A pro-reparative bioelectronic device for controlled delivery of ions and biomolecules.

Wound healing is a complex physiological process that requires precise control and modulation of many parameters. Therapeutic ion and biomolecule delivery has the capability to regulate the wound healing process beneficially. However, achieving controlled delivery through a compact device with the ability to deliver multiple therapeutic species can be a challenge. Bioelectronic devices have emerged as a promising approach for therapeutic delivery. Here, we present a pro-reparative bioelectronic device designed to deliver ions and biomolecules for wound healing applications. The device incorporates ion pumps for the targeted delivery of H+ and zolmitriptan to the wound site. In vivo studies using a mouse model further validated the device's potential for modulating the wound environment via H+ delivery that decreased M1/M2 macrophage ratios. Overall, this bioelectronic ion pump demonstrates potential for accelerating wound healing via targeted and controlled delivery of therapeutic agents to wounds. Continued optimization and development of this device could not only lead to significant advancements in tissue repair and wound healing strategies but also reveal new physiological information about the dynamic wound environment.

Rat primary cortical cell tri-culture to study effects of amyloid-beta on microglia function.

Introduction: The etiology and progression of sporadic Alzheimer's Disease (AD) have been studied for decades. One proposed mechanism is that amyloid-beta (Aß) proteins induce neuroinflammation, synapse loss, and neuronal cell death. Microglia play an especially important role in Aß clearance, and alterations in microglial function due to aging or disease may result in Aß accumulation and deleterious effects on neuronal function. However, studying these complex factors in vivo , where numerous confounding processes exist, is challenging, and until recently, in vitro models have not allowed sustained culture of microglia, astrocytes and neurons in the same culture. Here, we employ a tri-culture model of rat primary neurons, astrocytes, and microglia and compare it to co-culture (neurons and astrocytes) and mono-culture enriched for microglia to study microglial function (i.e., motility and Aß clearance) and proteomic response to exogenous Aß. Methods: We established cortical co-culture (neurons and astrocytes), tri-culture (neurons, astrocytes, and microglia), and mono-culture (microglia) from perinatal rat pups. On days in vitro (DIV) 7 - 14, the cultures were exposed to fluorescently-labeled Aß (FITC-Aß) particles for varying durations. Images were analyzed to determine the number of FITC-Aß particles after specific lengths of exposure. A group of cells were stained for ßIII-tubulin, GFAP, and Iba1 for morphological analysis via quantitative fluorescence microscopy. Cytokine profiles from conditioned media were obtained. Live-cell imaging with images acquired every 5 minutes for 4 hours was employed to extract microglia motility parameters (e.g., Euclidean distance, migration speed, directionality ratio). Results and discussion: FITC-Aß particles were more effectively cleared in the tri-culture compared to the co-culture. This was attributed to microglia engulfing FITC-Aß particles, as confirmed via epifluorescence and confocal microscopy. Adding FITC-Aß significantly increased the size of microglia, but had no significant effect on neuronal surface coverage or astrocyte size. Analysis of the cytokine profile upon FITC-Aß addition revealed a significant increase in proinflammatory cytokines (TNF-α, IL-1α, IL-1ß, IL-6) in tri-culture, but not co-culture. In addition, Aß addition altered microglia motility marked by swarming-like motion with decreased Euclidean distance yet unaltered speed. These results highlight the importance of cell-cell communication in microglia function (e.g., motility and Aß clearance) and the utility of the tri-culture model to further investigate microglia dysfunction in AD.

Electric field modulation of ERK dynamics shows dependency on waveform and timing.

Different exogenous electric fields (EF) can guide cell migration, disrupt proliferation, and program cell development. Studies have shown that many of these processes were initiated at the cell membrane, but the mechanism has been unclear, especially for conventionally non-excitable cells. In this study, we focus on the electrostatic aspects of EF coupling with the cell membrane by eliminating Faradaic processes using dielectric-coated microelectrodes. Our data unveil a distinctive biphasic response of the ERK signaling pathway of epithelial cells (MCF10A) to alternate current (AC) EF. The ERK signal exhibits both inhibition and activation phases, with the former triggered by a lower threshold of AC EF, featuring a swifter peaking time and briefer refractory periods than the later-occurring activation phase, induced at a higher threshold. Interestingly, the biphasic ERK responses are sensitive to the waveform and timing of EF stimulation pulses, depicting the characteristics of electrostatic and dissipative interactions. Blocker tests and correlated changes of active Ras on the cell membrane with ERK signals indicated that both EGFR and Ras were involved in the rich ERK dynamics induced by EF. We propose that the frequency-dependent dielectric relaxation process could be an important mechanism to couple EF energy to the cell membrane region and modulate membrane protein-initiated signaling pathways, which can be further explored to precisely control cell behavior and fate with high temporal and spatial resolution.

Dynamics of cutaneous atmospheric oxygen uptake in response to mechanical stretch revealed by optical fiber microsensor.

Skin expands and regenerates in response to mechanical stretch. This important homeostasis process is critical for skin biology and can be exploited to generate extra skin for reconstructive surgery. Atmospheric oxygen uptake is important in skin homeostasis. However, whether and how cutaneous atmospheric oxygen uptake changes during mechanical stretch remains unclear, and relevant research tools to quantify oxygen flux are limited. Herein, we used the scanning micro-optrode technique (SMOT), a non-invasive self-referencing optical fiber microsensor, to achieve real-time measurement of cutaneous oxygen uptake from the atmosphere. An in vivo mechanical stretch-induced skin expansion model was established, and an in vitro Flexcell Tension system was used to stretch epidermal cells. We found that oxygen influx of skin increased dramatically after stretching for 1 to 3 days and decreased to the non-stretched level after 7 days. The enhanced oxygen influx of stretched skin was associated with increased epidermal basal cell proliferation and impaired epidermal barrier. In conclusion, mechanical stretch increases cutaneous oxygen uptake with spatial-temporal characteristics, correlating with cell proliferation and barrier changes, suggesting a fundamental mechanistic role of oxygen uptake in the skin in response to mechanical stretch. Optical fiber microsensor-based oxygen uptake detection provides a non-invasive approach to understand skin homeostasis.

Reducing Sialylation Enhances Electrotaxis of Corneal Epithelial Cells.

Corneal wound healing is a complex biological process that integrates a host of different signals to coordinate cell behavior. Upon wounding, there is the generation of an endogenous wound electric field that serves as a powerful cue to guide cell migration. Concurrently, the corneal epithelium reduces sialylated glycoforms, suggesting that sialylation plays an important role during electrotaxis. Here, we show that pretreating human telomerase-immortalized corneal epithelial (hTCEpi) cells with a sialyltransferase inhibitor, P-3FAX-Neu5Ac (3F-Neu5Ac), improves electrotaxis by enhancing directionality, but not speed. This was recapitulated using Kifunensine, which inhibits cleavage of mannoses and therefore precludes sialylation on N-glycans. We also identified that 3F-Neu5Ac enhanced the responsiveness of the hTCEpi cell population to the electric field and that pretreated hTCEpi cells showed increased directionality even at low voltages. Furthermore, when we increased sialylation using N-azidoacetylmannosamine-tetraacylated (Ac4ManNAz), hTCEpi cells showed a decrease in both speed and directionality. Importantly, pretreating enucleated eyes with 3F-Neu5Ac significantly improved re-epithelialization in an ex vivo model of a corneal injury. Finally, we show that in hTCEpi cells, sialylation is increased by growth factor deprivation and reduced by PDGF-BB. Taken together, our results suggest that during corneal wound healing, reduced sialylated glycoforms enhance electrotaxis and re-epithelialization, potentially opening new avenues to promote corneal wound healing.

A system for bioelectronic delivery of treatment directed toward wound healing.

The development of wearable bioelectronic systems is a promising approach for optimal delivery of therapeutic treatments. These systems can provide continuous delivery of ions, charged biomolecules, and an electric field for various medical applications. However, rapid prototyping of wearable bioelectronic systems for controlled delivery of specific treatments with a scalable fabrication process is challenging. We present a wearable bioelectronic system comprised of a polydimethylsiloxane (PDMS) device cast in customizable 3D printed molds and a printed circuit board (PCB), which employs commercially available engineering components and tools throughout design and fabrication. The system, featuring solution-filled reservoirs, embedded electrodes, and hydrogel-filled capillary tubing, is assembled modularly. The PDMS and PCB both contain matching through-holes designed to hold metallic contact posts coated with silver epoxy, allowing for mechanical and electrical integration. This assembly scheme allows us to interchange subsystem components, such as various PCB designs and reservoir solutions. We present three PCB designs: a wired version and two battery-powered versions with and without onboard memory. The wired design uses an external voltage controller for device actuation. The battery-powered PCB design uses a microcontroller unit to enable pre-programmed applied voltages and deep sleep mode to prolong battery run time. Finally, the battery-powered PCB with onboard memory is developed to record delivered currents, which enables us to verify treatment dose delivered. To demonstrate the functionality of the platform, the devices are used to deliver H[Formula: see text] in vivo using mouse models and fluoxetine ex vivo using a simulated wound environment. Immunohistochemistry staining shows an improvement of 35.86% in the M1/M2 ratio of H[Formula: see text]-treated wounds compared with control wounds, indicating the potential of the platform to improve wound healing.

Protocol for electrotaxis of large epithelial cell sheets.

Here, we present a protocol for electrotaxis of large epithelial cell sheets without compromising the integrity of cell epithelia in a high-throughput customized directed current electrotaxis chamber. We describe the fabrication and use of polydimethylsiloxane stencils to control the size and shape of human keratinocyte cell sheets. We detail cell tracking, cell sheet contour assay, and particle image velocimetry to reveal the spatial and temporal motility dynamics of cell sheets. This approach is applicable to other collective cell migration studies. For complete details on the use and execution of this protocol, please refer to Zhang et al. (2022).1.

Electrotaxis of alveolar epithelial cells in direct-current electric fields.

PURPOSE: This study aims to elucidate the electrotaxis response of alveolar epithelial cells (AECs) in direct-current electric fields (EFs), explore the impact of EFs on the cell fate of AECs, and lay the foundation for future exploitation of EFs for the treatment of acute lung injury. METHODS: AECs were extracted from rat lung tissues using magnetic-activated cell sorting. To elucidate the electrotaxis responses of AECs, different voltages of EFs (0, 50, 100, and 200 mV/mm) were applied to two types of AECs, respectively. Cell migrations were recorded and trajectories were pooled to better demonstrate cellular activities through graphs. Cell directionality was calculated as the cosine value of the angle formed by the EF vector and cell migration. To further demonstrate the impact of EFs on the pulmonary tissue, the human bronchial epithelial cells transformed with Ad12-SV40 2B (BEAS-2B cells) were obtained and experimented under the same conditions as AECs. To determine the influence on cell fate, cells underwent electric stimulation were collected to perform Western blot analysis. RESULTS: The successful separation and culturing of AECs were confirmed through immunofluorescence staining. Compared with the control, AECs in EFs demonstrated a significant directionality in a voltage-dependent way. In general, type Ⅰ alveolar epithelial cells migrated faster than type Ⅱ alveolar epithelial cells, and under EFs, these two types of cells exhibited different response threshold. For type Ⅱ alveolar epithelial cells, only EFs at 200 mV/mm resulted a significant difference to the velocity, whereas for, EFs at both 100 mV/mm and 200 mV/mm gave rise to a significant difference. Western blotting suggested that EFs led to an increased expression of a AKT and myeloid leukemia 1 and a decreased expression of Bcl-2-associated X protein and Bcl-2-like protein 11. CONCLUSION: EFs could guide and accelerate the directional migration of AECs and exert antiapoptotic effects, which indicated that EFs are important biophysical signals in the re-epithelialization of alveolar epithelium in lung injury.

Electric field-guided collective motility initiation of large epidermal cell groups.

Recent research has elucidated mechanochemical pathways of single cell polarization, but much less is known about collective motility initiation in adhesive cell groups. We used galvanotactic assays of zebrafish keratocyte cell groups, pharmacological perturbations, electric field switches, particle imaging velocimetry, and cell tracking to show that large cell groups initiate motility in minutes toward the cathode. Interestingly, while PI3K-inhibited single cells are biased toward the anode, inhibiting PI3K does not affect the cathode-directed cell group migration. We observed that control groups had the fastest cathode-migrating cell at the front, while the front cells in PI3K-inhibited groups were the slowest. Both control and PI3K-inhibited groups rapidly repolarized when the electric field direction was reversed, and the group migration continued after the electric field was switched off. Inhibiting myosin disrupted the cohesiveness of keratocyte groups and abolished the collective directionality and ability to switch direction when the electric field is reversed. Our data are consistent with a model according to which cells in the group sense the electric field individually and mechanical integration of the cells results in coherent group motility.

Protocol for electrical modulation of ERK signaling dynamics in cell lines.

Here, we describe a protocol for modulating the dynamics of the extracellular signal-regulated kinases (ERK) pathway in a customized alternating current (AC) electric field stimulation chamber. We use an ERK translocation reporter that can accurately represent the intracellular ERK activity in real time without chemical agents or gene disruption. ERK activation is assessed by comparing the relative intensity of nuclear fluorescence to cytosolic fluorescence in live-cell conditions. The approach can be applied to other signaling pathways as well. For complete details on the use and execution of this protocol, please refer to Guo et al. (2021).

Propagation dynamics of electrotactic motility in large epithelial cell sheets.

Directional migration initiated at the wound edge leads epithelia to migrate in wound healing. How such coherent migration is achieved is not well understood. Here, we used electric fields to induce robust migration of sheets of human keratinocytes and developed an in silico model to characterize initiation and propagation of epithelial collective migration. Electric fields initiate an increase in migration directionality and speed at the leading edge. The increases propagate across the epithelial sheets, resulting in directional migration of cell sheets as coherent units. Both the experimental and in silico models demonstrated vector-like integration of the electric and default directional cues at free edge in space and time. The resultant collective migration is consistent in experiments and modeling, both qualitatively and quantitatively. The keratinocyte model thus faithfully reflects key features of epithelial migration as a coherent tissue in vivo, e.g. that leading cells lead, and that epithelium maintains cell-cell junction.

A machine learning based model accurately predicts cellular response to electric fields in multiple cell types.

Many cell types migrate in response to naturally generated electric fields. Furthermore, it has been suggested that the external application of an electric field may be used to intervene in and optimize natural processes such as wound healing. Precise cell guidance suitable for such optimization may rely on predictive models of cell migration, which do not generalize. Here, we present a machine learning model that can forecast directedness of cell migration given a timeseries of previous directedness and electric field values. This model is trained using time series galvanotaxis data of mammalian cranial neural crest cells obtained through time-lapse microscopy of cells cultured at 37 °C in a galvanotaxis chamber at ambient pressure. Next, we show that our modeling approach can be used for a variety of cell types and experimental conditions with very limited training data using transfer learning methods. We adapt the model to predict cell behavior for keratocytes (room temperature, ~ 18-20 °C) and keratinocytes (37 °C) under similar experimental conditions with a small dataset (~ 2-5 cells). Finally, this model can be used to perform in silico studies by simulating cell migration lines under time-varying and unseen electric fields. We demonstrate this by simulating feedback control on cell migration using a proportional-integral-derivative (PID) controller. This data-driven approach provides predictive models of cell migration that may be suitable for designing electric field based cellular control mechanisms for applications in precision medicine such as wound healing.

Electrically synchronizing and modulating the dynamics of ERK activation to regulate cell fate.

Intracellular signaling dynamics play fundamental roles in cell biology. Precise modulation of the amplitude, duration, and frequency of signaling activation will be a powerful approach to investigate molecular mechanisms as well as to engineer signaling to control cell behaviors. Here, we showed a practical approach to achieve precise amplitude modulation (AM), frequency modulation (FM), and duration modulation (DM) of MAP kinase activation. Alternating current (AC) electrical stimulation induced synchronized ERK activation. Amplitude and duration of ERK activation were controlled by varying stimulation strength and duration. ERK activation frequencies were arbitrarily modulated with trains of short AC applications with accurately defined intervals. Significantly, ERK dynamics coded by well-designed AC can rewire PC12 cell fate independent of growth factors. This technique can be used to synchronize and modulate ERK activation dynamics, thus would offer a practical way to control cell behaviors in vivo without the use of biochemical agents or genetic manipulation.

The different correlations between obesity and osteoporosis after adjustment of static mechanical loading from weight and fat free mass.

OBJECTIVES: To explore complex correlations between obesity (OB) and osteoporosis (OP) after adjustment of static mechanical loading from weight and fat free mass (FFM). METHODS: A total of 3749 Chinese aged ≥65 years were selected from our ongoing cohort study. OB indices and bone mineral density (BMD) were measured for each subject. Linear regression analyses were performed to explore the correlations between OB indices and OP under three adjustment models (unadjusted, adjusted with weight and adjusted with FFM). RESULTS: Under no adjustment, three general obesity indices (body mass index: BMI, fat mass: FM, and percentage FM: PFM) were positively associated with BMD at three skeletal sites (P<0.001) in the regression analyses. However, after the adjustment with weight, these associations were mostly significant but reverse i.e., negatively in direction. After adjustment with FFM, the three indices were still positively and significantly (P<0.001) associated with BMD but regression coefficients were smaller compared to the unadjusted associations. Similar associations were observed for central adiposity and lower limb adiposity indices. CONCLUSIONS: The combined relation of OB to OP due to the physiological factors secreted from adipose tissues and the static mechanical loading from FM is positive in direction.

Quantifying the impact of electric fields on single-cell motility.

Cell motility in response to environmental cues forms the basis of many developmental processes in multicellular organisms. One such environmental cue is an electric field (EF), which induces a form of motility known as electrotaxis. Electrotaxis has evolved in a number of cell types to guide wound healing and has been associated with different cellular processes, suggesting that observed electrotactic behavior is likely a combination of multiple distinct effects arising from the presence of an EF. To determine the different mechanisms by which observed electrotactic behavior emerges, and thus to design EFs that can be applied to direct and control electrotaxis, researchers require accurate quantitative predictions of cellular responses to externally applied fields. Here, we use mathematical modeling to formulate and parameterize a variety of hypothetical descriptions of how cell motility may change in response to an EF. We calibrate our model to observed data using synthetic likelihoods and Bayesian sequential learning techniques and demonstrate that EFs bias cellular motility through only one of a selection of hypothetical mechanisms. We also demonstrate how the model allows us to make predictions about cellular motility under different EFs. The resulting model and calibration methodology will thus form the basis for future data-driven and model-based feedback control strategies based on electric actuation.

Prevalence and determinants of potentially inappropriate medications prescribing in elderly patients in Chinese communities.

BACKGROUND: To assess the prevalence and associated risk of potentially inappropriate medications (PIMs) prescribing in community-dwelling elderly patients in China and to examine the most frequently used PIMs. This will provide a reference for the formulation of medication manuals for the community-dwelling elderly and further standardize the use of medications in elderly patients. METHODS: We conducted a cross-sectional retrospective study from April 1, 2020 to April 30, 2020. Data from elderly patients aged ≥65 years were collected from the Hengjie (N=2,294), Loujiang (N=3,972), and Tongxing communities (N=1,969) in Suzhou. The frequency of PIMs was detected using the 2019 Beers criteria and the 2017 Chinese criteria. Chi-square (for categorical variables), ANOVA (for continuous variables as applicable), and logistic regression were used to describe and identify potential predictors of PIMs. RESULTS: A total of 8,235 elderly patients were examined. Using the Chinese criteria, the prevalence of PIMs was 37.07%, which was slightly higher than that found using the 2019 Beers criteria (32.16%). The most prescribed PIMs were estazolam (21.53%) and insulin (4.60%) based on the Chinese criteria. Logistic regression analysis showed that advanced age, polypharmacy, and comorbid disease of patients were associated with a high risk of PIMs. Furthermore, the educational background and professional title of physicians were also associated with PIMs. CONCLUSIONS: Given the high prevalence of PIMs in the Chinese community-dwelling elderly population, the implementation of evidence-based interventions to promote rational clinical drug use could improve their quality of life.

Physiological electric fields induce directional migration of mammalian cranial neural crest cells.

During neurulation, cranial neural crest cells (CNCCs) migrate long distances from the neural tube to their terminal site of differentiation. The pathway traveled by the CNCCs defines the blueprint for craniofacial construction, abnormalities of which contribute to three-quarters of human birth defects. Biophysical cues like naturally occurring electric fields (EFs) have been proposed to be one of the guiding mechanisms for CNCC migration from the neural tube to identified position in the branchial arches. Such endogenous EFs can be mimicked by applied EFs of physiological strength that has been reported to guide the migration of amphibian and avian neural crest cells (NCCs), namely galvanotaxis or electrotaxis. However, the behavior of mammalian NCCs in external EFs has not been reported. We show here that mammalian CNCCs migrate towards the anode in direct current (dc) EFs. Reversal of the field polarity reverses the directedness. The response threshold was below 30 â€‹mV/mm and the migration directedness and displacement speed increased with increase in field strength. Both CNCC line (O9-1) and primary mouse CNCCs show similar galvanotaxis behavior. Our results demonstrate for the first time that the mammalian CNCCs respond to physiological EFs by robust directional migration towards the anode in a voltage-dependent manner.

Investigation of the psychological status of suspected patients during the Coronavirus disease 2019 epidemic.

We explored the psychological changes in suspected patients during the coronavirus disease 2019 (COVID-19) epidemic and obtained evidence for early psychological guidance and intervention in this group. A total of 31 inpatients with suspected COVID-19 were identified at our hospital. The depression module of the Patient Health Questionnaire (PHQ-9), the General Anxiety Disorder (GAD)-7 scale, and the Self-Reporting Questionnaire (SRQ-20) mental health self-assessment questionnaire were used to assess depression, anxiety, and overall mental health. Among the patients, 32.3% had symptoms of depression and 19.4% had symptoms of anxiety. Levels of anxiety and fear varied. In comparing the PHQ-9 and 7-item Generalized Anxiety Disorder Scale scores of suspected and confirmed patients, there was no significant difference in the distribution of severity of anxiety or depression in the 2 groups. The PHQ-9 scores indicated mild depression symptoms in 25.8% of suspected patients, moderate symptoms in 0%, and severe symptoms in 6.5%. Overall, 50% of confirmed patients had symptoms, with 30.8% classified as mild, 15.4% classified as moderate, and 3.8% classified as severe. The 7-item Generalized Anxiety Disorder Scale scores in the group of suspected patients showed that 9.7% had mild symptoms, 0% had moderate symptoms, and 9.7% had severe symptoms. In the group of confirmed patients, 38.4% had symptoms (34.6% mild, 0% moderate, and 3.8% severe). Diagnosed patients had more visible symptoms of depression and different total PHQ-9 scores. During the COVID-19 epidemic, suspected and diagnosed patients had different levels of mental health problems. Diagnosed patients had more visible symptoms. The performance of suspected patients was higher, but their mental state was more polarized. It may thus be important to monitor the psychological state of suspected patients as early as possible to enable timely interventions that promote psychological rehabilitation.

Protein array test detected three osteoporosis related plasma inflammatory cytokines in Chinese postmenopausal women.

Inflammatory cytokines were involved in pathological conditions of osteoporosis (OP). However, the specific OP-associated inflammatory cytokines are still awaiting to be detected by using a systemic method. Herein, we adopted an extreme sampling scheme and examined inflammatory cytokines between subjects with low and high bone mineral density (BMD) through protein microarray. First, 8 candidate cytokines including B lymphocyte chemoattractant (BLC), osteopontin (OPN) and insulin-like growth factor-binding protein 4 (IGFBP4) were identified in the discovery extreme sampling subgroup. Then, the different expressions for BLC, OPN and IGFBP4 were validated and replicated in two independent extreme sampling subgroups. Further functional experiments showed that the cytokine BLC was involved in bone metabolism by inhibiting bone formation and promoting bone resorption. Together, this study further revealed that inflammatory cytokines were closely related with OP, and that they highlighted critical roles of BLC in the pathogenesis of OP.

Electric Fields at Breast Cancer and Cancer Cell Collective Galvanotaxis.

Cancer growth interferes with local ionic environments, membrane potentials, and transepithelial potentials, resulting in small electrical changes in the tumor microenvironment. Electrical fields (EFs) have significant effects on cancer cell migration (galvanotaxis/electrotaxis), however, their role as a regulator of cancer progression and metastasis is poorly understood. Here, we employed unique probe systems to characterize the electrical properties of cancer cells and their migratory ability under an EF. Subcutaneous tumors were established from a triple-negative murine breast cancer cell line (4T1), electric currents and potentials of tumors were measured using vibrating probe and glass microelectrodes, respectively. Steady outward and inward currents could be detected at different positions on the tumor surface and magnitudes of the electric currents on the tumor surface strongly correlated with tumor weights. Potential measurements also showed the non-homogeneous intratumor electric potentials. Cancer cell migration was then surveyed in the presence of EFs in vitro. Parental 4T1 cells and metastatic sublines in isolation showed random migration in EFs of physiological strength, whereas cells in monolayer migrated collectively to the anode. Our data contribute to an improved understanding of breast cancer metastasis, providing new evidence in support of an electrical mechanism that promotes this phenomenon.