Synthesis and characterization of poly(amino acid methacrylate)-stabilized diblock copolymer nano-objects

Amino acids constitute one of Nature's most important building blocks. Their remarkably diverse properties (hydrophobic/hydrophilic character, charge density, chirality, reversible cross-linking etc.) dictate the structure and function of proteins. The synthesis of artificial peptides and proteins comprising main chain amino acids is of particular importance for nanomedicine. However, synthetic polymers bearing amino acid side-chains are more readily prepared and may offer desirable properties for various biomedical applications. Herein we describe an efficient route for the synthesis of poly(amino acid methacrylate)stabilized diblock copolymer nano-objects. First, either cysteine or glutathione is reacted with a commercially available methacrylate-acrylate adduct to produce the corresponding amino acid-based methacrylic monomer (CysMA or GSHMA). Well-defined water-soluble macromolecular chain transfer agents (PCysMA or PGSHMA macro-CTAs) are then prepared via RAFT polymerization, which are then chain-extended via aqueous RAFT dispersion polymerization of 2-hydroxypropyl methacrylate. In situ polymerization-induced self-assembly (PISA) occurs to produce sterically-stabilized diblock copolymer nano-objects. Although only spherical nanoparticles could be obtained when PGSHMA was used as the sole macro-CTA, either spheres, worms or vesicles can be prepared using either PCysMA macro-CTA alone or binary mixtures of poly(glycerol monomethacrylate) (PGMA) with either PCysMA or PGSHMA macro-CTAs. The worms formed soft free-standing thermo-responsive gels that undergo degelation on cooling as a result of a worm-to-sphere transition. Aqueous electrophoresis studies indicate that all three copolymer morphologies exhibit cationic character below pH 3.5 and anionic character above pH 3.5. This pH sensitivity corresponds to the known behavior of the poly(amino acid methacrylate) steric stabilizer chains

Kinetic Studies and Mechanism of Hydrogen Peroxide Catalytic Decomposition by Cu(II) Complexes with Polyelectrolytes Derived from L-Alanine and Glycylglycine

The catalytic decomposition of hydrogen peroxide by Cu(II) complexes with polymers bearing L-alanine (PAla) and glycylglycine (PGlygly) in their side chain was studied in alkaline aqueous media. The reactions were of pseudo-first order with respect to [H2O2] and [L-Cu(II)] (L stands for PAla or PGlygly) and the reaction rate was increased with pH increase. The energies of activation for the reactions were determined at pH 8.8, in a temperature range of 293–308 K. A suitable mechanism is proposed to account for the kinetic data, which involves the Cu(II)/Cu(I) redox pair, as has been demonstrated by ESR spectroscopy. The trend in catalytic efficiency is in the order PGlygly>PAla, due to differences in modes of complexation and in the conformation of the macromolecular ligands

L’appel du signal : portrait de Patrick Flandrin

National audienceTombé tout jeune dans la marmite des sciences, Patrick Flandrin questionne encore et toujours le signal

Polymers with Amino Acids in Their Side Chain: Conformation of Polymers Derived from Glycylglycine and Phenylalanine

Two polymethacrylamides bearing glycylglycine (PGlyGly) and phenylalanine (PPhe) in the side chain were synthesized by free radical polymerization of the corresponding monomers (general formulas: -[CH2-C(CH3)-CO-NH-CH2-CO-NH-CH2-COOH]-n and -[CH2-C(CH3)-CO-NH-CH(COOH)-CH2-C6H5]-n, respectively). PGlyGly behaves as a normal polyelectrolyte in relation with its hydrophilic nature. On the contrary PPhe takes a compact conformation in water. The free enthalpy of stabilization of this conformation is high as revealed by potentiometric titrations. The influence of some additives (metal ion, urea, organic solvent) on the compact conformation and the pH-induced conformational transition was investigated. It was concluded that the main factor responsible for the existence of this structure consists of hydrophobic domains with nonpolar interactions between the aromatic side chains. © 1994, American Chemical Society. All rights reserved

Polymers with amino acids in their side chain: Conformation of poly(N‐methacryloyl‐L‐methionine)

A homopolymer bearing L‐Methionine (PMet) in its side chain was synthesized by free radical polymerization of the corresponding vinyl monomer. Viscosimetric and pHmetric measurements indicate that PMet, in water at low pH, takes a compact conformation, which is destroyed (expanded) with increasing ionization of the carboxyl groups of the side chains. The influence of temperature and of some additives (neutral salt, urea, organic solvent, SDS) on the compact conformation and the pH‐induced conformational transition was investigated. It was concluded that hydrogen bonds are the main factors responsible for the existence of the compact conformation. © 1995 John Wiley & Sons, Inc. Copyright © 1995 John Wiley & Sons, Inc