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Oral delivery of insulin used for the management of Type 1 Diabetes could be referred to as one of the major long term goals of diabetes research. However, the bioavailability of orally administered insulin is significantly compromised by enzymatic degradation in the GI tract and poor enteral absorption of the protein due to its macromolecular size and hydrophilicity. Nano-sized polymer-protein polyelectrolyte complexes (PECS) formed by electrostatic interactions between insulin and Polyallylamine-based polymers at pH 7.4 have been adapted to facilitate oral insulin delivery. Polyallylamine (15kDa) was quaternised by methylation of its primary amines using methyl iodide to yield quaternised Paa (QPaa). Average level of polymer quaternisation was determined by elemental analysis and was found to be 72 ± 2mol%. Subsequent thiolation of Paa and QPaa using two different thiolation procedures involving carbodiimide mediated conjugation to N-acetylcysteine (NAC) and modification of the polymers using 2-iminothiolane hydrochloride yielded their respective NAC and 4-thiobutylamidine (TBA) conjugates: Paa-NAC/QPaa-NAC and Paa-TBA/QPaa-TBA. Estimation of the free thiol content of these thiomers by iodometric titration showed that both Paa-NAC and QPaa-NAC displayed 60 ± 1.2 and 60 ± 4.3ìmol free thiol groups per gram polymer, while Paa-TBA and QPaa-TBA conjugates displayed 490 ± 18 and 440 ± 21ìmol free thiol groups per gram polymer respectively. Mixing optimal mass ratios of each polymer and insulin in Tris buffer at pH 7.4 resulted in the formation of soluble nanocomplexes. Complexes were characterised by transmittance measurements, particle size analysis, zeta potential, complexation efficiency, and transmission electron microscopy (TEM). Stable polymer-insulin complexes were observed to have hydrodynamic sizes between 50-200nm, positively charged zeta potential values ranging between 20-40mV and high insulin complexation efficiency (> 90%). Complexation of insulin with TBA conjugates however appeared to alter insulin conformation affecting the detection of complexed insulin by HPLC. TEM analysis revealed the formation of bilayered nanovessicles as well as conventional single-layered nanoparticles on complexation of insulin with QPaa and thiolated Paa/QPaa derivatives. In-vitro assessments of enzyme-protective effect of QPaa, Paa-NAC and QPaa-NAC insulin complexes showed that when compared to a free insulin control, all the aforementioned complexes could protect insulin from degradation by trypsin and á-chymotrypsin, but not from pepsin. In-vitro mucin adsorption assays showed that all polymers exhibited a similar mucoadhesive profile with their corresponding insulin PEC, with thiolated Paa derivatives adsorbing >20% more mucin than Paa. Thiolation of QPaa did not result in a noticeable improvement in its mucoadhesive capacity indicating that polymer-mucin thiol-disulphide interactions may be hindered by the presence of quaternary groups. The IC50 of each polymer was determined by MTT assays carried out on Caco-2 cells with or without the inclusion of a 24-hour cell recovery period. An MTT assay conducted without a recovery period indicated that quaternisation of Paa was associated with a 6-fold improvement in its IC50; also cells subjected to a 24-hour recovery period following treatment with QPaa (0.001-4mgml-1) showed no signs of toxicity. Thiolation of Paa resulted in slight (≤ 2 fold) improvements in IC50, while thiolation of QPaa resulted in a decrease in IC50 values obtained both with and without a cell recovery period. Each polymer was subsequently labelled with rhodamine B isothiocyanate (RBITC) and complexed with fluorescein isothiocyanate (FITC)-insulin. Monitoring uptake of these complexes by Caco-2 cells using fluorescence microscopy with DAPI staining indicated that uptake of QPaa and QPaa-TBA complexes was mainly intracellular being localised within the perinuclear area of cells highlighted by DAPI. Hence, intracellular uptake of PECS by Caco-2 cells was enhanced by Paa quaternisation and TBA-based thiolation of QPaa.

The primary focus of my work was to chemically functionalize diamond as normal and reversed phases for solid phase extraction (SPE) and high performance liquid chromatography (HPLC). Diamond was functionalized with -NH2 groups via self-limiting adsorption of an amine-containing polymer, polyallylamine (PAAm), onto oxidized diamond particles. The chemical stability of these particles was improved by thermal curing or chemical crosslinking with 1,2,5,6-diepoxycyclooctane. The reversed phase material for SPE was synthesized by reacting amine-functionalized diamond particles with long chain alkyl and a perfluorinated isocyanate. Unlike commercially available silica, functionalized diamond particles were stable under extreme pH conditions (pH 0-14). Functionalized diamond particles were used for SPE, although their lack of porosity resulted in poor analyte capacity. To create materials with greater surface area, core-shell diamond particles were synthesized via layer-by-layer deposition of PAAm and nanodiamond onto solid microdiamond. These particles had higher surface areas than solid diamond particles, and their application in SPE and HPLC was demonstrated. As a related project, I demonstrated microlens array patterning (MAP) for selective adsorption of PAAm during microarray fabrication. Initially, alkyl monolayer terminated silicon surfaces were photopatterned with thousands of wells using a microlens array. PAAm was then deposited in the presence of a cationic surfactant to limit nonspecific adsorption of PAAm. Finally, reactions of selectively adsorbed PAAm were shown with glutaric anhydride, phenylenediisothiocyanate, biotin NHS-ester and an oligonucleotide (DNA). My third project concerned the synthesis of an abrasion resistant hydrophobic coating on the surface of nylon and silicon oxide substrates using chemical vapor deposition (CVD) of two silanes. The synthesis consists of four steps: 1) plasma oxidation of the substrate, 2) treatment with 3-isocyanatopropyltrimethoxysilane, 3) exposure of the treated surfaces to water vapors, and 4) treatment with a perfluorinated silane to make the surfaces hydrophobic. The coating is not visible to the eye and does not change the feel of the surface. Time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry, contact angle goniometry, scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), Rutherford backscattering spectroscopy (RBS) and nuclear reaction analysis (NRA) were used to characterize the resulting materials.