Bioelectrochemistry (v.104, #C)

Electrochemical red-ox therapy of prostate cancer in nude mice by Fabio L. Cury; Bimal Bhindi; Joice Rocha; Eleonora Scarlata; Katia El Jurdi; Michel Ladouceur; Stéphane Beauregard; Ashok K. Vijh; Yosh Taguchi; Simone Chevalier (1-9).
Minimally invasive therapies are increasingly in demand for organ-confined prostate tumors. Electrochemical therapy (EChT) is attractive, as it relies on locally-induced reduction–oxidation reactions to kill tumor cells. Its efficacy for prostate cancer was assessed in human PC-3 and LNCaP tumor xenografts growing subcutaneously in nude mice (n = 80) by applying 2 Stainless Steel vs. 4 Platinum–Iridium (Pt–Ir) electrodes to deliver current densities of 10 to 35 mA/cm2 for 30 or 60 min. The procedure was uneventful in 90% of mice. No difference in tumor vs. body temperature was observed. Changes at electrode-tumor junctions were immediate, with dryness and acidity (pH 2–3) at the anode and oedema and alkalinity (pH 10–12) at the cathode. This was accompanied by cellular alterations, found more pronounced at the cathode. Such acidic and alkaline conditions were cytotoxic in vitro and dissolved cells at pH > 10. In mice, tumor destruction was extensive by 24 h with almost undetectable blood prostate specific antigen (LNCaP model) and covered the whole tumor surface by 4 days. EChT was most efficient at 25–30 mA/cm2 for 60 min, yielding the longest recurrence-free survival and higher cure rates, especially with 4 Pt–Ir electrodes. EChT is a promising option to optimize for organ-confined prostate tumors.
Keywords: Prostate cancer; Prostate tumors; Minimally invasive therapy; Electrochemical redox therapy; Tumor electrolysis; Tissue destruction;

Thromboresistant/anti-biofilm catheters via electrochemically modulated nitric oxide release by Hang Ren; Alessandro Colletta; Dipankar Koley; Jianfeng Wu; Chuanwu Xi; Terry C. Major; Robert H. Bartlett; Mark E. Meyerhoff (10-16).
Inexpensive nitric oxide (NO) release strategies to prevent thrombosis and bacterial infections are desirable for implantable medical devices. Herein, we demonstrate the utility of electrochemically modulated NO release from a catheter model using an inner copper wire working electrode and an inorganic nitrite salt solution reservoir. These catheters generate NO surface fluxes of > 1.0 × 10− 10  mol min− 1  cm− 2 for more than 60 h. Catheters with an NO flux of 1.1 × 10− 10  mol min− 1  cm− 2 are shown to significantly reduce surface thrombus formation when implanted in rabbit veins for 7 h. Further, the ability of these catheters to exhibit anti-biofilm properties against bacterial species commonly causing bloodstream and urinary catheter infections is examined. Catheters releasing NO continuously during the 2 d growth of Staphylococcus aureus exhibit a 6 log-unit reduction in viable surface bacteria. We also demonstrate that catheters generating NO for only 3 h at a flux of 1.0 × 10− 10  mol min− 1  cm− 2 lower the live bacterial counts of both 2 d and 4 d pre-formed Escherichia coli biofilms by > 99.9%. Overall, the new electrochemical NO-release devices could provide a cost-effective strategy to greatly enhance the biocompatibility and antimicrobial properties of intravascular and urinary catheters, as well as other implantable medical devices.Display Omitted
Keywords: Nitric oxide; Copper electrode; Antimicrobial catheters; Thromboresistant catheters; Modulated NO release;

The effects of an external electric field on the binding affinity for protein–ligand complexes was determined by applying electric field E ext to a water cluster containing two electric dipoles separated by a certain distance. The mean forces on these two dipoles were computed from the trajectories of molecular dynamics simulations. The results showed that the mean attractive force and the binding affinity between these two dipoles decreased with increasing E ext. Two factors governing the effects of E ext on the binding affinity of protein–ligand interactions were proposed. (1) When E ext is applied to a water cluster containing protein–ligand complexes, the water molecules neighboring ligand will be repelled from the ligand; the mean van der Waals repulsive force exerted on the ligand by these water molecules would decrease, leading to a decrease in the binding affinity between the protein and the ligand. (2) The mean electrostatic force exerted on the ligand by the water molecules polarized by E ext is thought to result from the dielectric polarization ( P protein) in the region occupied by the protein, where P protein is proportional to − E ext.
Keywords: Mean force; Molecular dynamic simulations; Polar interaction; Hydrophobic interaction; Binding free energy;

Electrochemistry of LB films of mixed MGDG:UQ on ITO by Javier Hoyo; Ester Guaus; Juan Torrent-Burgués; Fausto Sanz (26-34).
The electrochemical behaviour of biomimetic monolayers of monogalactosyldiacylglycerol (MGDG) incorporating ubiquinone-10 (UQ) has been investigated. MGDG is the principal component in the thylakoid membrane and UQ seems a good substitute for plastoquinone-9, involved in photosynthesis chain. The monolayers have been performed using the Langmuir and Langmuir–Blodgett (LB) techniques and the redox behaviour of the LB films, transferred at several surface pressures on a glass covered with indium–tin oxide (ITO), has been characterized by cyclic voltammetry. The cyclic voltammograms show that UQ molecules present two redox processes (I and II) at high UQ content and high surface pressures, and only one redox process (I) at low UQ content and low surface pressures. The apparent rate constants calculated for processes I and II indicate a different kinetic control for the reduction and the oxidation of UQ/UQH2 redox couple, being kRapp(I) = 2.2 · 10− 5  s− 1, kRapp(II) = 5.1 · 10− 14 kOapp(I) = 3.3 · 10− 3  s− 1 and kOapp(II) = 6.1 · 10− 6  s− 1, respectively. The correlation of the redox response with the physical states of the LB films allows determining the positions of the UQ molecules in the biomimetic monolayer, which change with the surface pressure and the UQ content. These positions are known as diving and swimming.
Keywords: Ubiquinone; Monogalactosyldiacylglycerol; Langmuir–Blodgett film; Cyclic voltammetry; Modified ITO electrode; Electron transfer;

A ruthenium complex was prepared and structurally characterized using various techniques. Antibacterial and antifungal activities of ruthenium complex were evaluated. High significant antimicrobial activity against Escherichia coli, Staphylococcus aureus and Candida albicans was recorded. Minor cytotoxicity records were reported at the highest concentration level using MTT assay. The influence of Cu(II), Cr(III), Fe(III) and Ru(III) metal ions of salen Schiff base on the corrosion resistance of Ti-alloy in 0.5 M HCl was studied. In vitro corrosion resistance was investigated using electrochemical impedance spectroscopy (EIS) measurements and confirmed by surface examination via scanning electron microscope (SEM) technique. Both impedance and phase angle maximum (θmax) values were at maximum in the case of the ruthenium complex with promising antibacterial and antifungal activities. The surface film created by the ruthenium complex was highly resistant against attack or deterioration by bacteria. The EIS study showed high impedance values for the ruthenium complex with increasing exposure time up to 8 days. SEM images showed uniform distribution and adsorption of Ru(III) ions on Ti-alloy surface. The ruthenium complex, as a model of organic–inorganic hybrid complex, offered new prospects with desired properties in industrial and medical applications.Display Omitted
Keywords: Ruthenium complex; Electrochemical impedance spectroscopy; Cytotoxicity; Scanning electron microscope; Titanium alloy;

Effective immobilization of glucose oxidase on chitosan submicron particles from gladius of Todarodes pacificus for glucose sensing by J.R. Anusha; Albin T. Fleming; Hee-Je Kim; Byung Chul Kim; Kook-Hyun Yu; C. Justin Raj (44-50).
An effective enzymatic glucose biosensor was developed by immobilizing glucose oxidase on chitosan submicron particles synthesized from the gladius of Todarodes pacificus (GCSP). The chemically synthesized chitosan from gladius was pulverized to submicron particles by ball milling technique, which was further characterized and compared with the standard chitosan (SCS). The degree of deacetylation of GCSP was determined using FTIR spectroscopy which was comparable to the value of standard chitosan. The glucose oxidase (GOx) was immobilized over GCSP on porous zinc oxide/platinum nanoparticle (ZnO/Pt) based electrode. The morphological and structural properties of the electrodes were analyzed using scanning electron microscopy and X-ray diffraction analysis. The glucose sensing behavior of electrode was estimated using electrochemical analysis and showed an excellent analytical performance. The electrode ZnO/Pt/GCSP conjugated with GOx displayed high sensitivity (88.76 μA mM− 1  cm− 2) with low detection limit in short response time. In addition, the very low value of Michaelis–Menten constant for GCSP based electrode contributes a better affinity of the electrode surface towards glucose oxidase.Display Omitted
Keywords: Biopolymers; Chitosan; Submicron particles; Glucose oxidase; Biosensors;

A carbon nanotube/poly [Ni-(Protoporphyrin IX)] composite for amperometric detection of long chain aliphatic amines by Romina Carballo; Ana L. Rinaldi; Paula C. Dabas; Irene N. Rezzano (51-57).
Poly [Ni-Protoporphyrin] film (pNiPP), containing multiwall carbon nanotubes (MWCNT) was used to cover a glassy carbon electrode. The hybrid material (pNiPP/MWCNT) successfully combines the permselectivity of pNiPP with the high conductivity of MWCNT.The modified electrode was used to perform amperometric detection of long chain aliphatic amines (LCAA) in order to prevent the passivation effect of the aliphatic chain. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrated that the pNiPP/MWCNT facilitates the electron transfer reaction. The charge transfer resistance (Rct) values were significantly lower by up to one order of magnitude compared to the bare electrode. Differential pulse polarography (DPP) showed a marked decrease of the overpotential generated by the aliphatic chain. The calibration of the amperometric peak area vs. concentrations of derivatized LCAA exhibits a linear response within the range of 0.018 and 28 μM and correlation coefficient (R2) higher than 0.999 (n = 5). The quantitation limit of the pNiPP/MWCNT electrode is about 400 times lower than the UV–visible detection. RSD of 7.2%, 5.8%, 2.5% and 2.3% was obtained for concentrations of 0.028, 0.28, 2.8 and 28 μM of ferrocenyl octadecylamine. A solution of sphingosine, 0.23 μM, was exclusively detected with HPLC-ECD with pNiPP/MWCNT electrode.Display Omitted
Keywords: Poly [Ni-Protoporphyrin]; MWCNT; Hybrid material; Aliphatic amines; Amperometric detection;

Simultaneous electricity generation and microbially-assisted electrosynthesis in ceramic MFCs by Iwona Gajda; John Greenman; Chris Melhuish; Ioannis Ieropoulos (58-64).
To date, the development of microbially assisted synthesis in Bioelectrochemical Systems (BESs) has focused on mechanisms that consume energy in order to drive the electrosynthesis process. This work reports – for the first time – on novel ceramic MFC systems that generate electricity whilst simultaneously driving the electrosynthesis of useful chemical products. A novel, inexpensive and low maintenance MFC demonstrated electrical power production and implementation into a practical application. Terracotta based tubular MFCs were able to produce sufficient power to operate an LED continuously over a 7 day period with a concomitant 92% COD reduction. Whilst the MFCs were generating energy, an alkaline solution was produced on the cathode that was directly related to the amount of power generated. The alkaline catholyte was able to fix CO2 into carbonate/bicarbonate salts. This approach implies carbon capture and storage (CCS), effectively capturing CO2 through wet caustic ‘scrubbing’ on the cathode, which ultimately locks carbon dioxide.
Keywords: Terracotta MFC; Wet scrubbing; Catholyte generation; Water recovery; Microbially assisted electrosynthesis;

Immobilization of membrane-bounded (S)-mandelate dehydrogenase in sol–gel matrix for electroenzymatic synthesis by Ievgen Mazurenko; Wissam Ghach; Gert-Wieland Kohring; Christelle Despas; Alain Walcarius; Mathieu Etienne (65-70).
Membrane-bounded (S)-mandelate dehydrogenase has been immobilized on the surface of glassy carbon and carbon felt electrodes by encapsulation in a silica film obtained by sol–gel chemistry. Such bioelectrochemical system has been used for the first time for electroenzymatic conversion of (S)-mandelic acid to phenylglyoxylic acid. Apparent Km in this sol–gel matrix was 0.7 mM in the presence of ferrocenedimethanol, a value in the same order of magnitude as reported previously for vesicles in solution with other electron acceptors, i.e., Fe(CN)6 3 − or 2,6-dichloroindophenol. The bioelectrode shows very good operational stability for more than 6 days. This stability was definitively improved by comparison to a bioelectrode prepared by simple adsorption of the proteins on the electrode surface (fast activity decrease during the first 15 h of experiment). Optimal electroenzymatic reaction was achieved at pH 9 and 40 °C. Apparent Km of the protein activity was 3 times higher in carbon felt electrode than on glassy carbon surface, possibly because of transport limitations in the porous architecture of the carbon felt. A good correlation was found between electrochemical data and chromatographic characterization of the reaction products in the bioelectrochemical reactor.Display Omitted
Keywords: Membrane protein; Electrosynthesis; Bioelectrochemical system; Sol–gel;

A simple and inexpensive methodology was used to develop a new method in order to inspect the DNA damage due to dopamine and some ionic metals. In addition, the inhibitory and repair effects of some antioxidant such as glutathione and ascorbic acid were studied and compared with each other using electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). In this work a pencil graphite electrode (PGE) was modified with multiwall carbon nanotubes (MWCNTs) and chitosan (CHIT), then it was decorated with a ds-DNA (ds-DNA/CHIT–MWCNTs/PGE). Due to interaction of ds-DNA and the damaging agents (dopamine + metallic ions), electrochemical and spectroscopy properties of ds-DNA at the surface of the modified electrode was changed, and these changes are followed with EIS and DPV methods. Our study showed that dopamine, Cu(II) and Fe(III) alone could not destroy DNA, but dopamine + Cu(II) and dopamine + Fe(III) can damage DNA. In addition, the ability of dopamine–Cu(II) was greater than dopamine–Fe(III). Moreover, some antioxidant such as glutathione and ascorbic acid can overcome and/or minimize the influence of these damaging interactions.
Keywords: DNA damage; DNA-biosensor; Antioxidants; Electrochemical methods; Dopamine;

H2O2 generated during water radiolysis was measured electrochemically as an alternative dosimetry method. A biosensor was fabricated by immobilising modified horseradish peroxidase (HRP) on a glassy carbon electrode (GCE) followed by evaluation of its analytical parameters. Anthraquinone 2-carboxylic acid was used to modify HRP. To assess sensor performance, phosphate buffer solutions were irradiated with 0.510 Gy of gamma ray emitted from 60Co. The results showed that this sensor can detect low quantities of hydrogen peroxide in water radiolysis. Sensitivity, detection limit and linear range of the biosensor were 260 nA/Gy, 0.392 Gy and 0.5–5 Gy, respectively. Long term stability studies showed that sensor responses were stable for at least a month. The cathodic peak current, as biosensor response, subsequently decreased to 20% of its initial value.
Keywords: Water radiolysis; Dosimetry; Ionising radiation; Hydrogen peroxide; Modified horseradish peroxidase;

Synthesis, biological and electrochemical evaluation of novel nitroaromatics as potential anticancerous drugs by Muhammad Shabbir; Zareen Akhter; Iqbal Ahmad; Safeer Ahmed; Hammad Ismail; Bushra Mirza; Vickie Mckee; Michael Bolte (85-92).
Nitroaromatics i.e. 1-nitro-4-phenoxybenzene (1), 4-(4-nitrophenyloxy) biphenyl (2), 1-(4-nitrophenoxy) naphthalene (3) and 2-(4-nitrophenoxy) naphthalene (4) were synthesized by Williamson etherification and characterized by elemental analysis, FTIR, NMR (1H, 13C), UV–visible spectroscopy, mass spectrometry and single crystal X-ray diffraction analysis. Their brine shrimp cytotoxicity resulted in LD50 values < 1 μg/mL indicating significant antitumor activity with IC50 values ranging from 29.0 to 8.4 μg/mL. They are highly active in protecting DNA against hydroxyl free radicals in a concentration dependent manner. Voltammetric studies showed one electron reversible reduction at a platinum electrode with diffusion coefficient (Do) values of the order ~ 10− 6–10− 7  cm2  s− 1. Strong interaction with the human blood DNA through intercalative mode was contemplated through electrochemical and UV–visible spectroscopic studies which are in agreement with the conclusions drawn from biological analysis, unravelling the potential anticancerous nature of the synthesized compounds.Display Omitted
Keywords: Nitroaromatics; Reversible electron transfer; Drug–DNA intercalation;