1. Could you explain the significance of your article to the non-specialist?

Biofuel cells are energy-conversion devises based on bioelectrocatalysis. For the communication between enzymes and electrodes, direct electron transfer (DET) is the ultimate or ideal system in view of the reaction scheme. This work has realized one-compartment enzymatic biofuel cell utilizing DET with a maximum power of about 1 mW cm^-2, which is comparable with or larger than that of mediated electron transfer (MET)-type biofuel cells reported to date. This suggests that the new era is coming in biofuel cell technology and the bio-nano interface science.

2. What has motivated you to conduct this work? 

One of the advantages of biofuel cells is that the substrate recognition of the enzymes allows one-compartment cells without separator. DET-type bioelectrocatalysis is the suitable system to draw out the advantage, although it is very difficult to realize at large current density. Therefore, it is challenging work to show a prototype of DET-type biofuel cell.

3. Where do you see this work developing in the future? 

One-compartment biofuel cells may be developed as power sources of implantable devises within humans such as pacemakers, insulin pumps, sensor and prosthetic units. However, disposable style seems to be suitable for biofuel cells in practice, until enough stability can be secured. Combination with second batteries or capacitors is also interesting and important challenge.

4. Are there any particular challenges facing future research in this area? 

Search of better enzymes
Preparation and characterization novel carbon electrode materials
Understanding of the determinants governing the DET reaction
Development in the field of nano-bio science
Mutation of enzymes to tune the redox potential, to improve DET kinetics, or to reduce the enzyme size
and 
Improvement of biofuel cells up to the commercial level!