M.R. Phadatare

Studies on colloidal stability of PVP-coated LSMO nanoparticles for magnetic fluid hyperthermia

La0.7Sr0.3MnO3 (LSMO) nanoparticles with a size of ∼23 nm have been prepared by a combustion method and functionalized with polyvinylpyrrolidone (PVP) for their possible application in magnetic fluid hyperthermia (MFH). Uncoated and PVP-coated samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy and vibrating sample magnetometer studies. Magnetic measurements of both coated and uncoated particles reveal the superparamagnetic nature at room temperature. Colloidal stability has been measured in terms of zeta potential. The resulting PVP-coated particles form a stable suspension in phosphate buffer saline (PBS) and double distilled water (DDW) and possess a narrow hydrodynamic size distribution. The induction heating studies of these nanoparticles at different alternating magnetic fields (167.6, 251.4 and 335.2 Oe) were carried out by dispersing nanoparticles in DDW and PBS. These PVP-coated LSMO NPs exhibit a higher specific absorption rate in PBS than in DDW. The results suggest that combustion-synthesized LSMO nanoparticles coated with PVP can be used as potential heating agents in MFH.

Structured superparamagnetic nanoparticles for high performance mediator of magnetic fluid hyperthermia: Synthesis, colloidal stability and biocompatibility evaluation

Core-shell structures with magnetic core and metal/polymer shell provide a new opportunity for constructing highly efficient mediator for magnetic fluid hyperthermia. Herein, a facile method is described for the synthesis of superparamagnetic LSMO@Pluronic F127 core-shell nanoparticles. Initially, the surface of the LSMO nanoparticles is functionalized with oleic acid and the polymeric shell formation is achieved through hydrophobic interactions with oleic acid. Each step is optimized to get good dispersion and less aggregation. This methodology results into core-shell formation, of average diameter less than 40 nm, which was stable under physiological conditions. After making a core-shell formulation, a significant increase of specific absorption rate (up to 300%) has been achieved with variation of the magnetization (<20%). Furthermore, this high heating capacity can be maintained in various simulated physiological conditions. The observed specific absorption rate is almost higher than Fe3O4. MTT assay is used to evaluate the toxicity of bare and core-shell MNPs. The mechanism of cell death by necrosis and apoptosis is studied with sequential staining of acridine orange and ethidium bromide using fluorescence and confocal microscopy. The present work reports a facile method for the synthesis of core-shell structure which significantly improves SAR and biocompatibility of bare LSMO MNPs, indicating potential application for hyperthermia.

Low-temperature synthesis of MnxMg1?xFe2O4(x?=?0?1) nanoparticles: cation distribution, structural and magnetic properties

Nanoferrites having composition MnxMg1−xFe2O4(x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) are synthesized by a low-temperature combustion method. The particle size measured from transmission electron microscopy and x-ray diffraction (XRD) patterns confirms the nanosized dimension of the as-prepared powder. From the analysis of XRD data with Scherrers formula, the average crystallite size ranges from 23 to 33 nm and the lattice parameter ranges from 8.385 to 8.468 A. Substitution of Mn2+ in MgFe2O4 causes an increase in the lattice constant, and this moderately distorts the lattice. Magnetic properties such as magnetization (Ms), coercivity (Hc) and remanence (Mr) with increasing Mn2+ concentration are studied at room temperature by a vibrating sample magnetometer. Substitution of Mn2+ for Mg2+ increases Ms from 34.5 to 54.5 emu g−1 and decreases Hc from 51.0 to 45.0 Oe. The results imply that the low-temperature combustion method is an efficient route for synthesis of nanoferrites without any extra calcination step. The as-prepared Mg–Mn ferrites are suitable for memory and switching circuits in digital computers.

Enhancement of specific absorption rate by exchange coupling of the core–shell structure of magnetic nanoparticles for magnetic hyperthermia

Conversion of electromagnetic energy into heat by nanoparticles (NPs) has the potential to be a powerful, non-invasive technique for biomedical applications such as magnetic fluid hyperthermia, drug release, disease treatment and remote control of single cell functions, but poor conversion efficiencies have hindered practical applications so far. In this paper, an attempt has been made to increase the efficiency of magnetic thermal induction by NPs. To increase the efficiency of magnetic thermal induction by NPs, one can take advantage of the exchange coupling between a magnetically hard core and magnetically soft shell to tune the magnetic properties of the NP and maximize the specific absorption rate, which is the gauge of conversion efficiency. In order to examine the tunability of magnetocrystalline anisotropy and its magnetic heating power, a representative magnetically hard material (CoFe2O4) has been coupled to a soft material (Ni0.5Zn0.5Fe2O4). The synthesized NPs show specific absorption rates that are of an order of magnitude larger than the conventional one.

Natural radioactivity study in soil samples of South Konkan, Maharashtra, India

This study assesses the level of natural radioactivity due to radionuclides, ²³⁸U, ²³²Th and ⁴⁰K, in 50 soil samples collected from South Konkan, Maharashtra, India. The mean activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K are 44.97 ± 1.22 Bq kg⁻¹, 59.70 ± 2.17 Bq kg⁻¹ and 217.51 ± 8.75 Bq kg⁻¹, respectively, measured from all the soil samples studied. The good correlation between activity concentration of U-238 and Th-232; U-238 and K-40 as well as between activity concentration of Th-232 and K-40 was observed. The average calculated absorbed dose rate in air (68.08 nGy h⁻¹) was found to be higher than the world average of 57 nGy h⁻¹ (UNSCEAR 2000). Radium equivalent activity for all the villages was found to be lower than the worldwide value. The values of external hazard index and internal hazard index determined from all the soil samples were found to be within recommended limit. The calculated average annual effective dose was found to be 0.42 mSv y⁻¹, and it is lower than the worldwide value of 0.46 mSv y⁻¹.The annual effective dose values calculated from present study were comparable with previous studies carried out in other countries and in India. The data established from the study can be useful as baseline information on natural radioactivity in South Konkan, Maharashtra, India.

Anti-microbial surfaces: An approach for deposition of ZnO nanoparticles on PVA-Gelatin composite film by screen printing technique

Initially micro-organisms get exposed to the surfaces, this demands development of anti-microbial surfaces to inhibit their proliferation. Therefore, herein, we attempt screen printing technique for development of PVA-GE/ZnO nanocomposite (PG/ZnO) films. The synthesis of PG/ZnO nanocomposite includes two steps as: (i) Coating of Zinc Oxide nanoparticles (ZnO NPs) by poly ethylene glycol in order to be compatible with organic counterparts. (ii) Deposition of coated nanoparticles on the PG film surface. The results suggest the enhancement in anti-microbial activity of PG/ZnO nanocomposite over pure ZnO NPs against both Gram positive Bacillus subtilis and Gram negative Escherichia coli from zone of inhibition. The uniformity in deposition is further confirmed by scanning electron microscopy (SEM) images. The phase identification of ZnO NPs and formation of PG/ZnO nanocomposite has been confirmed by X-ray diffraction (XRD) analysis and UV-vis spectroscopy (UV-vis). The Attenuated total reflection Spectroscopy (ATR) analysis indicates the ester bond between PVA and gelatin molecules. The thermal stability of nanocomposite is studied by thermogravimetric analysis (TGA) revealing increase in crystallinity due to ZnO NPs which could be utilized to inhibit the growth of micro-organisms. The tensile strength is found to be higher and percent elongation is double of PG/ZnO nanocomposite than PG composite film.