Journal of Power Sources 183 (2008) 533–538 Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour Enzymatic biofuel cell based on electrodes modified with lipid liquid-crystalline cubic phases Ewa Nazaruk a , Slawomir Smoli ´ nski a , Marta Swatko-Ossor b , Gra ˙ zyna Ginalska b , Jan Fiedurek c , Jerzy Rogalski d , Renata Bilewicz a,∗ a Department of Chemistry, University of Warsaw, Pasteura Street 1, 02-093 Warsaw, Poland b Department of Biochemistry, Medical University of Lublin, Chodzki Street 1, 20-093 Lublin, Poland c Department of Industrial Microbiology, Maria Curie-Sklodowska University, Akademicka Street 19, 20-033 Lublin, Poland d Department of Biochemistry, Maria Curie Sklodowska University, Sklodowskiej Sq 3, Lublin 20-031, Poland article info Article history: Received 4 January 2008 Received in revised form 20 April 2008 Accepted 17 May 2008 Available online 29 May 2008 Keywords: Biofuel cell Monoolein Laccase Glucose oxidase Liquid-crystal Cubic phase abstract Two glassy carbon electrodes modified with enzymes embedded in lyotropic liquid-crystalline cubic phase were used for the biofuel cell construction. The monoolein liquid-crystalline film allowed to avoid separa- tors in the biofuel cell. Glucose and oxygen as fuels, and glucose oxidase and laccase as anode and cathode biocatalysts, respectively were used. The biofuel cell parameters were examined in McIlvaine buffer, pH 7 solution containing 15mM of glucose and saturated with dioxygen. A series of mediators were tested taking into account their formal potentials, stability in the cubic phase and efficiency of mediation. Most stable was the biofuel cell based on tetrathiafulvalene (TTF) and 2,2 ′ -azino-bis(3-ethylbenzothiazoline- 6-sulfonate) (ABTS) as anode and cathode mediators, respectively. The open-circuit voltage was equal to 450 ± 40mV. The power densities and current densities were measured for all the systems studied. © 2008 Elsevier B.V. All rights reserved. 1. Introduction The role of enzymatic biofuel cell is to convert the chemical energy into electrical current using the redox enzymes as biocata- lysts. The power output generated by such system is high enough to supply microelectronics systems, microdevices and pace makers that require relatively low power [1–15]. The future goals include the use of these devices in physiological media and to power implanted medical devices. For these applications the biofuel cells have to be biocompatible, safe but also cheap since the enzyme film in the devices should be easily replaced. The main advantage of this type of fuel cell is the application of natural compounds, e.g. glucose or ethanol, as fuels and the abil- ity to operate under mild condition (at temperature of 20–40 ◦ C and at pH near to neutral). These properties make biofuel cells attractive for applications where generating high temperature is difficult or where severe reaction conditions are unfavourable. Most of the biofuel cells rely on the primary alcohols and sugars as the substrates and alcohol or glucose dehydrogenases or glucose oxi- ∗ Corresponding author. Tel.: +48 228220211; fax: +48 228225996. E-mail address: bilewicz@chem.uw.edu.pl (R. Bilewicz). dase as the anode biocatalysts. Glycerol was found a convenient alternative since better power densities could be achieved than for common ethanol biofuel cells and swelling the matrix (com- mon difficulty with the Nafion matrix) was avoided [16]. One of the critical challenges in developing direct biofuel cells is inef- ficient electron conduction between biocatalysts and electrodes. Using carbon substrates, usually a mediator to be employed in order to connect electrically the enzyme with the electrode and provide high catalytic efficiency of the system [17–19]. Recently proposed biocathodes and bioanodes are often based on metal electrodes, e.g. platinum or on employing osmium complex-linked polymers as the mediators. Examples of applica- tion of osmium complexes in biofuel cells are collected in Table 1 [8]. On the other hand, attempts have been made to both avoid Pt electrodes, and osmium complexes as mediating moieties. Osmium complexes rise some concern among the medical community in case of applications in living organisms. Using organic biocompati- ble mediators or new ways to eliminate the necessity of mediators would bring a solution to these problems. Vitamin K 3 -immobilized polymers were found useful as bioanode mediators [20]. Only few direct electron transfer-type (DET-type) biofuel cell have been presented in the literature [21,22]. A notable fructose/dioxygen bio- 0378-7753/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2008.05.061