A Swiss army knife for the treatment of bone cancers: a new multifunctional platform based upon SPIONs@copper-doped bioactive glass core–shell nanoparticles

Abstract

Core–shell nanometric heterostructures combining a magnetic core and a mesoporous bioactive glass shell doped with copper ions (γ-Fe₂O₃@SiO₂–CaO–CuO) were synthesised via iron salt coprecipitation and a modified Stöber sol–gel method using a cationic surfactant (CTAB) as a templating agent. Heterostructures with different dopant concentrations were obtained, and their structure, morphology and composition were characterized using a large set of techniques (XRD, FTIR, TEM, nitrogen gas sorption, ICP-OES and MAS-NMR). Their magnetic properties were assessed by AC magnetometry and their specific absorption rate was determined under multiple sets of magnetic field amplitudes (4–24 kA m⁻¹) and frequencies (146 and 280 kHz), proving their capacity to produce heat under an alternative magnetic field. NMR relaxometry experiments were performed, confirming the possibility of using these materials as negative (T₂-weighted) contrast agents in magnetic resonance imaging. Their in vitro bioactivity was evaluated after immersion in simulated body fluid (SBF) at 37 °C. All samples showed rapid hydroxyapatite crystal formation, only slightly delayed (from 3 to 24 h) when Cu-doped. Cytotoxic evaluations indicated a dose-dependent effect, but at a concentration of 0.25 mg mL⁻¹, none of the samples presented signs of cytotoxicity after 7 days. The antibacterial property of the most doped sample was assessed on Staphylococcus aureus. This study represents the first step in the development of a multifunctional synthetic biocompatible nanomaterial combining bone regeneration and antibacterial effect, under possible monitoring by MRI, and a potential cancer treatment by magnetic hyperthermia.