Novel Poly(3-hydroxybutyrate-g-vinyl alcohol) Polyurethane Scaffold for Tissue Engineering.

The design of new synthetic grafted poly(3-hydroxybutyrate) as composite 3D-scaffolds is a convenient alternative for tissue engineering applications. The chemically modified poly(3-hydroxybutyrate) is receiving increasing attention for use as biomimetic copolymers for cell growth. As of yet, these copolymers cannot be used efficiently because of the lack of good mechanical properties. Here, we address this challenge, preparing a composite-scaffold of grafted poly(3-hydroxybutyrate) polyurethane for the first time. However, it is unclear if the composite structure and morphology can also offer a biological application. We obtained the polyurethane by mixing a polyester hydroxylated resin with polyisocyanate and the modified polyhydroxyalkanoates. The results show that the poly(3-hydroxybutyrate) grafted with poly(vinyl alcohol) can be successfully used as a chain extender to form a chemically-crosslinked thermosetting polymer. Furthermore, we show a proposal for the mechanism of the polyurethane synthesis, the analysis of its morphology and the ability of the scaffolds for growing mammalian cells. We demonstrated that astrocytes isolated from mouse cerebellum, and HEK293 can be cultured in the prepared material, and express efficiently fluorescent proteins by adenoviral transduction. We also tested the metabolism of Ca(2+) to obtain evidence of the biological activity.

Radiation-induced graft polymerization of chitosan onto poly(3-hydroxybutyrate).

Chitosan is among the most studied biopolymers and offers important advantages, such as biodegradability, biocompatibility and nontoxicity. In this study, this polysaccharide was grafted onto poly(3-hydroxybutyrate) using the simultaneous gamma-irradiation-initiated polymerization method. The polyester was immersed in diverse solvents, which allowed the preparation of graft copolymers with different yields and crystallinities. A successful synthesis and the estimation of the degree of crystallinity were verified by spectroscopic and calorimetric techniques. The most suitable method was found to be the thermoanalytical approach because it displayed a linear relationship between the degree of crystallinity and the increasing degree of grafting. The results also indicated that the lowest degree of grafting was seen for acetic acid (14.27%), while the highest degree corresponded to ethyl acetate (32.11%). The mechanism of grafting was proposed on the basis of the experimental results.

Preparation of fullerene (C60) based SiO2 sonogel hybrid composites: UV laser induced photo-polymerization, morphological, and optical properties.

Fullerene (C60) spheres were successfully embedded by diffusion into a catalyst-free SiO2 sonogel network. By this method, homogeneous and stable solid state hybrid samples suitable for optical characterization were produced. Due to the high porosity exhibited by the sonogel matrix on the nanometric length-scale, the preparation of several C60 doped composites with variable dopant concentrations was achieved. The obtained bulk hybrids were irradiated with a pulsed Kr-F laser system in order to induce photo-polymerization of the implanted C60 guest molecules at optimal experimental conditions established according to the pulsed laser photoacoustic technique (LPAT). The adequate purity level displayed by the sonogel route allowed us to perform optimal optical characterizations of these composites (reference hybrids and photo-polymerized samples) in order to evaluate their photo-physical properties for potential photonic applications. In this work the sonolysis process used to prepare amorphous catalyst-free SiO2:C60 sonogel hybrids and their linear and nonlinear optical (NLO) properties are extensively discussed. UV-VIS absorption-, Photo Luminescent (PL)-, and Raman-spectroscopies in conjunction with nonlinear optical limiting (OL) measurements, gave experimental evidence of the inclusion of C60 molecules within the sonogel environment, the laser induced photo-polymerization process and the induced changes of the optical and NLO-properties. Results are discussed in combination with atomic force microscopy (AFM) studies in order to explore the surface morphology of these samples.