Self‐aggregates of cholic acid hydrazide–dextran conjugates as drug carriers

Abstract

AbstractCholic acid hydrazide–dextran conjugates (CAH–DEX's) with stable acryl hydrazone linkages were synthesized from cholic acid hydrazide and poly(aldehyde dextran) and were characterized by Fourier transform infrared (FTIR) spectroscopy, 1H‐NMR, and surface tension measurements. The conjugates developed a lower critical aggregation concentration, which was determined by 1,6‐diphenyl‐1,3,5‐hexatriene dye solubilization methods, 1.41 and 2.10 × 10−2 mg/mL for CAH–DEX 9.0 and CAH–DEX 6.5, respectively. A hydrophobic drug, indomethacin (IN), was physically entrapped inside the self‐aggregates, and the IN‐loaded self‐aggregates were analyzed with a dynamic light‐scattering system, transmission electron microscopy, and atomic force microscopy. The maximum loading of IN reached 29.9% of the CAH–DEX self‐aggregates, which suggested a high loading efficiency of 51.2%. The size of the self‐aggregates increased when the drug was entrapped. IN was released from CAH–DEX self‐aggregates at pH 4 much slower than at pH 7.4, and in pH 4 media, the release profile was pseudo‐zero‐order in kinetic terms for up to 14 days. There was almost no change in the FTIR spectra of the CAH–DEX's, which were incubated in buffers of pH 7.4 and pH 4 for 24 h, which indicated that acryl hydrazone was considerably resistant to hydrolysis. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 487–493, 2005