Controlling the rate of release of molecules from a hydrogel is of high interest for various drug delivery systems and medical devices. A strategy to alter the release profiles of soluble and poorly soluble active ingredients from hydrogels can be to combine the hydrogel forming ability of alginate with the inclusion forming ability of cyclodextrins. Here, β-CD was grafted to alginate in a three-step synthesis using periodate oxidation, reductive amination and copper(I)-catalyzed azide-alkyne cycloaddition. A grafting degree of 4.7% mol β-CD/mol sugar residues was obtained. The grafting degree was controlled by varying the reaction parameters where the amount of linker used in reductive amination was especially influential. Ca-alginate gel beads grafted with β-CD showed increased uptake of the model molecule methyl orange (first line in photo above). Release experiments showed that the grafted material had a prolonged release of methyl orange and an increased total amount of released methyl orange (second line in photo above). These results show that the β-CD grafted alginate is still able to form a hydrogel while the grafted cyclodextrins retain their ability to form inclusion complex with methyl orange.
Efficient Grafting of Cyclodextrin to Alginate and Performance of the Hydrogel for Release of Model Drug
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