Synthesis and Characterization of a beta-CD-Alginate Conjugate

C.E. GÓMEZ; G. CHAMBAT; A. HAYRAUD; M.A. VILLAR; R. AUZELY-VELTY

POLYMER

Elsevier Science Ltd.

Lugar: Kidlington, Oxford; Año: 2006 vol. 47 p. 8509 - 8516

0032-3861

Selective chemical modification of both b-cyclodextrin (b-CD) and sodium alginate (alg) was performed in order to produce an alginate derivative possessing pendant b-CD cavities along the chain. The latter was then fully characterized in terms of chemical integrity and purity, complexation properties and ability to form hydrogels. Thus, a sodium alginate derivative modified with adipic dihydrazide (alg-ADH) and a b-cyclodextrin derivative possessing an aldehyde function on the primary face were synthesized, and both were selectively coupled by a reductive amination-type reaction. Comparison of the complexation properties of the grafted and natural b-CDs by isothermal titration calorimetry using sodium adamantane acetate as a model guest gave similar enthalpy values suggesting similar mechanisms of binding. However, the association constant for the grafted CD is slightly lower as a result of a less favorable change in the binding entropy. Investigation of the gelation ability in the presence of calcium ions led to the following order: alg > alg-ADH > alg-CD. The decrease of gelation efficiency for the modified alginate samples reflected the reduction of ionic interchain bonds as a result of the unavailability or non-accessibility of G units on the alginate backbone, due to the chemical modification and steric effect of the CD molecule for alg-CD.