Thesis presented to Dublin City University in fulfilment of the requirements for the degree of Doctor of Philosophy - School of Mechanical and Manufacturing Engineering, Dublin City University, Ireland – 2009. – 277 p.PVA cryogelation is a physical hydrogel formation method, which yields cryogels with comparable mechanical properties to vascular tissue. However PVA cryogels are not suitable for cell attachment and proliferation alone. This can be overcome by the development of composite cryogels. Moreover, cryogelation provides a unique opportunity for encapsulation and storage of cells in one-step; if the correct composite structure and gelation conditions can be attained. In this study, PVA/Biomacromolecule composite cryogels were produced with a two step physical crosslinking (cryogelation and coagulation bath treatment) in the presence of different additives and a novel procedure to produce cell encapsulated PVA cryogels was developed for vascular tissue engineering. Also it was postulated that the disturbed shear stress could be used to facilitate endothelialisation of the PVA cryogel surface.
The results demonstrated that, the two step gel formation method was beneficial for degradation resistance and mechanical properties. All composites used supported cell attachment and proliferation, however PVA/Gelatin composites were superior compared to the others. Endothelialisation of PVA/Gelatin cryogels was achieved both under static and shear stress conditions with low levels of apoptosis and steady secretion of Nitric Oxide. It was shown that application of disturbed shear stress dramatically facilitated endothelialisation of the cryogel surface.
A general method of encapsulation via cryogelation was developed and robust cell-laden cryogels which promoted cell proliferation were obtained. Storage in frozen conditions did not affect the viability of the encapsulated cells, which suggests the prospect of safe long-term storage. Smooth muscle cell-laden cryogels were also able to support co-culture with endothelial cells. The results suggest that the novel encapsulation system developed is suitable for vascular and possibly other tissue engineering applications.
