A novel water-soluble copolymer, agarosegraft-hyaluronan (Ag-g-HA), was synthesized as a peptide carrier, and selected properties were evaluated. In brief, agarose was degraded by hydrogen peroxide to achieve agarose with a low gelling temperature and a low molecular weight, activated by epichlorohydrin, and grafted with hyaluronic acid. The IR spectrum results of the Ag-g-HA copolymer showed that there were specific absorption peaks of hyaluronan at 1609 cm(-1) (C=O), which proved that hyaluronan was successfully grafted onto the agarose chain. The elemental analysis results showed that the nitrogen content of Ag-g-HA was 2.57%. The grafting ratio of epoxy groups was deduced to be 66.41% according to the N content of the copolymer. The zeta potential analysis results disclosed that Ag-g-HA became negative with increasing pH above 3. Ag-g-HA/insulin (INS)polyelectrolyte complexes were formed via electrostatic interaction at pH 3-5.4. The results of atomic force microscopy and C potential analyses demonstrated that Ag-g-HA and INS could spontaneously form microparticles with average diameters of 2-10 mu m. The result of an INS-releasing experiment in vitro disclosed that these particles had a significant burst release effect during the initial 30 min of release at pH 1.2 or 7.4, but the release behavior was ideal in the environment of pH 6.8. The release data could be described by the Weibull equation. These results demonstrate that the Ag-g-HA copolymer possessed potential as a peptide carrier. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 3568-3574, 2010