A Cross-Linker Free Enzyme Immobilization for Direct Bioelectrocatalysis Using Aqueous Phase Inversion of a High-Ionic-Strength, Liquid Complex Coacervate

Monday, 14 October 2019: 16:40
Room 308 (The Hilton Atlanta)
K. Lim (University of Utah), M. Sima (University of utah), R. Stewart, and S. D. Minteer (University of Utah)
Immobilization of enzymes on an electrode surface is critical in facilitating bioelectrocatalysis. Here, we present cross-linker free immobilization using aqueous phase inversion of a high-ionic-strength, liquid complex coacervate to create a porous solid electrode coating for direct bioelectrocatalysis of horseradish peroxidase (HRP) and laccase. The liquid complex coacervate (PGP6) was made by mixing a polycationic polymer with guanidinium moiety (PG) and polyanionic polymer of hexametaphosphate (P6) in 1.4 M NaCl at a 1:1 positive to negative polymer charge ratio. A mixture of 18 µL of the condensed liquid phase (PGP6) and 2 µL of 50 mg ml-1 of laccase or HRP was made. A total of 1.5 µL of this mixture was deposited on a 0.25 cm2 AvCarb electrode and submerged in DI water for 30 minutes to induce phase inversion and solidification of the coating. A confocal microscopic image of fluorescently tagged laccase showed the entrapment of enzymes within the solids, not in the pores. Both immobilized enzymes successfully generated a catalytic current corresponding to the addition of their respective substrates. Also, the square wave voltammograms of these electrode coatings showed no apparent redox peaks which indicated direct electron transfer. These results show the convenience of an aqueous phase inversion coating system for direct bioelectrocatalysis and advance to the potential for mediated electron transfer.