Cation Effect on Slow Release from Alginate Beads: A Fluorescence Study
In this study spherical alginate beads containing pyranine (P-y) as a fluorescence probe were prepared by ionotropic gelation of a sodium alginate solution. The steady state fluorescence technique was used to study pyranine release from the alginate beads crosslinked with calcium barium and aluminum ions respectively. The slow release of P-y was observed with the time drive mode of the spectrophotometer at 512 nm. Fluorescence emission intensity (I-p) from P-y was monitored during the release process and the encapsulation efficiency (EE) of pyranine from the alginate beads was calculated. The Fickian Diffusion model was used to measure the release coefficients D-sl. It was seen that the slow release coefficients of pyranine from the alginate beads crosslinked with Ca2+ Ba2+ and Al3+ ions increased in the following order: D-sl (Al3+)> D-sl (Ca2+)> D-sl (Ba2+). In contrast the initial amount of pyranine and EE into the beads showed the reverse behavior.