Electrospun silk-elastin-like fiber mats for tissue engineering applications

Protein-based polymers are present in a wide variety of organisms fulfilling structural and mechanical roles. Advances in protein engineering and recombinant DNA technology allow the design and production of recombinant protein-based polymers (rPBPs) with an absolute control of its composition. Although the application of recombinant proteins as biomaterials is still an emerging technology, the possibilities are limitless and far superior to natural or synthetic materials, as the complexity of the structural design can be fully customized. In this work, we report the electrospinning of two new genetically engineered silk-elastin-like proteins (SELPs) consisting of alternate silk- and elastin-like blocks. Electrospinning was performed with formic acid and aqueous solutions at different concentrations without addition of further agents. The size and morphology of the electrospun structures was characterized by scanning electron microscopy showing to be dependent of concentration and solvent used. Treatment with air saturated with methanol was employed to stabilize the structure and promote water insolubility through a time-dependent conversion of random coils into β-sheets (FTIR). The resultant methanol-treated electrospun mats were characterized for swelling degree (570-720%), water vapour transmission rate (1083 g/m2/day) and mechanical properties (modulus of elasticity of ~126 MPa). Furthermore, the methanol-treated SELP fiber mats showed no cytotoxicity and were able to support adhesion and proliferation of normal human skin fibroblasts. Adhesion was characterized by a filopodia-mediated mechanism. These results demonstrate that SELP fiber mats can provide promising solutions for the development of novel biomaterials suitable for tissue engineering applications.

Expectativas sobre la independencia del auditor: evidencias empíricas

La Unión Europea pretende renovar la Octava Directiva, entre otras razones, para reforzar la independencia de los auditores y abordar los conflictos de intereses inherentes al panorama actual. Este trabajo plantea conocer las expectativas sobre estas propuestas 2 concretando los factores que afectan, tanto positiva como negativamente, a que el auditor mantenga su independencia ante el cliente. Se comprueba que se perciben como factores negativos todos los relacionados con la dependencia económica y los conflictos de intereses en la negociación entre el auditor y la empresa. Sin embargo no se perciben como positivos los mecanismos empleados habitualmente como salvaguardas (como por ejemplo el Comité de Auditoría y la rotación), considerando que la independencia depende fundamentalmente de la persona del auditor y su carácter.