Targeted cancer therapy through self-regulated magnetic hyperthermia using biocompatible zirconium-doped LSMO nanoparticles

This work examined the efficacy of novel La³⁺ substituted Zr⁴⁺ in Lanthanum strontium manganese oxide (LSMO) superparamagnetic nanoparticles (SPMNPs) for self-regulated magnetic hyperthermia therapy. The effects of Zr doping on the structural, morphological, elemental, compositional, colloidal, hydrodynamic, thermal, magnetic, and heating properties of La_0.76-xZr_xSr_0.24MnO₃ (x = 0, 0.01, 0.03, and 0.05; labeled LZ1-LZ4). The XRD and Rietveld refinement analysis confirmed the synthesized SPMNPs exhibit rhombohedral R-3c space group with high phase purity. The nanoparticles sizes reduced from 28.3 to 24.8 nm by added Zr⁴⁺ concentration. EDS and XPS analysis confirmed the presence of La³⁺, Zr⁴⁺, Sr²⁺, Mn³⁺, and Mn⁴⁺ in the synthesized SPMNPs. The TGA/DSC analysis confirmed that the addition of Zr⁴⁺ into the LSMO SPMNPs enhanced their thermal stability up to 900 °C. Magnetic property analysis revealed that the synthesized SPMNPs exhibit superparamagnetic behaviour, with both magnetization and Curie temperature decreasing in a size-dependent manner. Notably, LZ2 exhibited a Curie temperature of 317 K, optimal for self-regulated magnetic hyperthermia. Inductance heating study demonstrated that LZ2 reached 317 K within 900 sec and exhibited a high specific absorption rate (SAR) of 54.38 W/g and intrinsic loss parameter value is 8.382 nHm²g⁻¹. The in vitro cytotoxicity assay confirmed that the synthesized SPMNPs exhibited excellent biocompatibility up to 1000 µg/mL. This work highlights the potential of Zr⁴⁺-doped LSMO SPMNPs, particularly LZ2 SPMNPs, as biocompatible, self-regulating agents for targeted magnetic hyperthermia in cancer therapy.