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Sci Pharm. 2008; 76: 77–89

The Influence of Selected Parameters on the Size and Shape of Alginate Beads Prepared by Ionotropic Gelation

Polona SMRDEL 1,2, Marija BOGATAJ * 2, Aleš MRHAR 2

1 Lek Pharmaceuticals d.d., Verovškova 57, 1526 Ljubljana, Slovenia
2 Faculty of Pharmacy, University of Ljubljana, Aškerčeva 7, 1000 Ljubljana, Slovenia

* Corresponding author: Tel.: +386-1-4769-510; Fax: +386-1-4258-031.
E-mail: (M. Bogataj).


Many bead biopharmaceutical characteristics are dependent on the bead shape. Furthermore, the shape is one of crucial parameters for incorporation of beads in more complex drug delivery system. Therefore, the aim of this study was to evaluate the influence of various processing parameters such as hardening time, temperature and concentration of calcium chloride solution and drying conditions on size, shape and morphology of alginate beads prepared by ionotropic gelation method. Theophylline was selected as a model drug. It was found that all studied parameters markedly affected bead form, resembling in most cases to ellipsoid spheres. Their sphericity was estimated three-dimensionally by measuring diameters of frontal and lateral side which were perpendicular to each other. Smaller and more spherical beads were obtained at longer hardening time and higher temperature of calcium chloride solution. The freeze-dried beads were the largest and the most spherical. It was demonstrated that optimization of bead shape as well as size and morphology could be achieved by altering processing parameters.


alginate beads • ionotropic gelation • shape • sphericity

Received February 29th, 2008 | Accepted March 12th, 2008 | Published Online March 30th, 2008