Chemical gradients and bioactive hydrogels for mechanistic studies of protein binding and cell adhesion

Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)




Yan-Yeung Luk

Second Advisor

Dacheng Ren


Chemical gradients, Hydrogels, Protein binding, Cell adhesion

Subject Categories



The interactions among cells, biological molecules and surfaces have long been the subject of much study. These ubiquitous interactions are critically important for such processes as growth and development, but can also be problematic, as in biofouling caused by bacterial biofilm growth. A fundamental understanding of these interactions is important in engineering systems to control them or exploit them for a variety of purposes. The bulk of this work consists of a study of the mechanisms and the control of cell adhesion on surfaces, and the development of systems to detect specific biological molecules in water. The first two chapters herein describe two different methods of producing chemical gradients of alkanethiol self-assembled monolayers on gold films, and using these chemical gradients for the study of cell adhesion. One of these methods depends on gradient nanometer-scale topography in the gold film. The other involves modifying a gold surface with two components, such that the ratio of the components changed in a gradient fashion along the length of the surface. Cells cultured on these gradients had a significant difference in cell growth from one end of the gradient to the other. This work revealed mechanistic differences between mammalian and bacterial cell adhesion on surfaces. The third and fourth chapters contain details of efforts to produce a system to quickly and reliably detect the presence of specific antigens in water. These systems involve hydrogels modified with antigen-antibody pairs to respond to the target antigen. In one method, the hydrogels have an integrated diffraction grating, such that exposure to the target antigen will be reflected as a change in the diffraction of a beam of light projected through the gel. The other method uses fluorescently tagged antibodies to signal detection. The fifth chapter involves an investigation into the molecular organization of liquid crystal phases of disodium cromoglycate (DSCG), and presents a new hypothesis for the arrangement of molecules in DSCG solutions. Cholesteric phase was produced in polymer dispersions of DSCG by doping with chiral molecules, and these dispersions were used as templates for porous hydrogels with unique pore structure.


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