Claudia Innocenti

Water-Dispersible Sugar-Coated Iron Oxide Nanoparticles. An Evaluation of their Relaxometric and Magnetic Hyperthermia Properties

Synthesis of functionalized magnetic nanoparticles (NPs) for biomedical applications represents a current challenge. In this paper we present the synthesis and characterization of water-dispersible sugar-coated iron oxide NPs specifically designed as magnetic fluid hyperthermia heat mediators and negative contrast agents for magnetic resonance imaging. In particular, the influence of the inorganic core size was investigated. To this end, iron oxide NPs with average size in the range of 4-35 nm were prepared by thermal decomposition of molecular precursors and then coated with organic ligands bearing a phosphonate group on one side and rhamnose, mannose, or ribose moieties on the other side. In this way a strong anchorage of the organic ligand on the inorganic surface was simply realized by ligand exchange, due to covalent bonding between the Fe(3+) atom and the phosphonate group. These synthesized nanoobjects can be fully dispersed in water forming colloids that are stable over very long periods. Mannose, ribose, and rhamnose were chosen to test the versatility of the method and also because these carbohydrates, in particular rhamnose, which is a substrate of skin lectin, confer targeting properties to the nanosystems. The magnetic, hyperthermal, and relaxometric properties of all the synthesized samples were investigated. Iron oxide NPs of ca. 16-18 nm were found to represent an efficient bifunctional targeting system for theranostic applications, as they have very good transverse relaxivity (three times larger than the best currently available commercial products) and large heat release upon application of radio frequency (RF) electromagnetic radiation with amplitude and frequency close to the human tolerance limit. The results have been rationalized on the basis of the magnetic properties of the investigated samples.

A Smart Platform for Hyperthermia Application in Cancer Treatment: Cobalt-Doped Ferrite Nanoparticles Mineralized in Human Ferritin Cages

Magnetic nanoparticles, MNPs, mineralized within a human ferritin protein cage, HFt, can represent an appealing platform to realize smart therapeutic agents for cancer treatment by drug delivery and magnetic fluid hyperthermia, MFH. However, the constraint imposed by the inner diameter of the protein shell (ca. 8 nm) prevents its use as heat mediator in MFH when the MNPs comprise pure iron oxide. In this contribution, we demonstrate how this limitation can be overcome through the controlled doping of the core with small amount of Co(II). Highly monodisperse doped iron oxide NPs with average size of 7 nm are mineralized inside a genetically modified variant of HFt, carrying several copies of α-melanocyte-stimulating hormone peptide, which has already been demonstrated to have excellent targeting properties toward melanoma cells. HFt is also conjugated to poly(ethylene glycol) molecules to increase its in vivo stability. The investigation of hyperthermic properties of HFt-NPs shows that a Co doping of 5% is enough to strongly enhance the magnetic anisotropy and thus the hyperthermic efficiency with respect to the undoped sample. In vitro tests performed on B16 melanoma cell line demonstrate a strong reduction of the cell viability after treatment with Co doped HFt-NPs and exposure to the alternating magnetic field. Clear indications of an advanced stage of apoptotic process is also observed from immunocytochemistry analysis. The obtained data suggest this system represents a promising candidate for the development of a protein-based theranostic nanoplatform.

Dynamical Formation of Spatially Localized Arrays of Aligned Nanowires in Plastic Films with Magnetic Anisotropy

We present a simple technique for magnetic-field-induced formation, assembling, and positioning of magnetic nanowires in a polymer film. Starting from a polymer/iron oxide nanoparticle casted solution that is allowed to dry along with the application of a weak magnetic field, nanocomposite films incorporating aligned nanocrystal-built nanowire arrays are obtained. The control of the dimensions of the nanowires and of their localization across the polymer matrix is achieved by varying the duration of the applied magnetic field, in combination with the evaporation dynamics. These multifunctional anisotropic free-standing nanocomposite films, which demonstrate high magnetic anisotropy, can be used in a wide field of technological applications, ranging from sensors to microfluidics and magnetic devices.

Synthesis and behaviour of size controlled cyano-bridged coordination polymer nanoparticles within hybrid mesoporous silica

Size controlled cyano-bridged coordination polymer nanoparticles Mn+/[M′(CN)m]3− (where Mn+ = Ni2+, Fe2+, Co2+ and M′ = Fe3+, Co3+(m = 6); Mo5+ (m = 8)) have been synthesised and organised by using mesostructured hybrid silica hosts of various sizes (3.4, 5.3 and 7.5 nm) containing –(CH2)2C5H4N groups. The obtained composite materials were studied by transmission electronic microscopy (TEM), infrared and electronic spectroscopies, nitrogen sorption, X-ray diffraction and magnetic measurements. These analyses reveal the formation of hetero- or homo-metallic cyano-bridged nanoparticles with controlled stoichiometry uniform in size and shape within the silica matrix. The size of the nanoparticles is controlled by the pore size of the silica used. The magnetic study of these nanocomposite materials reveal an appearance of a spin-glass like regime which can be caused by a spin frustration on the surface of the nanoparticles and/or by interparticle magnetostatic interactions.

Top-down synthesis of multifunctional iron oxide nanoparticles for macrophage labelling and manipulation

Multifunctional iron oxide (FeOx) magnetic nanoparticles (MNPs) are promising items for biomedical applications. They are studied as theranostic agents for cancer treatment, selective probes for bioanalytical assays, controllable carriers for drug delivery and biocompatible tools for cell sorting or tissue repair. Here we report a new method for the synthesis in water of FeOx–MNPsvia a top-down physical technique consisting in Laser Ablation Synthesis in Solution (LASiS). LASiS is a green method that does not require chemicals or stabilizers, because nanoparticles are directly obtained in water as a stable colloidal system. A gamut of characterization techniques was used for investigating the structure of FeOx–MNPs that have a polycrystalline structure prevalently composed of magnetite (ca. 75%) and hematite (ca. 22%). The FeOx–MNPs exhibit very good magnetic properties if compared to what is usually reported for iron oxide nanoparticles, with saturation magnetization close to the bulk value (ca. 80 emu g−1) and typical signatures of the coexistence of ferrimagnetic and antiferromagnetic phases in the same particle. The functionalization of FeOx–MNPs after the synthesis was possible with a variety of ligands. In particular, we succeeded in the functionalization of FeOx–MNPs with carboxylated phosphonates, fluorescent alkylamines, fluorescent isothiocyanates and bovine serum albumin. Our FeOx–MNPs showed excellent biocompatibility. Multifunctional FeOx–MNPs were exploited for macrophage cell labelling with fluorescent probes as well as for cell sorting and manipulation by external magnetic fields.

Water-Soluble Rhamnose-Coated Fe3O4 Nanoparticles

Water-soluble biocompatible rhamnose-coated Fe(3)O(4) nanoparticles of 4.0 nm are obtained by covalent anchorage of rhamnose on the nanoparticles surface via a phosphate linker. These nanoparticles present superparamagnetic behavior and nuclear relaxivities in the same order of magnitude as Endorem that make them potential magnetic resonance imaging (MRI) contrast agents of a second generation, where the saccharides represent also specific ligands able to target lectins on skin cells.

Measuring inner scale of atmospheric turbulence by angle of arrival and scintillation

A new method for measuring inner scale of atmospheric turbulence based on simultaneous measurements of differential angle of arrival and intensity fluctuations of a wave propagating horizontally in a turbulent medium is presented. An experimental laboratory test of the method is also presented.

Synthesis of Iron Oxide Nanoparticles in Listeria innocua Dps (DNA‐Binding Protein from Starved Cells): A Study with the Wild‐Type Protein and a Catalytic Centre Mutant

A comparative analysis of the magnetic properties of iron oxide nanoparticles grown in the cavity of the DNA-binding protein from starved cells of the bacterium Listeria innocua, LiDps, and of its triple-mutant lacking the catalytic ferroxidase centre, LiDps-tm, is presented. TEM images and static and dynamic magnetic and electron magnetic resonance (EMR) measurements reveal that, under the applied preparation conditions, namely alkaline pH, high temperature (65 degrees C), exclusion of oxygen, and the presence of hydrogen peroxide, maghemite and/or magnetite nanoparticles with an average diameter of about 3 nm are mineralised inside the cavities of both LiDps and LiDps-tm. The magnetic nanoparticles (MNPs) thus formed show similar magnetic properties, with superparamagnetic behaviour above 4.5 K and a large magnetic anisotropy. Interestingly, in the EMR spectra an absorption at half-field is observed, which can be considered as a manifestation of the quantum behaviour of the MNPs. These results indicate that Dps proteins can be advantageously used for the production of nanomagnets at the interface between molecular clusters and traditional MNPs and that the presence of the ferroxidase centre, though increasing the efficiency of nanoparticle formation, does not affect the nature and fine structure of the MNPs. Importantly, the self-organisation of MNP-containing Dps on HRTEM grids suggests that Dps-enclosed MNPs can be deposited on surfaces in an ordered fashion.

Superparamagnetic cellulose fiber networks via nanocomposite functionalization

We present a simple and cost-effective method for rendering networks of cellulose fibers, such as paper, fabrics or membranes, superparamagnetic by impregnating the individual fibers with a reactive acrylic monomer. The cellulose fibers are wetted by a cyanoacrylate monomer solution containing superparamagnetic manganese ferrite colloidal nanoparticles. Upon moisture initiated polymerization of the monomer on the fiber surfaces, a thin nanocomposite shell forms around each fiber. The nanocomposite coating renders the cellulose fibers water repellent and magnetically responsive. Magnetic and microscopy studies prove that the amount of the entrapped nanoparticles in the nanocomposite shell is fully controllable, and that the magnetic response is directly proportional to this amount. A broad range of applications can be envisioned for waterproof magnetic cellulose materials (such as magnetic paper/tissues) obtained by such a simple yet highly efficient method.

Polymeric Films with Electric and Magnetic Anisotropy Due to Magnetically Assembled Functional Nanofibers

We demonstrate the fabrication of free-standing polymeric nanocomposite films, which present magnetic and electrically conductive anisotropic properties. Magnetically functionalized carbon nanofibers are dispersed in a polymeric solution and, upon casting under a weak external magnetic field, are easily oriented and permanently assembled in a head-to-tail orientation in the polymer film during solvent evaporation. Magnetic and conductive property studies reveal that the resulting films have a high degree of anisotropy in both cases, thus allowing their use in functional complex devices. As a proof of concept, we demonstrate the potential application of these films as flexible THz polarizers. The detailed study shows that very high attenuation values per unit film thickness and fiber mass concentration are achieved, paving thus the way for cost-effective fabrication of substrate-free systems that have advantage over conventional devices realized so far.