K. C. Barick

Fe3O4 embedded ZnO nanocomposites for the removal of toxic metal ions, organic dyes and bacterial pathogens

We report a facile soft-chemical approach for the fabrication of Fe3O4 embedded ZnO magnetic semiconductor nanocomposites (Fe3O4–ZnO MSN), and investigate and compare their efficacy for the detoxification of water with respect to their individual counterparts (Fe3O4 and ZnO). The formation of Fe3O4–ZnO MSN was evident from the detailed structural analyses by XRD, TEM and magnetic measurements. It has been observed that these nanocomposites have a strong tendency for the simultaneous removal of Ni2+, Cd2+, Co2+, Cu2+, Pb2+, Hg2+ and As3+ from waste-water due to their porous network structure, surface polarity and high surface area. These nanocomposites also show a good photocatalytic activity for the degradation of organic dyes under UV irradiation, and are found to be efficient in the easy and rapid capturing of bacterial pathogen. It has been observed that the efficiency of capturing bacteria is strongly dependent on the concentration of nanoadsorbents and their inoculation time. It is investigated that these nanoadsorbents can be used as highly efficient separable and reusable materials for the simultaneous removal of toxic metal ions, organic dyes and bacterial pathogen.

Carboxyl decorated Fe3O4 nanoparticles for MRI diagnosis and localized hyperthermia

We report the development of carboxyl decorated iron oxide nanoparticles (CIONs) by a facile soft-chemical approach for magnetic resonance imaging (MRI) and hyperthermia applications. These superparamagnetic CIONs (~10 nm) are resistant to protein adsorption under physiological medium and exhibit good colloidal stability, magnetization and cytocompatibility with cell lines. Analysis of the T2-weighted MRI scans of CIONs in water yields a transverse relaxivity (r2) value of 215 mM(-1) s(-1). The good colloidal stability and high r2 value make these CIONs as promising candidates for high-efficiency T2 contrast agent in MRI. Further, these biocompatible nanoparticles show excellent self-heating efficacy under external AC magnetic field (AMF). The infrared thermal imaging confirmed the localized heating of CIONs under AMF. Thus, these carboxyl decorated Fe3O4 nanoparticles can be used as a contrast agent in MRI as well as localized heat activated killing of cancer cells. Furthermore, the active functional groups (COOH) present on the surface of Fe3O4 nanoparticles can be accessible for routine conjugation of biomolecules/drugs through well-developed bioconjugation chemistry.

Functional Oxide Nanomaterials and Nanocomposites for the Removal of Heavy Metals and Dyes

Water scarcity and its contamination with toxic metal ions and organic dyes represent a serious worldwide problem in the 21st century. A wide range of conventional approaches have been used to remove these contaminants from waste. Recently, nanotechnology has been given great scope for the fabrication of desirable nanomaterials with large surface-to-volume ratios and unique surface functionalities to treat these pollutants. Amongst these, oxide-based nanomaterials emerge as promising new materials for water purication. In this review article, we explore a broad-spectrum overview of recent developments in the area of oxide-based nanomaterials, such as Fe3O4, ZnO and TiO2, as well as their binary and ternary nanocomposites, for the removal of various toxic metal ions and organic dyes. The possible adsorption mechanism and the surface modification of adsorbents for the removal of heavy metal ions and dyes are discussed in detail. The sorption properties of the different adsorbents depend on the surface functionalization of nanomaterials, the pH of the medium, and the reaction time and concentration, etc. In addition, we provide a short overview on the study of the selective adsorbents in multi-component sorption systems, along with the future prospects of oxide nanomaterials in water purification.

Shape-controlled hierarchical ZnO architectures: photocatalytic and antibacterial activities

A simple soft chemical approach has been successfully adopted for the synthesis of ZnO in spherical assemblies (SA), nanorods assemblies (NRA), cauliflower-like assemblies (CFA) and mushroom-like assemblies (MA). The morphology of self-assembled ZnO nanostructures composed of numerous nanocrystals has been confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction and optical studies suggest an anisotropic nature of ZnO and presence of structural defects in ZnO nanostructures, respectively. N2 adsorption–desorption isotherm curves of these nanostructures (except MA) indicate predominantly 3D-mesoporous nature. These nanostructures are useful for their potential application in photocatalytic degradation of organic dyes (e.g. methylene blue, Rhodamine B) and inhibition of bacterial growth (S. aureus). Among these ZnO architectures, CFA exhibits excellent photocatalytic and antibacterial activities. In addition, the inhibition of bacterial growth of S. aureus is more effective under UV light than in dark conditions.

Non-aqueous to aqueous phase transfer of oleic acid coated iron oxide nanoparticles for hyperthermia application

Iron oxide magnetic nanoparticles (MNPs) alone are suitable for a broad spectrum of applications, but the low stability and heterogeneous size distribution in aqueous medium represent major setbacks. These setbacks can however be reduced or diminished through functionalization of MNPs with various biocompatible surfactants. In this study, magnetite (Fe3O4) nanoparticles were modified using oleic acid (OA) to reduce their agglomeration. To render hydrophilicity and to increase the colloidal stability of the MNPs, they were further functionalized with betaine-HCl (BTH). The physiochemical properties were well characterized using X-ray diffraction, Fourier transform infrared, thermogravimetric analysis, transmission electron microscopy and superconducting quantum interference device of the OA-BTH coated Fe3O4 MNPs in order to use them for hyperthermia application. Zeta potential study and size distribution of nanoparticles showed increased stability of the nanoparticles. The coated MNPs show increase in specific absorption rate value of 91.03 W g−1 at 335.2 Oe, making them more suitable for hyperthermia application. Cytotoxicity study was performed by MTT assay on L929 cell line for 24 h incubation period.

Biocompatible phosphate anchored Fe3O4 nanocarriers for drug delivery and hyperthermia

We demonstrate the preparation of biocompatible, water-dispersible phosphate anchored Fe3O4 magnetic nanocarriers (PAMN) by a facile soft-chemical approach. The surface functionalization of Fe3O4 nanoparticles (∼10 nm) with bioactive phosphate molecules (sodium hexametaphosphate) was evident from infrared, thermal and light scattering measurements. These superparamagnetic nanoparticles show better aqueous colloidal stability, good magnetic response and excellent self-heating efficacy under an external AC magnetic field. The bioactive shell not only provides colloidal stability to the particles but also creates functionalized exteriors with high densities of phosphate moieties for conjugation of drug molecules. The drug loading and release behavior of PAMN was investigated using doxorubicin hydrochloride (DOX) as a model drug to evaluate their potential as a carrier system. The cell viability and hemolysis assay suggests that PAMN do not have adverse toxic effects for further in vivo use. Specifically, high loading affinity for DOX with their sustained release profile and self-heating capacity makes these novel nanocarriers suitable for drug delivery and magnetic hyperthermia.

Highly water-dispersible surface-functionalized LSMO nanoparticles for magnetic fluid hyperthermia application†

The purpose of the present investigation is to develop highly water dispersible and biocompatible La0.7Sr0.3MnO3 (LSMO) magnetic nanoparticles (MNPs), which can be used as an effective heating source for the hyperthermal treatment of cancer. LSMO MNPs are synthesized by a novel combustion technique and functionalized with oleic acid (OA). The phase transfer of OA-functionalized LSMO MNPs from non-polar to polar solvents is achieved by further interaction with betaine HCl (with mean particle size ∼25 nm). Magnetic measurements of both coated and uncoated particles revealed their superparamagnetic nature at room temperature. The OA–betaine coated LSMO particles form a stable suspension in aqueous and physiological media, and possess a narrow hydrodynamic size distribution. Magnetic fluid hyperthermia studies clearly show the higher heating efficacy (specific absorption rate) of OA–betaine functionalized LSMO compared with bare LSMO. In addition, these functionalized LSMO nanoparticles are biocompatible with cell lines (HeLa and L929) and do not have toxic effects for further in vivo use. Specifically, the developed nanoparticles show better colloidal stability, high magnetization, excellent self-heating capacity under an external AC magnetic field and biocompatibility on L929 and HeLa cell lines.

Folic acid conjugated Fe3O4 magnetic nanoparticles for targeted delivery of doxorubicin

The interfacial engineering of magnetic nanoparticles (MNPs) with specific functional groups or targeting ligands is important for their in vivo applications. We report here the preparation and characterization of bifunctional magnetic nanoparticles (BMNPs) which contain a carboxylic moiety for drug binding and an amine moiety for folate mediated drug targeting. BMNPs were prepared by introducing bioactive cysteine molecules onto the surface of undecenoic acid coated Fe3O4 magnetic nanoparticles (UMNPs) via a thiol-ene click reaction and then, folic acid was conjugated with these BMNPs through an EDC-NHS coupling reaction. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis indicate the formation of highly crystalline single-phase Fe3O4 nanostructures. The changes in the interfacial characteristics of the nanoparticles and the presence of an organic coating are evident from Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), zeta-potential measurement, and thermogravimetric analysis (TGA). These nanocarriers have an average size of 10 nm, and have a pH dependent charge conversional feature and protein resistance characteristic in physiological medium. These nanoparticles also show high loading affinity for an anticancer drug, doxorubicin hydrochloride (DOX) and its pH dependent release. This is highly beneficial for cancer therapy as the relatively low pH in tumors will specifically stimulate the drug release at the site of interest. Furthermore, our fluorescence microscopy and flow cytometry studies confirmed the higher cellular internalization capability of these folic acid conjugated nanoparticles in cancer cells over-expressing folate receptors.

Roles of solvent, annealing and Bi3+ co-doping on the crystal structure and luminescence properties of YPO4:Eu3+ nanoparticles

YPO4:Eu3+ nanoparticles have been prepared in different solvents such as polyethylene glycol (PEG), PEG-diacid and water. These nanoparticles crystallize in a mixture of tetragonal and hexagonal phases. The ratio of tetragonal to hexagonal phases in PEG and PEG-diacid mediums is much lower than that in water. Interestingly, luminescence intensity upon excitation at 260 and 395 nm for the sample prepared in water is higher than that for the sample prepared in PEG or PEG-diacid. This is because of association of water molecules trapped inside the pores of the hexagonal phase and this induces a non-radiative rate. In order to study the effect of Bi3+ co-doping on the luminescence intensity, we have carried out detailed crystal structure evolutions in different solvents. However, the luminescence intensity decreases significantly upon Bi3+ co-doping because it enhances conversion of a mixture into the hexagonal phase. Upon heating at 900 °C, the luminescence intensity increases significantly because of the conversion of hexagonal to tetragonal phase. An increase in the lifetime value of Eu3+ as well as the red light enhancement has been observed in 900 °C heated samples by Bi co-doping.

Citrate-functionalized hydroxyapatite nanoparticles for pH-responsive drug delivery

The design and fabrication of multifunctional nanocarriers that can trigger the release of drugs with external stimuli such as pH, temperature is gaining increasing importance, and shows promising potential for clinical applications. This study demonstrates the synthesis of citrate-functionalized hydroxyapatite nanoparticles (Cit-HANPs) using a co-precipitation method and its in situ surface modification for drug delivery applications. The surface modification of nanoparticles with citric acid was evident from infrared spectroscopy, thermal analysis and zeta potential measurements. The nitrogen adsorption–desorption isotherm reveals formation of mesoporous Cit-HANPs with a large surface area of 182.9 m2 g−1. The anticancer drug, doxorubicin hydrochloride (DOX) was used as a model drug to evaluate the potential use of Cit-HANPs in drug delivery. The complexation of positively charged DOX to Cit-HANPs was apparent from the UV-visible spectroscopy. A loading efficiency of ∼85% (w/w) was observed with a drug to particle ratio of 1:10 and the loaded drug showed a pH dependent sustained release behaviour. The high drug loading capacity of Cit-HANPs has been attributed to the electrostatic binding of the positively charged drug to the negatively charged Cit-HANPs as well as their porous nature. The cell viability and hemolysis assay suggests that Cit-HANPs have insignificant toxicity. Furthermore, the cellular internalization capability of these citrate functionalized nanoparticles was substantiated by fluorescence microscopy studies.