Design, synthesis, characterization and applications of conjugated polyelectrolytes for biosensing and as biocides

A series of water soluble, cationic conjugated polyelectrolytes (CPEs) with backbones based on a poly(phenylene ethynylene) repeat unit structure and tetraakylammonium side groups have been designed, synthesized and characterized for their applications for biosensing purposes and as potential biocidal agents.;This research work involved developing a simpler method for surface grafting anionic and cationic polymers onto borosilicate microspheres. Characterization techniques were employed to evaluate their capabilities as sensing platforms and for biocidal activity. CPEs were further investigated to understand their behavior after being coated onto silica microspheres. They were then layered with a lipid bilayer to design a stable sensing platform enabling the development of a convenient and simple assay for the quantification of Phospholipase A 2, an enzyme emerging as a biomarker for atherosclerosis. Investigating factors like the best support format (physisorbed or surface grafted), charge on the polymers, and the interaction of negatively charged DMPG lipid bilayers with the polymers, it was shown that CPEs can be used as a stable sensing platform to develop a highly sensitive assay that can quantify PLA2 in the nanomolar range.;A series of CPEs were investigated for their biocidal activity to develop non-leachable antimicrobial surfaces. The photophysical properties of the CPEs are studied in solution to demonstrate that direct excitation produces a triplet excited-state in moderate yield, and this triplet is shown to be effective in sensitizing the production of singlet oxygen. Biocidal activity of CPEs was then correlated to their photophysical properties. Using these polymers in a format where they are physisorbed or covalently grafted to the surface of colloidal silica particles (5 and 30 mum diameter), this study demonstrates that they exhibit light-activated biocidal activity, effectively killing Cobetia marina and Pseudomonas aeruginosa . The light-induced biocidal activity was further correlated with a requirement for oxygen suggesting that interfacial generation of singlet oxygen is the crucial step in the light-induced biocidal activity.