Preparation and characterization of polymeric host molecules, β-cyclodextrin linked chitosan derivatives having different linkers

Reductive alkylation of the amino group of chitosan with β-cyclodextrin (CD) aldehyde derivatives, i.e., 6-deoxy-6-(4-oxobutyramido)-β-CD and 6-oxo-β-CD, gave two β-CD-linked chitosan derivatives with C4 (4-butylamido) and C0 linking arms, respectively. Degree of substitution (D.S.) of both C4-β-CD and C0-β-CD linked chitosan was controlled by the ratio of starting materials. The structures of the products were confirmed by 1H and 13C NMR and FT-IR spectra. Their inclusion properties of C4-β-CD (D.S. 18%) and C0-β-CD linked chitosan (D.S. 17%) with a fluorescent probe, 6-(p-toluidino)-2-napthalene-6-sulfonate (TNS) were investigated in acetate buffer (pH 4.3) at 25 °C. Continuous variation of Job's method revealed that the stoichiometry of inclusion complex of C4-β-CD linked chitosan-TNS was 1:1, whereas that of C0-β-CD linked chitosan was not 1:1. The stability constant of C4-β-CD linked chitosan determined by Benesi–Hildebrand plot was 2.3 × 103 M−1. These results suggested that length of the linking arms between CD and chitosan is influenced on their inclusion property.