolymers became self-assembled in water in 100–200 nm diameter particles. • Glu-containing copolymers were efficient for loading and pH-mediated releasing of DOX. • Lys-containing copolymers entrapped and condensed DNA by forming ionic polyplexes. Two sets of ionically charged polypentadecalactone-polypeptide diblock copolymers (PPDL x - b -PAA y , with x = 15 or 20 and y ranging from 30 to 200), one containing α-L-glutamic acid (LGA) and the other containing α-L-lysine (LL), were obtained from their respective precursors with the side groups of LGA and LL protected as γ O -benzyl and ε N -carbobenzoxy, respectively. The copolymers were semicrystalline with the polyester block crystallized in the usual pseudo-rhombic lattice and the polypeptide in the α-helix or β-sheet conformation depending on the amino acid and the length of the block. Copolymers with PAA blocks with y ≥ 80 were water-soluble and they adopted the α-helix conformation in the aqueous medium when they are in the non-ionized state. Both LGA and LL containing copolymers self-assembled in nanoparticles with a size between 150 and 180 nm in diameter. PPDL- b -PLGA nanoparticles were able to load DOX with an efficiency of ~70% whereas PPDL- b -PLL displayed a noticeable capacity for condensing DNA. In both cases hosting was based on the ionic complexation taking place between the ionized copolymer and the guest compound. Accordingly DOX release rate was found to be noticeably depending on pH. [ABSTRACT FROM AUTHOR]