Giuseppina Luciani

Tg and FTIR of (2.5 − x)CaO·x/3M2O3·2SiO2 (M=Y, La, In, Al, Ga) glasses

A comparative study of the effect of substituting oxides of (M=Y, La, In, Al, Ga) to CaO in 2.5CaO2SiO2 glass in the narrow compositional range of the binary CaO–SiO2 system in which homogeneous glasses can be obtained (0.4 < CaO/(CaO + SiO2) < 0.55). A plot of glass transformation temperature, Tg, vs the ionic field strength, Z/r2, where Z and r are the charge and the radius of the cation, is useful in discussing the role of oxides in the glassy structure. It is hypothesized that, in the composition range, studied Al2O3 and Ga2O3 act as network forming oxides, while La2O3, Y2O3 and In2O3 act as network modifying oxides. FTIR spectra agree with this hypothesis and with the expectations based on the criteria reported in the literature, in particular with the one proposed by McMillan that the network modifier cations have an ionic field strength Z/r2 < 5 A−2.

Hydroxyapatite coating of titanium by biomimetic method

The biomimetic method was used in order to deposit, on titanium substrates, an hydroxyapatite (HA) coating. The bioactive HA layer was obtained by using, in the first stage of the process, a glass having the composition 2.5CaOċ2SiO2 different from the one proposed for the application of the biomimetic method. This glass can be obtained via sol–gel, a method that allows one to obtain, easily, very pure products. The growth of HA crystals was confirmed by Fourier transform infrared, SEM, EDS and X-ray photoelectron spectroscopy (XPS) results. The experimental results suggest that, as reported in the literature for other supports, the silicate ions released from the glass in the first stage bind themselves to the titanium support. In particular, from XPS analysis it is evident that the titanium substrate is well covered by a calcium phosphate layer of the type of HA.

The Role of Trivalent Element Oxides in Cao (Na2O)–M2O3–SiO2 Glasses From Tg

In this paper Tg values of calcium (sodium) silicate glasses containing added with oxides of trivalent elements are reported. The plots of Tg as a function of composition or vs. the ionic field strength prove to be useful in discussing the role of the oxides in the glass structure. It is found that, at least in the studied composition range, Sc2O3, Y2O3, La2O3, and In2O3, behave as network modifier oxides.In the compositional ranges studied, the hypothesis based on them well agree with the expectations based on the known criteria reported in literature and on FTIR spectra.

Antimicrobial activity of eumelanin-based hybrids: The role of TiO2 in modulating the structure and biological performance

Eco-friendly hybrid Eumelanin-TiO2 nanostructures, recently obtained through in situ methodology based on hydrothermal route, have shown a striking antimicrobial activity, after exposure to oxidative environment, even under visible light induction condition. Nevertheless, the role of each component in defining the efficacy of these biological properties is far from being clearly defined. Furthermore, the effect of oxidative step on hybrids structure has not yet addressed. This study aims at elucidating the role of the ratio between eumelanin precursor, 5,6-dihydroxyindole-2-carboxylic acid (DHICA), and TiO2, for its polymerization in defining morphology and structural organization of TiO2-melanin nanostructures. Furthermore, tests on a Gram-negative Escherichia coli DH5α strain under UV irradiation and even visible light allowed to assess the contribution of each component, as well as of the TiO2-DHICA charge transfer complex to overall biological performance. Finally, results of biocide characterization were combined with spectroscopic evidences to prove that oxidative treatment induces a marked structural modification in melanin thus enhancing overall antimicrobial efficacy.

Titania as a driving agent for DHICA polymerization: a novel strategy for the design of bioinspired antimicrobial nanomaterials

Organic materials are widely employed to tune surface chemistry and/or as structuring agents of inorganic materials. Here, we propose a novel synthesis approach whereby TiO2 not only promotes 5,6-dihydroxyindole-2-carboxylic acid (DHICA) polymerization but also acts as a templating agent for the formation itself. Hybrid TiO2-DHICA melanin nanostructures have been produced, showing biocide activity even under visible light conditions (activation). Hybrid nanostructures have been analyzed and characterized by multiple techniques, proving that both organic and inorganic phases strongly affect each other during in situ formation, as far as it concerns both morphology and microstructure, conferring unique biocide properties to the resulting nanomaterials. This strategy ensures much more far-reaching implementation in the synthesis of hybrid nanosystems, opening new perspectives in the design of multifunctional materials.

Hydroxyapatite coating of polyelectrolite hydrogels by means of the biomimetic method

Abstract Polyelectrolite hydrogels were submitted to the biomimetic method. The experimental results clearly show that the method has coated them with HA globular crystals of ∼500 nm in diameter. Moreover, the method strongly influences the swelling of the hydrogels. The results strongly suggest that a biologically active HA layer forms also on the surface of the internal pores. Therefore, it is a powerful method for producing micro- and nano-patterned structures of biologically active apatite on the surface of hydrogels and of their pores.

Learning From Nature: Bioinspired Strategies Towards Antimicrobial Nanostructured Systems

Microbial contamination still remains a major issue of the modern era, due to the widespread of drug-resistant pathogens. This has prompted researchers to come up with novel antimicrobial systems that could overcome antibiotic-resistance. In this context, nature can provide inestimable source of inspiration to design high-performance multifunctional materials with potent activity against drug-resistant pathogens. Actually, integrating the bio-inspired-approach with nanotechnology can provide cutting-edge solutions for drug-resistant infections. In this context, this review will examine recent advances in the development of bio-inspired antimicrobial nanostructures. Advantages of bioinspired approach to nanomaterials over conventional routes have been highlighted. Generally, bionspired synthesis can be carried out either by mimicking the functions of natural materials/ structures or by mimicking the biological processes employed to produce substances or materials. The review provides an overview of both strategies as applied to the synthesis of inorganic, organic as well as hybrid nanostructures. Antimicrobial efficacy and biological properties of these systems have been highlighted. Antimicrobial and antibiofouling nanostructured surfaces are also discussed.

Thermal evolution of ferromagnetic metallic glasses

A traditional TG apparatus was modified by placing two permanent magnets producing a controlled magnetic field (TG(M): Magneto Thermogravimetry). This technique proved to be useful to study both structural relaxation and crystallisation of ferromagnetic metallic glasses. Results obtained for the amorphous alloys Fe40Ni40P14B6 and Fe62.5Co6Ni7.5Zr6Nb2Cu1B15, are reported in this paper. Structural relaxation can be evaluated by measuring changes in Curie temperature induced by thermal treatments. Crystallisation in TG(M) is detected through a change in the measured apparent mass (difference between the sample mass and magnetic force driving it upward). These results were confirmed by DSC analysis. Whether the obtained crystalline phase is ferromagnetic, it can be identified through its Curie temperature, measured by TG(M). In fact the value of 770°C measured as Curie temperature of crystallised Fe62.5Co6Ni7.5Zr6Nb2Cu1B15led to conclude that the only ferromagnetic crystalline phase is a-Fe. These hypothesis was confirmed by XRD analysis, showing that the first crystallisation yields to a-Fe nanocrystals.

Probing the Eumelanin–Silica Interface in Chemically Engineered Bulk Hybrid Nanoparticles for Targeted Subcellular Antioxidant Protection

We disclose herein the first example of stable monodispersed hybrid nanoparticles (termed MelaSil-NPs) made up of eumelanin biopolymer intimately integrated into a silica nanoscaffold matrix and endowed with high antioxidant and cytoprotective effects associated with a specific subcellular localization. MelaSil-NPs have been fabricated by an optimized sol-gel methodology involving ammonia-induced oxidative polymerization of a covalent conjugate of the eumelanin building block 5,6-dihydroxyindole-2-carboxylic acid (DHICA) with 3-aminopropyltriethoxysilanes (APTS). They displayed a round-shaped (ca. 50-80 nm) morphology, exhibited the typical electron paramagnetic resonance signal of eumelanin biopolymers, and proved effective in promoting decomposition of hydrogen peroxide under physiologically relevant conditions. When administered to human ovarian cancer cells (A2780) or cervical cancer cells (HeLa), MelaSil-NPs were rapidly internalized and colocalized with lysosomes and exerted efficient protecting effects against hydrogen peroxide-induced oxidative stress and cytotoxicity.

Agglomeration-free silica NPs in dry storage for PBT nanocomposite

Dispersion of nanoparticles actually plays a key role in preparing high-performance nanocomposites. Within sol–gel procedures, the Stöber method is widely used to produce monodisperse systems of silica particles with controlled size and morphology. However, if stored as dried, the Stöber silica nanoparticles form stable agglomerates that no longer resuspend. Herein, we propose a novel straightforward methodology that overcomes the irreversible aggregation of particles, ultimately leading to a very good dispersion of the filler within the polymeric matrix without any coupling agent, even long time after their preparation. This synthesis approach has been exploited to produce PBT/SiO2 nanocomposites, as a model system. The produced nanocomposites have been analyzed and characterized by multiple techniques proving a fine dispersion of the filler within the matrix, as well as a significant increase in both thermal and dynamic mechanical properties. The proposed strategy ensures high compatibility with current industrial compounding facilities and far-reaching implementation in the preparation of polymer nanocomposites.Graphical Abstract