Enhanced entrapment efficiency and modulated drug release of alginate beads loaded with drug-clay intercalated complexes as microreservoirs

Calcium alginate (CA) beads loaded with intercalated complexes of propranolol HCI (PPN) and magnesium aluminum silicate (MAS), which serve as microreservoirs, were prepared using an ionotropic gelation method. The surface and matrix morphology, drug entrapment efficiency, thermal behavior, mechanical properties, and PPN release of the CA beads were characterized. The results showed that the molecular interaction of MAS with PPN and sodium alginate (SA) resulted in PPN-MAS intercalated complex particles as microservoirs and denser matrix structure formation in the CA beads. The small particles of the PPN-MAS complexes were embedded on the surface and in the matrix of the CA beads, which was revealed using SEM and EDX. The PPN entrapment efficiency of the PPN-MAS complex-loaded CA beads was significantly higher than that of the PPN-loaded CA beads. Increased MAS content caused an increase in PPN entrapment efficiency, thermal stability, and the strength of the CA beads. Moreover, the PPN-MAS complexes in the CA beads could remarkably reduce the initial burst of PPN release as well as its release rate in both 0.1 M HCI and phosphate buffer at pH 6.8, depending on the MAS content added. Additionally, the PPN-MAS complex-loaded CA beads also produced a sustained release pattern of PPN in simulated gastro-intestinal conditions. In conclusion, the CA beads containing drug-clay intercalated complexes as microreservoirs could enhance drug entrapment efficiency, reduce initial burst release and modulate drug release. Furthermore, these beads represent a promising oral drug delivery system for highly water-soluble cationic drugs. (C) 2010 Elsevier Ltd. All rights reserved.