Electrical activity of cellobiose dehydrogenase adsorbed on thiols: Influence of charge and hydrophobicity.

The interface between protein and material surface is of great research interest in applications varying from implants, tissue engineering to bioelectronics. Maintaining functionality of bioelements depends greatly on the immobilization process. In the present study direct electron transfer of cellobiose dehydrogenase from Humicola insolens (HiCDH), adsorbed on four different self-assembled monolayers (SAMs) formed by 5-6 chain length carbon thiols varying in terminal group structure was investigated. By using a combination of quartz crystal microbalance with dissipation, ellipsometry and electrochemistry the formation and function of the HiCDH film was studied. It was found that the presence of charged pyridinium groups was needed to successfully establish direct electron contact between the enzyme and electrode. SAMs formed from hydrophilic charged thiols achieved nearly two times higher current densities compared to hydrophobic charged thiols. Additionally, the results also indicated proportionality between HiCDH catalytic constant and water content of the enzyme film. Enzyme films on charged pyridine thiols had smaller variations in water content and viscoelastic properties than films adsorbed on the more hydrophobic thiols. This work highlights several perspectives on the underlying factors affecting performance of immobilized HiCDH.

Performance of enzymatic fuel cell in cell culture.

Here we present the very first study of an enzymatic fuel cell (EFC) in a cell culture. An EFC with Corynascus thermophilus cellobiose dehydrogenase (CDH) based bioanode and Myrothecium verrucaria bilirubin oxidase (BOx) based biocathode was constructed at the bottom of a medusa cell culture plate. The constructed EFC had a power density of up to 25 µW cm(-2) at 0.5 V potential in simple buffer solution and in cell culturing medium. L929 murine fibroblast cells were seeded on top of the EFC and possible effects of the EFC on the cells and vice versa were studied. It was shown that on average the power of the EFC drops by about 70% under a nearly confluent layer of cells. The EFC appeared to have a toxic effect on the L929 cell line. It was concluded that the bioanode, consisting of CDH, produced hydrogen peroxide at toxic concentrations. However, the toxic effect was circumvented by co-immobilizing catalase on the bioanode.