Yildirimer, EL; (2014) A novel biodegradable poly(ε-caprolactone urea)urethane incorporating polyhedral oligomeric silsesquioxane nanocomposite and applications for skin tissue engineering. Doctoral thesis , UCL (University College London).

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Abstract

Skin protects our bodies for a lifetime and extensive loss of this barrier renders the individual susceptible to infections and death. Clinically available treatment options, however, are limited in establishing both functional and cosmetic satisfaction. The work described in this thesis is therefore concerned with the development and characterization of a novel biodegradable nanocomposite system displaying suitable properties as skin tissue engineering scaffolds. A novel family of segmented polyurethanes (PU) with increasing hard segment content based on a poly(ε-caprolactone urea)urethane backbone incorporating POSS nanoparticles was synthesized and analysed in terms of material characteristics and biocompatibility. Incorporation of POSS nanoparticles into the PU backbone yielded mostly amorphous materials as corroborated by distinct glass transitions visible on differential scanning calorimetry spectra. With incrementally increasing hard segment content, ultimate tensile strength increased from ~10 to 21 MPa accompanied by increased values for elastic moduli from 0.03 to 0.06 MPa. Number average molecular weights (Mn) decreased with increasing hard segment content due to a corresponding decrease in the proportion of PCL. Sterilization studies raised fundamental concerns regarding the suitability of conventionally available techniques since hydrolytically and temperature labile polymers are susceptible to degradation. The results obtained suggest 70 % ethanol to be a suitable laboratory-based disinfectant which was further demonstrated to have favourable effects on skin cell compatibility. Degradation studies revealed hard segment-dependent modulation of the degradation rate and the materials’ viscoelasticity. In vivo implantation studies of porous scaffolds demonstrated firm integration with the subcutaneous tissue and extensive vascularization. The results obtained in this work highlight (i) the ability to control scaffold degradation rates and mechanical properties and (ii) cellular as well as in vivo biocompatibility, all of which fundamental in the development of a versatile skin tissue engineering scaffold.

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