Flexible heteroionic calcium-magnesium alginate beads for controlled drug release

•Magnesium ions and alginate can form hydrogels but to date non attention has been addressed to drug release applications.•Simple and straightforward approach to obtain heteroionic alginate beads.•Beads present different swelling and drug release behavior than calcium alginate beads.•Calcium gives mechanical stability preventing rapid dissolution of the gels.•Incorporation of magnesium tunes the swelling/erosion process and the release of the active substance. In the present work heteroionic calcium-magnesium alginate beads have been prepared by ionotropic gelation using different Ca:Mg ratios. This simple and straightforward approach allowed the obtention of CaMg-alginate beads presenting different mechanical performance depending on the Mg:Ca ratio. The dynamic swelling behavior of the beads was investigated. Increase in the quantity of Mg2+ incorporated in the beads increased the rate of swelling at pH 1.2 and pH 7.2. Finally, the release of ibuprofen was investigated. It was found that increasing the Mg2+ present in the beads raised the drug release rate.