In this work we report on the self-assembly of monodisperse iron oxide nanocrystals on silica-coated Au surfaces achieved by magnetic field-assisted solution deposition techniques and discuss the effects of the interactions that contribute to promote their ordered arrangement into small clusters, chain-like structures or high-density particle multilayer superlattices. The results highlight the roles of inter-particle and nanocrystalsubstrate interactions in controlling the nucleation and growth of self-assembled clusters and superstructures made of spherical magnetic nanocrystals. © 2013 by American Scientific Publishers.

The natural properties of chitosan (CHI), such as biocompatibility and biodegradability, have stimulated its use as drug delivery carrier in several applications, including layer-by-layer assembly and polymer self assembly. In this work we have aimed at producing chitosan microtubes by using CaCO3 rods doped with poly allylamine hydrochloride (PAH) as templates. The shape of the CaCO3 particles could be controlled upon addition of PAH during synthesis. A CHI-PgA complex was formed upon electrostatic binding of polygalacturonic acid (PgA) to CHI, to produce capsules for bromopyruvic acid delivery. Morphological investigations of the size and shape of CaCO3 rods were performed by means of scanning and transmission electron microscopy techniques. Infrared spectroscopy was used to monitor the characteristic bands in PAH, CHI, PgA and CaCO3. Cellular uptake and cytotoxicity were investigated. Control of CaCO3 growth during synthesis towards elongated shapes by using PAH was confirmed. These results envisage the use of chitosan-polygalacturonic acid micro/nanotubes as efficient drug delivery system for encapsulation of bromopyruvic acid as blocker for glycolytic enzymes.

Multicompartment, spherical microcontainers were engineered through a layer-by-layer polyelectrolyte deposition around a fluorescent core while integrating a ruthenium polyoxometalate (Ru4POM), as molecular motor, vis-à-vis its oxygenic, propeller effect, fuelled upon H2O2 decomposition. The resulting chemomechanical system, with average speeds of up to 25 ?m s-1, is amenable for integration into a microfluidic set-up for mixing and displacement of liquids, whereby the propulsion force and the resulting velocity regime can be modulated upon H2O2-controlled addition.

Fluoro-magnetic nanoparticles play an important role in biomedical applications since their size and concentration in tumors allow a very high resolution and an accurate mapping of lesions. Fluorescein isothiocyanate (FITC) has been entrapped inside crystals of magnetic nanoparticles (MNPs) during crystallization. This causes changes of nanoparticle crystal architecture towards elongated rods. TEM and SEM-EDX show elongated crystals with high iron concentration. The intensity of fluoro-MNP fluorescence was detected by fluorescence spectrophotometry and confocal microscopy. The benzene ring structure of FITC and its carboxylic group were clearly detected in the fluoro-MNP spectrum by using FTIR, compared to MNPs prepared in the absence of FITC. Rods were functionalized by hydrogel cross-linking structure (PEG-CMC) onto the fluoro-MNPs surface by using alternate layer-by-layer (LbL) adsorption. These hydrogel properties are used as a preserver for protein delivery. ALK1fc as specific TGF beta 1 inhibitor, was encapsulated inside (PEG-CMC) layers during LbL assembly. Zeta potential measurement, X-ray diffraction and SDS PAGE-silver staining results confirmed the encapsulation of ALK1fc. The efficiency of encapsulated ALK1fc was quantified by immunofluorescence assay against localization of TGF beta 1. Stained TGF beta 1 appeared a purple color and is distributed in the cytoplasm of untreated HLF (a liver cancer invasive cell line), whereas it disappeared in a HLF sample treated with encapsulated ALK1fc.

Halloysite is a nanostructured clay mineral withhollow tubular structure, which has recently found an importantrole as delivery system for drugs or other active molecules. Oneof these is curcumin, main constituent in the rhizome of the plantCurcuma Longa, with a series of useful pharmacologicalactivities, hindered by its poor bioavalaibility and solubility inwater. In this study, Halloysite Clay Nanotubes (HNTs) werecharacterized in terms of both structure and biocompatibilityand they were used for curcumin delivery to cancer cells. Theperformed 3 -(4,5 - dimethythiazol - 2- yl) - 2,5 - diphenyl -tetrazolium bromide (MTT) assay showed that HNTs have a highbiocompatibility, also when coated with polymers, whilecurcumin is highly toxic for cancer cells. The release kinetics ofcurcumin from HNTs was investigated by the dialysis bagmethod, showing a slow and constant release of the drug, whichcan be further controlled by adding layers of polyelectrolytes tothe external surface of the tubes. Successful polymer coating wasfollowed by Zeta potential. The Trypan Blue assay showed acytotoxic effect of loaded HNTs, proportional to theconcentration of tubes and the incubation time. Successful HNTsuptake by breast cancer cells was demonstrated by ConfocalLaser Scanning Microscopy images. All results indicate thatHalloysite Nanotubes are a promising carriers for polyphenoldelivery and release.

The aim of the present work is to study the influence of the precipitation temperature in the synthesis of nanohydroxyapatite (n-HAp) on the properties of the resulting n-HAp powder for the fabrication of highly porous scaffolds for bone tissue engineering. The n-HAp powder was obtained by a wet precipitation technique starting from calcium nitrate tetrahydrate (Ca(NO3)(2)*4H(2)O) and phosphoric acid (H3PO4) at different temperatures: 10 degrees C, 37 degrees C and 50 degrees C. Highly porous scaffolds were fabricated using the three different powders by the sponge replica method and sintering at 1300 degrees C. Combined X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses on powders indicated that on increasing the precipitation temperature the formation of pure n-HAp is accelerated, without significant changes in particles morphology and size. Scaffolds characterized by high porosity (89%) and good compressive strength (0.53 MPa for n-HAp prepared at 37 degrees C) were obtained. XRD analyses on sintered n-HAp confirmed the thermal stability of the material. Therefore, the as-synthesized n-HAp powder can be successfully used for the fabrication of highly porous scaffolds as bone substitutes.

In the realm of semiconductor nanomaterials, a crystal lattice heavily doped with cation/anion vacancies or ionized atomic impurities is considered to be a general prerequisite to accommodating excess free carriers that can support localized surface plasmon resonance (LSPR). Here, we demonstrate a surfactant-assisted nonaqueous route to anisotropic copper sulfide nanocrystals, selectively trapped in the covellite phase, which can exhibit intense, size-tunable LSPR at near-infrared wavelengths despite their stoichiometric, undoped structure. Experimental extinction spectra are satisfactorily reproduced by theoretical calculations performed by the discrete dipole approximation method within the framework of the Drude-Sommerfeld model. The LSPR response of the nanocrystals and its geometry dependence are interpreted as arising from the inherent metallic-like character of covellite, allowed by a significant density of lattice-constitutional valence-band free holes. As a consequence of the unique electronic properties of the nanocrystals and of their monodispersity, coherent excitation of symmetric radial breathing modes is observed for the first time in transient absorption experiments at LSPR wavelengths.

Integrating nanocrystals (NCs) into magnetic tunnel structures is of considerable interest due to expectation of novel properties from their spin selective transport and single electron features. Superstructures by cplloidal NCs having translational and orientational order and interesting collective magnetic properties can be prepared by solution casting through sensitive interparticle and particle-substrate interactions. In this work, we discuss the study on magnetic field induced assembly of mono-dispersed iron oxide NCs to obtain spin filter effect across (he superlattice array, when sandwiched between gold electrodes. The deposition of mixed phase Fe3O4@gamma-Fe2O3 NCs on SiO2/Au surface proceeds through slow solvent evaporation and are studied for controlled interparticle spacing. For specific NC concentration, the ordering depends on the substrate chemistry and the ligands passivating NC surface, which affects the concentration of cluster nuclei formed. In presence of a magnetic field, the tunnel structure exhibits enhanced positive tunnel magnetoresistance at low temperatures, which could be related to their ferromagnetism and the attempts by electrons to percolate NC superlattice with preserved spin. A sign reversal for magnetoresistance is exhibited by the vertical tunnel junctions on raising the temperature.

Magnetic tunnel junctions sandwiching a superlattice thin film of iron oxide nanocrystals (NCs) have been investigated. The transport was found to be controlled by Coulomb blockade and single-electron tunneling, already at room temperature. A good correlation was identified to hold between the tunnel magnetoresistance (TMR), the expected magnetic properties of the NC arrays, the charging energies evaluated from current-voltage curves, and the temperature dependance of the junction resistance. Notably, for the first time, a switching from negative to positive TMR was observed across the Verwey transition, with a strong enhancement of TMR at low temperatures.