Marco Diociaiuti

Experimental imaging of silicon nanotubes

Transmission electron microscopy (TEM), electron energy loss near edge structures (EELNES) and scanning tunneling microscopy (STM) were used to distinguish silicon nanotubes (SiNT) among the reaction products of a gas phase condensation synthesis. TEM images exhibit the tubular nature with a well-defined wall. The EELNES spectra performed on each single nanotube show that they are constituted by nonoxidized silicon atoms. STM images show that they have diameter ranging from 2 to 35 nm, have an atomic arrangement compatible with a puckered structure and different chiralities. Moreover, the I-V curves showed that SiNT can be semiconducting as well as metallic in character.

Cultured phototrophic biofilms for phosphorus removal in wastewater treatment

Culture experiments with phototrophic biofilms taken from the sedimentation tank of the wastewater treatment plant at the Fiumicino Airport in Rome, Italy were carried out in a prototype continuous flow incubator. Biofilms grown at varying photosynthetic photon flux density (PPFD), temperature and flow velocity were sampled at three developmental stages to quantify biofilm dry weight, chlorophyll a concentration and total cellular phosphorus content. While no coherent significant effects by flow and temperature were evidenced, maximum biofilm dry weight and phosphorous concentration significantly increased across all featured PPFDs. Maximum chlorophyll a concentration was saturated above 60 micromol m(-2)s(-1). A highly significant association between organic biomass and phosphorous content was observed for most light conditions, including a larger proportional increase of phosphorus concentration with respect to chlorophyll a at high PPFD. Up to 112 mg P m(-2)d(-1) maximal phosphorous removal rates were achieved. Elemental analysis by energy filtering transmission electron microscopy showed subcellular localization of phosphorus, confirming the accumulation in phototrophic microorganisms in biofilms grown in high light conditions.

Physico-chemical characterisation of the inhalable particulate matter (PM10) in an urban area: an analysis of the seasonal trend

Between October 1998 and February 2000, 11 particulate samplings were conducted in an urban area of Rome to evaluate the seasonal trend of PM10 characteristics: seven samplings were made at ground-level and four 30 m above ground level. The samples were analysed by scanning electron microscopy equipped with an EDS X-ray attachment and by transmission electron microscopy and an electron energy-loss spectrometer. The airborne particulate matter was characterised from a physico-chemical point of view to provide information on the particle composition and on the compounds carried on their surface. The data sets, consisting of the atomic concentrations of the constituent chemical elements of the fine (PM3.3) and of the coarse (PM10-3.3) particulate, were subjected to cluster analysis to determine the principal components of PM10. In the particulate matter, the statistical analysis methods allowed us to identify seven groups (clusters) of particles: C-rich particles; carbonates; silica; silicates; sulfates; Fe-rich particles; and metals. Carbonaceous and silicate particles with a surface coating containing S were observed. This sulfur-enriched coating turned out to be a PM3.3 feature strongly dependent upon season.

Large photocurrent generation in multiwall carbon nanotubes

The authors demonstrate the ability of multiwall carbon nanotubes to generate photocurrents in the near ultraviolet and visible spectral ranges using electrochemical photocurrent measurements. The photogenerated current depends on the excitation wavelength similar to that for single wall carbon nanotubes. Its intensity and modulation can be related to the carbon nanotubes morphology. The maximum photon-to-current conversion efficiency is approximately 7%, about 50 times higher than that reported for single wall carbon nanotubes. This result is of particular relevance for photovoltaic nanodevices and solar energy conversion applications.

Size effects on the linewidths of the Auger spectra of Cu clusters

Abstract We discuss the role of the size distribution of Cu clusters deposited on graphite in determining the broadening and the shifting of the Auger L 3 VV Lineshapes observed when the average cluster size decreases. In our interpretation this broadening is only due to the superposition of various narrow Auger lines relative to the various cluster dimensional classes, each shifted towards lower kinetic energies because their small sizes. The Auger peak shifts are mainly due to the change in the valence band and core levels as the cluster size decreases. The model used to reproduce the Auger line broadening, following the Cini-Sawatzky approach, takes into account the broad distribution of the different diameters.

Lipid raft disruption protects mature neurons against amyloid oligomer toxicity.

A specific neuronal vulnerability to amyloid protein toxicity may account for brain susceptibility to protein misfolding diseases. To investigate this issue, we compared the effects induced by oligomers from salmon calcitonin (sCTOs), a neurotoxic amyloid protein, on cells of different histogenesis: mature and immature primary hippocampal neurons, primary astrocytes, MG63 osteoblasts and NIH-3T3 fibroblasts. In mature neurons, sCTOs increased apoptosis and induced neuritic and synaptic damages similar to those caused by amyloid beta oligomers. Immature neurons and the other cell types showed no cytotoxicity. sCTOs caused cytosolic Ca(2+) rise in mature, but not in immature neurons and the other cell types. Comparison of plasma membrane lipid composition showed that mature neurons had the highest content in lipid rafts, suggesting a key role for them in neuronal vulnerability to sCTOs. Consistently, depletion in gangliosides protected against sCTO toxicity. We hypothesize that the high content in lipid rafts makes mature neurons especially vulnerable to amyloid proteins, as compared to other cell types; this may help explain why the brain is a target organ for amyloid-related diseases.

Candida rugosa lipase immobilization on hydrophilic charged gold nanoparticles as promising biocatalysts: Activity and stability investigations.

In this work, a simple and versatile methodology to obtain two different bioconjugated systems has been developed by the immobilization of Candida rugosa lipase (CRL) on hydrophilic gold nanoparticles functionalized with 2-diethylaminoethanethiol hydrochloride (DEA) or with sodium 3-mercapto-1-propanesulfonate (3MPS), namely Au-DEA@CRL and Au-3MPS@CRL. Both spectroscopic and morphological properties of metal nanoparticles have been deeply investigated. The enzyme loading and lipolytic activity of AuNPs@CRL bioconjugates have been studied with respect to different surface functionalization and compared with the free enzyme. Some physical and chemical parameters had a strong effect on enzyme activity and stability, that were improved in the case of the Au-DEA@CRL bioconjugate, which showed a remarkable biocatalytic performance (95% of residual lipolytic activity compared with free CRL) and stability in experimental conditions concerning pH (range 5-8) and temperature (range 20-60°C), as often required for the industrial scale up of catalytic systems.

Amyloid Oligomer Neurotoxicity, Calcium Dysregulation, and Lipid Rafts

Amyloid proteins constitute a chemically heterogeneous group of proteins, which share some biophysical and biological characteristics, the principal of which are the high propensity to acquire an incorrect folding and the tendency to aggregate. A number of diseases are associated with misfolding and aggregation of proteins, although only in some of them—most notably Alzheimers disease (AD) and transmissible spongiform encephalopathies (TSEs)—a pathogenetic link with misfolded proteins is now widely recognized. Lipid rafts (LRs) have been involved in the pathophysiology of diseases associated with protein misfolding at several levels, including aggregation of misfolded proteins, amyloidogenic processing, and neurotoxicity. Among the pathogenic misfolded proteins, the AD-related protein amyloid β (Aβ) is by far the most studied protein, and a large body of evidence has been gathered on the role played by LRs in Aβ pathogenicity. However, significant amount of data has also been collected for several other amyloid proteins, so that their ability to interact with LRs can be considered an additional, shared feature characterizing the amyloid protein family. In this paper, we will review the evidence on the role of LRs in the neurotoxicity of huntingtin, α-synuclein, prion protein, and calcitonin.

Chitosan Nanogels by Template Chemical Cross-Linking in Polyion Complex Micelle Nanoreactors

Chitosan covalent nanogels cross-linked with genipin were prepared by template chemical cross-linking of chitosan in polyion complex micelle (PIC) nanoreactors. By using this method, we were able to prepare chitosan nanogels using only biocompatible materials without organic solvents. PIC were prepared by interaction between chitosan (X(n) = 23, 44, and 130) and block copolymer poly(ethylene oxide)-block-poly[sodium 2-(acrylamido)-2-methylpropanesulfonate] (PEO-b-PAMPS) synthesized by single-electron transfer-living radical polymerization (SET-LRP). PIC with small size (diameter about 50 nm) and low polydispersity were obtained up to 5 mg/mL. After cross-linking of chitosan with genipin, the nanoreactors were dissociated by adding NaCl. The dissociation of the nanoreactors and the formation of the nanogels were confirmed by (1)H NMR, DLS, and TEM. The size of the smallest nanogels was about 50 nm in the swollen state and 20 nm in the dry state. The amount of genipin used during reticulation was an important parameter to modulate the size of the nanogels in solution.

Characterisation of aerosol individual particles in a controlled underground area

The aim of this study is to determine the sources and provide a physico-chemical description of the airborne particulate present in two communicating underground areas: a highway tunnel with heavy vehicular traffic and a controlled underground laboratory. Individual particles were collected in the two zones and examined using scanning electron microscopy with EDS X-ray attachment. The principal components of the particulate were analysed using principal factor analysis and hierarchical cluster analysis. The data obtained suggest that three main factors determine airborne particulate pollution in the laboratory: the ventilation system for air replacement, the access of motor vehicles into the laboratory, and the metallic installations and structure of the laboratory itself.