Building an aprismatic enamel-like layer on a demineralized enamel surface by using carboxymethyl chitosan and lysozyme-encapsulated amorphous calcium phosphate nanogels

Objectives: The purpose of this study was to prepare carboxymethyl chitosan (CMC) and lysozyme nanogels that could encapsulate amorphous calcium phosphate (ACP) for achieving its controlled delivery, thus forming an aprismatic enamel-like layer on the demineralized enamel surface. Methods: CMC/LYZ-ACP nanogels were developed, and the controlled delivery of ACP from the nanogels was induced by the presence of NaCl. The nanogel morphologies at various NaCl concentrations was measured by transmission electron microscopy (TEM). The particle sizes and zeta potentials (zeta-potential) of the samples were determined using a combined dynamic light scattering/particle electrophoresis instrument. Comparing the remineralization effect of the CMC/LYZ-ACP nanogels on the demineralized enamel surface with that of a fluoride treatment, the remineralization effect was examined by nanoindentation tests, X-ray diffraction (XRD), confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM). Results: CMC/LYZ-ACP nanogels were negatively charged spherical structures with a particle size of approximately 300 nm. At high concentrations of NaCl (0.15 M), ACP was dissociated from the disassembled nanogels and transformed into hydroxyapatite (HAP). Groups treated with the CMC/LYZ-ACP nanogels showed the regeneration of an aprismatic enamel-like layer on an acid-etched enamel surface, which provided increased mechanical properties (P < 0.05) and a high impermeability (P < 0.01) compared to those of the fluoride-treated group. Conclusions: This research provides a new idea for the stable and controllable delivery of ACP from CMC/LYZ-ACP nanogels, which can form an aprismatic enamel-like layer in situ on the surface of demineralized enamel. In regard to further clinical development, this material and method may be promising for treating early enamel caries.

Automated summary

This study aimed to prepare CMC/LYZ-ACP nanogels for controlled delivery of amorphous calcium phosphate (ACP) to form an aprismatic enamel-like layer on demineralized enamel. The nanogels were negatively charged spherical structures with a particle size of approximately 300 nm, and at high concentrations of NaCl, ACP was dissociated from the nanogels and transformed into hydroxyapatite (HAP).