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A smart membrane based on an antigen‐responsive hydrogel
Author(s) -
Zhang Rongsheng,
Bowyer Adrian,
Eisenthal Robert,
Hubble John
Publication year - 2007
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.21255
Subject(s) - fluorescein , chemistry , dextran , membrane , covalent bond , fluorescein isothiocyanate , isothermal titration calorimetry , biophysics , confocal microscopy , chromatography , fluorescence , biochemistry , organic chemistry , quantum mechanics , biology , microbiology and biotechnology , physics
Hydrogel membranes have been fabricated that incorporate antibody/antigen moieties. The permeability of large solutes through these membranes is dependent on the presence of soluble antigen that can compete with the internal interactions between antibody and antigen leading to an increase in gel mesh size. Specifically, the membrane's structure is based on a dextran backbone grafted with a fluorescein isothiocyanate (FITC) antigen and a sheep anti‐FITC IgG antibody. The backbone is covalently cross‐linked by conjugated divinyl sulfone (DVS) groups. The gel structure is additionally stabilized by affinity crosslinks formed by biospecific interactions between the bound IgG and FITC. FTIR spectra of the gel are consistent with formation of covalent bonds between cysteine groups in the IgG and DVS groups in the dextran. Results obtained using isothermal titration calorimetry (ITC) confirmed the competitive interaction binding between IgG‐FITC‐dextran and free sodium fluorescein at pH 5.0. Scanning electron microscopy (SEM) of samples prepared using cryofixation and cryofracturing techniques showed that observed changes in permeability correlate with free fluorescein‐dependent structural changes in the gel. Three‐dimensional images obtained from confocal laser scanning microscopy show that these changes occur throughout the gel and indicate that SEM results are not artifacts of sample preparation. The permeability of these gels, as shown by blue‐dextran (12 kDa) diffusion, increases in response to the presence of free fluorescein of the external medium, which causes competitive displacement of the affinity cross‐links. Sequential addition and removal of sodium fluorescein showed that these permeability changes are reversible. Biotechnol. Bioeng. 2007;97: 976–984. © 2006 Wiley Periodicals, Inc.