In the study, a complex composed of alginate blended with a water-soluble chitosan (N,O-carboxymethyl chitosan, NOCC)
was prepared to form microencapsulated beads by dropping aqueous alginate–NOCC into a Ca2+ solution. These
microencapsulated beads were evaluated as a pH-sensitive system for delivery of a model protein drug (bovine
serum albumin, BSA). The main advantage of this system is that all procedures used were performed in aqueous medium
at neutral environment, which may preserve the bioactivity of protein drugs. The swelling characteristics of these hydrogel
beads at distinct compositions as a function of pH values were investigated. It was found that the test beads with an alginate-to-
NOCC weight ratio of 1:1 had a better swelling characteristic among all studied groups. With increasing the total concentration
of alginate–NOCC, the effective crosslinking density of test beads increased significantly and a greater amount of drug was
entrapped in the polymer chains (up to 77%). The swelling ratios of all test groups were approximately the same (B3.0) at pH 1.2.
At pH 7.4, with increasing the total concentration of alginate–NOCC, the swelling ratios of test beads increased significantly
(20.0–40.0), due to a larger swelling force created by the electrostatic repulsion between the ionized acid groups (–COO).
It was shown that BSA was uniformly distributed in all test beads. At pH 1.2, retention of BSA in hydrogels may be improved
by rinsing test beads with acetone (the amount of BSA released was below 15%). At pH 7.4, the amounts of BSA released
increased significantly (B80%) as compared to those released at pH 1.2. With increasing the total concentration of alginate–
NOCC, the release of encapsulated proteins was slower. Thus, the calcium–alginate–NOCC beads with distinct total
concentrations developed in the study may be used as a potential system for oral delivery of protein drugs to different regions of
the intestinal tract.
In the study, a complex composed of alginate blended with a water-soluble chitosan (N,O-carboxymethyl chitosan, NOCC)was prepared to form microencapsulated beads by dropping aqueous alginate–NOCC into a Ca2+ solution. Thesemicroencapsulated beads were evaluated as a pH-sensitive system for delivery of a model protein drug (bovineserum albumin, BSA). The main advantage of this system is that all procedures used were performed in aqueous mediumat neutral environment, which may preserve the bioactivity of protein drugs. The swelling characteristics of these hydrogelbeads at distinct compositions as a function of pH values were investigated. It was found that the test beads with an alginate-to-NOCC weight ratio of 1:1 had a better swelling characteristic among all studied groups. With increasing the total concentrationof alginate–NOCC, the effective crosslinking density of test beads increased significantly and a greater amount of drug wasentrapped in the polymer chains (up to 77%). The swelling ratios of all test groups were approximately the same (B3.0) at pH 1.2.At pH 7.4, with increasing the total concentration of alginate–NOCC, the swelling ratios of test beads increased significantly(20.0–40.0), due to a larger swelling force created by the electrostatic repulsion between the ionized acid groups (–COO).It was shown that BSA was uniformly distributed in all test beads. At pH 1.2, retention of BSA in hydrogels may be improvedby rinsing test beads with acetone (the amount of BSA released was below 15%). At pH 7.4, the amounts of BSA releasedincreased significantly (B80%) as compared to those released at pH 1.2. With increasing the total concentration of alginate–NOCC, the release of encapsulated proteins was slower. Thus, the calcium–alginate–NOCC beads with distinct totalconcentrations developed in the study may be used as a potential system for oral delivery of protein drugs to different regions ofthe intestinal tract.
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