The Effect of Silica Coatings on the Structural, Magneticand Antimicrobial Properties of Silver Doped ManganiteMagnetic Nanoparticles for Biomedical Applications

Surface modification of magnetic nanoparticles with biocompatible materials is usually required for biomedical applications. La0�80Ag0�15MnO3 (LAMO) magnetic nanoparticles (MNPs) were synthesized by the sol–gel auto combustion synthesis with the nanoparticles subsequently coated with silica. The effect of the coatings on the structural, morphology, magnetic properties, colloidal stability and antimicrobial properties of LAMO nanoparticles were studied using powder X-ray diffraction, thermogravimetric analysis, field emission scanning electron microscopy, zeta potential and vibrating sample magnetometer. The crystalline perovskite structure of LAMO was retained after silica coating but with a reduction in crystallinity. Also, there was a reduction of agglomeration and average crystallite size (48 nm) were the same after silica coating. The zeta potential of the coated sample revealed a considerable high colloidal stability value (−27.70 mV) at physiological pH 7.4. The magnetization values of 26 emu/g and 25 emu/g recorded for bare and coated LAMO samples, respectively show that LAMO MNPs retained its ferromagnetic behaviour after silica coating. Bare and silica coated LAMO gave very high bactericidal effect against S. aureus however, there was no change in the antimicrobial properties of LAMO MNPs with silica coating. These results show that while the silica coating influences greatly the morphology and colloidal stability of LAMO nanoparticles, it had virtually no effect on the crystalline structure and size, magnetization and the antimicrobial properties.