title: Polypeptide grafted hyaluronan: synthesis and characterization.
abstract: Poly(l-leucine) grafted hyaluronan (HA-g-PLeu) has been synthesized via a Michael addition reaction between primary amine terminated poly(l-leucine) and acrylate-functionalized HA (TBAHA-acrylate). The precursor hyaluronan was first functionalized with acrylate groups by reaction with acryloyl chloride in the presence of triethylamine in N,N-dimethylformamide. (1)H NMR analysis of the resulting product indicated that an increase in the concentration of acryloylchoride with respect to hydroxyl groups on HA has only a moderate effect on functionalization efficiency, f. A precise control of stoichiometry was not achieved, which could be attributed to partial solubility of intermolecular aggregates and the hygroscopic nature of HA. Michael addition at high [PLeu-NH(2)]/[acrylate](TBAHA) ratios gave a molar grafting ratio of only 0.20 with respect to the repeat unit of HA, indicating grafting limitation due to insolubility of the grafted HA-g-PLeu. Soluble HA-g-PLeu graft copolymers were obtained for low grafting ratios (<0.039) with <8.6% by mass of PLeu and were characterized thoroughly using light scattering, (1)H NMR, FT-IR, and AFM techniques. Light scattering experiments showed a strong hydrophobic interaction between PLeu chains, resulting in aggregates with segregated nongrafted HA segments. This yields local networks of aggregates, as demonstrated by atomic force microscopy. Circular dichroism spectroscopy showed a β-sheet conformation for aggregates of poly(l-leucine).
authors.affiliation: Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Wang
authors.forename: Jamie
authors.initials: J
authors.lastname: Messman
authors.forename: Jimmy W
authors.initials: JW
authors.lastname: Mays
authors.forename: Durairaj
authors.initials: D
authors.lastname: Baskaran
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis / Q000737:chemistry; D002942:Circular Dichroism; D006820:Hyaluronic Acid / Q000138:chemical synthesis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D018625:Microscopy, Atomic Force; D010455:Peptides / Q000737:chemistry*; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D001672:Biocompatible Materials; D010455:Peptides; D011108:Polymers; C027819:polyleucine; D006820:Hyaluronic Acid