Preparation and characterization of polymeric hard tissue supports

Endoğan, Tuğba
In recent years, the demand for the use of artificial materials have increased drastically in biomedical field since autografts have limited availability and allografts lead to immune response problems. The aim of this thesis was to prepare polymer based materials which will be used for either supportive or regenerative materials for hard tissue applications. In the first part of the thesis, hydroxyapatite (HAp) containing acrylic based bone cements as supportive materials were prepared. In this thesis, bone cements with different compositions were prepared by using PMMA microspheres and ground and sieved PMMA particles, with particle sizes in the range of 50–150 µm (BC1), 1–50 µm (BC2) and 1 µm (BC3). Formulations were obtained by addition of HAp to enhance the biocompatibility and mechanical strength of the cements. Various bone cement formulations were obtained by application of oxygen plasma to increase the compatibility of polymeric and inorganic components. Some formulations contained ammonium nitrate, zeolite or chitosan. Plasma application improved the mechanical properties of all groups but increased the maximum curing temperature which is undesirable for bone cements. Addition of zeolite served as reinforcement and increased the mechanical strength of bone cements. Chitosan containing bone cement formulation was used in the in vivo applications in rats and new bone tissue formation was observed. In the second part of the thesis, 2D and 3D porous scaffolds were prepared as regenerative materials for bone tissue engineering applications. In the preparation of scaffolds, chitosan and poly(lactic acid-co-glycolic acid) (PLGA) were used as the biodegradable polymeric component and HAp as the mineral component. Scaffolds were produced by three different techniques: microfabrication, freeze drying and electrospinning. They were characterized by chemical, thermal, mechanical and in vitro tests. Microfabrication technique yielded porous 2D membranes with regular square holes at micron level. 3D scaffolds having interconnected macroporous structure and 77-89% porosity were produced by freeze drying. PLGA and HAp containing scaffolds had the highest compressive modulus in the hydrated state. Fibers with diameters in the range of 180–525 nm were obtained with electrospinning technique. It was shown that degradation rate of chitosan scaffolds could be controlled by addition of PLGA. Cell culture tests showed that SaOs-2 cells properly attached and proliferated on all the prepared scaffolds. The results indicated that CH-PLGA blend scaffolds that combined the advantages of both the polymers could be good candidates for use in bone tissue engineering applications.


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Citation Formats
T. Endoğan, “Preparation and characterization of polymeric hard tissue supports,” Ph.D. - Doctoral Program, Middle East Technical University, 2013.