Evaluation of the Drug Release Mechanism of pH-Sensitive Calcium Alginate Hydrogels in Simulated Physiological Fluids

Abstract

Calcium alginate hydrogels were prepared and loaded with ampicillin to evaluate their release mechanism in simulated physiological fluids. The calcium alginate hydrogels were characterized using FTIR spectroscopy and the Flory-Rehner equation of equilibrium swelling to calculate the molecular weight between crosslinks and crosslinking density. The loading capacity of ampicillin was followed the Langmuir isotherm model. The drug release and degradation of crosslinked alginate hydrogels were performed in simulated gastric fluid (pH 1.2) and simulated intestinal fluid (pH 7.5). The alginate with higher calcium content exhibited lower drug release rate and degradation rate. The release rate of ampicillin in SIF was higher than that in SGF and followed a Fickian diffusion mechanism. The results were shown that the release kinetics and degradation were significantly dependent on the crosslinking degree of the alignate hydrogels and the physiological pH. SEM micrographs were shown an eroded surface after in the simulated intestinal fluid. The results were indicated that calcium alginate hydrogels might be useful for the localized delivery of drug in the intestinal environment.