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

Abstract

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)₂HPO₄ to SA (m_{(NH₄)₂HPO₄} /m_SA), 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)₂HPO₄} /m_SA = 0.1. The release rate of DS from the SA/HA/HNTs-DS 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.