Effect of Ca²⁺, Ba²⁺, and Sr²⁺ on Alginate Microbeads
2006
Mørch, Ýrr A. | Donati, Ivan | Strand, Berit L. | Skjåk-Bræk, Gudmund
Microcapsules of alginate cross-linked with divalent ions are the most common system for cell immobilization. In this study, we wanted to characterize the effect of different alginates and cross-linking ions on important microcapsule properties. The dimensional stability and gel strength increased for high-G alginate gels when exchanging the traditional Ca²⁺ ions with Ba²⁺. The use of Ba²⁺ decreased the size of alginate beads and reduced the permeability to immunoglobulin G. Strontium gave gels with characteristics lying between calcium and barium. Interestingly, high-M alginate showed an opposite behavior in combination with barium and strontium as these beads were larger than beads of calcium−alginate and tended to swell more, also resulting in increased permeability. Binding studies revealed that different block structures in the alginate bind the ions to a different extent. More specifically, Ca²⁺ was found to bind to G- and MG-blocks, Ba²⁺ to G- and M-blocks, and Sr²⁺ to G-blocks solely.
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