Effect of sugar alcohol on colloidal stabilization of magnetic nanoparticles for hyperthermia and drug delivery applications

We have successfully introduced sugar alcohol (mannitol) onto the surface of iron oxide magnetic nanoparticles and investigated its role on their colloidal stabilization. The mannitol functionalized magnetic nanoparticles (MMNPs) were prepared through co-precipitation of Fe+2 and Fe3+ ions in basic medium under N-2 atmosphere followed by in-situ coating of D-mannitol. The formation of iron oxide nanoparticles is evident from XRD and TEM analysis. The coating of nanoparticles with mannitol is analyzed by FTIR, TGA, DLS and zeta-potential measurements. It has been observed that the presence of mannitol on the surface of nanoparticles strongly affect their surface potential and colloidal stability. They show room temperature superparamagnetism with optimal magnetization of 60.5 emu/g at 20 kOe and protein resistant behaviour in physiological medium. These MMNPs were employed as drug delivery carrier using anticancer drug, doxorubicin hydrochloride (DOX). The drug molecules were loaded onto the surface of nanoparticles through electrostatic interactions between positively charged DOX and negatively charged MMNPs. A loading efficiency of 60% has been observed at DOX to MMNPs ratio (w/w) of 1: 10 and the loaded drug showed pH dependent sustained release characteristics. Further, MMNPs exhibited good self-heating ability under applied AC magnetic field, thus they can be used as efficient heating source for hyperthermia therapy. (C) 2017 Elsevier B.V. All rights reserved

Self-assembly of colloidal nanoscale particles: fabrication, properties and applications

Self-assembly is a spontaneous process by which molecules to macroscopic entities assembled into one-, two- and three-dimensional ordered array. Even though, much attention has been focused on molecular self-assembly, numerous fascinating applications of self-assembling processes can be found at nanoscale to microscale level. Well-defined ordered structures prepared through the self-assembly of colloidal nanoscale to microscale particles, provide new opportunities for optimizing, tuning and/or enhancing the properties and performance of the materials. In this review, we have provided a concise and comprehensive account of the latest research and development activities in the fabrication, properties and applications of self-assembled structures from colloidal building blocks of various metals, semiconductors, oxides and polymers. The applicability, limitations and potential of different self-assembly techniques are also discussed

Influence of Mn doping on structural and vibrational properties of self-assembled Mn doped ZnO nanocrystals

Nanocrystallites (15-25 nm) of Mn doped ZnO prepared by refluxing their acetate precursors in the presence of diethylene glycol, self-assemble into polydisperse spheres of broad size distributation (100-400 nm). The center of X-ray diffraction peaks shifts towards lower angle and the line gets broadened on increasing Mn concentration. Compared to the vibration modes of wurtzite ZnO, one additional vibration mode is observed in the range of 522-518 cm(-1) in Raman spectra of Mn doped ZnO whose intensity increases on increasing the Mn concentration. The origin of this peak could be related to the incorporation of Mn(2+) in Zn(2+) lattice site. Further, on increasing Mn concentration, infrared band red shifted and surface phonon mode absorption get pronounced due to the incorporation of Mn(2+) in Zn(2+) lattice site resulting changes in the local structure parameters (effective mass, force constant, bond length)

Nanoscale assembly of mesoporous ZnO: A potential drug carrier

Highly mesoporus spherical three dimensional (3D) ZnO nanoassemblies have been fabricated by a simple, facile soft-chemical approach. It has been observed that the mesoporous (average pore diameter of 28 nm) nanoscale assembly comprised of numerous nanocrystals of average size similar to 20 nm is fairly stable, well-defined and discrete, with a hexagonal wurtzite structure. The drug-loading efficiency of the nanoassemblies was investigated using doxorubicin hydrochloride (DOX) as a model drug to evaluate their potential as a carrier system. The quenching of the fluorescence intensity as well as the change in band positions and spectra shapes strongly suggest the interaction of drug molecules with ZnO. More specifically, the present investigation discusses a method for entrapping drugs at sites capable of complexing with transition metal ions and suggests that drug release is dependent on the pH of the medium and externally applied ultrasound (continuous or pulsatile), as well as the nature of the materials which encapsulate the drug. In addition, nanoassemblies are biocompatible with HeLa cells and do not have toxic effects for further in vivo use. Specifically, a new paradigm for precise control of targeted, on-demand drug delivery using ultrasound irradiation is demonstrated

Inactivation of bacterial pathogens under magnetic hyperthermia using Fe3O4-ZnO nanocomposite

We demonstrate the antibacterial activities of superparamagnetic Fe3O4 embedded porous ZnO nanocomposite (NC) against the Gram-positive, Staphylococcus aureus (S. aureus) and Gram-negative, Escherichia coli (E. coli) bacteria. The chemical interaction between Fe3O4 and ZnO in nanocomposite is evident from X-ray photoelectron spectroscopy (XI'S). The NC exhibits stronger antibacterial activity towards S. aureus than E. colt. Further, antibacterial activity is found to be strongly dependent on the concentration of NC and their incubation time. The Fe3O4-ZnO NC shows excellent heat activated killing of bacteria under AC magnetic field (ACMF) than normal heating. This novel method of killing bacterial pathogens can be a new approach towards the treatment of a variety of microbial infectious diseases. Furthermore, it can be used as highly efficient separable and reusable materials for inhibition of bacterial growth under magnetic field. (C) 2014 Elsevier B.V. All rights reserved

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. N-2 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

Fabrication and properties of Co doped ZnO spherical assemblies

Spherical assemblies of Co doped ZnO comprised of numerous nanocrystals of size 10-15 nm were prepared by refluxing their acetate precursors in diethylene glycol medium. The detailed structural analysis by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) reveal that Co ions are successfully incorporated into the hexagonal wurtzite ZnO nanostructure and do not appear as precipitates or secondary phases. These Co ions are uniformly distributed in the ZnO host lattice and exist in +2 oxidation state. Further, HRTEM analysis also confirmed the oriented attachment of nanocrystals as well as their defects structure. Raman spectra clearly indicate the incorporation of Co2+ ions into ZnO nanostructures at Zn2+ site (appearance of an additional Raman mode at 527 cm (1)) and the resulted defects and lattice disorder in host lattice (shifting, broadening and weakening of 2E(2) (low) and E-2 (high) phonon modes). These Co doped ZnO samples exhibit ferromagnetic like behavior at room temperature, presumably due to the presence of defects in host ZnO lattice. (C) 2013 Elsevier B. V. All rights reserved

Development of citrate-stabilized Fe(3)O(4) nanoparticles: Conjugation and release of doxorubicin for therapeutic applications

We demonstrate a single-step facile approach for the fabrication of citric acid functionalized (citrate-stabilized) Fe(3)O(4) aqueous colloidal magnetic nanoparticles (CA-MNP) of size 8-10 nm using soft chemical route. The surface functionalization of Fe(3)O(4) nanoparticles with citric acid was evident from infrared spectroscopy, thermal and elemental analyses, and zeta-potential measurements. The drug-loading efficiency of CA-MNP was investigated using doxorubicin hydrochloride (DOX) as a model drug to evaluate their potential as a carrier system. The quenching of fluorescence intensity and decrease in surface charge of drug loaded CA-MNP strongly suggest the interaction/attachment of drug molecules with CA-MNP. More specifically, the present investigation discusses a method for entrapping positively charged drugs on to the surface of negatively charged CA-MNP through electrostatic interactionsandsuggeststhatbounddrugmoleculeswillbereleasedinappreciableamountsinthe mild acidic environments of the tumors. Furthermore, the aqueous colloidal stability, optimal magnetization, good specific absorption rate (under external AC magnetic field) and cytocompatibility with cells suggested that CA-MNP is appropriate candidate for biomedical applications. (C) 2010 Elsevier B.V. All rights reserved

Porosity and photocatalytic studies of transition metal doped ZnO nanoclusters

Highly mesoporous self-aggregated nanoclusters of pure and transition metal (Mn, Co and Ni) doped ZnO have been synthesized by refluxing their acetate precursors in diethylene glycol (DEG) medium It was found that the porous spherical nanoclusters comprised of numerous nanocrystals are fairly stable, well-defined and discrete with hexagonal wurtzite structure The transition metal ions, Mn, Ni and Co were successfully doped into the ZnO structure and are uniformly distributed in the samples The presence of pronounced hysteresis loop in N(2) adsorption-desorption isotherm curves indicates the 3D intersection network of the pores (predominantly mesoporous in nature) Transmission electron microscopy (TEM) analysis indicates that the pores are irregular in shape and randomly distributed throughout the nanocluster Furthermore, we have explored the photocatalytic activity of these mesoporus pure/doped ZnO nanoclusters using methylene blue as a model dye. It has been observed that these mesoporous ZnO could be a promising photocatalyst for degradation of organic molecules as compared to transition metal doped ZnO under UV ligh

Fe3+ doped SiO2 nanostructured gel-glasses: Structural, optical and magnetic properties

Transparent crack-free and bubble-free Fe3+ doped SiO2 nanostructured gel-glasses were obtained by the sol-gel process. The process involves the hydrolysis and condensation of an appropriate molar ratio of tetraethoxysilane (TEOS), absolute ethanol, nitric acid and ferric nitrate, followed by stepwise annealing at temperatures ranging from 110 degrees C to 1000 degrees C. The structural variation of the gel-glasses and their influence on physical properties during annealing has been studied. It has been observed that monolithicity and chemical environment around Fe3+ in the gel-glasses are strongly dependent on the annealing temperatures. The colour of gel-glass samples is different for different annealing temperatures, mainly due to the different co-ordination state of Fe3+ and the generation of Fe2O3 colloids of size 20-60 nm in the silica matrix. The annealing process facilitates the tuning of the UV-visible transmission cut-off edge in high optical quality Fe3+ doped silica gel-glasses. A marked difference in the magnetic properties of these glasses is, also observed with annealing temperatures. (c) 200