Abstract
Calcium-induced alginate gel bead (Alg-Ca) coated with an alginate hydrolysate (Alg), e.g. the guluronic acid block (GB) was prepared and the model drug, hydrocortisone release profiles were investigated under simulated gastrointestinal conditions. Their molecular weights were one sixth or one tenth that of Alg and the diffraction patterns of the hydrolysates resembled that of Alg. The drug release rate from Alg-Ca coated with GB apparently lowered than that of Alg-Ca (coating-free) in the gastric juice (pH1.2). And the coating did not resist the disintegration of Alg-Ca in the intestinal juice (pH 6.8) and the gel erosion accelerated the drug release. On the other hand, for the coated Alg-Ca containing chitosan, the drug release showed zero-order kinetics without rapid erosion of Alg-Ca. The drug release rate from Alg-Ca was able to be controlled by the coating and modifying the composition of the gel matrix.
Highlights
Alginic acid (Alg), a natural anionic polysaccharide, has been used as a medicine for stomach ulcers as well as a food additive because of the protective effect for the gastric mucosa on per oral administration
alginate hydrolysate (Alg) consists of α–L-guluronic acid (G) and β-D-mannuronic acid (M), and it is known that the composition of Alg, such as M/G ratio changes the characteristics of the Alg-Ca prepared with the Alg [6]
We have reported that the rheological properties of the Alg-Ca and the drug release profile from the beads were affected by the addition of GB to the gel matrix [8]
Summary
Alginic acid (Alg), a natural anionic polysaccharide, has been used as a medicine for stomach ulcers as well as a food additive because of the protective effect for the gastric mucosa on per oral administration. A sequence of G-G, G-blocks (GB) in the Alg molecule is closely related with the gel matrix formed between Alg and calcium ions. The drug release profile from Alg-Ca is affected by both the structure of the gel matrix and the properties of drug itself, such as its solubility.
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