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Colloid filtration experiments were performed using latex particles (50 nm, 110 nm and 1500 nm) in both the presence and absence of 5.0 mg/L humic acid (HAs). At low ionic strengths (1 -- 10 mM KCl), an increase in attachment efficiency (alpha) with increasing particle size was observed, which contrasts with predictions based on DLVO theory. The presence of HAs generally resulted in a decrease in alpha. Characterization experiments to better understand this behaviour included particle sizing using dynamic light scattering (DLS) and zeta potential using laser Doppler velocimetry (LDV). The particles' hydrodynamic diameters were unchanged in the presence of HAs. HAs lead to an increase in absolute zeta potential for the 50 nm and 110 nm colloids and a decrease in zeta potential for the 1500 nm particles. A discussion of the apparent deviations from Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and explanations for the observed behaviour are provided.

Knee injuries are a major cause of orthopedic disabilities in the United States. Current reconstruction techniques for torn anterior cruciate ligaments (ACL) require extensive surgery and long physical rehabilitation times since the tissue does not heal upon injury. A common ACL injury occurs where the gap at the rupture site remains open after injury and fails to heal, which can lead to premature osteoarthritis and disability. Hydrogels are a popular material used for tissue engineering applications due to their ability to retain water and good biocompatibility. Previous work has shown that hydrogels can be made through the mixed-mode reaction of radically crosslinked thiol groups and acrylate end groups. This project explores mixed-mode oligo[poly(ethylene glycol) fumarate] (OPF)-based hydrogels as alternate carriers for regeneration of partial tear ligament defects. The main purpose of this project was to determine the degradative properties of and cell response to thiol-PEG-thiol (PEG-diSH), a novel hydrogel material. The swelling and degradative properties of hydrogels containing three components OPF, PEG-diacrylate (PEG-DA), and PEG-diSH were characterized by their fold swelling. In addition, cell viability, morphology changes, proliferation and collagen production were analyzed in tri-ratio hydrogels with and without the presence of RGD over three weeks. Results showed that the hydrogels containing PEG-diSH demonstrated significantly larger fold swelling and promoted cell clustering (as shown by increased area of clusters), probably due to the larger mesh size and possibly due to the presence of free thiol functional groups present in the network from the mixed-mode reaction. However, an increase in cell number was not found in these gels up to eight days, suggesting that cell migration may play a role in the appearance of clusters. Additionally, increased cell spreading in response to RGD was observed inside gels containing PEG-diSH; no spreading was seen in the non PEG-diSH gels (± RGD), possibly because the mesh size was too small to allow for clustering or spreading within the matrix. Results from this work suggest that the presence of PEG-diSH could promote cell-cell contact within the clusters which could be useful in systems where direct contact promotes tissue formation or cell differentiation.

Hydrophobic colloidal suspensions are common in nature and industry. DLVO theory has been used to model the interactions between colloidal particles for decades, however the origin of long-ranged attractive forces observed between hydrophobic colloids remains the subject of much debate. In an effort to understand these forces and improve the prediction of colloidal stability, the colloidal stability of synthetic silica and titania was studied at various concentrations of dissolved gas, KCl electrolyte and pH. / Thesis (PhD)--University of South Australia, 2003

Thesis (PhD)--University of South Australia, 2002.

Thesis (PhD)--University of South Australia, 1997

Hydrophobic colloidal suspensions are common in nature and industry. DLVO theory has been used to model the interactions between colloidal particles for decades, however the origin of long-ranged attractive forces observed between hydrophobic colloids remains the subject of much debate. In an effort to understand these forces and improve the prediction of colloidal stability, the colloidal stability of synthetic silica and titania was studied at various concentrations of dissolved gas, KCl electrolyte and pH. / Thesis (PhD)--University of South Australia, 2003

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--Drexel University, 2008. / Includes abstract and vita. Includes bibliographical references (leaves 251).

Thesis (Ph.D.) -- McMaster University, 1999. / Includes bibliographical references (leaves 179-187). Also available via World Wide Web.