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

The major themes of this dissertation are to develop molecular design principles of sensory polydiacetylene (PDA) and establish efficient and convenient 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.;A probe modified PDA liposome microarray system to detection 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 microarray system with superior probe immobilization functionality. In this work the probe DNA was conveniently 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 a target melamine molecule. The hydrogen bonding between the target melamine molecules and the surface tethered cyanuric acids resulted in a notable color transition as well as red fluorescence emission due to the stress generated by intra-liposomal repulsion as well as 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 mime units for selective interaction with nerve agents, were embedded into solid membrane filters for convenient use. Hydrophobic organophosphorous (OP) nerve agent molecules induced large intra repulsion and also massive inter-liposomal aggregation by reacting with the mime probes 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 gel heads. This novel multi-phased PDA micro-bead system can provide selective and sensitive multiple analytes detection simultaneously in aqueous solutions.;In addition to biosensor development, a functional PDA liposome system was investigated to be applicable to immunofluorescence labeling. The dye-loaded PDA having biotin as a model receptor at the liposome surface visualized avidin patterns by producing dual green and red fluorescence emission produced by the dye and mechanochromism of PDA, respectively. A novel PDA system having light-driven color change capability was also developed and its photochromism was demonstrated.