Bioelectricity Buzz

Recent Bioelectricity-Related Articles Selected by Ann M. Rajnicek, Media Editor of Bioelectricity

Once again, the Bioelectricity Buzz finds something for everyone, with articles spanning a range of biological scales from molecules, bacteria, yeast, leeches, zebra fish, mammalian cells, nanoelectrodes, and adult humans. Topics cover conductive hydrogels that crosslink in live tissues, electrical stimulation to aid upper limb function after stroke, a model of heterogeneous electrical activity in beta cells, monitoring cell-substratum adhesion using electrical signaling, protecting retinal cells from light stress using electrical stimulation, and wine preservation by electrical pulses.

Becoming Gel-Fish: Endogenous Metabolites Polymerize Conductive Gels in Living Zebra Fish and Leeches Using

Advances in neural stimulation technologies are progressing at a dizzying pace but their implementation in clinical contexts is limited by the availability of optimal conductive materials. Strakosas and colleagues describe a clever method for synthesizing flexible electro conductive materials in vivo using the body's own metabolites.

Devices that rely on electrical stimulation, including neural prosthetics, deep brain stimulation, and cochlear implants typically incorporate conductive materials such as platinum, titanium, gold, or hybrids. These metals are considered safe but also have several drawbacks, especially for long-term use: degradation over time, creation of cytotoxic environments at the material-tissue interface, and a mechanical mismatch between the relatively soft tissue and the stiffer electrode. In addition, integrating solid state electronics with the natural characteristics of biological cells and tissues is complicated.

Previous studies from several laboratories have demonstrated in vivo synthesis of conductive polymers by introducing precursors followed by electrical or chemical stimuli to induce polymerization, but the conditions required for polymer formation can be cytotoxic. A more biological approach has been successful in nematodes manipulated genetically to express enzymes for polymer formation in cells near the desired site for polymerization. Strakosas and colleagues have built on that biological approach but avoided genetic modification, because it limits extension of the technique to human clinical applications.

Instead, they built the technology around an organic trithiophene-based monomer with a 2,5-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)thiophene (ETE) derivative with a 2-ethoxyacetic acid sodium salt side chain (ETE-COONa). This is polymerized in tissues by the ROx–horse radish peroxidase (HRP) enzyme cascade, where ROx is glucose oxidase (GOx) or lactose oxidase (LOx). The ROx consumes physiological glucose or lactose-based metabolites present naturally in the target tissue, so no harmful polymerization mediators are required. The H₂O₂ generated by this reaction then acts as an electron acceptor in the oxidation of ETE-COONa by HRP. When injected the ETE-COONa gel cocktail is brownish in color but it turns dark blue on enzymatic polymerization, making the final product easy to detect visually.

The electrical performance of the conductive films was tested ex vivo. Materials were imposed to repeated voltage cycling (1000 cycles) without significant loss of capacitance, and the electrical performance was not affected after 72 h of incubation with phaeochromocytoma cells. To test whether the gel cocktail would polymerize in tissues in vivo, it was injected into the tail fins or brains of albino zebra fish. The blue reaction product was observed in both tissues. Lactate and glucose were both identified as reaction substrates, with lactate predominating in brain tissue due to relatively less endogenous glucose in the brain. Three hours after gel injection, brains were removed and dehydrated tissue slices were then subjected to electrophysiological recordings. A −0.5 to 0.5 V stimulus elicited a linear current in brains injected with the cocktail, which was larger than that recorded from control brain slices, confirming that the conductive properties of the gel persisted when synthesized in natural tissues using endogenous enzymes.

Polymerization was also observed in zebrafish hearts immersed into gels containing either GOx or LOx, revealing potential utility for the materials outside the nervous system. Strands of polymer were observed on the surface of the heart that grew larger over time. When the electrophysiological properties of the gel-infiltrated tissues were tested, a linear current response was recorded on application of a linear voltage sweep for hearts incubated in LOx gels but not for the electrolyte-only control hearts.

Coating micro-scale metal electrodes with hydrogels increases their electroactive area and therefore reduces their electrochemical impedance, improving performance. As proof of concept that metal electrodes could be similarly coated with the new polymers, an LOx-based gel was coated on gold electrodes patterned on a flexible base substrate while positioned near the connecting nerve of a leech. Although identifying optimal conditions proved more challenging in the leech nervous system, the blue polymerized gel was observed at the electrode and surrounding the nerve. Electrochemical impedance spectroscopy indicated that the gel increased the capacitance of the gel-coated gold electrode.

Collectively, these results prove that the gel cocktail can polymerize in vivo to produce an electrically conductive polymer that is more suitable to the brain's soft tissues than implanted metal electrodes, which can induce immune reactions as they move or migrate unexpectedly. Because the polymerization reaction can use a plethora of different endogenous metabolites, it has the potential to be useful in a variety of tissues and can be tailored to suit the desired situation.

Although this novel gel coating improves the properties of metal electrodes, further work is required to perfect the speed of gel polymerization and to identify a better animal model to test stimulation of the nervous system more precisely than was possible in leech. Another hurdle is figuring out how to connect such soft materials, which polymerize with unpredictable geometries (a consequence of the dynamic distribution of natural metabolites required for polymerization) to a power supply for use in neuro- (or other tissue) stimulation. Nonetheless, the ability to build an electrode in a living system using natural molecules is very exciting.

Put Your Hands in the Air: Electrical Stimulation Improves Arm and Hand Movement After Chronic Stroke

The debilitating consequences of a stroke may be permanent, and loss of limb function reduces quality of life. One therapeutic approach is to use technologies that substitute for, or enhance, the missing nerve signals. Using electrical stimulation to improve motor function is a clinically recognized therapy in the context of improving lower limb function (locomotion) after spinal cord injury. However, it is not yet used for upper limb deficits following stroke, which rely more heavily on the corticospinal tracts connecting the brain and spinal cord.

Depending on its site, a stroke that damages the brain's motor cortex can have a significant detrimental impact on arm and hand strength and dexterity (paresis). However, the descending neuronal circuitry in the corticospinal tract (CST) is typically spared, making the CST a target for electrostimulation to improve function. Powell and collaborators describe pilot data for the first in-human cases using stimulation of cervical spinal circuits to facilitate arm and hand control after chronic stroke.

Both people in the pilot group had hemiparesis from a stroke 3 or 9 years before becoming participants, with motor tests scores at the start of the trial indicating severe and moderate arm impairment, respectively. For the tests, two linear strip electrodes were implanted epidurally in the cervical region of the spinal cord (between C3 and T1) to target the spinal nerve roots that drive hand and arm movements. Positioning the strips mediolaterally (rather than medially) targeted the dorsal root entry zones more effectively.

Once the ideal position had been established, electrical stimulation was delivered continuously through the electrodes at frequencies of 20, 40, or 60 Hz (depending on experiment) and the stimulation intensity was adjusted daily so it allowed volitional (but not passive) arm and joint movements. Control conditions needed special consideration. Due to sensations elicited by the stimulator, it was not possible to perform sham (no stimulation) trials, but to identify any motivational bias the stimulation was instead delivered to muscle groups that would oppose the intended movement, meaning the participant still felt the sensation of stimulation for both the control and experimental condition.

Functional outcome was assessed beginning on day 4 after implantation and continued until day 29. Participants were assessed five times per week for about 4 h per day and function was evaluated with and without stimulation delivered through percutaneous leads, which were removed after day 29.

Continuous stimulation through specific contact points that were paired to selected muscles improved strength (grip force), kinematics (speed of movement), and functional movements (drawing, lifting an object). The benefit is that the participants could do tasks that were not possible without stimulation, though finger control was not targeted or assessed specifically. For example, one participant could lift her arm above her head during stimulation.

Interestingly, both participants maintained some of the improvements even without stimulation, and both participants described the stimulation positively, as a “feeling of power in the arms” or a feeling of “being able to control my arm as if I know what I should do to move it.” The authors concluded that electrical stimulation was assistive during stimulation episodes but that the improvements sustained without stimulation (up to 4 weeks after the study ended) indicate that the treatment also had a “restorative” aspect.

Overall, these short-term pilot data from a larger ongoing trial are very encouraging. When a similar stimulation strategy is used for spinal cord injury, rigorous treadmill training is often incorporated alongside the electrical aspect, but Powell and colleagues did not incorporate any physical training in their protocol. Therefore, future efforts could use a combination of physical training and electrical stimulation to optimize outcome and a longer study duration. I look forward to seeing those data.

A Little Gassy: Bacterial Energy Extraction from Atmospheric Hydrogen

Our beloved planet is facing a growing environmental crisis. Though humans might be letting the side down, it is good to know that aerobic bacteria are doing their bit by maintaining the atmospheric redox state. Despite its significance, there are gaps in understanding of the biological mechanisms for the oxidation of atmospheric hydrogen, including the catalytic enzymes involved.

It was recognized recently that aerobic bacteria play an essential role in oxidation of atmospheric hydrogen (H₂), accounting for ∼75% of the total H₂ removed from the air each year. When nutrients are limited in soil, atmospheric H₂ is a source of supplemental energy for aerobic bacteria, so they can grow mixotrophically or survive in a dormant state using only air. Nonetheless, no chemical catalysts had been identified capable of using the extremely low concentration of atmospheric H₂ as a substrate compared with the relatively high concentration of O₂, which is a catalytic poison, and it is not understood how electrons are transferred to the respiratory chain.

Outstanding issues include resolving whether the hydrogenases underpinning oxidation of atmospheric H₂ have a naturally high affinity, or whether their affinity is modulated by interaction with the respiratory chain. Studying the hydrogenases in isolation would help to answer these questions. The aerobic bacterium Mycobacterium smegmatis was, therefore, studied by Grinter and colleagues because it has two hydrogenases, Huc and Hhy, that both oxidize H₂ to sub-atmospheric levels. The oxygen-insensitive enzyme Huc, which couples the oxidation of atmospheric H₂ to the hydrogenation of the respiratory electron carrier menaquinone, was isolated.

The isolated Huc hydrogenase was found to consist of three protein subunits and could oxidize H₂ in ambient air to below the detection limit of the gas chromatograph, indicating tolerance to inhibition by O₂. It was also shown that in the absence of an alternative electron acceptor, O₂ stimulated H₂ oxidation by Huc, indicating direct transfer of electrons to O₂.

Cryo-electron microscopy and single-particle reconstruction of Huc revealed that the molecule has a four-leaf clover-like structure. The Huc catalytic subunits form a complex around a membrane-associated stalk that transports and reduces menaquinone 94 Å from the membrane. A narrow hydrophobic gas channel preferentially permits the entry of atmospheric H₂ at the active Huc site, whereas O₂ is inhibited sterically. Configuration of the three iron-sulfur clusters [3Fe–4S] makes atmospheric H₂ oxidation energetically feasible. Indeed, the large electrochemical overpotential is well suited for the oxidation of minute quantities of H₂ and for the direct donation of the resulting electrons to the respiratory cofactor menaquinone.

Overall, this study identifies a bacterial catalytic enzyme that is responsible for aerobic bacterial atmospheric H₂ oxidation and reveals mechanistic details for its function. In addition to aiding understanding of the basis for atmospheric redox, this information may lead to the development of biocatalysts.

Model Behavior: Using Machine Learning to Understand Cells' Electrical Activity Patterns

We cannot escape it. Artificial Intelligence (AI) has infiltrated all aspects of our professional lives and its use will increase, so let us embrace the power of AI to use it for good. Here, machine learning has been exploited to model the enormous complexity of electrical activity in a heterogeneous population of mammalian cells to shed light on cell signaling.

Biological systems are inherently complex and dynamic. Cells and tissues use their array of cellular and sub-cellular components to respond to external heterogeneous signals with diverse responses, which permit flexibility and confer robustness. Attempts to model biological systems tend to use oversimplified parameters, with cellular dynamics models focusing on one or two “typical” aspects to mimic behaviors of an “average” cell. Key parameters can then be tested using bifurcation analysis to further refine the model, but this analysis is not suitable for all models, including some derived from electrophysiological data, which can have unpredictable aspects.

Electrophysiology is integral to all living systems, so it is an important target for such modeling. Pancreatic beta cells exist in a heterogeneous population and their responses under various conditions have been modeled using multinomial logistic regression to identify which ion currents drive distinct behaviors. Andrean and Pedersen extend this idea for human insulin-secreting beta cells, because although the heterogeneity of the beta cell population is important for their glucose-sensing ability, the contributions of distinct ion currents in beta cell dynamics are unclear. They used several machine-learning techniques and population modeling extracted from single-cell electrophysiological data to make a realistic population model that incorporates beta cell ion channel parameters.

The authors built on their previous model developed for human beta cells in which the glycolytic enzyme phosphofructokinase (PFK) generates metabolic oscillations through positive feedback by its product fructobisphosphate (FBP). In the glycolytic sub model, FBP is the output that is transformed into adenosine triphosphate (ATP), providing a link to the electrophysiological submodel because ATP closes ATP-sensitive potassium K(ATP)-channels. K(ATP)-channel closure allows other currents to depolarize the cell, opening voltage-gated Ca²⁺ (CaV) and Na⁺ (NaV) channels and triggering action potentials (APs). The AP depolarization opens voltage-gated potassium channels (Kv), small conductance calcium-activated potassium channels (SK), big potassium channels (BK), and human ether-a-go-go-related gene (HERG) potassium channels, causing voltage- and calcium-sensitive K⁺ currents that terminate APs.

The model was used to simulate a population of beta cells by generating random values for ion channel conductances and time scales, with some values extracted from physiological data measured from human cells and others generated randomly. The results were analyzed with logistic regression models, classification trees, and random forests.

Analysis revealed that the maximal whole-cell conductance of the HERG K⁺ channels was one of the most important parameters distinguishing silent cells (in which electrical activity did not exceed −40 mV) from active cells, whereas increased K(ATP) channel conductance reduced the probability of cell activity, and that other K⁺ channels (Kv, SK, and BK) did not play a significant role in beta cell activation. Calcium and sodium channels promoted activation, with fast bursting influenced by the time scale of channel activation, and by the type of Ca²⁺ channels coupled to BK channels in the BK-CaV complexes. Slow, metabolically driven oscillations were promoted mainly by K(ATP) channels.

Overall, the combination of population modeling with machine-learning techniques demonstrates the strategy's ability to appreciate the complexity of cell behavior in heterogeneous populations, even at the subcellular level. This offers the prospect that existing, published data sets (e.g., electrophysiological recordings) could be used to model behaviors for various cell types and ion channels. Importantly, machine-learning models could be used to compare cells in different states (e.g., genetic modification, pharmacological treatment) to build better predictive models for drug discovery and other advances in silico.

Mirror, Mirror: Evaluating Cell-Substratum Adhesion and Proliferation Fluorescently Using Electrical Signals

Readers of Bioelectricity know that cell many key cellular processes are impacted by the inherent electrical properties of cells, even non-excitable cells. Dynamic monitoring of cell behavior and relating it to the electrical state of cells can aid mechanistic understanding of these phenomena. However, some recording procedures interfere with normal cell activities, demonstrating a need for non-invasive techniques.

Most standard techniques for recording bioelectrical dynamics in cells and tissues are invasive. For example, microelectrode measurements, which can require penetration of the cell membrane, or use of fluorescent reporter molecules. These techniques have proven useful, but they may introduce artifacts as a consequence of cell membrane trauma near electrodes, dye effects on membrane fluidity or other properties, or possible toxicity by pharmacological reagents.

Charge mirroring is a non-invasive method for recording APs in excitable cells that is developed from the working principle of electrochemical cells. Moreddu and co-workers are developing a nanoplatform that provides passive, non-invasive, high-throughput recording of electrical signals from non-excitable cells adhering to 3D microelectrodes.

The fluorescence technology developed operates by optically mirroring the cell's electrical condition by recording the surface charge density at the electrical double layer (EDL) established at a gold−electrolyte interface. A silicone chip holds a suspended Si₃Ni₄ membrane patterned with a 3D gold electrode matrix electrodeposited through holes (∼200 nm diameter) in the membrane. A glass well is bonded to the Si₃Ni₄ membrane to permit cell culture on the electrode array. The electrodes consist of concentric squares, with the working electrode (pass through structure) in the center and the reference electrode surrounding it. The working electrode connects directly to the 3D electrodes on the top surface of the membrane, but the reference electrode interfaces only with the chamber containing fluorescent molecules.

Rhodamine fluorophores in suspension (in the optical chamber) are separated from cell medium (in the biological chamber) by the membrane, and the 3D nanoelectrodes provide communication between the chambers. When a cell is in contact with the 3D electrode, its electrical signal (EDL_cell) is detected by the working electrode and the background signal (EDL_bg) comes from the surrounding reference electrode. Charged fluorophores (anionic) migrate in the optical chamber and sit at the EDL, creating a static signal that depends on the cell charge. Exciting the optical chamber leads to fluorescence emission that mirrors the cell signal, which is detected with a confocal microscope. Since each array contains multiple 3D electrodes, the data represent recordings from many cells.

Feasibility experiments used Human embryonic kidney 293 (HEK-293) cells plated onto the electrode array in the biological chamber. The presence of cells increased the fluorescence intensity by about 5.8% relative to bare electrode conditions, indicating that the system can detect electrical signals associated with cells.

The technique is still in an early development phase, but it has clear promise for determining cell viability (or at least the electrical state of cells). Its utility could be for detecting when cells are proliferating, the extent of cell-substratum contact, and to compare the relative electrical properties of cells. This is important, for example in cancer, where metastatic cells have a distinctly different electrical profile. The ability to acquire information from many cells at once adds to its potential as a research or diagnostic tool, but cost will be an important consideration if it is to find wide use.

A Defense Field: Electric Field Exposure Protects Light-Stressed Retina Photoreceptor Cells

A few years ago, my retina and I literally had a falling out. An unpleasant emergency surgery re-attached it, but the experience heightened my appreciation of the complexities of retinal function and repair. Blue light is increasingly prevalent in our home and work environments, so it is worrying that it is a recognized specific stressor for retina, especially its photoreceptors. Bola and colleagues tested the notion that an electric field (EF) could be protective for retinal cells exposed to blue light and sought to understand the protective mechanism at the molecular level.

In animal studies and retinal tissue explants, blue light (Li) causes oxidative stress, protein- and lipid-oxidation, disrupted mitosis, pigmented epithelium damage, and cell death. The retina is inherently electrical, so it seems sensible that electrical stimulation is emerging as a therapy for the degenerating retina, in some cases partially restoring function.

Bola and co-workers exposed mouse photoreceptor-derived 661W cells in a microfluidic chamber to an EF of 0.25 V/cm for 10 min and then challenged them with blue light (405 nm) of 1.5 mW/cm² intensity for 4 h. Li exposure caused cells to adopt a rounded morphology and reduced cell viability over 6 h, but EF treatment after Li (LiEF) improved viability at 6 h compared with Li alone. Time lapse observation of cell movements showed that Li treatment impaired cell migration speed compared with controls, but LiEF treatment increased speed compared with Li alone.

Immunofluorescence of the DNA damage marker phosphorylated histone H2AX (γH2AX) was not significantly different in control and EF stimulated cells but LiEF reduced H2AX staining, suggesting that the EF reduced the DNA damaged resulting from Li exposure.

Intracellular levels of heme-oxygenase 1 (HO-1) and superoxide were quantified to test whether EF treatment influences oxidative stress in LiEF-treated cells. Levels of HO-1 were elevated at both the gene and protein levels after Li exposure relative to control cells at 3 h but LiEF treatment reduced this effect at the gene level, with a decrease in HO-1 protein under LiEF conditions at 6 h compared with Li. Measurement of superoxide radicals using a fluorescent dye revealed an increase in both Li and LiEF conditions compared with controls at the 3 h time point but at 6 h, levels of superoxide radicals LiEF cells were increased compared with Li alone.

Mitochondrial membrane potential was monitored using a fluorescent indicator, showing a decrease in Li-treated cells compared with control and LiEF cells. Mitochondrial reactive oxygen species levels were also measured using a fluorescent indicator, with increased levels at 3 and 6 h in Li-treated cells compared with controls, and a decrease in LiEF conditions compared with controls. Measurements of mitochondrial respiration and ATP synthesis in the presence of malate and pyruvate indicated that Li treatment inhibited those processes after Li treatment compared with controls, but ATP production was elevated in LiEF compared with Li alone. Collectively, these data suggest that mitochondrial function is restored in LiEF cells.

Mitochondria were morphologically longer and more plentiful in LiEF cells compared with Li cells. Their respiratory capacity was tested using extracellular flux analysis. The rate of oxygen consumption reflects the rate of mitochondrial respiration, and this was increased in LiEF cells compared with Li alone. The data suggest that EF treatment restores the mitochondrial respiratory capacity that was reduced by the Li treatment.

The RNA sequencing analysis pointed to activation of unfolded protein response (UPR) pathways as a key element in rescuing Li-treated cells. This is a novel observation and points to manipulation of UPR signaling as a potential therapy target for retinal degeneration in response to blue light exposure. Together, the studies suggest that EF application is beneficial to rescue photoreceptor health after Li treatment, which is good news for folks like me.

Cheers! Improving Red Wine Quality with Pulsed EFs

If you fancy sipping a relaxing glass of wine as you read Bioelectricity, you might be interested to know that electricity can help protect the quality of that wine. Some productive bioelectricity-related research collaborations have been spawned by a glass (or two… ahem) of vino at conferences but Delso and colleagues now describe how pulsed EFs (PEFs) can improve wine quality, closing the loop neatly.

The low (3.0–3.9) pH and ethanol (8–16%) content of wine help to curtail proliferation of pathogen contamination after the fermentation stage but some organisms may still grow, potentially spoiling the final product. To combat undesirable microbe contamination, sulfur dioxide (SO₂) is used to disinfect surfaces in wineries but SO₂ has additional benefits to the wine industry. It is an antioxidant sometimes added when grapes arrive at the winery, after fermentation, and before bottling to preserve the stability of the final product.

Drawbacks to SO₂ as an additive are that some people are sensitive to it, there are questions around its potential toxicity, and a there is a growing negative consumer attitude to the use of food additives and preservatives. Filtration can be used as an alternative in decontamination, but it is hindered by incomplete bacterial capture through standard filters, and it can alter the flavor and characteristics of wines, especially red varieties.

An emerging mode of food decontamination uses PEFs of microseconds duration and high voltage (kV) to samples between a pair of electrodes, which breaks down the microbial membrane, killing the cells and preventing their proliferation. Previous studies have shown that PEFs at 20 kV/cm were effective in killing microorganisms, and that PEF does not impact the properties of wine, even after long term storage. Delso and co-workers characterized the susceptibility to PEF for two microbes used in red wine production during alcoholic fermentation (Saccharomyces cerevisiae) and malolactic fermentation (Oenococcus oeni) and determined the oenological properties of the treated red (Grenache) wine after storage.

Square waveform monopolar pulses up to 20 kV and at a repetition rate of 8 to 80 Hz were delivered using parallel titanium electrodes with a 0.4 cm gap in a chamber measuring 3.0 × 0.5 cm. The constant flow of wine through the chamber at 10 L/h ensured that it experienced the PEF for only 0.22 s and the heat generated by PEF was counteracted by cooling the wine to below 20°C within 5 s. A useful way to standardize PEF treatment intensity is to calculate the total specific energy, an integrated parameter of the EF strength and treatment time. Treatments used in this study corresponded to 35 to 120 kJ/kg. In some experiments, SO₂ was added to wine samples immediately after PEF to test for synergistic effects.

Microbial survival curves for S. cerevisiae and O. oeni at EFs of 15, 20, and 25 k/cm demonstrated that inactivation of both microorganisms increased with increasing PEF strength. Altering the PEF (maintaining the constant specific energy) did not influence lethality on Saccharomyces, but for O. oeni the total specific energy required for lethality was lower when the PEF intensity was increased, suggesting increased susceptibility.

Since some cells in the wine might be damaged sub-lethally by PEF treatment, growth curves were also measured when SO₂ was added immediately after PEF treatment to test for a combination effect. Although adding 20 ppm SO₂ alone did not influence the growth of either organism significantly, the survival of S. cerevisiae was not affected over PEF alone, whereas O. oeni demonstrated a synergistic effect of exposure to both PEF and SO₂.

The main purpose of this study was to determine the usefulness of PEF for wine preservation. When S. cerevisiae survival was measured in wines stored for 4 months after PEF treatment, no viable yeasts were detected after ethanolic fermentation, even without SO₂ addition. For malolactic fermentation conditions, very few O. oeni cells were viable after 4 months in PEF-treated wine when SO₂ was also added, with a clear synergistic effect observed as soon as 24 h. For both microbes the viable populations decreased more rapidly after PEF treatment, indicating an antimicrobial benefit of PEF.

To be considered a replacement for sulfite additives, it is imperative that any preservation method should retain the desirable characteristics of the final product. Therefore, the pH, glucose-fructose, % ethanol, and total and volatile acidity were analyzed, comparing the initial and final oenological parameters of the wines with and without PEF. No significant differences were observed.

Finally, human testers (but sadly, not me) compared a commercial red wine ready for bottling that was treated using PEF or by standard filtration and then stored for 1 month. No differences were found for oenological parameters and testers could not detect a difference between PEF and filtration-treated samples. The only evident difference was a lighter color for the filtered wine. Therefore, overall PEF appears to be an effective method for wine preservation.

That is a wrap for this instalment of the Buzz, but I have already spotted a few exciting bioelectricity-related topics for next time!