Analytical and Electroanalytical Applications of Filamentous Bacteriophages and Development of Sensitivity-Tunable Ion Sensing Platform based on Reverse Electrodialysis

Abstract

Chapter 1: Analytical and Electroanalytical Applications of Filamentous Bacteriophages Filamentous bacteriophage is one of the most highlighted biomaterial, thanks to its unique properties: 1) Easy modification of its major coat protein with genetic engineering and bioconjugation, 2) The regularity of the virions along with large population and fast generation time, and 3) The high aspect ratio, 7 nm in width and 880 nm in length, which make it an excellent biomaterial for nanomaterial applications. First, filamentous bacteriophages are applied as a scaffold of antibody immobilization for bead-based 3D suspension multiplex immunoassay. The size and the fluorescence signal of virus-tethered gold microbead is measured at a DC impedance-based flow cytometer. The large quantity of antibody loading and flexible movement of filamentous virus enabled signal enhancement, elevating sensitivity by up to 5.7-fold compared to the beads without virus. This system successfully accomplished multiplex immunoassay involving four biomarkers: prostate specific antigen, cardiac troponin I, myoglobin, and creatine kinase MB in undiluted human serum. Second, filamentous bacteriophages are genetically engineered to display 3,4-dihydroxyl-L-phenylalanine (DOPA) onto the major coat protein, where cobalt oxide-based oxygen evolution catalyst (Co-OEC) are deposited spontaneously. It was demonstrated that the catalyst formed on the virus shows improved durability and decrease oxidation state compared with electrodeposited Co-OEC. The DOPA-displaying virus proposes unconventional way of generating electrocatalysts by introducing DOPA as a nucleation site as well as a dopant for Co-OEC.

Chapter 2: Development of Sensitivity-Tunable Ion Sensing Platform based on Reverse Electrodialysis Reverse elecrodialysis (RED) is a salinity gradient-based power generation system, of which the output voltage is proportional to the 1) concentration difference between river water and seawater, and 2) the number of stacks comprising RED. Inspired by those features mentioned above, RED-based ion sensing platform is proposed. The cation exchange membranes and anion exchange membranes constituting traditional RED are substituted to home-made ion- selective membranes and reference membranes, which generate sample dependent and independent potential, respectively, and the sensitivity is freely modulated by changing the number of stacks. This sensing platform is integrated with a colorimetric detection system based on polyaniline, which is a well-known electrochromic dye, electrodeposited on one bipolar electrode to display sample concentration-dependent colors. Combined with the colorimetric detection system, the RED-based ion sensing platform serves as a power generator as well as an ion concentration selective signal producer, which realize self-powered and disposable ion sensor with tunable sensitivity