In situ generation of sodium alginate/hydroxyapatite/halloysite nanotubes nanocomposite hydrogel beads as drug-controlled release matrices

Diclofenac sodium-loaded sodium alginate/hydroxyapatite/halloysite nanotubes (SA/HA/HNTs-DS) nanocomposite hydrogel beads were prepared by the in situ generation of HA nanoparticles during the sol-gel transition of the SA/HNTs suspension. The nanocomposite beads were characterized by FT-IR spectroscopy, thermogravimetric analysis and field emission scanning electron microscopy, etc. Factors, e.g., the weight ratio of HNTs to SA (m(HNTs)/m(SA)), the weight ratio of (NH4)(2)HPO4 to SA (m(NH4)(2)HPO4/mS(A)), and the concentration of SA, which influenced the entrapment efficiency (EE) and release of DS, were investigated. The EE was enhanced from 62.85 +/- 0.29% to 74.63 +/- 1.65%, and the burst release of DS was overcome by introducing appropriate amounts of HA and HNTs. An almost constant rate release of DS is achieved when m(HNTs)/m(SA) = 0.3 and m((NH4)2)HPO(4)/mS(A) = 0.1. The release rate of DS from the SA/HA/HNT-sDS beads was 9.19 mg g(-1) h(-1). The release of DS is controlled by Case-II transport. The tubular structure of the HNTs and the in situ-formed HA nanoparticles can restrict movability of the SA polymer chains, which is the main reason for the improved drug loading and release behavior.