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Abstract
The use of polymer nanocomposites (NCs) in industrial applications has received growing attention over the past decade due to their improved mechanical properties. However, little work has been reported which analyses the efficacy of NCs in biological applications, including drug delivery systems and implantable materials. This thesis examines the effect of the chemistry of the organic modifier (OM) on the structure and biological performance of poly(ether)urethane NCs (PUNCs) and the influence of the method of drug incorporation on interactions between drug and NC. Organically modified silicates (OMS) were prepared using OMs varying in terminal functionality and alkyl chain length. PUNCs were solvent cast containing 1 and 3wt% OMS and particle dispersion analysed using X-ray diffraction and transmission electron microscopy. Findings revealed that use of an OM with methyl terminal, dodecylamine (12CH3), resulted in superior dispersion of OMS compared with a carboxyl terminated OM, aminododecanoic acid (12COOH), of equivalent alkyl chain length. This is believed to result from increased self interaction of 12COOH compared with 12CH3. Additionally, increased alkyl chain length was shown to improve NC dispersion with a chain length of sixteen units resulting in the optimum dispersion with a partially exfoliated NC structure. Analysis of cellular interactions with the PUNCs revealed a significant difference in both fibroblast and platelet adhesion to NCs incorporating 12CH3 compared with 12COOH. Surface analysis using ToF-SIMS demonstrated the presence of 12CH3 fragments on the NC surface supporting the hypothesis that surface expressed OMs alter cellular interactions with the NC. Altering the alkyl chain length also affected cellular interaction with an alkyl chain length of twelve units or greater, substantially reducing fibroblast adhesion without affecting cell growth inhibition or viability. Incorporation of a model drug, crystal violet, into the PUNCs demonstrated a lower degree of disruption to OMS dispersion when loaded post NC fabrication compared with pre fabrication. This is believed to result from interactions between the drug and NC constituents which also impacted on drug release from the NC system. Results show PUNC properties and biological interactions can be modulated through OM variation and fabrication method, thus showing potential for use in biomedical applications.