Magnetic Hyperthermia of Polyvinylpyrrolidone Coated La_0.6Sr_0.4MnO₃ Nanoparticles Synthesized by Sol-Gel Auto Combust Method

Abstract

Lanthanum strontium manganite (La0.6Sr0.4MnO3) nanoparticles have been synthesized by sol-gel auto combustion method. Four sets of LSMO nanoparticles have been synthesized by varying the reaction pH from 10 to 13. LSMO nanoparticles were further functionalized with Polyvinylpyrrolidone (PVP). Structural properties of LSMO nanoparticles were determined by powder X-ray diffraction. Rietveld refinement of diffractograms revealed that irrespective of synthesis conditions, LSMO nanoparticles were synthesized with rhombohedral and orthorhombic crystal phases. Magnetic properties (saturation magnetization, domain magnetization and Curie temperature) of LSMO nanoparticles have been determined by vibration sample magnetometer. Synthesized LSMO nanoparticles are soft ferromagnetic and possesses Curie temperature in between 360 – 370 K. Their saturation magnetization increases with increases in reaction pH, which is in good agreement with the corresponding increase in their rhombohedral phase fraction. PVP coated LSMO nanoparticles when exposed to AC magnetic field produces magnetic hyperthermia temperature (45 °C) within 10 minutes of exposure. Hyperthermia efficiency of LSMO nanoparticles measured in terms of specific loss power (SLP) increases with magnetic field frequency and field strength and it decreases with nanoparticle concentration. LSMO nanoparticles synthesized at pH 10, 11 and 12 are suitable for the magnetic hyperthermia therapy of cancer while the one synthesized at pH 13 is not suitable for magnetic hyperthermia as it could not produce the requisite temperature of 45 °C needed to induce cell apoptosis in in-vivo experiments. Highest hyperthermia efficiency (15.69 W/g) was observed for PVP coated LSMO nanoparticles (concentration: 12.5 mg/mL) synthesized at pH 10 when exposed to an AC magnetic field of strength 10 mT and field frequency of 935.6 KHz.