Aniello Costantini

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.

Silica Treatments: A Fire Retardant Strategy for Hemp Fabric/Epoxy Composites

In this paper, for the first time, inexpensive waterglass solutions are exploited as a new, simple and ecofriendly chemical approach for promoting the formation of a silica-based coating on hemp fabrics, able to act as a thermal shield and to protect the latter from heat sources. Fourier Transform Infrared (FTIR) and solid-state Nuclear Magnetic Resonance (NMR) analysis confirm the formation of –C–O–Si– covalent bonds between the coating and the cellulosic substrate. The proposed waterglass treatment, which is resistant to washing, seems to be very effective for improving the fire behavior of hemp fabric/epoxy composites, also in combination with ammonium polyphosphate. In particular, the exploitation of hemp surface treatment and Ammonium Polyphosphate (APP) addition to epoxy favors a remarkable decrease of the Heat Release Rate (HRR), Total Heat Release (THR), Total Smoke Release (TSR) and Specific Extinction Area (SEA) (respectively by 83%, 35%, 45% and 44%) as compared to untreated hemp/epoxy composites, favoring the formation of a very stable char, as also assessed by Thermogravimetric Analysis (TGA). Because of the low interfacial adhesion between the fabrics and the epoxy matrix, the obtained composites show low strength and stiffness; however, the energy absorbed by the material is higher when using treated hemp. The presence of APP in the epoxy matrix does not affect the mechanical behavior of the composites.

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

The fate of silica based Stöber particles soaked into growth media (RPMI and M254): A DLS and ζ-potential study.

Understanding the mechanisms involved in the interaction of biological systems with inorganic materials is of great importance and interest in both fundamental and applied disciplines in several different fields such as astrobiology, ecology, biology, biotechnology, engineering, and medicine. In this context, this paper investigates the interaction of biomacromolecules with submicrometric silica gel particles (NP) obtained through the Stöber method. Surprisingly, particles size reduction is observed after their dispersion into two different reconstituted growth media (RPMI and M254). This effect was related to the nature of the Stöber particles and the mechanism of their formation. The experimental results can be explained arguing that a biomacromolecule corona rapidly forms on NP incubated in both RPMI and M254 growth media. The results suggest that hydrolytic attack at incompletely condensed internal surface valence sites as well as interactions between NPs surface and the components of the growth media reverse the aggregation process, giving smaller disaggregated particles surrounded by a biomacromolecule corona. Moreover it was assessed that, at longer incubation time, the particles slightly grow probably due to interlocking of biomacromolecules in the corona. Furthermore, experimental results confirm that formation of this corona is a competitive and dynamic process. The present paper shows that the described effects (as size changes) are strongly dependent on the nature of the growth medium.

Thermal and devitrification behavior of (2.5−x)CaO·(x/3)In2O3·2SiO2 glasses

Abstract A study of the influence of the substitution of In 2 O 3 for CaO at constant O/Si ratio on thermal properties and non-isothermal devitrification of 2.5CaO·2SiO 2 is reported. Differential thermal analysis (DTA) and X-ray diffraction analysis were used. The X-ray diffraction pattern of the crystallized In 2 O 3 base glass shows that the α-CaO·SiO 2 , that should be stable only above 1125°C, forms in the temperature range 900–1000°C. A new ternary crystalline phase whose reflections are not reported in the JCPDS cards, was found to form during crystallization of the glass. As their intensity progressively increases with substitution, they should refer to a In 2 O 3 rich phase. The glass transformation temperature T g results can be explained on the basis of the increased structural rigidity when Ca 2+ ions are substituted by In 3+ with the formation of stronger bond to the oxygen, while crystal growth activation energy ( E c ) values can be explained considering the increasing of the crystallization temperature T p . Devitrification involves a mechanism of surface nucleation; surface nuclei behaving as bulk nuclei in samples that soften and sinter before devitryfing.

A note on incrustations on a mosaic floor fragment from Punta Epitaffio in Baia

Abstract This paper reports the results of scientific research on a fragment of mosaic flooring recovered from the Ninfeo of Punta Epitaffio in Baia (Italy). The tesserae were made of calcite; the mortar present among the tesserae was made of slaked lime. Incrustations of mixed carbona tic and silicatic nature were found on the surface of the tesserae; silicatic components were also found in the upper layers of the tesserae. One explanation is that a reaction involving solution and re-precipitation occurred between the calcium carbonate of the mosaic fragment and the pozzolanic sands present in the Baia area, during the centuries the tesserae remained submerged under the sea.

Low-magnetostriction Co-P layers with mixed crystalline/amorphous structure prepared by electrochemical deposition

Abstract A Co-P alloy having a mixed amorphous/crystalline structure was produced by electrochemical deposition. X-ray spectra, differential scanning calorimetry and scanning electron microscopy were performed in order to obtain the structural characterization. A comparison of the new kind of material with known amorphous and crystalline alloys was also made on the basis of initial magnetization curves, electrical resistivity and standing magnetoelastic wave amplitudes. Differential scanning calorimetry reveals that the amorphous component in the mixed structure sample does not include one of the two disordered phases that are present in the completely amorphous material. The measured physical properties are explained by means of the structural characteristics and the related phosphorous content. In the new type of material a very low magnetostriction value is predicted and its effect on the magnetoelastic wave amplitude is demonstrated.