Long Tethers Binding Redox Centers to Polymer Backbones Enhance Electron Transport in Enzyme “Wiring” Hydrogels

• Published in: Journal of the American Chemical Society 2003-04, Vol.125 (16), p.4951-4957
• Main Authors: Mao, Fei, Mano, Nicolas, Heller, Adam
• Format: Article
• Language: English
• Subjects: 2,2'-Dipyridyl - analogs & derivatives; 2,2'-Dipyridyl - chemistry; Applied sciences; Electrochemistry; Exact sciences and technology; Flavin-Adenine Dinucleotide - chemistry; Glucose Oxidase - chemistry; Hydrogels - chemistry; Imidazoles - chemistry; Inorganic and organomineral polymers; Organometallic Compounds - chemistry; Oxidation-Reduction; Physicochemistry of polymers; Polyvinyls - chemistry; Properties and characterization
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja029510e

A redox hydrogel with an apparent electron diffusion coefficient (D app) of (5.8 ± 0.5) × 10-6 cm2 s-1 is described. The order of magnitude increase in D app relative to previously studied redox hydrogels results from the tethering of redox centers to the backbone of the cross-linked redox polymer backbone through 13 atom spacer arms. The long and flexible tethers allow the redox centers to sweep electrons from large-volume elements and to collect electrons of glucose oxidase efficiently. The spacer arms make the collection of electrons from glucose oxidase so efficient that glucose is electrooxidized already at −0.36 V versus Ag/AgCl, the reversible potential of the redox potential of the FAD/FADH2 centers of the enzyme at pH 7.2. The limiting current density of 1.15 mA cm-2 is reached at a potential as low as −0.1 V versus Ag/AgCl. The novel redox center of the polymer is a tris-dialkylated N,N‘-biimidazole Os2+/3+ complex. Its redox potential, −0.195 V versus Ag/AgCl, is 0.8 V reducing relative to that of Os(bpy)2+/3+, its 2,2‘-bipyridine analogue.