Propranolol hydrochloride binding in calcium alginate beads

The interaction of propranolol hydrochloride with alginate molecular chains in calcium alginate beads was investigated. The drug was either incorporated into formed calcium alginate gel beads or incorporated simultaneously with the gelation of alginate beads by Ca2+. Beads produced by the former method had a higher drug content and lower Ca2+ level compared to those prepared by the latter method. The extent of drug binding to the alginate molecules increased with decreasing Ca2+ levels in the beads, indicating that propranolol and Ca2+ shared common binding sites in the alginate chains. The appearance of the beads and the morphology of the alginate polymer in the beads were affected by the amounts of both propranolol and Ca2+ in the beads. Differential scanning calorimetry (DSC) analyses showed that the formation of the calcium alginate gel structure was impeded in the presence of propranolol molecules.