(Invited) Redox Active Metallic and Glyco-Based Nanoparticles for Enzymatic Bioelectrocatalysis

Abstract

The clean production of electrical energy from renewable resources has received recently a growing attention from the research community. A way to achieve this goal is the use of biological catalysts to catalyze the oxidation of renewable fuels. One of the streamlines on the research dealing with green electrical energy production is represented by oxidoreductase enzymes as the biocatalysts. Thanks to their specificity towards their respective substrates and activity in relatively mild conditions (pH, temperature, etc…), they are ideal candidates to replace noble metals regularly found in fuel cells. However, due to low power densities achieved utilizing these redox proteins and their limited stability; enzymatic fuel cells (EFCs) are so far only envisioned to power small and disposable electronic devices. In most literature reports, the redox enzymes are essentially immobilized on chemically modified electrode surfaces. There, they harvest and convert the chemical energy stored in fuels and turn it into electrical energy. The growing field in bioelectrocatalysis is beneficial not only for the biofuel cell technology but also for the design of efficient biosensing or bioreactor devices. In this presentation, we will focus on two different approaches for the design of EFCs currently studied in our laboratory. The rationalization of the electrode surface requirement to achieve efficient bioelectrocatalysis (mediated or direct electron transfer) [1] allowed for the synthesis of redox active gold nanoparticles (AuNPs) bearing electroactivable nitro groups and negatively charged groups. The obtained hydroxylamine-modified AuNPs are catalytically active for nicotinamide adenine dinucleotide (NADH) oxidation and for NAD+ regeneration in bioelectrocatalysis (with NAD-dependent glucose dehydrogenase). In contrast, the same particles possessing also negatively charged carboxylic groups had been shown to favorably orientate some multi-copper oxidases having their T1 copper center facing the metallic particles and consequently enhancing oxygen electroreduction. On the other hand, we will also present our recent strategy to design solubilized enzymatic fuel cell (SEFC). The entrapment of different redox mediator is accomplished by host-guest interaction with β-cyclodextrin-coated glyconanoparticles for the mediated glucose and oxygen conversion [2,3]. Hence, the cell was designed with permselective membranes to enable substrate and proton diffusion while trapping the enzymes and redox glyconanoparticles in separate compartments. The SEFC suffered a limited power loss of about 25% after 7 days of continuous charge-discharge cycling at 50 µA [3].