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 Ca ²⁺ , Ba ²⁺ , and Al ³⁺ ions increased in the following order: D _sl (Al ³⁺ )> D _sl (Ca ²⁺ )> D _sl (Ba ²⁺ ). In contrast, the initial amount of pyranine and EE into the beads showed the reverse behavior.