Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Chemistry

Language

English (en)

Date of Award

1-1-2011

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Kevin Moeller

Abstract

Microarrays are powerful tools for high-throughput screening of small molecule libraries. Our group is using a microelectrode array variant on these efforts that allows us to construct and screen the libraries in a rapid, cost effective fashion. In this approach, the small molecules are attached to polymer-coated microelectrodes, which can be used to detect ligand-receptor interactions as they happen by means of impedance. Impedance experiment work by monitoring the current associated with a redox couple in solution. When a protein binds a ligand on the array, it sterically prevents the redox couple from reaching the electrode surface and thus causes a reduction in the current being measured. In order to realize the construction of a library and measurement of the electrochemical impedance on the array, the polymer coating applied on the array needs to be stable for long periods of time, stable to washing the array, compatible with the array-based reactions, compatible with electrochemical impedance experiments, and relatively inert with respect to its non-specific binding with receptors. This work makes progress towards this goal by first exploring the Pd(0) chemistry on the array, identifying the incompatibility of palladium chemistry with the agarose coating that was being used on the surface of the arrays, and the designing and synthesizing new polymer coatings for microelectrode arrays. Three different block copolymers were made to investigate the compatibility of the polymers with the array-based reactions and signaling experiments. All three types of polymers consisted of a PCEMA block for UV-cross-linking reactions to improve the stability of the coating. The prototype polymer PBrSt-b-CEMA used 4-bromostyrene as the second block for functionalization purpose. It was proven to be a very versatile polymer which was stable, and compatible with all the electrochemical experiments conducted on the array. As a result this coating was extensively utilized in the study of the behavior of signaling experiments on the array. The major drawback of this polymer was its non-specific binding to proteins at higher protein concentrations. In order to fix this problem, a second polymer PCEMA-b-PEGMA with PEG as side chains was made in the hope that PEG would reduce non-specific binding to the surface. Unfortunately the polymer was not stable enough as coating for the array. Finally, a copolymer with boronic acid functionality, PCEMA-b-BoSt was made in order to test the versatility of the boronic acid as a starting material for building other functionalities. The boronic acid derived polymer performs better than the previous coating in terms of array-based reactions. However, it was found to be incompatible with the electrochemical impedance experiments.

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Permanent URL: http://dx.doi.org/10.7936/K7MK69Z7

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