Molecular Design and Self-assembly of Polydiacetylene for Biosensors and Sensor Arrays.

Abstract

The major themes of this dissertation are to develop molecular design principles of sensory polydiacetylene (PDA) and establish efficient chemo/biosensor device fabrication strategies for selective and sensitive detection of target analytes. We rationally designed probe-modified PDA liposomes such a way that analyte binding at the surface-immobilized probes produces steric repulsion that induces the perturbation of the conjugated ene-yne backbone of PDA and generates optical color change from blue to read and red fluorescence emission, as well. PDA liposome microarray to detect potassium was first developed to utilize the strong intra-repulsion strain caused by the formation of a potassium/aptamer G-quadruplex structure. We further expanded the design principle to a mercury detection system with superior immobilization functionality. In this work the probe DNA was microarrayed onto a glass substrate having immobilized PDA liposomes, opening up a possibility to build high throughput microarray having multiple probe molecules for spontaneous multiple detections. Molecular recognition through hydrogen bonding was also investigated in our colorimetric melamine sensor development. PDA molecules were modified with cyanuric acid that forms multiple hydrogen bondings with melamine molecules. The hydrogen bonding between melamine molecules and the cyanuric acids resulted in a notable color transition as well as red fluorescence emission due to the stress by intra-liposomal repulsion and inter-liposomal aggregation. The intra- and inter-liposomal interactions were also applied to the development of a convenient nerve gas detection system. PDA liposomes, modified with oxime units for selective interaction with nerve agents, were embedded into solid membrane filters for convenient use. Hydrophobic organophosphorous (OP) molecules induced large intra repulsion and also massive inter-liposomal aggregation by reacting with the oxime at the surface of the PDA liposomes. Multi-targeting PDA sensory system was also developed by encapsulating PDA liposomes having different probes into a multi-faced micron-size agarose beads to provide selective/sensitive multiple analytes detection. In addition to biosensor development, a functional PDA liposome system was investigated for immunofluorescence labeling application. The dye-loaded PDA liposomes with a receptor visualized patterns by producing dual green/red fluorescence emission. A novel PDA system having light-driven color change capability was also developed and its photochromism was demonstrated.