J. Biomater. Sci. Polymer Edn, Vol. 19, No. 1, pp. 47–59 (2008)  VSP 2008. Also available online - www.brill.nl/jbs Ionically cross-linked carrageenan-alginate hydrogel beads Z. MOHAMADNIA, M. J. ZOHURIAAN-MEHR ∗ , K. KABIRI, A. JAMSHIDI and H. MOBEDI Iran Polymer and Petrochemical Institute (IPPI), P.O. Box 14965-115, Tehran, Iran Received 4 December 2006; accepted 17 July 2007 Abstract—Hydrogel beads based on the carbohydrate biopolymers kappa-carrageenan and sodium alginate were newly prepared. Both classical and experimental design (Taguchi) methods were used to obtain the optimum conditions for the full-polysaccharide hydrogel preparation. The carrageenan- alginate (Caralgi) beads exhibited a surface morphology smoother than that of the one-polysaccharide network beads. Infrared spectroscopy and DSC/TGA thermal methods were used to study the chemical structure and thermal properties of the beads. The carrageenan parts appreciably enhanced thermostability of the networks. The fully carbohydrate-based hydrogel beads are expected to be biologically compatible and degradable. They are being considered as new carriers for drug loading and controlled delivery systems. Key words: Hydrogel; carrageenan; sodium alginate; ionic cross-linking; bead. INTRODUCTION Carbohydrate polymers from marine sources have been studied and utilized in pharmaceutical and biotechnological industries for many years. Alginates are a family of linear polysaccharides, produced by brown algae which contain varying amounts of 1,4-linked β -D-mannuronic acid and α-L-guluronic acid residues [1]. The structure of these units is shown in Fig. 1. Besides its desired mucoadhesive properties, which enabled it to be used as a matrix for the entrapment and delivery of variety of proteins cell, biotechnological applications are based either on specific biological effects of the alginate molecule itself or on its unique, gentle and almost temperature-independent sol/gel transition in the presence of multivalent cations, e.g., Ca 2+ [1, 2]. Alginate gelation takes place when divalent (usually Ca 2+ ) or trivalent cations interact ionically with blocks of guluronic acid residues, resulting ∗ To whom correspondence should be addressed. E-mail: m.zohuriaan@ippi.ac.ir or mjzohuriaan@yahoo.com