2.7. In vitro release measurement
GLS release from encapsulated beads as a function of time was studied.
Glucose, a commonly used marker for polysaccharide was measured
to monitor the GLS release rate [24]. To mimic the drug release
in the gastrointestinal (GI) tract, the GLS loaded alginate beads were
firstly incubated in simulated stomach solution (SS1, pH 1.8) for 3 h
and then in simulated intestinal solution (SI1, pH 7.5) for another 3 h.
Briefly, approximately 50 mg GLS/A beads prepared at the applied voltage
of 0, 5 and 10 kV and dried by three different drying methods were
placed into 20 mL fresh buffer media incubated at 37 ± 0.5 °C. At
predetermined intervals (e.g. 30 min), a 2 mL aliquot of the test solution
was withdrawn periodically and replaced with an equal volume of the
fresh buffer medium. The GLS concentration in the removed solution
was detected by measuring the absorbance of glucose at 488 nm using
a UV–VIS spectrophotometer (LAMBDA 950, PerkinElmer, UK). The percentage
of GLS release was calculated by the following method [25]:
GLS released ð Þ¼ % At
A∞
where At and A∞ are the absorbance of releasing GLS at time t and the
absorbance of complete releasing, respectively.