Preparation, characterization, and in vitro release of carboxymethyl starch/β-cyclodextrin microgel–ascorbic acid inclusion complexes

Carboxymethyl starch (CMS)/β-cyclodextrin (β-CD) microgels have been synthesized. The percentages of effective β-CD in the microgels have been determined by measuring the amount of iodine retained in its hydrophobic cavity. A microgel–ascorbic acid inclusion complex has been prepared and characterized by Fourier-transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). In vitro release of ascorbic acid from the microgel has been investigated. Most of the microgel particles had diameters distributed between 10 and 25 μm. The effective β-CD contents in microgels with weight ratios Rβ-CD/CMS of 0.05, 0.1, 0.2, and 0.4 were 1.04, 2.27, 3.96, and 4.12%, respectively. The ascorbic acid loading of the microgels increased as ascorbic acid concentration was increased, but the encapsulation efficiencies of the microgels decreased with increasing its concentration. FTIR and DSC data demonstrated the formation of a microgel–ascorbic acid inclusion complex. In vitro release results indicated that the CMS/β-CD microgels may potentially be applied as a carrier system to prevent the early release of ascorbic acid in the stomach and target its delivery to the intestine.