title: A novel pH- and ionic-strength-sensitive carboxy methyl dextran hydrogel.
abstract: A fast and simple method for the preparation of pH-sensitive hydrogel membranes for drug delivery and tissue engineering applications has been developed using carbodiimide chemistry. The hydrogels were formed by the intermolecular cross-linking of carboxymethyl dextran (CM-dextran) using 1-ethyl-(3-3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). Infrared spectra of the hydrogels suggest the formation of ester bonds between the hydroxyl and carboxyl groups in the CM-dextran. The porosity of the hydrogels produced, as shown by protein diffusion, increases in response to changes in the pH and the ionic strength of the external medium. The results show pH-dependent swelling behaviour arising from the acidic pedant groups in the polymer network. The diffusion of the protein lysozyme through the hydrogel membranes increased with increases in both pH (5.0-9.0) and ionic strength. The effect of changes of pH and ionic strength on the hydrogel's permeability was shown to be reversible. Scanning electron microscopy of these hydrogels showed that pH-dependent changes in permeability are mirrored by morphological changes in gel structure.
authors.affiliation: Department of Chemical Engineering, University of Bath, Claverton Down Bath, Banes BA2 7AY, UK.
authors.forename: Rhongsheng
authors.initials: R
authors.lastname: Zhang
authors.forename: Mingguo
authors.initials: M
authors.lastname: Tang
authors.forename: Adrian
authors.initials: A
authors.lastname: Bowyer
authors.forename: Robert
authors.initials: R
authors.lastname: Eisenthal
authors.forename: John
authors.initials: J
authors.lastname: Hubble
mesh_terms: D003911:Dextrans / Q000737:chemistry*; D020100:Hydrogels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D009994:Osmolar Concentration; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D003911:Dextrans; D020100:Hydrogels; C014392:carboxymethyl dextran