Enrico Marsano

Simultaneous electrospin-electrosprayed biocomposite nanofibrous scaffolds for bone tissue regeneration.

Currently, the application of nanotechnology in bone tissue regeneration is a challenge for the fabrication of novel bioartificial bone grafts. These nanostructures are capable of mimicking natural extracellular matrix with effective mineralization for successful regeneration of damaged tissues. The simultaneous electrospraying of nanohydroxyapatite (HA) on electrospun polymeric nanofibrous scaffolds might be more promising for bone tissue regeneration. In the current study, nanofibrous scaffolds of gelatin (Gel), Gel/HA (4:1 blend), Gel/HA (2:1 blend) and Gel/HA (electrospin-electrospray) were fabricated for this purpose. The morphology, chemical and mechanical stability of nanofibres were evaluated by means of field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy and with a universal tensile machine, respectively. The in vitro biocompatibility of different nanofibrous scaffolds was determined by culturing human foetal osteoblasts and investigating the proliferation, alkaline phosphatase (ALP) activity and mineralization of cells. The results of cell proliferation, ALP activity and FESEM studies revealed that the combination of electrospinning of gelatin and electrospraying of HA yielded biocomposite nanofibrous scaffolds with enhanced performances in terms of better cell proliferation, increased ALP activity and enhanced mineralization, making them potential substrates for bone tissue regeneration.

Free radical grafting onto cellulose in homogeneous conditions 1. Modified cellulose-acrylonitrile system

Abstract Synthesis of cellulose–polyacrylonitrile copolymers has been studied in a homogeneous solution of N,N-dimethylacetamide/LiCl. The method is based on the preliminary reaction of a portion of OH cellulosic groups with acryloyl chloride to give cellulose with a certain number of pendant double bonds. Successively, acrylonitrile is grafted onto the unsaturated groups by free radical polymerization using azobisisobutyronitrile as initiator. The optimum grafting conditions are evaluated by changing reaction temperature, as well as monomer/initiator and monomer/unsaturated group molar ratios. The products are characterized by size exclusion chromatography, i.r. and 13C n.m.r. spectroscopy and a possible reaction mechanism is deduced.

Regenerated cellulose-silk fibroin blends fibers.

Fibers made of cellulose and silk fibroin at different composition were wet spun from solutions by using N-methylmorpholine N-oxide hydrates (NMMO/H(2)O) as solvent and ethanol as coagulant. Different spinning conditions were used. The fibers were characterized by different techniques: FTIR-Raman, scanning electron microscopy, wide-angle x-ray diffraction, DSC analysis. The results evidence a phase separation in the whole blends compositions. The tensile characterization, however, illustrates that the properties of the blends fibers are higher respect to a linear behaviour between the pure polymers, confirming a good compatibility between cellulose and silk fibroin. The fibers containing 75% of cellulose show better mechanical properties than pure cellulose fibers: modulus of about 23 GPa and strength to break of 307 MPa.

Cellulose methacrylate: synthesis and liquid crystalline behaviour of solutions and gels

Abstract A new derivative of cellulose was synthesized by reaction of the polymer dissolved in dimethylacetamide (DMAc)/5% LiCl and methacryloyl chloride. The control of the molar ratio between the reagents and the temperature permits one to obtain a specific degree of substitution (DS). Cellulose methacrylate (CEMA) is a semirigid polymer with a persistence length which decreases as the DS increases. Consequently, the polymer concentration C ′ p at which the anisotropic phase becomes stable gets higher as the DS increases. CEMA solutions gellify when irradiated by UV, due to the crosslinking reaction of lateral double bonds. Swelling in DMAc/5% LiCl and water depends on the CEMA concentration and irradiation time. The first appearance of optical anisotropy may be observed at a polymer critical concentration which is always lower than the C ′ p of the uncrosslinked polymer.

On a novel catalytic system based on electrospun nanofibers and M-POSS.

We report on a novel catalytic system based on electrospun polymer nanofibers, which were modified with a metal-containing polyhedral oligomeric silsesquioxanes (M-POSS). In particular, a titanium-based POSS, characterized by an amino group as reactive side, was contacted with poly(styrene-co-maleic anhydride) (PSMA) nanofibers, which were dispersed in a solvent capable of solubilizing the above metal silsesquioxane. FTIR measurements evidenced the occurrence of the reaction between the MA group of PSMA and the amino group of POSS molecule. The catalytic activity of the PSMA/Ti-POSS-NH(2) system was proved in the degradation of sulforhodamine B under UV light. The presence of metal center, directly attached to the nanofiber surface, renders the system catalytically active.

Supramolecular organization of regenerated silkworm silk fibers.

The microstructures of N-methylmorpholine-N-oxide (NMMO) regenerated silk fibers have been characterized by atomic force microscopy from the micrometer to the nanometer scale and compared with those previously found from natural silks. Regenerated fibers show poor tensile properties and a brittle behavior, but their mechanical properties improve if subjected to post-spinning drawing. Consequently, it was hypothesized that post-spinning drawing would lead to a microstructure more similar to that of the natural material. Here we show that the microstructure of the samples not subjected to post-spinning drawing is composed of nanoglobules that differ from those found in natural silkworm silk both in size and orientation with respect to the macroscopic axis of the fiber. The microstructure of samples subjected to post-spinning drawing evolves in the sense of decreasing the size but increasing the orientation of the nanoglobules, but these effects are only observed in some regions of the fibers.

Optically anisotropic polymer blends: hydroxypropylcellulose/polyvinylpyrrolidone

In this paper, solid blends of HPC/PVP obtained by polymerization in situ of NVP are analyzed. These blends retain the initial organization of HPC in NVP in terms of liquid crystalline structure and banded texture. It is also demonstrated that the banded texture may be stabilized with respect to thermal cycles by crosslinking the samples.

Alginate-polymethacrylate hybrid hydrogels for potential osteochondral tissue regeneration

Porous scaffolds based on alginate-polymethacrylate hybrid hydrogels intended for bone and cartilage regeneration were prepared through controlled calcium ions diffusion from an agar mould. The double interconnected network of such materials combines into a single porous structure maintained by both noncovalent crosslinks (calcium ions for alginate) and covalent crosslinks (polymethacrylate crosslinked by the addition of mixtures of mono and bifunctional monomers). The alginate component ensures the appropriate micro-environment to mimic the extra-cellular matrix, whereas the polymethacrylate improves the mechanical performances of the hybrid hydrogels, helping to overcome the mechanical limitations of the alginate component. Morphological characterization and porosity analysis of the hybrid scaffolds were assessed by scanning electron microscopy and micro-computed tomography. Relative concentration and distribution of calcium ions were evaluated by atomic absorption and dispersive X-ray analysis, respectively. Uniaxial compressive mechanical tests were conducted to evaluate the compressive elastic modulus of the hybrid hydrogels that was correlated with their swelling ratio and crosslinking degree. As was envisaged a much higher modulus (about seven times) was obtained for the hybrid Alg/HE hydrogel than with alginate alone.

Dependence of surface properties of silylated silica on the length of silane arms

Amorphous precipitated Zeosil 1165 MP silica was silylated with low grafting degrees of organosilicons bearing different alkoxy and hydrocarbon tails, like monomethoxy(dimethyl)octadecylsilane (DMODMS), monomethoxytrimethylsilane (TMMS), trimethoxymercaptopropylsilane (MPTS), and 3-octanoylthio-1-propyltriethoxysilane (NXT®). Thermogravimetry and Elemental Analysis were used to determine the degree of silane grafting and the final number of free silanol OH groups/nm2 on the modified Zeosil surface. Free energy, enthalpy and entropy of adsorption of hydrocarbon probes were determined by Inverse Gas Chromatography at infinite dilution and dispersive component,

Spider Silk as an Inspiration for Biomimicking

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