Synthesis of Polyacrylamide Nanogels by Intramolecular Disulfide Cross-linking

摘要

Nondegradable polyamides with protein-like properties were designed and prepared as a copolymeric hydrogel by the free-radical polymerization of acrylamide with a disulfide-containing cross-linking agent,N,N'-bisacryloylcystamine.Copolyacrylamides containing pendent thiol groups (-SH) were obtained after reduction of the disulfide bonds in the hydrogel,followed by precipitation in methanol.Ellman's analysis and gel-permeation chromatography (GPC) were used to characterize the copolymer.Re-dissolution of the copolymer in water at very dilute concentrations,followed by air oxidation under physiological conditions (pH 7.5),resulted in nanoparticles (nanogels).The dilute concentration favored intramolecular disulfide cross-linking in the polymer chain,resulting primarily in a single-chain nanogel.Nanogel formation was confirmed and characterized using GPC,dynamic light scattering and atomic force microscopy.The size of the nanogels ranged from 20-200 nm.