Influence of a silica interlayer on the structural and magnetic properties of sol-gel TiO2-coated magnetic nanoparticles.

Superparamagnetic iron oxide nanoparticles coated with titanium dioxide have been synthesized, growing the titanium dioxide directly either on the magnetic nuclei or on magnetic nanoparticles previously coated with a semihydrophobic silica layer. Both coatings have been obtained by sol-gel. Since it is well-known that the existence of the intermediate silica layer influences the physicochemical properties of the material, a detailed characterization of both types of coatings has been carried out. The morphology, structure, and composition of the synthesized nanomatrices have been locally analyzed with subangstrom spatial resolution, by means of aberration corrected transmission electron microscopy (HRTEM and STEM-HAADF). Besides magnetization measurements, proton relaxivity experiments have been also performed on water suspensions of the as-synthesized nanoparticles to investigate the role of the silica interlayer in the relaxometric properties. The silica interlayer leads to nanoparticles with much higher water stability and to higher relaxivity of the suspensions.

Absorption and translocation to the aerial part of magnetic carbon-coated nanoparticles through the root of different crop plants.

The development of nanodevices for agriculture and plant research will allow several new applications, ranging from treatments with agrochemicals to delivery of nucleic acids for genetic transformation. But a long way for research is still in front of us until such nanodevices could be widely used. Their behaviour inside the plants is not yet well known and the putative toxic effects for both, the plants directly exposed and/or the animals and humans, if the nanodevices reach the food chain, remain uncertain. In this work we show that magnetic carbon-coated nanoparticles forming a biocompatible magnetic fluid (bioferrofluid) can easily penetrate through the root in four different crop plants (pea, sunflower, tomato and wheat). They reach the vascular cylinder, move using the transpiration stream in the xylem vessels and spread through the aerial part of the plants in less than 24 hours. Accumulation of nanoparticles was detected in wheat leaf trichomes, suggesting a way for excretion/detoxification. This kind of studies is of great interest in order to unveil the movement and accumulation of nanoparticles in plant tissues for assessing further applications in the field or laboratory.

Quantum dot and superparamagnetic nanoparticle interaction with pathogenic fungi: internalization and toxicity profile.

For several years now, nanoscaled materials have been implemented in biotechnological applications related to animal (in particular human) cells and related pathologies. However, the use of nanomaterials in plant biology is far less widespread, although their application in this field could lead to the future development of plant biotechnology applications. For any practical use, it is crucial to elucidate the relationship between the nanomaterials and the target cells. In this work we have evaluated the behavior of two types of nanomaterials, quantum dots and superparamagnetic nanoparticles, on Fusarium oxysporum, a fungal species that infects an enormous range of crops causing important economic losses and is also an opportunistic human pathogen. Our results indicated that both nanomaterials rapidly interacted with the fungal hypha labeling the presence of the pathogenic fungus, although they showed differential behavior with respect to internalization. Thus, whereas magnetic nanoparticles appeared to be on the cell surface, quantum dots were significantly taken up by the fungal hyphae showing their potential for the development of novel control approaches of F. oxysporum and related pathogenic fungi following appropriate functionalization. In addition, the fungal germination and growth, accumulation of ROS, indicative of cell stress, and fungal viability have been evaluated at different nanomaterial concentrations showing the low toxicity of both types of nanomaterials to the fungus. This work represents the first study on the behavior of quantum dots and superparamagnetic particles on fungal cells, and constitutes the first and essential step to address the feasibility of new nanotechnology-based systems for early detection and eventual control of pathogenic fungi.

Spatially-resolved EELS analysis of antibody distribution on biofunctionalized magnetic nanoparticles.

Spatially resolved electron energy loss spectroscopy (SR-EELS) using scanning transmission electron microscope (STEM) allows the identification and determination of the spatial distribution of the components/elements of immuno-functionalized core-shell superparamagnetic magnetite nanoparticles. Here, we report that SR-EELS measurements allow the direct identification and study of the biological moieties (protein G and anti-HRP antibody) in complex bionanocarriers of relevance for biomedical applications. Our findings show that the biomacromolecules are located on specific areas on the nanoparticles' surface. In addition, efficiency of this functionalization was evaluated by means of biochemical techniques.