# Zoledronic acid-loaded HAp–SiO2–CaMoO4:Eu3+ with luminescent properties as a novel drug delivery system

## TL;DR

Researchers created a new nanocomposite that can deliver a cancer drug and emit light for imaging, showing promise for bone cancer treatment.

## Contribution

The first synthesis of HAp–SiO2–CaMoO4:Eu3+ nanocomposites for drug delivery and luminescent imaging.

## Key findings

- The nanocomposites showed strong red emission at 615 nm suitable for luminescence-based imaging.
- Zoledronic acid was efficiently loaded and released in a sustained manner following a non-Fickian diffusion mechanism.
- ZA-loaded nanocomposites exhibited antiproliferative activity against osteosarcoma cells with an IC50 of 56.33 μM.

## Abstract

CaMoO4:Eu3+-functionalized hydroxyapatite–silica (HAp–SiO2–CaMoO4:Eu3+) core–shell nanocomposites were synthesized for the first time and evaluated as a multifunctional drug delivery and imaging platform. HAp–SiO2 nanocomposites were prepared via a hydrothermal route and subsequently functionalized with a luminescent CaMoO4:Eu3+ shell using the Pechini sol–gel method. Structural analyses confirmed the successful coexistence of HAp, SiO2, and CaMoO4:Eu3+ phases, while electron microscopy revealed spherical core–shell morphologies. Dynamic light scattering measurements showed average hydrodynamic particle sizes of approximately 1085 nm for HAp–SiO2 and 1427 nm for HAp–SiO2–CaMoO4:Eu3+ nanocomposites, indicating particle clustering in aqueous media, which is consistent with the low surface charge of the particles. The Eu3+-doped shell exhibited a strong red emission centered at 615 nm, demonstrating suitability for luminescence-based imaging. Zoledronic acid (ZA) was efficiently loaded onto the nanocomposites under supercritical CO2 conditions, providing high loading efficiency and sustained release behavior. In vitro release studies in phosphate-buffered saline (pH 7.4, 37 °C) followed the Korsmeyer–Peppas kinetic model (n = 0.83), indicating a non-Fickian diffusion mechanism. Cytotoxicity assays on Saos-2 osteosarcoma cells demonstrated that ZA-loaded nanocomposites exhibited enhanced antiproliferative activity, with an IC50 value of 56.33 μM after 48 h. These results highlight the potential of HAp–SiO2–CaMoO4:Eu3+ nanocomposites as an integrated theranostic system for targeted bone cancer therapy. Overall, the results demonstrate that the proposed nanocomposite design successfully translates the intended theranostic concept into experimentally validated structural, optical, and biological performance.