Preparation and swelling properties of pH-sensitive sodium alginate/layered double hydroxides hybrid beads for controlled release of diclofenac sodium.

Layered double hydroxides (LDHs) are promising materials for the preparation of novel drug delivery matrices. To reveal the interaction between LDHs and polymers, a series of pH-sensitive sodium alginate/layered double hydroxides (SA/LDHs) hybrid beads were prepared using the simple surface crosslinking method. The SA/LDHs hybrid beads were characterized by FTIR, XRD, and SEM to study their structure and the role that LDHs play. Swelling behaviors in various aqueous solutions and drug loading as well as controlled release behavior of the SA/LDHs hybrid beads were also investigated by using diclofenac sodium (DS) as the model drug to reveal the effects of introduced LDHs. The results indicate that the positively charged LDHs layers are adsorbed on the negatively charged SA polymer chains through electrostatic interaction and act as inorganic crosslinkers in the three-dimensional network. In addition, a small part of DS molecules intercalate into layers of LDHs through an anion exchange process. The electrostatic interaction between LDHs and SA has restricted movability of the SA polymer chains, and then slows down swelling and dissolution rates of the SA/LDHs hybrid beads in aqueous solutions. The electrostatic interaction and the intercalation of DS into layers of LDHs have also improved the entrapment efficiency (EE) and controlled release behavior of SA/LDHs hybrid beads for DS. (c) 2009 Wiley Periodicals, Inc.