Cyclodextrin mediated polymer coupling via thiol-maleimide conjugation: facile access to functionalizable hydrogels

Fabrication of well-defined chemically cross-linked poly(ethylene glycol) (PEG)-based hydrogels using the thiol-maleimide addition reaction is reported. Maleimide containing homobifunctional PEGs with different molecular weights were synthesized and reacted with thiol functionalized beta-cyclodextrin (beta-CD(SH)(7)) to yield hydrogels with high efficiency under mild conditions. The resulting hydrogels were characterized by their water uptake properties, surface morphologies and rheological behaviours. In order to introduce reactive functional groups into the hydrogels, the stoichiometry of the thiol and maleimide groups was varied to obtain either thiol or maleimide functionalized hydrogels. Efficient functionalization of these reactive hydrogels in a tailored fashion was demonstrated through conjugation of appropriately functionalized fluorescent dye molecules.