Modification of selectively acid-etched halloysite by mucoadhesive chitosan derivatives: New bionanocomposites with improved functional properties

Abstract

In this study, the modification of selectively acid-etched halloysite (eHal) by low molecular weight chitosan (LChi) and its methacrylated derivative (MeLChi) is investigated to form new bionanocomposites with improved functional properties. The formation of nanocomposites was confirmed by various instrumental techniques (ζ-potential measurements, SEM, FT-IR, DSC, XRD and 1H NMR). Both nanocomposites exhibited improved functional properties while preserving the tubular structure of halloysite. The cytotoxic activity of eHal and eHal-polycation nanocomposites against normal human lung fibroblasts (MRC5) was determined using MTT assay. The results showed good biocompatibility of the prepared nanocomposites, with a cell survival rate of more than 90 %. The mucoadhesive properties of eHal and the corresponding chitosan nanocomposites were investigated in vitro. Primarily, ζ-potential measurements revealed electrostatic interactions between the eHal-polycation nanocomposites and mucin. The absorption study showed that the eHal-MeLChi nanocomposites could adsorb a greater amount of mucin (≈82 %) than the eHal-LChi nanocomposites (≈72 %) and eHal (≈58 %) after 8 h of incubation. Furthermore, the compacts of the tested samples were prepared by direct compression, and the detachment force against the mucin compact was measured using a texture analyzer. A significantly higher detachment force of the eHal-MeLChi nanocomposite compact (1.59 ± 0.07 N) from the mucin compact was determined compared to the eHal-LChi (1.35 ± 0.08 N) and eHal (0.98 ± 0.08 N) samples, demonstrating their improved mucoadhesive potential. In summary, this study demonstrates that functionalization of eHal with MeLChi may be a useful approach for the preparation of nanocomposites as potential carriers for mucoadhesive dosage forms.