title: Rapidly in situ-forming degradable hydrogels from dextran thiols through Michael addition.
abstract: Thiol-functionalized dextrans (dex-SH) (M(n,dextran) = 14K or 31K) with degrees of substitution (DS) ranging from 12 to 25 were synthesized and investigated for in situ hydrogel formation via Michael type addition using poly(ethylene glycol) tetra-acrylate (PEG-4-Acr) or a dextran vinyl sulfone conjugate with DS 10 (dex-VS DS 10). Dex-SH was prepared by activation of the hydroxyl groups of dextran with 4-nitrophenyl chloroformate and subsequent reaction with cysteamine. Hydrogels were rapidly formed in situ under physiological conditions upon mixing aqueous solutions of dex-SH and either PEG-4-Acr or dex-VS DS 10 at polymer concentrations of 10 to 20 w/v%. Rheological studies showed that these hydrogels are highly elastic. By varying the DS, concentration, dextran molecular weight, and type of cross-linker, hydrogels with a broad range of storage moduli of 9 to 100 kPa could be obtained. Varying the ratio of thiol to vinyl sulfone groups from 0.9 to 1.1 did not alter the storage modulus of the hydrogels, whereas larger deviations from equimolarity (thiol to vinyl sulfone ratios of 0.75 and 1.5) considerably decreased the storage modulus. The plateau value of hydrogel storage modulus was reached much faster at pH 7.4 compared to pH 7, due to a higher concentration of the thiolate anion at higher pH. These hydrogels were degradable under physiological conditions. Degradation times were 3 to 7 weeks for dex-SH/dex-VS DS 10 hydrogels and 7 to over 21 weeks for dex-SH/PEG-4-Acr hydrogels, depending on the DS, concentration, and dextran molecular weight.
authors.affiliation: Department of Polymer Chemistry and Biomaterials, Faculty of Science and Technology, Institute for Biomedical Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Christine
authors.initials: C
authors.lastname: Hiemstra
authors.forename: Leonardus J van der
authors.initials: LJ
authors.lastname: Aa
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Zhong
authors.forename: Pieter J
authors.initials: PJ
authors.lastname: Dijkstra
authors.forename: Jan
authors.initials: J
authors.lastname: Feijen
mesh_terms: D003911:Dextrans / Q000138:chemical synthesis / Q000737:chemistry*; D020100:Hydrogels / Q000138:chemical synthesis* / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry*; D012212:Rheology; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D003911:Dextrans; D020100:Hydrogels; D013438:Sulfhydryl Compounds; C521883:poly(ethylene glycol) tetra-acrylate; D011092:Polyethylene Glycols