Papers by Author: Sigurd Schrader

Abstract: The present study is focused on the design and fabrication of novel functional 3D-hydrogel scaffolds for regenerative medicine. In order to critically analyzing the effect of the microarchitecture of 3D scaffolds for driving the cellular fate and diffusion of progenitor stem cells we have fabricate a number of scaffolds with different geometry, stiffness and composition. The physical characteristics of the scaffold determine indeed, as well the biochemical factors, the fate of the cells. We use an innovative composite material consisting of hydrogel with different molecular weight and with suitable accordion-like and woodpile structures in order to tailor stiffness and elasticity conferred to the final structure.These novel 3D bioinspired scaffolds were obtained by both single- (1PP) and two-photon polymerization (2PP) processing. In particular, 2PP scaffolds represent a great advantage with respect to previous achievements based on traditional methods. 3D-structures were fabricated with lateral resolution of some microns, allowing an advanced control of pore microarchitecture of defined tensile strength, and the inclusion of albumin microspheres with various functionalities. The morphological, biochemical and functional characteristics are discussed. Moreover, the effects of the structured hydrogel scaffolds on the proliferation and differentiation of adult stem cells is analyzed in view of the fabrication of portion of contractile cardiac muscle to be obtained In Vitro.

Abstract: Thin layers of the OLED related polyphenylene-vinylene (PPV) deposited by a precursor on micro-fabricated Si cantilevers were studied by applying the vibrating-reed technique during repeated temperature cycling between 100 and 520 K. By means of the Langmuir-Blodgett method for film production, the dependence of damping and elastic modulus on well defined values of film thickness (16 to 69 nm) was determined. Simultaneous measurements of these quantities showed four damping peaks during heating around 130 K (called γ), 250 K (β), 350 K (β’), and 400 K (called C). Three of them (γ, β’, C) disappeared after heating to the highest temperature (520 K) indicating their presence in the precursor only. The activation parameters of the relaxation peaks (γ, β, β’) were estimated and assigned to specific atomic movements in the molecule. Peak C occurs during the conversion process of precursor to polymer. Earlier results are essentially substantiated, indicating only slight differences to those for layers produced previously by spin coating. The observed thickness dependence of damping for the γ and β peaks suggests a weaker contribution of molecules in the surface region than of those in the bulk, while the β’ peak is supposed to result from molecules in the interface region between layer and substrate.