Bioelectrochemistry (v.115, #C)

Study of overall and local electrochemical responses of oxide films grown on CoCr alloy under biological environments by I. Diaz; J.F. Martinez-Lerma; R. Montoya; I. Llorente; M.L. Escudero; M.C. García-Alonso (1-10).
The interaction of the physiological medium and living tissues with the implant surfaces in biological environments is regulated by biopotentials that induce changes in the chemical composition, structure and thickness of the oxide film. In this work, oxide films grown on CoCr alloys at 0.5 V vs Ag/AgCl and 0.7 V vs Ag/AgCl have been characterized through overall and localized electrochemical techniques in a phosphate buffer solution and 0.3% hyaluronic acid. Nanopores of 10–50 nm diameter are homogeneously distributed along the surface in the oxide film formed at 0.7 V vs Ag/AgCl. The distribution of the Constant Phase Element studied by local electrochemical impedance spectroscopy showed a three-dimensional (3D) model on the oxide films grown at 0.5 V vs Ag/AgCl and 0.7 V vs Ag/AgCl. This behaviour is especially noticeable in oxide films grown at 0.7 V vs Ag/AgCl, probably due to surface inhomogeneities, and resistive properties generated by the potentiostatic growth of the oxide film.
Keywords: CoCr implant; EIS; LEIS; Hyaluronic acid; CPE distribution;

Spatiometabolic stratification of anoxic biofilm in prototype bioelectrogenic system by G. Mohanakrishna; Sai Kishore Butti; R. Kannaiah Goud; S. Venkata Mohan (11-18).
A prototype bio-catalyzed electrogenic system integrated with a biological treatment process (SBR-BET) was evaluated to study specific function of anoxic condition on the electrogenic activity. A multiphasic approach was employed, where the influence of DO on bio-electrogenic activity was optimized initially, later optimal anode to cathode inter-electrode distance was enumerated. Amongst the four electrode distances evaluated, 2 cm showed higher power output. Bioelectrokinetics analysis was used to validate the system performance with the experimental variation studied. The redox behavior showed an increase in cathodic catalytic activity with an increase in the inter-electrode distance. Spatiometabolic distribution depicted the microbial stratification on the anode. Electrochemically active bacteria present on the anode surface (inner and outer layers of biofilms) showed relatively uniform diversity compared with the suspension culture.
Keywords: Sequencing batch reactor (SBR); Electrode assembly; Dissolved oxygen (DO); Activated sludge process (ASP); Electrode; Proteobacteria;

Caspase dependent apoptosis induced in yeast cells by nanosecond pulsed electric fields by Povilas Simonis; Skirmantas Kersulis; Voitech Stankevich; Vytautas Kaseta; Egle Lastauskiene; Arunas Stirke (19-25).
Saccharomyces cerevisiae yeast cells were used as a model organism to investigate the effects of various pulsed electric fields on the programed death of such cells. These were exposed to electric field pulses with field strengths (E) of up to 220 kV/cm. The effects of square shaped pulses having different durations (τ = 10–90 ns) and different pulse numbers (pn = 1–5) were then analysed. The obtained results show that nanosecond pulses can induce the death of such cells, which in turn is dependent on the electric field pulse parameters and increase with the rise in E, τ and pn. The decrease of the cells' viability was accompanied by an increase in the active form of intracellular yeast metacaspases. It was thus shown that nanosecond electric field pulses induced the caspase-dependent yeast cell death.
Keywords: Yeast; Apoptosis; Metacaspase; Electroporation; Nanosecond;

Electrical activity of cellobiose dehydrogenase adsorbed on thiols: Influence of charge and hydrophobicity by P. Lamberg; J. Hamit-Eminovski; M.D. Toscano; O. Eicher-Lorka; G. Niaura; T. Arnebrant; S. Shleev; T. Ruzgas (26-32).
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.
Keywords: Cellobiose dehydrogenase; Direct electron transfer; Self-assembled monolayers; Surface charge; Hydrophobicity; Thiol;

Impedance spectroscopy as an indicator for successful in vivo electric field mediated gene delivery in a murine model by Reginald M. Atkins; Timothy J. Fawcett; Richard Gilbert; Andrew M. Hoff; Richard Connolly; Douglas W. Brown; Anthony J. Llewellyn; Mark J. Jaroszeski (33-40).
In vivo gene electro transfer technology has been very successful both in animal models and in clinical trials over the past 20 years. However, variable transfection efficiencies can produce inconsistent outcomes. This can be due to differences in tissue architecture and/or chemical composition which may effectively create unique biological environments from subject to subject that may respond differently to the identical electric pulses. This study investigates the integration of impedance spectroscopy into the gene electro transfer process to measure murine skin impedance spectra before, during (after pulse delivery), and after gene electro transfer pulse application to determine if changes in impedance correlate with reporter gene expression. Both post-treatment impedance spectra and gene expression were dependent upon the applied electric field strength. These results indicate that alterations in tissue impedance produced by the applied electric field represent an excellent parameter to predict degrees of transfection and gene expression. These results could ultimately be used to alter pulsing parameters in order to optimize delivery/expression.
Keywords: Impedance spectroscopy; Electroporation;

Anolyte acidification is a drawback restricting the electricity generation performance of the buffer-free microbial fuel cells (MFC). In this paper, a small amount of alkali-treated anion exchange resin (AER) was placed in front of the anode in the KCl mediated single-chamber MFC to slowly release hydroxyl ions (OH) and neutralize the H+ ions that are generated by the anodic reaction in two running cycles. This short-term alkaline intervention to the KCl anolyte has promoted the proliferation of electroactive Geobacter sp. and enhanced the self-buffering capacity of the KCl-AER-MFC. The pH of the KCl anolyte in the KCl-AER-MFC increased and became more stable in each running cycle compared with that of the KCl-MFC after the short-term alkaline intervention. The maximum power density (P max) of the KCl-AER-MFC increased from 307.5 mW·m− 2 to 542.8 mW·m− 2, slightly lower than that of the PBS-MFC (640.7 mW·m− 2). The coulombic efficiency (CE) of the KCl-AER-MFC increased from 54.1% to 61.2% which is already very close to that of the PBS-MFC (61.9%). The results in this paper indicate that short-term alkaline intervention to the anolyte is an effective strategy to further promote the performance of buffer-free MFCs.
Keywords: Microbial fuel cell (MFC); Buffer-free; Anion exchange resin (AER); Self-buffering;

This study aimed to determine how electric field strength, pulse width and shape, and specific energy input relate to the effect of pulsed electric fields (PEF) on viability and membrane permeabilization in Candida humilis and Saccharomyces cerevisiae suspended in potassium phosphate buffer.Cells were treated with a micro-scale system with parallel plate electrodes. Propidium iodide was added before or after treatments to differentiate between reversible and irreversible membrane permeabilization. Treatments of C. humilis with 71 kV/cm and 48 kJ/kg reduced cell counts by 3.9 ± 0.6 log (cfu/mL). Pulse shape or width had only a small influence on the treatment lethality. Variation of electric field strength (17–71 kV/cm), pulse width (0.086–4 μs), and specific energy input (8–46 kJ/kg) demonstrated that specific energy input correlated to the membrane permeabilization (r2  = 0.84), while other parameters were uncorrelated. A minimum energy input of 3 and 12 kJ/kg was required to achieve reversible membrane permeabilization and a reduction of cell counts, respectively, of C. humilis.Energy input was the parameter that best described the inactivation efficiency of PEF.This study is an important step to identify key process parameters and to facilitate process design for improved cost-effectiveness of commercial PEF treatment.
Keywords: Pulsed electric fields; Candida humilis; Saccharomyces cerevisiae; Propidium iodide; Bleomycin; Electric field strength; Specific energy input;