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Nanoparticles emitted by incinerator |
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Nanoparticles
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Combustion process in incinerators usually generates fly ashes mainly made up by metal oxides, silica and carbon-based particles, often associated to metals. Physicochemical properties of the particles are influenced by many incinerator parameters. In collaboration with other Universities the Centre could prepare model solids of well defined chemical composition and particle size resembling the NP present in the emission of incinerators to evaluate their potential toxicity. Furthermore a study on the presence of nanoparticles in the environment and in some body compartments in the normal population may help to understand occupational and individual exposure to emitted NP. |
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Aggregation of silica nanoparticles and effect on silica toxicity |
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Nanoparticles
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A well-defined silica nanoparticle model system was developed to study the effect of the size and structure of aggregates on their membranolytic activity. The aggregates were stable and characterized using transmission electron microscopy, dynamic light scattering, nitrogen adsorption, small-angle X-ray scattering, infrared spectroscopy, and electron paramagnetic resonance. Human red blood cells were used for assessing the membranolytic activity of aggregates. We found a decreasing hemolytic activity for increasing hydrodynamic diameter of the nanoparticle aggregates, in contrast to trends observed for isolated particles. We propose here a qualitative model that considers the fractal structure of the aggregates and its influence on membrane deformation to explain these observations. The open structure of the aggregates means that only a limited number of primary particles, from which the aggregates are built up, are in contact with the cell membrane. The adhesion energy is thus expected to decrease resulting in an overall lowered driving force for membrane deformation. Hence, the hemolytic activity of aggregates, following an excessive deformation of the cell membrane, decreases as the aggregate size increases. Our results indicate that the aggregate size and structure determine the hemolytic activity of silica nanoparticle aggregates.
Our bibliography on the subject
Thomassen et al, 2011 (doi:10.1021/tx2002178) |
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Translocation of titanium nanoparticles through the nervous system |
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Nanoparticles
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Nanoparticles are used in a wide range of human applications from industrial to bio-medical fields. However, the unique characteristics of nanoparticles, such as the small size, large surface area per mass and high reactivity raises great concern on the adverse effects of these particles on ecological systems and human health. There are several pioneer studies reporting translocation of inhaled particulates to the brain trough a potential neuronal uptake mediated by the olfactory nerve. However, no direct evidences have been presented up to now on the pathway followed by the nanoparticles from the nose to the brain. In addition to a neuronal pathway, nanoparticles could gain access to the central nervous system (CNS) trough extracellular pathways (perineuronal, perivascular and cerebrospinal fluid paths). In the present study we investigate the localization of intranasally delivered fluorescent nanoparticles in the olfactory epithelium and in the brain. To this purpose we used two different kind of nanoparticles: 1) titanium dioxide conjugated with the fluorescein isothiocyanate (FITC) and 2) carboxyl quantum dots as a model of innovative fluorescent semiconductor nanocrystals commonly used in cell and animal biology. Intranasal treatments with nanoparticles were performed both subcronically for 5 days and acutely on adult CD1 mice. The olfactory epithelium and olfactory bulb were collected and analysed by confocal microscopy and ICP-AES at different survival time after treatment. Our results indicate that titanium dioxide nanoparticles delivered in the nose enter the brain. In vitro experiments on primary cultures of olfactory bulb neurons suggest that these cells are able to internalize nanoparticles, and ongoing studies are trying to characterize a possible toxic effects of these nanoparticles on olfactory neurons. We are also analysing their localization in the different cellular compartments of the olfactory epithelium. Data obtained following intranasal irrigation of quantum dots indicate that non neuronal compartments of the olfactory mucosa are preferentially involved in nanoparticles uptake, thus supporting the extracellular pathways as the most likely route to access the CNS. The possible selection of different penetration routes may be ascribed either at the different surface chemistry of the two kind of nanoparticles employed or to their difference in size and aggregation.
our bibliography on the subject
Garzotto et al. Symposium on Breakthroughs in Nanoparticles for Bio-Imaging. Roma-Avril 2010 |
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Oxidative potential of titanium dioxide nanoparticles |
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Nanoparticles
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Titania is generally considered to be an inert and safe material. Several studies, however, have reported that nanosized TiO2 may elicit toxic effects. In some cases the observed adverse effects have been related to free radicals. Although new studies mainly concern irradiated titania, the role and the mechanisms of the generation of free radicals by TiO2 in the absence of UV irradiation are not well known. The purpose of the present study is to investigate the free-radical-generation mechanisms by nano- and micronsized anatase or rutile powders under normal laboratory illumination or in the dark by means of a spin-trapping/ESR spectroscopy technique. This technique is used to identify the nature and the amount of free radicals released in solution, and in the solid-state to characterise the paramagnetic centres at the surface of particles that may participate in the reactions. The following radical-generating mechanisms have been considered: 1) the generation of oxygenated free radicals (HO2., O2.−, HO.) following the reaction of TiO2 with oxygen, water or H2O2 and 2) the generation of carbon-centred radicals following the cleavage of the C![[BOND]](http://onlinelibrarystatic.wiley.com/undisplayable_characters/00f8ff.gif) H bond in a model molecule. Although no free radicals were detected in a simply buffered solution, anatase and rutile generated O2.− and HO., respectively, in the presence of H2O2. Both polymorphs were also active in the cleavage of the CH bond. Although the formation of O2.− appears to be related to exposure to sunlight, the generation of HO. and carbon-centred free radicals also occurs in the dark. When samples of equal surface area were tested, micron- and nanosized anatase was found to react in the same way indicating that a reduction in diameter does not generate new kinds of reactive sites. The data presented herein may have implications in the assessment of the health risk associated with the exposure to TiO2 nanoparticles and in the ecotoxicological impact following their possible leakage into the environment.
Our bibliography on the subject
Fenoglio et al., 2009
Livraghi et al., 2010 |
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Interaction between proteins and silica nanoparticles |
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Nanoparticles
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The rapid development of nanotechnology has raised some concerns about the effects of engineered nanoparticles
(NPs) on human health and the environment. At the same time, NPs have attracted intense interest because of their
potential applications in biomedicine. Hence, the requirement of detailed knowledge of what takes place at the
molecular level when NPs get inside living organisms is a necessary step in assessing and likely predicting the behavior
of an NP. The elicited effects strongly depend on the early events occurring when NPs reach biological fluids, where
the interaction with proteins is the primary process. Whereas the adsorption of proteins on biomaterials has been
thoroughly investigated, the mechanisms underlying the interaction of proteins with NPs are still largely unexplored.
Here we report a study of the behavior of four model proteins differing in their resistance to conformational changes,
net charge, and surface charge distributions, adsorbed on two nanometric silica powders with distinct hydrophilicity.
An integrated picture of the adsorption process has been obtained by applying a whole set of techniques: the extent of
coverage of the silica surface and the reversibility of the process were evaluated by combining the adsorption
isotherms with the changes in the ζ potential and the point of zero charge for NPs at different protein coverages; the
occurrence of protein deformation was evaluated by Raman spectroscopy, and EPR spectroscopy of spin-labeled
proteins provided insight into their orientation on the silica surface. We have found that the extent of coverage of the
nanoparticle surface is strongly influenced by the protein structural stability as well as by the distribution of charges at
the protein surface.
Our bibliography on the subject
Turci et al., 2010 (doi:10.1021/la904758j)
Fubini et al., 2010 (doi:10.3109/17435390.2010.509519)
Fenoglio et al., 2011 (doi:10.1016/j.addr.2011.08.001) |
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Different reactivity of ethylene and benzene carbon soot |
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Nanoparticles
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In urban environments combustion-derived NP such as soot dominate PM number concentration. At present, it is hypothesized that the toxicity of ultrafine soot particles is largely driven by adsorbed redox-active components (e.g. PAH) which may participate to generate ROS. Structural differences of soot particles affect its reactivity in dependence of synthesis/combustion conditions. The physico-chemical tests performed by the Centre may be helpful in evaluating the oxidative potential of different sources of soot particles.
Our publications on the subject:
Alfé et al, 2010 (doi:xxxxxx -> link a http://dx.medra.org/xxxxxx) |
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Effect of different coating on cytotoxicity, translocation through the skin of TiO2 nanoparticles |
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Nanoparticles
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under construction...
our bibliography on the subject
under construction... |
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Role of cristallinity in the silica toxicity |
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Crystalline silica
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Silica related diseases have usually been associated with exposure to dusts generated by some crystalline silica polymorphs. As silicosis and lung cancer are also found among workers exposed to an amorphous silica form, incorrect named “quartz glass”, the question arises of whether crystallinity is the prerequisite feature that makes a silica dust toxic. A combined study on physico-chemical properties, in vitro cellular and in vivo tests by the Centre may evidence a possible hazard for silicosis and lung cancer in workers exposed to an amorphous silica form.
Our bibliography on the subject:
Ghiazza et al, 2010 (DOI 10.1021/tx900369x)
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Research
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