pH-sensitive behavior of two-component hydrogels composed of N,O-carboxymethyl chitosan and alginate.

Division of Applied Chemistry, Department of Applied Science, Chinese Naval Academy, 669 Jiun Shiaw Road, Kaohsiung, Taiwan 813, ROC.
Journal of Biomaterials Science Polymer Edition (Impact Factor: 1.36). 02/2005; 16(11):1333-45. DOI: 10.1163/156856205774472317
Source: PubMed

ABSTRACT A two-component pH-sensitive hydrogel system composed of a water-soluble chitosan derivative (N,O-carboxymethyl chitosan, NOCC) and alginate cross-linked by genipin, glutaraldehyde or Ca2+ was investigated. Preparation and structures of these hydrogels and their swelling characteristics and release profiles of a model protein drug (bovine serum albumin, BSA) in simulated gastrointestinal media are reported. At pH 1.2, the swelling ratios of the hydrogels cross-linked by distinct methods were limited. Of note is that the lowest swelling ratios of test hydrogels were found at pH 4.0. At pH 7.4, the carboxylic acid groups on test hydrogels became progressively ionized and led to a significant swelling. There was barely any BSA released from the glutaraldehyde-cross-linked hydrogel throughout the entire course of the study. The amounts of BSA released at pH 1.2 from the genipin- and Ca(2+)-cross-linked hydrogels were relatively low (approx. 20%). At pH 4.0, there was still significant BSA release from the Ca(2+)-cross-linked hydrogel, while the cumulative BSA released from the genipin-cross-linked hydrogel was limited due to its shrinking behavior. At pH 7.4, the amount of BSA released from the genipin- and Ca(2+)-cross-linked hydrogels increased significantly (approx. 80%) because the swelling of both test hydrogels increased considerably. The aforementioned results indicated that the swelling behaviors and drug-release profiles of these test hydrogels are significantly different due to their distinct cross-linking structures.

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