Ilaria Cacciotti

Sol-gel derived 45S5 bioglass: synthesis, microstructural evolution and thermal behaviour

In this work, the 45S5 bioactive glass was synthesized through an aqueous sol–gel method. Characteristic functional groups were evidenced by Fourier transform infrared spectroscopy, the thermal behaviour was investigated by thermogravimetric and differential thermal analysis, crystallization kinetics and phase evolution were followed by X-ray diffraction measurements. The sintering behaviour of the sol–gel derived 45S5 was then studied by dilatometry and the microstructural evolution was followed step-by-step, interrupting the thermal cycle at different temperatures. In vitro dissolution tests were performed in order to assess the degradation behaviour of sol–gel derived 45S5 samples thermally treated at different temperatures. A relevant influence of the calcination conditions (namely, dwelling time and temperature) of the as-prepared powder on the phase appearance and its sintering behaviour as well as on the porosity features, in terms of pore dimension and interconnectivity, of the fired materials was stated.

Effect of silver nanoparticles and cellulose nanocrystals on electrospun poly(lactic) acid mats: Morphology, thermal properties and mechanical behavior

The fabrication of ternary fibrous mats based on poly(lactic) acid (PLA), cellulose nanocrystals (CNCs, both pristine (p-CNCs) and modified with a commercial surfactant (s-CNCs)) and silver (Ag) nanoparticles by electrospinning is reported. Amounts of 1 and 5 wt.% were selected for Ag and CNCs, respectively. Neat PLA and binary PLA/Ag, PLA/p-CNCs and PLA/s-CNCs were produced as references. The CNCs and Ag influence on the microstructural, thermal and mechanical properties was investigated. The Ag and/or p-CNCs addition did not remarkably affect fiber morphology and average size dimension (between (468 ± 111) and (551 ± 122)nm), whereas the s-CNCs presence led to the deposition of a honeycomb-like network on a underneath layer of randomly oriented fibers. The efficiency of the surfactant use in promoting the CNC dispersion was demonstrated. A slight enhancement (e.g. around 25%, in terms of strength) of the mechanical properties of p-CNCs loaded fibers, particularly for PLA/Ag/p-CNCs, was revealed, whereas mats with s-CNCs showed a decrement (e.g. around 35-45%, in terms of strength), mainly imputable to the delamination between the upper honeycomb-like layer and the lower conventional fibrous mat.

Tuning multi/pluri-potent stem cell fate by electrospun poly(L-lactic acid)-calcium-deficient hydroxyapatite nanocomposite mats

In this study, we investigated whether multipotent (human-bone-marrow-derived mesenchymal stem cells [hBM-MSCs]) and pluripotent stem cells (murine-induced pluripotent stem cells [iPSCs] and murine embryonic stem cells [ESCs]) respond to nanocomposite fibrous mats of poly(L-lactic acid) (PLLA) loaded with 1 or 8 wt % of calcium-deficient nanohydroxyapatite (d-HAp). Remarkably, the dispersion of different amounts of d-HAp to PLLA produced a set of materials (PLLA/d-HAp) with similar architectures and tunable mechanical properties. After 3 weeks of culture in the absence of soluble osteogenic factors, we observed the expression of osteogenic markers, including the deposition of bone matrix proteins, in multi/pluripotent cells only grown on PLLA/d-HAp nanocomposites, whereas the osteogenic differentiation was absent on stem-cell-neat PLLA cultures. Interestingly, this phenomenon was confined only in hBM-MSCs, murine iPSCs, and ESCs grown on direct contact with the PLLA/d-HAp mats. Altogether, these results indicate that the osteogenic differentiation effect of these electrospun PLLA/d-HAp nanocomposites was independent of the stem cell type and highlight the direct interaction of stem cell-polymeric nanocomposite and the mechanical properties acquired by the PLLA/d-HAp nanocomposites as key steps for the differentiation process.

Core–shell Zn-doped TiO2–ZnO nanofibers fabricated via a combination of electrospinning and metal–organic chemical vapour deposition

Zn-doped TiO2 nanofibers shelled with ZnO hierarchical nanoarchitectures have been fabricated combining electrospinning of TiO2 (anatase) nanofibers and metal–organic chemical vapor deposition (MOCVD) of ZnO. The proposed hybrid approach has proven suitable for tailoring both the morphology of the ZnO external shell as well as the crystal structure of the Zn-doped TiO2 core. It has been found that the Zn dopant is incorporated in calcined electrospun nanofibers without any evidence of ZnO aggregates. Effects of different Zn doping levels of Zn-doped TiO2 fibers have been scrutinized and morphological, structural, physico-chemical and optical properties evaluated before and after the hierarchical growth of the external ZnO shell over the electrospun nanofibers. Moreover, doping promotes the incipient transition from the anatase to rutile phase in the core–shell Zn-doped TiO2–ZnO nanostructures at lower temperature than that observed for pure TiO2. Finally, the present core–shell hierarchical nanofibers possess a very large surface to volume ratio and exhibit a marked cathodoluminescence with a strong UV and visible emission.

Poly (L-lactic acid)/calcium-deficient nanohydroxyapatite electrospun mats for bone marrow stem cell cultures

Electrospinning of bioresorbable polymers is a promising and valuable scaffolding technique. To improve its potential applications, the addition of specific fillers has been considered. This paper reports the fabrication of electrospun poly(L-lactic acid)/Ca-deficient-hydroxyapatite (PLLA/dHAp) mats, the content of nanosized d-HAp ranged between 1 and 8 wt%. All samples consisted of micrometric and submicrometric fibers, comprising 2D voids of 8 and 13 µm for PLLA and PLLA/d-HAp mats, respectively. The surface of the electrospun fibers was characterized by an uniform distribution of nanopores. Hybrid mats loaded with 1 wt% d-HAp showed the most homogeneous microstructure, differently from the mats loaded with 4 and 8 wt% d-HAp due to the presence of microagglomerates. The viscoelastic properties of PLLA/d-HAp hybrids were characterized by a decreasing trend of the storage modulus with increases in the nanofiller content. The microstructure, viscoelastic behavior, and cytocompatibility were investigated using murine bone marrow mesenchymal stem cells. On the basis of the biological data, the electrospun PLLA and PLLA/d-HAp mats can be regarded as potential scaffolds for bone marrow mesenchymal stem cells culture.

Improving the integrity of natural biopolymer films used in food packaging by crosslinking approach: A review

Currently used approaches for biopolymer modification are either expensive, poisonous or do not lead into the well-desired characteristics to the final film materials. Development of crosslinking procedure is an innovative strategy to improve mechanical, physical and thermal properties of biopolymer films. This review provides a brief description of film-forming biopolymers (e.g. chitosan, whey protein, alginate and starch) followed by a detailed introduction to definition and classification of various crosslinkers, the effect of crosslinking on emerging attributes of biopolymer films including physical, mechanical and thermal properties, identification of crosslinking occurrence, and cytotoxicity status of commonly used crosslinkers in the field of food and food-related packaging materials.

Super-Hydrophobic Multi-Walled Carbon Nanotube Coatings for Stainless Steel

We have taken advantage of the native surface roughness and the iron content of AISI 316 stainless steel to directly grow multi-walled carbon nanotube (MWCNT) random networks by chemical vapor deposition (CVD) at low-temperature (1000°C) without the addition of any external catalysts or time-consuming pre-treatments. In this way, super-hydrophobic MWCNT films on stainless steel sheets were obtained, exhibiting high contact angle values (154°C) and high adhesion force (high contact angle hysteresis). Furthermore, the investigation of MWCNT films with scanning electron microscopy (SEM) reveals a two-fold hierarchical morphology of the MWCNT random networks made of hydrophilic carbonaceous nanostructures on the tip of hydrophobic MWCNTs. Owing to the Salvinia effect, the hydrophobic and hydrophilic composite surface of the MWCNT films supplies a stationary super-hydrophobic coating for conductive stainless steel. This biomimetical inspired surface not only may prevent corrosion and fouling, but also could provide low friction and drag reduction.

Differentiation of osteoblast and osteoclast precursors on pure and silicon-substituted synthesized hydroxyapatites

Calcium phosphate-based materials should show excellent bone-bonding and cell-mediated resorption characteristics at the same time, in order to be employed for bone replacement. In this perspective, pure (HAp) and silicon-substituted hydroxyapatite (Si-HAp, 1.4% wt) porous cylinders were prepared starting from synthesized powders and polyethylene spheres used as porogens, and investigated as supports for osteoblast and osteoclast progenitor differentiation. A systematic and detailed biological characterization is reported, in terms of cell adhesion, viability, proliferation, differentiation and bioresorption, aimed at proposing a complete and reliable picture of bone cell in vitro behavior, comprehensive of both the osteogenesis and the bone resorption processes. In order to achieve this purpose, cytocompatibility, differentiation and gene expression by quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) were carried out using parietal bone-derived pre-osteoblasts obtained from neonatal mice and the bioresorption capability was assessed by seeding human peripheral blood monocytes, as osteoclast precursors. It resulted that both pure and Si-substituted HAps were able to promote differentiation of precursor cells in mature osteoblasts and osteoclasts. In particular, the Si-HAps enhanced the pre-osteoblast proliferation and showed higher osteoclast-mediated bioresorption capability, as supported by the presence of larger and more numerous resorption lacunae, whereas HAps promoted a more robust cell differentiation in terms of both osteocalcin gene expression by qRT-PCR and cell morphological evaluation by SEM analysis.

Multi-Fractal Hierarchy of Single-Walled Carbon Nanotube Hydrophobic Coatings

A hierarchical structure is an assembly with a multi-scale morphology and with a large and accessible surface area. Recent advances in nanomaterial science have made increasingly possible the design of hierarchical surfaces with specific and tunable properties. Here, we report the fractal analysis of hierarchical single-walled carbon nanotube (SWCNT) films realized by a simple, rapid, reproducible, and inexpensive filtration process from an aqueous dispersion, then deposited by drytransfer printing method on several substrates, at room temperature. Furthermore, by varying the thickness of carbon nanotube random networks, it is possible tailoring their wettability due to capillary phenomena in the porous films. Moreover, in order to describe the wetting properties of such surfaces, we introduce a two-dimensional extension of the Wenzel-Cassie-Baxter theory. The hierarchical surface roughness of SWCNT coatings coupled with their exceptional and tunable optical and electrical properties provide an ideal hydrophobic composite surface for a new class of optoelectronic and nanofluidic devices.

Electrospun PHBV/PEO co-solution blends: Microstructure, thermal and mechanical properties

Blending allows to tailor and modulate the properties of selected polymers. Blends of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polyethylene oxide (PEO) were fabricated by electrospinning in different weight ratios i.e. 100:0, 80:20, 70:30, 50:50, 0:100. In order to evaluate the influence of PEO addition on the final properties of PHBV, a complete microstructural, thermal and mechanical characterization of PHBV/PEO blends has been performed. The two neat polymeric membranes were also considered for the sake of comparison. The following characterization techniques were employed: scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy, simultaneous thermogravimetric and differential analyses (TG-DTA), differential scanning calorimetry (DSC), and uniaxial tensile tests. All electrospun mats consisted of randomly oriented and uniform fibers. It has been observed that the microstructure of PHBV/PEO was remarkably affected by blend composition. The average fiber size ranged between 0.5 μm and 2.6 μm. It resulted that the electrospun polymeric blends consisted of separate crystalline domains associated to an amorphous interdisperse phase. PHBV/PEO blends presented intermediate mechanical properties, in terms of tensile modulus and ultimate tensile stress, with respect to the two neat components.