POLYMER SCAFFOLDS FOR TISSUE ENGINEERING
Vanja Kokol 1994: Graduate in textile chemistry (University of Maribor = UM, Slovenia) with thesis Ecological and technological optimization of parameters in reactive printing of viscose. From 1994: Employed at UM 1996-1997: Scientific visit at Institut für Textilchemie der Deutschen Institut für Textil- und Faser-forschung, Denkendorf, Germany 1998: MSc in textile chemistry (UM) with thesis: The consequence of interactions between the guar thickener and different types of reactive dyes. 2001: PhD in textile chemistry (UM) with thesis: Investigation of interactions between guar gums, reactive dyes and surfactants. 2002: Postdoc at German Wool Research Institute, Aachen, Germany 2005: Habilitation in Textiles at University of Ljubljana. 2006 and 2008: Scientific visit at Institute for Environmental Biotechnology, TUG, Austria 2007: Scientific visit at Lund University, Physical Chemistry, Sweeden 2009: Scientific visit at Max Planck Institute of Colloids and Interfaces, Golm, Germany 2010: Habilitation in Textile Chemistry and Eco-textile Engineering at UM From 2011: Employed at UM (100%) and at CoE NAMASTE (20%). Most important work: CORTEZ, J., FATARELLA, E., NESTI, S., KOKOL, V., SCHROEDER, M.. Process for functionalising polymer materials and functionalised polymer materials so obtained : WO patent, 2009/019567 A2, 12. 2009; PCT/IB2008/002030, filling date: 1. August 2008. WIPO, International Bureau, 2009. JUS, S., KOKOL, V., GÜBITZ, G. M. Tyrosinase-catalysed coating of wool fibres with different protein-based biomaterials. J. biomater. sci., Polym. ed., 2009, 20, no. 2, 253-269. SOUSA, F. de, GÜBITZ, G. M., KOKOL, V.. Antimicrobial and antioxidant properties of chitosan enzymatically functionalized with flavonoids. Process biochem. (1991), July 2009, vol. 44, iss. 7, 749-756
Scaffolds used in tissue engineering should meet many different requirements, from the biocompatibility of the scaffold building blocks to the scaffold’s physical properties, like porosity, which directs tissue formation, enables oxygen and nutrition diffusion toward the cells and drains waste products from the matrix. Both, the composition and pore interconnectivity are essential for the promotion of cell attachment, growth, migration and angiogenesis. Biodegradability is another issue that plays a significant role in cell attachment, and ECM replacement of the live tissue. It is one of the most desirable properties of a smart implant to degrade on exactly the same time scale as nature tissue can restore its own ECM. Gelatin-based scaffolds The main advantages of the gelatine are bio and cyto-compatibility, where desirable cellular responses are engaged with the Arg–Gly–Asp (RGD)like sequence of gelatin, promoting cell adhesion and migration and being responsible for its helicoidal restructuring at specific temperature conditions, low-level immunogenicity and cytotoxicity, good biodegradability and bioresorbability, and great capacity for modification at the level of aminoacids. Thus, one of our activities is to optimize the preparation procedure and composition of gelatin-based scaffold and increase its biocompatibility with certain cell types, depending on the scaffold application. Research activities are conducted comprising both bio-engineering of the scaffolds, including gelatin biochemical processing like modification and functionalization, as well as the formation of three-dimensional (3D) structures.
Figure 5.24: Gelatin scaffolds, prepared in carbonate (top) and in phosphate buffer (bottom) under physiological conditions via fuorescence confocal microscopy; field of view is 500 m
Non-cytotoxic crosslinking agents (biochemical and enzymatic) and medias (water, ethanol) are used to formulate the porous matrices of different surface/interfacial properties, strength, viscoelasticity, and thermal and biostability. Combinations with other (nano)biopolymers (e.g. chitosan, bacterial cellulose) are also combined with gelatin to overcome these limitations. We showed that only by changing the freezing dynamic in the lowtemperature range and media used during cross-linking, it was able to influence the thermal and mechanical stability of the gelatine matrix, which can be further modulated by the procedure and the strength of the cross-linking.
Different preparation conditions using temperature and time-regulated freezing and crosslinking steps, with or without an intermediate lyophilisation, are applied to Enable the formation of an appropriately sized and interconnected porous structure and facilitate the proliferation of cells and guarantee the appropriate stability of the scaffolds in solutions at physiological conditions.
It was shown that the gelatine scaffold microstructure can be modulated by employing a cryogenic pre-treatment using the end-temperature and time variation, lyophilisation and subsequent crosslinking of the gelatine with zero-length crosslinkers (EDC/NHS) in different molar concentrations, reaction times (1-24 h) and medium used
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