title: Enzyme-mediated fast in situ formation of hydrogels from dextran-tyramine conjugates.
abstract: Dextran hydrogels were formed in situ by enzymatic crosslinking of dextran-tyramine conjugates and their mechanical, swelling and degradation properties were evaluated. Two types of dextran-tyramine conjugates (M(n,dextran)=14k, M(w)/M(n)=1.45), i.e. dextran-tyramine linked by a urethane bond (denoted as Dex-TA) or by an ester-containing diglycolic group (denoted as Dex-DG-TA), with different degrees of substitution (DS) were prepared. Hydrogels were rapidly formed under physiological conditions from Dex-TA DS 10 or 15 and Dex-DG-TA DS 10 at or above a concentration of 2.5 wt% in the presence of H(2)O(2) and horseradish peroxidase (HRP). The gelation time ranged from 5s to 9 min depending on the polymer concentration and HRP/TA and H(2)O(2)/TA ratios. Rheological analysis showed that these hydrogels are highly elastic. The storage modulus (G'), which varied from 3 to 41 kPa, increased with increasing polymer concentration, increasing HRP/TA ratio and decreasing H(2)O(2)/TA ratio. The swelling/degradation studies showed that under physiological conditions, Dex-TA hydrogels are rather stable with less than 25% loss of gel weight in 5 months, whereas Dex-DG-TA hydrogels are completely degraded within 4-10d. These results demonstrate that enzymatic crosslinking is an efficient way to obtain fast in situ formation of hydrogels. These dextran-based hydrogels are promising for use as injectable systems for biomedical applications including tissue engineering and protein delivery.
authors: Department of Polymer Chemistry and Biomaterials, Faculty of Science and Technology, Institute for Biomedical Technology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
authors: Rong
authors: R
authors: Jin
authors: Christine
authors: C
authors: Hiemstra
authors: Zhiyuan
authors: Z
authors: Zhong
authors: Jan
authors: J
authors: Feijen
mesh_terms: D003432:Cross-Linking Reagents / Q000737:chemistry; D003911:Dextrans / Q000138:chemical synthesis / Q000737:chemistry*; D020100:Hydrogels / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D014439:Tyramine / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D003911:Dextrans; D020100:Hydrogels; D014439:Tyramine