M.C. Tanzi

Electrospun silk fibroin tubular matrixes for small vessel bypass grafting

Abstract Electrospinning (ES) silk fibroin (SF) offers attractive opportunities for producing matrixes (ES–SF mats) with great potential for tissue regeneration. Scanning electron microscopy (SEM) analyses showed that uniform ES–SF mats containing nanometric fibres were obtained by electrospinning a 7·5% w/v SF solution in formic acid, with an electric field of 2·4 kV cm−1 and a spinneret collector distance of 10 cm. The structure of ES–SF mats before and after immersion in methanol (5, 10 and 15 min) was investigated by Fourier transform infrared (FT-IR) and differential scanning calorimetry (DSC) analyses. Crystallinity was enhanced by dipping time as shown by trends of FT-IR crystallinity index and DSC melting/decomposition temperature. Electrospun silk fibroin mats were seeded with L929 murine fibroblasts, incubated for 1, 3 and 7 days at 37°C and, at each time point, SEM investigations and Alamar blue test were performed. The SEM images showed good cell adhesion after 1 day and cell confluence at the 7th day. Alamar blue test showed very low differences between cell viability on ES-SF mats and control.

Polyurethane-maleamides for cardiovascular applications: synthesis and properties.

Several polyurethane-maleamides (PUMAs) containing polyether or polycarbonate soft segments, and aromatic or aliphatic hard segments were synthesized by solution or bulk polymerization, using maleic acid (MA) or a mixture of MA and butanediol as chain extenders. Using this process, activated double bonds are introduced into the polymer chains and the base polyurethanes may undergo further modification via specific grafting, thus improving their tissue compatibility. PUMAs chemicophysical properties were evaluated by gel permeation chromatography (GPC), intrinsic viscosity analyses, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR) and tensile mechanical tests. Polycarbonate diol (PCU)-based PUMAs showed higher molecular weights than polyether diol (PEU)-based ones. The use of butanediol in mixture with maleic acid led to an increase of molecular weights. FT-IR confirmed the presence of the bands related to the amide groups and to the conjugated double bond, yet more evident for the polymer obtained in solution. The higher crystallinity shown by this polymer was also indicative of a better phase separation. All the PCU-PUMAs exhibited similar tensile properties with a higher stiffness than PEU-PUMAs. Among the PEU-PUMAs, the highest tensile properties were shown by the polymer obtained in solution, and by the one derived from a mixture of maleic acid and butanediol.

Effects of polyol composition on physico-morphological and mechanical properties of polyurethane foams

In the last years, increasing interest has been paid to polyurethane (PU) foams with open porosity to be used as scaffold in numerous tissue engineering applications. In fact, they possess good cyto- and biocompatibility, and they can be synthesized with tunable chemico-physical and mechanical properties by varying the base reagents used for their synthesis (polyol, isocyanate, and expanding agent) and the stoichiometric ratio between them. The aim of this work was to design and develop novel PU foams with high open porosity and tunable physical and mechanical properties by varying the polyol composition and the stoichiometric ratio between the base reagents. PU foams were synthesized by a one step gas foaming method (stoichiometric and not stoichiometric foams), by reacting a polyol mixture ad hoc set up with MDI prepolymer, using Fe-AA as catalyst, and water as expanding agent. Different polyol mixtures were prepared by varying the ratio between the main polyol components, e.g. a polyether-polyol (component A), a polyether-polyol containing styrene (component B), and an amine-based tetrafunctional polyether-polyol (component C). The PU foams were characterized by SEM, micro-CT, ATR-FTIR analysis, and evaluation of density, water uptake, and mechanical properties by uniaxial compressive tests in dry and wet conditions. Polyol composition do not affect PU foam open porosity, while the pore size and water uptake increase with the increase of components B and C. All the foams show higher compressive properties in dry than in wet state, due to the plasticizing effect of water. PU foams synthesized with an excess of diisocyanate are significantly stiffer than the stoichiometric ones. In addition the compressive properties of the PU foams are mostly affected by the amine-based tetrafunctional component, that causes a higher level of cross-linking, stiffness and strenght. Preliminary tests show no cytotoxic effects for all the tested PU foams.