PolyHIPEs for biological cells growth via thiol-ene polymerisations : phd thesis

english

doktorska dela

2014

Univerza v Mariboru, Fakulteta za kemijo in kemijsko tehnologijo

Tissue engineering is a technique based on the regeneration of various types of cells which grow on appropriate support and has shown great promise in generating living alternatives for harvested tissues and organs for transplantation and reconstructive surgery. The use of appropriate materials is critically important for tissue engineering in designing artificial extra-cellular matrices (scaffolds), which support three-dimensional tissue formation. Polymers are the primary materials for appropriate supports in various tissue engineering applications, including bone, cartilage, blood vessels, bladder, skin and other tissues. Tissue engineering is the use of a combination of cells and material methods, and suitable biochemical and physio-chemical factors to improve or replace biological functions. For successful growth of tissue and proliferation of cells appropriate support is necessary and it is therefore very important to control the morphology, porous structure and pore size distribution of the supporting material. It is known that the growth of cells proceeds better on three dimensional porous supports. Furthermore, the biocompatibility and biodegradability of the support needs to be taken into account. Different porous polymers with 3D porous struc-ture have been prepared. Porosity of polymeric material can be achieved via different pro-cesses, among them is emulsion templating. Emulsion templating uses the internal phase of the emulsion for the production of large pores in the micrometer range. If the volume space of the internal phase of the emulsion exceeds 74.05 %, the emulsion is termed a high internal phase emulsion. One of the main goals in our PhD work has been the development of 3D scaffolds that guide cells to form functional tissue. Photopolymerisable (meth) acrylate based formulations are frequently used for the preparation of scaffolds since a large variety of monomers is com-mercially available. Biocompatible and biodegradable monomers have frequently been inves-tigated in the last decade. Although these materials have some obvious advantages over PLA (polylactic acid) (tunable mechanical properties and degradation behaviour), monomer irritancy and high molecular polyacrylic acid as degradation product are some serious disad-vantages. Therefore we have developed a new generation of biocompatible and biodegrada-ble photopolymers based on vinylesters, acrylates and thiols that have all the advantages of (meth) acrylates and circumvent most of their drawbacks. Besides easy synthesis and very low monomer cytotoxicity, non-toxic degradation products are formed that can easily been excreted from the human body. Research work of the PhD thesis presents a preparation of biocompatible and biodegradable porous polymers via high internal phase emulsion templating and the introduction of a second hierarchical level in the 50-100 um range using layer-by-layer macrostructuring. By using monomers such as trimethylolpropantriacrylate (TMPTA; Sartomer 351), ethoxylated-20-trimethylolpropantriacrylate (ETA; Sartomer 415), divinyl adipate (DVA) and tetrakis(3-mercaptopropionate) (TT) the issue of biocompatibility is addressed, as recent in-vivo studies have shown no inflammatory round cells and good bony ingrowth has been observed. A new class of vinylester, thiols and acrylate-based monomers have shown to have similar photoreactivity and mechanical properties to methacrylates. Fur-thermore, non-toxic and low molecular polyvinylalcohol is produced as a degradation product. Special attention had been given to the choice of appropriate surfactant as the surfactant activity is one of the main factors affecting the emulsion stability. Produced materials were characterized using FTIR spectroscopy, scanning electron micros-copy, gas adsorptions porosimetry and mercury porosimetry. In collaboration with the Tech-nical University Vienna (prof. Robert Liska) and the Medical University of Vienna (ddr. Günter Russmüller) measurements regarding biodegradability will be performed. Promising materials has been printed by DL

07.08.2023