Fabrication of a nano-drug delivery system based on layered rare-earth hydroxides integrating drug-loading and fluorescence properties

Abstract

We demonstrate the first example of intercalation of naproxen (abbr. NPX) into layered europium hydroxide (LEuH) and investigate the structure, chemical composition, thermostability, morphology, luminescence properties, cytotoxic effect, and controlled-release behaviors. Different deprotonation degrees lead to NPX–LEuH composites with diverse structures (horizontal or vertical arrangement), and the thermal stability of organics is enhanced after intercalation. The Eu³⁺ luminescence in NPX–LEuH composites is enhanced, especially for the NPX–LEuH-1 : 0.5 composite. The content of naproxen in the intercalation material can be confirmed by HPLC. The cytotoxic effect of LEuH is observed with a sulforhodamine B (SRB) colorimetric assay, which reveals that the LEuH has low cytotoxic effects on most cells. In addition, the NPX–LEuH nanocomposites can control the release of NPX in Na₂HPO₄–NaH₂PO₄ buffer solution at pH 6.86 and 37 °C, and the complete release needs about 200 min. The release mechanism can be ascribed to the ion-exchange reaction between NPX and HPO₄²⁻/H₂PO₄⁻ in bulk solution. The ion-exchange velocity is fast at the beginning and slows down gradually with the exchange reaction. The construction of LRH composites with drug molecules provides a beneficial pathway for preparing a nano-drug delivery system based on LRHs integrating drug-loading and fluorescence properties.