Bis-aniline-crosslinked enzyme-metal nanoparticle composites on electrodes for bioelectronic applications

The electrical contacting of redox enzymes with electrodes is the most fundamental requirement for the development of amperometric biosensors and biofuel cell elements. We describe a novel method to prepare electrically contacted metallic nanoparticles (NPs) or carbon nanotubes (CNTs)/enzyme hybrid composites on electrodes that act as amperometric biosensors or as the constituents of biofuel cells. Au NPs or Pt NPs were modified with thioaniline electropolymerizable groups, and so were the enzymes glucose oxidase (GOx) or bilirubin oxidase (BOD). Electrochemical polymerization of the thioaniline-functionalized Pt NPs and GOx on a thioaniline monolayer-modified Au surface led to the formation of a bis-aniline-bridged Pt NPs/GOx composite electrode that enabled the analysis of glucose through the electrocatalyzed reduction of H₂O₂. Similarly, a Pt NPs/BOD composite-functionalized electrode showed electrocatalytic activity toward the reduction of O₂ to H₂O. Also, a Au NPs/GOx composite-functionalized electrode revealed direct electrical contacting between the enzyme and the electrode through the electrocatalytic reduction of the bis-aniline bridges, and this enabled the bioelectrocatalytic oxidation and the amperometric sensing of glucose. Finally, a biofuel cell consisting of an anode modified with Nile blue/NAD⁺/alcohol dehydrogenase on carbon nanotubes, and a cathode composed of the bis-aniline-crosslinked Pt NPs/BOD composite was constructed. The biofuel cell operates with a power output corresponding to 200μW cm^-2.