Bioelectrochemistry (v.110, #C)

Effects of high voltage nanosecond electric pulses on eukaryotic cells (in vitro): A systematic review by Tina Batista Napotnik; Matej Reberšek; P. Thomas Vernier; Barbara Mali; Damijan Miklavčič (1-12).
For this systematic review, 203 published reports on effects of electroporation using nanosecond high-voltage electric pulses (nsEP) on eukaryotic cells (human, animal, plant) in vitro were analyzed. A field synopsis summarizes current published data in the field with respect to publication year, cell types, exposure configuration, and pulse duration. Published data were analyzed for effects observed in eight main target areas (plasma membrane, intracellular, apoptosis, calcium level and distribution, survival, nucleus, mitochondria, stress) and an additional 107 detailed outcomes. We statistically analyzed effects of nsEP with respect to three pulse duration groups: A: 1–10 ns, B: 11–100 ns and C: 101–999 ns. The analysis confirmed that the plasma membrane is more affected with longer pulses than with short pulses, seen best in uptake of dye molecules after applying single pulses. Additionally, we have reviewed measurements of nsEP and evaluations of the electric fields to which cells were exposed in these reports, and we provide recommendations for assessing nanosecond pulsed electric field effects in electroporation studies.
Keywords: Electroporation; Nanosecond electric pulses; Systematic review; Cells;

Electricity-consuming microbial communities can serve as biocathodic catalysts in microbial electrochemical technologies. Initiating their functionality, however, remains a challenge. One promising approach is the polarity inversion of bioanodes. The objective of this study was to examine the impact of bioanode substrate and electrode potentials on inverted electrotrophic activity. Bioanodes derived from domestic wastewater were operated at − 0.15 V or + 0.15 V (vs. standard hydrogen electrode) with either acetate or formate as the sole carbon source. After this enrichment phase, cathodic linear sweep voltammetry and polarization revealed that formate-enriched cultures consumed almost 20 times the current (− 3.0 ± 0.78 mA; − 100 ± 26 A/m3) than those established with acetate (− 0.16 ± 0.09 mA; − 5.2 ± 2.9 A/m3). The enrichment electrode potential had an appreciable impact for formate, but not acetate, adapted cultures, with the + 0.15 V enrichment generating twice the cathodic current of the − 0.15 V enrichment. The total charge consumed during cathodic polarization was comparable to the charge released during subsequent anodic polarization for the formate-adapted cultures, suggesting that these communities accumulated charge or generated reduced products that could be rapidly oxidized. These findings imply that it may be possible to optimize electrotrophic activity through specific bioanodic enrichment procedures.Display Omitted
Keywords: Biocathode; Microbial electrochemical systems; Electrode inversion; Electrotroph;

Electroporation and lipid nanoparticles with cyanine IR-780 and flavonoids as efficient vectors to enhanced drug delivery in colon cancer by Julita Kulbacka; Agata Pucek; Małgorzata Kotulska; Magda Dubińska-Magiera; Joanna Rossowska; Marie-Pierre Rols; Kazimiera Anna Wilk (19-31).
Nanocarriers and electroporation (also named electropermeabilization) are convenient methods to increase drug transport. In the current study, we present an effective support of drug delivery into cancer cells, utilizing these methods. We compare the efficiency of each of them and their combination. Multifunctional solid lipid nanoparticles (SLNs) loaded with a cyanine-type IR-780 — acting as a diagnostic agent and a photosensitizer, and a flavonoid derivative — baicalein (BAI) or fisetin (FIS) as a therapeutic cargo — were fabricated via solvent-diffusion method. A therapy supplemented with flavonoids may provide a more precise method to apply desirable lower drug doses and is more likely to result in lower toxicity and a decrease in tumor growth. The SLNs were stabilized with Phospholipon 90G at various concentrations; cetyl palmitate (CP) was applied as a solid matrix. The obtained nanosystems were characterized by dynamic light scattering (size along with size distribution), UV–vis (cargos encapsulation efficiency) and atomic force microscopy (morphology and shape). The obtained SLNs were used as drug carriers alone and in combination with electropermeabilization induced by millisecond pulsed electric fields of high intensity.Two cell lines were selected for the study: LoVo and CHO-K1. The viability was assessed after electroporation alone, the use of electroporation and nanoparticles, and nanoparticles or drugs alone. The intracellular accumulation of cyanine IR-780 and the impact on intracellular structure organization of cytoskeleton was visualized with confocal microscopy method with alpha-actin and beta-tubulin. In this study, the efficacy of nanoparticles with mixed cargo, additionally enhanced by electroporation, is demonstrated to act as an anticancer modality to eliminate cancer cells.Display Omitted
Keywords: Solid lipid nanoparticles; Electroporation; Flavonoids; Photodynamic reaction;

Dielectric study of interaction of water with normal and osteoarthritis femoral condyle cartilage by E. Marzec; J. Olszewski; J. Kaczmarczyk; M. Richter; T. Trzeciak; K. Nowocień; R. Malak; W. Samborski (32-40).
The main goal of this paper is the in vitro study of healthy and osteoarthritis (OA) human cartilage using the dielectric spectroscopy in the alpha-dispersion region of the electric field and in the temperatures from 25 to 140 °C. The activation energy of conductivity needed to break the bonds formed by water in the extracellular matrix takes the average values of 61 kJ/mol and 44 kJ/mol for the control and OA cartilages, respectively. At 28 °C, the small difference appears in the permittivity decrement between the control and OA cartilages, while the conductivity increment is about 2 times higher for the control tissue than that for the OA tissue. At 75 °C, the conductivity increment for both of these samples is 8 times higher than their respective permittivity decrement. In addition, at 140 °C the values of these both parameters for the OA tissue decrease by 8 times as compared to those recorded for the control sample. The relaxation frequency of about 10 kHz is similar for both of these samples. The knowledge on dielectric properties of healthy and OA cartilage may prove relevant to tissue engineering focused on the repair of cartilage lesions via the layered structure designing.
Keywords: Dielectric spectroscopy; Osteoarthritis cartilage; Water protons; Electrical conduction; Temperature;

SR-XRD in situ monitoring of copper-IUD corrosion in simulated uterine fluid using a portable spectroelectrochemical cell by Rosie A. Grayburn; Mark G. Dowsett; Pieter-Jan Sabbe; Didier Wermeille; Jorge Alves Anjos; Victoria Flexer; Michel De Keersmaecker; Dirk Wildermeersch; Annemie Adriaens (41-45).
The objective of this work is to study the initial corrosion of copper in the presence of gold when placed in simulated uterine fluid in order to better understand the evolution of active components of copper-IUDs. In order to carry out this study, a portable cell was designed to partially simulate the uterine environment and provide a way of tracking the chemical changes occurring in the samples in situ within a controlled environment over a long period of time using synchrotron spectroelectrochemistry. The dynamically forming crystalline corrosion products are determined in situ for a range of copper–gold surface ratios over the course of a 10-day experiment in the cell. It is concluded that the insoluble deposits forming over this time are not the origin of the anticonception mechanism.
Keywords: Corrosion; Copper IUD; XRD; In situ analysis; Contraception;

Oxygen reducing biocathodes were formed at − 0.2 V/SCE (+ 0.04 V/SHE) from compost leachate. Depending on whether aeration was implemented or not, two different redox systems responsible for the electrocatalysis of oxygen reduction were evidenced. System I was observed at low potential (− 0.03 V/SHE) on cyclic voltammetries (CVs). It appeared during the early formation of the biocathode (few hours) and resisted the hydrodynamic conditions induced by the aeration. System II was observed at higher potential on CV (+ 0.46 V/SHE); it required a longer lag time (up to 10 days) and quiescent conditions to produce an electrochemical signal. The hydrodynamic effects produced by the forced aeration led to its extinction. From their different behaviors and examples in the literature, system I was identified as being a membrane-bound cytochrome-related molecule, while system II was identified as a soluble redox mediator excreted by the biofilm. This study highlighted the importance of controlling the local hydrodynamics to design efficient oxygen reducing biocathodes able to operate at high potential.
Keywords: Biocathode; Oxygen reduction; Microbial fuel cell; Aeration; Hydrodynamics; Cyclic voltammetry;

Biocorrosion is also known as microbiologically influenced corrosion (MIC). Most anaerobic MIC cases can be classified into two major types. Type I MIC involves non-oxygen oxidants such as sulfate and nitrate that require biocatalysis for their reduction in the cytoplasm of microbes such as sulfate reducing bacteria (SRB) and nitrate reducing bacteria (NRB). This means that the extracellular electrons from the oxidation of metal such as iron must be transported across cell walls into the cytoplasm. Type II MIC involves oxidants such as protons that are secreted by microbes such as acid producing bacteria (APB). The biofilms in this case supply the locally high concentrations of oxidants that are corrosive without biocatalysis. This work describes a mechanistic model that is based on the biocatalytic cathodic sulfate reduction (BCSR) theory. The model utilizes charge transfer and mass transfer concepts to describe the SRB biocorrosion process. The model also includes a mechanism to describe APB attack based on the local acidic pH at a pit bottom. A pitting prediction software package has been created based on the mechanisms. It predicts long-term pitting rates and worst-case scenarios after calibration using SRB short-term pit depth data. Various parameters can be investigated through computer simulation.Display Omitted
Keywords: Biocorrosion; Microbiologically influenced corrosion; Mechanism; Model; Charge transfer; Mass transfer;

We studied the effect of spectrin denaturation at 49.5 °C (T A ) on the dielectric relaxations and related changes in the complex impedance, Z*, complex capacitance, C*, and dielectric loss curve of suspensions containing human erythrocytes, erythrocyte ghost membranes (EMs) and Triton-X-100 residues of EMs. The loss curve prior to, minus the loss curve after T A , resulted in a bell-shaped peak at 1.5 MHz. The changes in the real and imaginary components of Z* and C* at T A , i.e., ΔZ re , ΔZ im , ΔC re and ΔC im , calculated in the same way, strongly varied with frequency. Between 1.0 and 12 MHz the − ΔZ im vs ΔZ re , and ΔC im vs ΔC re plots depicted semicircles with critical frequencies, f cr, at 2.5 MHz expressing recently reported relaxation of spectrin dipoles. Between 0.02 and 1.0 MHz the − ΔZ im vs ΔZ re plot exhibited another relaxation whose f cr mirrored that of beta relaxation. This relaxation was absent on Triton-X-shells, while on erythrocytes and EMs it was inhibited by selective dissociation of either attachment sites between spectrin and bilayer. Considering above findings and inaccessibility of cytosole to outside field at such frequencies, the latter relaxation was assumed originating from a piezoelectric effect on the highly deformable spectrin filaments.
Keywords: Spectrin repeat unit; Piezoeffect on spectrin; Dielectric spectroscopy;

Comparative assessment of raw and digested pig slurry treatment in bioelectrochemical systems by Míriam Cerrillo; Judit Oliveras; Marc Viñas; August Bonmatí (69-78).
Both raw and anaerobically digested pig slurries were investigated in batch assays in two chambered bioelectrochemical systems (BES) run in Microbial Fuel Cell (MFC) and Microbial Electrolysis Cell (MEC) mode. Chemical Oxygen Demand (COD) removal, nitrogen recovery, cation transport and anode microbial population evolutions were assessed. The Anaerobic Digestion-MEC (AD-MEC) integrated system achieved the highest COD removal (60% in 48 h); while the maximum NH4 + removal efficiency (40%, with an ammonia flux of 8.86 g N–NH4 + d−1  m−2) was achieved in MFC mode fed with digested pig slurry in 24 h. On the other hand, the high pH (12.1) achieved in MEC mode (NaCl solution as catholyte), could favour ammonium recovery in a subsequent stripping and absorption process. Ammonia was the main cation involved in maintaining the electroneutrality between both compartments. Regarding microbial population, Desulfuromonadaceae, a known family of exoelectrogenic bacteria, was enriched under MEC mode, whereas hydrogenotrophic and methylotrophic methanogen phylotypes belonging to Thermoplasmatales were also favoured against acetotrophic Methanosaetaceae. From these results, the integration of anaerobic digestion in BES seems to be an interesting alternative for the treatment of complex substrates, since a polished effluent can be obtained and ammonium can be simultaneously recovered for further reuse as fertilizer.Display Omitted
Keywords: Bioelectrochemical systems (BES); Anaerobic digestion; Ammonia recovery; Raw and digested pig slurry; Desulfuromonadaceae; System integration;

Synthesis of one-dimensional gold nanostructures and the electrochemical application of the nanohybrid containing functionalized graphene oxide for cholesterol biosensing by Seetharamaiah Nandini; Seetharamaiah Nalini; M.B. Madhusudana Reddy; Gurukar Shivappa Suresh; Jose Savio Melo; Pathappa Niranjana; Jakkid Sanetuntikul; Sangaraju Shanmugam (79-90).
This manuscript reports a new approach for the synthesis of one dimensional gold nanostructure (AuNs) and its application in the development of cholesterol biosensor. Au nanostructures have been synthesized by exploiting β-diphenylalanine (β-FF) as an sacrificial template, whereas the Au nanoparticles (AuNPs) were synthesized by ultrasound irradiation. X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive analysis of X-rays (EDAX) have been employed to characterize the morphology and composition of the prepared samples. With the aim to develop a highly sensitive cholesterol biosensor, cholesterol oxidase (ChOx) was immobilized on AuNs which were appended on the graphite (Gr) electrode via chemisorption onto thiol-functionalized graphene oxide (GO-SH). This Gr/GO-SH/AuNs/ChOx biosensor has been characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy and chronoamperometry. CV results indicated a direct electron transfer between the enzyme and the electrode surface. A new potentiostat intermitant titration technique (PITT) has been studied to determine the diffusion coefficient and maxima potential value. The proposed biosensor showed rapid response, high sensitivity, wide linear range and low detection limit. Furthermore, our AuNs modified electrode showed excellent selectivity, repeatability, reproducibility and long term stability. The proposed electrode has also been used successfully to determine cholesterol in serum samples.Display Omitted
Keywords: Gold nanostrucutres; Functionalized graphene oxide; Electrochemical biosensor; β-diphenylalanine; Peptide nanotubes; Cholesterol;

The utilization of Ag and Cu ions to prevent both microbial corrosion and biofilm formation has recently increased. The emphasis of this study lies on the effects of Ag and Cu ions on the microbial corrosion of 316L stainless steel (SS) induced by Desulfovibrio sp. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization were used to analyze the corrosion behavior. The biofilm formation, corrosion products and Ag and Cu ions on the surfaces were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS) and elemental mapping. Through circuit modeling, EIS results were used to interpret the physicoelectric interactions between the electrode, biofilm and culture interfaces. EIS results indicated that the metabolic activity of Desulfovibrio sp. accelerated the corrosion rate of SS in both conditions with and without ions. However, due to the retardation in the growth of Desulfovibrio sp. in the presence of Ag and Cu ions, significant decrease in corrosion rate was observed in the culture with the ions. In addition, SEM and EIS analyses revealed that the presence of the ions leads to the formation on the SS of a biofilm with different structure and morphology. Elemental analysis with EDS detected mainly sulfide- and phosphorous-based corrosion products on the surfaces.
Keywords: 316L stainless steel; Microbiologically influenced corrosion; Desulfovibrio sp.; Biofilms; Electrochemical tests; Ag and Cu ions;