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Physicochemical characterization of a pectin/calcium matrix containing a large fraction of calcium chloride: Implications for sigmoidal release characteristics
Author(s) -
Wei Xiuli,
Chen Zhukang,
Lu Yi,
Xu Huinan,
Chen Guiliang,
Wu Wei
Publication year - 2009
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.30306
Subject(s) - pectin , calcium , chemistry , matrix (chemical analysis) , chemical engineering , swelling , aqueous solution , nuclear chemistry , materials science , chromatography , organic chemistry , biochemistry , composite material , engineering
The physicochemical properties of pectin/calcium matrix tablets were studied with an emphasis on the effect of over 50% of calcium chloride to better understand the fundamentals of the drug‐release mechanisms. The absence of the adsorption of methylene blue onto the calcium‐containing pectin matrix served as evidence of the calcium‐ion‐induced in situ crosslinking of pectin chains. Visual and scanning electron microscopy observation showed the reinforced robustness of the pectin/calcium matrix, whereas cryo‐SEM revealed the formation of a pectin aggregate network as a result of calcium‐induced crosslinking. The aggregate network underwent gradual erosion to a lower density, which indicated the erosion of the matrix. However, little change in the texture of the pectin/calcium matrix was observed at earlier times, which was interpreted as the initial stages of drug‐release retardation. The apparent viscosity of the pectin aqueous dispersion increased biphasically as the calcium amount increased. The initial sharp increase was interpreted as calcium‐induced crosslinking, whereas the following gradual increase was ascribed to a possible salt effect. We concluded that the salt effect and calcium‐induced crosslinking contributed to a series of physical changes of the pectin matrix, which correlated to the sigmoidal release of indomethacin from the pectin/calcium matrix tablet. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009