Membrane Electrical Properties Research Articles

Conductive polyurethane nanofiber membrane prepared through high-power impulse magnetron sputtering using brass alloy

In this work, a copper-rich α-phase brass alloy was deposited on the surface of polyurethane nanofiber membranes with different densities using high-power impulse magnetron sputtering technology. The microstructural and electrical properties of the brass-coated membranes were investigated using a cold field emission scanning electron microscope with an energy dispersive spectrometer, atomic force microscope, a multipurpose thin-film X-ray diffractometer, and low impedance meter with a four-point probe. A network analyzer with a coaxial tube was used to analyze the resistance characteristics and electromagnetic shielding effectiveness of the samples. Results indicated that the brass alloy was evenly deposited on the surface and inner layers of the nanofiber membrane. Brass nodules were stacked on the surface of nanofibers and had a granular structure. The nanofibers of all membranes were neither damaged nor degraded after deposition. The brass-coated membrane provided a good conductive path on the surface. When the deposition time increased, the deposition of brass nodules on the membrane was more complete and uniform, which reduced the surface resistance and improved the electromagnetic shielding performance of the membrane.

P.599 Differential responsiveness to a dexamethasone challenge of vulnerable and resilient animals previously exposed to the chronic mild stress paradigm

Cajal–Retzius cells (CRc) represent a mostly transient neuronal cell type localized in the uppermost layer of the developing neocortex. The observation that CRc are a major source of the extracellular matrix protein reelin, which is essential for the laminar development of the cerebral cortex, attracted the interest in this unique cell type. In this review we will (i) describe the morphological and molecular properties of neocortical CRc, with a special emphasize on the question which markers can be used to identify CRc, (ii) summarize reports that identified the different developmental origins of CRc, (iii) discuss the fate of CRc, including recent evidence for apoptotic cell death and a possible persistence of some CRc, (iv) provide a detailed description of the electrical membrane properties and transmitter receptors of CRc, and (v) address the role of CRc in early neuronal circuits and cortical development. Finally, we speculate whether CRc may provide a link between early network activity and the structural maturation of neocortical circuits.

ELECTROSPUN STRONTIUM CROSS-LINKED SULFONATED POLY (ETHER ETHER KETONE) SPEEK NANOFIBER FOR PROTON EXCHANGE MEMBRANE FUEL CELL

Strontium (Sr) cross-linked nanofibrous membranes of sulfonated polyether ether ketone (SPEEK) were successfully prepared using the electrospinning technique. Metal-polymer physical cross-linked has been proposed as a way to improve the mechanical and chemical stabilities of the electrospun SPEEK membrane which we found in this finding can help to reduced water uptake compared with the non-crosslinked membrane. Physical cross-linked of Sr-SPEEK membranes were fabricated by immersion process which were than electrospun into nanofibrous membranes. The morphologies of electrospun Sr-SPEEK membrane, fabricated under different concentrations of Sr were presented which show up to 6% concentration of Strontium was able to be electrospun. On the electrical properties of the electrospun membrane, conductivity for the sample with 6% Sr weight percentage has given 0.188 S/cm which is about 80% higher than the film cast Nafion-117 at 80˚C as cited before. This particular result is a hallmark of the studies as it shows that a combination of nanostructured with crosslink is proven to work in favor of producing proton exchange membrane fuel cell (PEMFC) which performed much better than Nafion based membrane.

Modulation of Interfacial Hydration by Carbonyl Groups in Lipid Membranes.

The lack of carbonyl groups and the presence of ether bonds give the lipid interphase a different water organization around the phosphate groups that affects the compressibility and electrical properties of lipid membranes. Generalized polarization of 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine (14:0 diether PC) in correlation with Fourier transform infrared (FTIR) analysis indicates a higher level of polarizability of water molecules in the membrane phase around the phosphate groups both below and above Tm. This reorganization of water promotes a different response in compressibility and dipole moment of the interphase, which is related to different H bonding of water molecules with phosphates (PO) and carbonyl (CO) groups.

Thermodynamic, viscoelastic and electrical properties of lipid membranes in the presence of astaxanthin

Among numerous compounds found in marine organisms, astaxathin has received considerable research interest due to beneficial impact on health such as anti-inflammatory, antioxidant and neuroprotective activity. Recently new functionalities of this xanthophyll have been revealed indicating important applications in nutrition and pharmacy. However, astaxanthin, as the bioactive, has limited value without a protecting carrier that provides controlled release in a human body. Fabrication of liposomes as efficient drug delivery systems is promising strategy that may overcome these problems. However, the development of new delivery systems requires comprehensive understanding of physicochemical properties of carotenoids and their carriers as well as the interactions between them. The aim of this study was to investigate the mixed lipid-sterol monolayer in the presence of astaxanthin in terms of thermodynamic, morphological and viscoelastic behaviour. The results have been discussed in relation to pure lipid-sterol films. In addition we determined the surface charge density of the liposomes built of these components. The results are helpful in better understanding the role of interfacial viscoelasticity in the quality of liposomal drug delivery forms.

The Modulating Effect of p-Coumaric Acid on The Surface Charge Density of Human Glioblastoma Cell Membranes.

p-Coumaric acid (p-CoA), a phenolic acid belonging to the hydroxycinnamic acids family, is a compound with tentative anticancer potential. Microelectrophoretic mobility measurements conducted at various pH values of electrolyte solution were applied to study p-CoA effects on electrical properties of human glioblastoma cell membranes. The obtained results demonstrated that after the p-CoA treatment, the surface charge density of cancer cells changed in alkaline pH solutions, while no noticeable changes were observed in cell membranes incubated with p-CoA compared to control at acidic pH solutions. A four-equilibrium model was used to describe the phenomena occurring on the cell membrane surface. The total surface concentrations of both acidic and basic functional groups and their association constants with solution ions were calculated and used to define theoretical curves of membrane surface charge density versus pH. The resulting theoretical curves and the experimental data were compared to verify the reliability and validity of the adopted model. The deviation of both kinds of data obtained at a higher pH may be caused by disregarding interactions between the functional groups of cancer cells. Processes occurring in the cell membranes after their incubation with p-CoA can lead to disorders of existing equilibria, which result in changes in values of the parameters describing these equilibria.

Transient dynamics of Pearson diffusions facilitates estimation of rate parameters

Estimation of parameters in stochastic processes has been thoroughly investigated for decades and the asymptotic properties of the estimators are known. However, reaching the regime where the asymptotic properties are valid might require such a long time that the well based theoretical results have no practical value. One example of this situation is at the center of our interest. It concerns determination of the time constant in stochastic Langevin equations with additive or multiplicative white-noise terms. Often the number of observations to achieve the asymptotic conditions is beyond the physical limits. Here we show how to overcome the problem by external perturbation of the system. Furthermore, we show that the perturbation is not at the price of deterioration of the estimates of other parameters unless the observation interval is very short compared to the typical time constant of the system. Three processes from the class of Pearson diffusions are studied. They are frequently used in many applications, in particular, they are examples of leaky integrate-and-fire models, which describe the electrical properties of a neuronal membrane. These neuronal models are often used as examples of systems with excitable dynamics. The most commonly investigated process is the Ornstein-Uhlenbeck process, which has additive noise. Furthermore, the square-root process and the Jacobi process are examples of processes with multiplicative noise. The results are illustrated on computer experiments, which show a striking improvement of the estimates of the rate parameter. It has implications for experimental design, where the information about the parameters can be increased for the same amount and cost of data, which is particularly important when samples are expensive or difficult to obtain.

The modulating effect of lipid bilayer/p-coumaric acid interactions on electrical properties of model lipid membranes and human glioblastoma cells

Biological membranes are one of the most important elements of living cells determining their permeability to the active compounds. Still, little is known about the drug-membrane interactions in terms of pharmacological properties of potential drugs. Chemoprevention based on natural compounds is becoming a strong trend in modern oncopharmacology, and p-coumaric acid (p-CoA) is one such compound with tentative anticancer activity. The microelectrophoretic mobility measurements and electrochemical impedance spectroscopy were applied to study the effects of p-CoA on electrical properties of liposomes, spherical bilayers, and human glioblastoma cell membranes. Our results demonstrated that after treatment with p-CoA, the surface charge of LBC3, LN-229 and LN-18 cell lines was significantly changed in alkaline pH solutions, but not in acidic pH solutions. In contrast, no changes in surface charge density values were registered for phosphatidylethanolamine liposomal membranes and A172 cell membranes after p-CoA treatment. The impedance data showed an increase in values of both the electrical capacitance and the electrical resistance, indicating that p-CoA can be partially inserted into the phosphatidylcholine bilayers. The MTT assay showed cell line-dependent cytotoxic effect of p-CoA. Further molecular analyses revealed the ATP depletion and gene transcription modulation, which might indicate organelle membrane-crossing potential of p-CoA. These results suggest, that changes in surface charge of membranes of living cells not only might be potential predictor of membrane permeability, but also indicate differential composition of cell membranes in various cell lines. Thus further multidirectional analyses are required to implement electrochemical methods as standard testing procedures during drug development process.

Characterization of Cellulosa Coconut Fiber-Fiber Glass Membrane as a Separator in Water Electrolizer

Characterizations of membranes made from cellulose coconut fiber-fiber glass as H<sub>2</sub>O separators in water of electrolyzer has been done. The separators membrane was successfully made with a manual and simple technique, mixing cellulose fiber material produced from the modification of coconut fibers with NaOH immersion process. Cellulose fiber mixed with fiber glass in the composition of 50:0, 40:10, 30:20, 20:30, 10:40, 0:50 (%wt) to get hybrid composite. The results of testing the ability of the membrane as a separator produce H<sub>2</sub> gas concentrations that are more increased than without using a separator. The optimum value produced is 300 ppm in sample 1 which is 50:0:50 %wt, while the H<sub>2</sub> gas production without using a separator which is 51 ppm. For physical properties testing, the addition of mass percent of celluose coconut fiber affects the physical and electrical properties of membrane where the optimum value of % porosity of the material obtained is 73 %, swealling value is 77,5 % and the conductivity value of the material amounting to 1,572 x 10 <sup>-7</sup> S/cm.

A modified bulge test for in-situ study of ionic permeation properties of membranes under continuously tunable, uniform pressure.

The bulge test is a well-known material test to measure the mechanical properties of metal plates, thin films, and membranes. Also, two different experimental setups are needed to apply pressure and make a measurement. In this work, we describe a modified bulge test to both apply pressure and measure the electrical and ionic permeation properties of membranes in situ. A membrane, clamped at its periphery, with a circular window for measurement, is sandwiched between two liquids. The liquids serve dual purpose by facilitating the application of differential pressure and thus stress, by controlling the extent of immersion of the membrane in the liquid below the membrane, as well as enabling measurement of electrical and mass percolation properties. This was achieved with a stepper motor, a load cell, and a microcontroller. Relevant mathematical models are developed and discussed. Nafion was used to test and validate this approach, using electroimpedance spectroscopy in a 2-electrode configuration with gallium on both sides and in a 3-electrode configuration with electrolyte on one side and gallium on the other. Frequency-dependent response was modeled using equivalent circuits. The resistance of Nafion increases with the depth of immersion and therefore applied pressure. For Nafion in the 2-electrode configuration, conductivity was calculated to be ∼6.4 × 10-3 S/cm at the equilibrium position, where stress on the membrane is zero. This value matches well with existing literature values for partially hydrated Nafion. Also, it was observed that the response is symmetric about the equilibrium position.

The Effect of UVB Irradiation and Oxidative Stress on the Skin Barrier-A New Method to Evaluate Sun Protection Factor Based on Electrical Impedance Spectroscopy.

Sunlight is vital for several biochemical processes of the skin organ. However, acute or chronic exposure to ultraviolet radiation (UVR) has several harmful effects on the skin structure and function, especially in the case of the failing function of antioxidative enzymes, which may lead to substantial tissue damage due to the increased presence of reactive oxygen species (ROS). The aim of this work was to investigate the combined effect of ultraviolet B (UVB) irradiation and oxidative stress on the skin barrier integrity. For this, we employed electrical impedance spectroscopy (EIS) to characterize changes of the electrical properties of excised pig skin membranes after various exposure conditions of UVB irradiation, oxidative stress, and the inhibition of antioxidative enzymatic processes. The oxidative stress was regulated by adding hydrogen peroxide (H2O2) as a source of ROS, while sodium azide (NaN3) was used as an inhibitor of the antioxidative enzyme catalase, which is naturally present throughout the epidermis. By screening for the combined effect of UVB and oxidative stress on the skin membrane electrical properties, we developed a new protocol for evaluating these parameters in a simple in vitro setup. Strikingly, the results show that exposure to extreme UVB irradiation does not affect the skin membrane resistance, implying that the skin barrier remains macroscopically intact. Likewise, exposure to only oxidative stress conditions, without UVB irradiation, does not affect the skin membrane resistance. In contrast to these observations, the combination of UVB irradiation and oxidative stress conditions results in a drastic decrease of the skin membrane resistance, indicating that the integrity of the skin barrier is compromised. Further, the skin membrane effective capacitance remained more or less unaffected by UVB exposure, irrespective of simultaneous exposure of oxidative stress. The EIS results were concluded to be associated with clear signs of macroscopic tissue damage of the epidermis as visualized with microscopy after exposure to UVB irradiation under oxidative stress conditions. Finally, the novel methodology was tested by performing an assessment of cosmetic sunscreen formulations with varying sun protection factor (SPF), with an overall successful outcome, showing good correlation between SPF value and protection capacity in terms of skin resistance change. The results from this study allow for the development of new skin sensors based on EIS for the detection of skin tissue damage from exposure to UVB irradiation and oxidative stress and provide a new, more comprehensive methodology, taking into account both the influence of UVB irradiation and oxidative stress, for in vitro determination of SPF in cosmetic formulations.

Silver nanoparticles induce abnormal touch responses by damaging neural circuits in zebrafish embryos

Although silver nanoparticles (AgNPs) are used in various commercial products, the biological effects of AgNPs on fish embryogenesis and the underlying molecular mechanisms are still poorly understood. In this study, both touch responses and neuron membrane potential were found to be abnormal in AgNPs-stressed embryos. Moreover, neurogenesis genes were unveiled to be down-regulated and were enriched in ligand-gated ion channel activity, dopamine receptor signaling pathway, etc. in AgNPs-stressed embryos by microarray assays. Additionally, the down-regulated expression of otpa/sncgb - gad1b/gad2 dopaminergic neurotransmitter genes, robo2 - vim and glrbb synaptic transmission genes, and motor neuron genes isl1 &isl2a was further identified in both AgNPs- and Ag+-stressed embryos by qPCR, whole-mount in situ hybridization (WISH), and by using specific promoter-derived GFP fluorescence transgenic zebrafish. Moreover, the reduced expression of gad1b, gad2, and isl1 could be recovered by adding Ag+ chelating compound l-cysteine in AgNPs stressed embryos. Our results reveal for the first time that it is through damaging the formation of neural circuits, including dopaminergic neurotransmitter, synaptic transmission, and motor activities, that AgNPs induce abnormal electrical membrane properties, leading to dysfunctional touch responses and locomotor escape responses mostly via their released Ag+ during embryogenesis.

Interaction of Lorazepam with Planar Bilayer Lipid Membrane and Development of Impedimetric Sensor

Artificial planar bilayer phospholipid membrane was formed in KCl bath solutions and its electrical properties have been analyzed using electrochemical impedance spectroscopy. The stability of planar bilayer lipid membrane depends on concentration of KCl in the bath. Changes in the electrical properties of planar bilayer lipid membrane with the addition of lorazepam were also studied using electrochemical impedance spectroscopy. Lorazepam gets partitioned into bilayer lipid membrane and exhibited a fluidization effect. The ionic conductance across the bilayer lipid membrane increased with the addition of lorazepam to the bath. An impedimetric sensor was developed for quantification of lorazepam in solution.

Involvement of Group II Metabotropic Glutamate Receptors in Modulation of Evoked Activity in Frog Spinal Motoneurons

The effect of the agonist of group II mGluRs, including mGluR2 and mGluR3 (mGluR 2/3) receptor subtypes, on evoked activity and electric membrane properties of frog spinal (lumbar) motoneurons was studied electrophysiologically on sections of the isolated spinal cord. Extracellular recordings revealed a decrease in the amplitude of short-latency components of spinal reflexes and in the overall response area under the effect of DCG-IV [2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine], a mGluR 2/3 agonist, within its concentration range of 0.05-5 μM. The half-maximal effective concentration (EC50) of the agonist for the suppression of short-latency response components was about 0.5 μM. Intracellular recordings of postsynaptic potentials from motoneurons upon DCG-IV application demonstrated a decrease in the number of spikes and the overall area of responses evoked by dorsal root stimulation. Most of motoneurons studied responded with hyperpolarization, increased amplitude of antidromic action potentials, altered afterpotential amplitude and increased excitability, indicative of the agonist effect on postsynaptic group II mGluRs in frog spinal motoneurons.

Giant Vesicles and Their Use in Assays for Assessing Membrane Phase State, Curvature, Mechanics, and Electrical Properties.

Giant unilamellar vesicles represent a promising and extremely useful model biomembrane system for systematic measurements of mechanical, thermodynamic, electrical, and rheological properties of lipid bilayers as a function of membrane composition, surrounding media, and temperature. The most important advantage of giant vesicles over other model membrane systems is that the membrane responses to external factors such as ions, (macro)molecules, hydrodynamic flows, or electromagnetic fields can be directly observed under the microscope. Here, we briefly review approaches for giant vesicle preparation and describe several assays used for deducing the membrane phase state and measuring a number of material properties, with further emphasis on membrane reshaping and curvature.

On the mechanism of the electrophysiological changes and membrane lesions induced by asbestos fiber exposure in Xenopus laevis oocytes

The so-called amphibole asbestos fibers are enriched with mineral iron ions, able to stimulate ROS production. We recently reported that crocidolite asbestos was able to interact with the cell membranes of Xenopus laevis oocytes, to alter their electrical membrane properties. Here, we found that applied iron ions (Fe3+) or H2O2 (for ROS generation) mimicked these effects, suggesting that at least one effect of iron-containing asbestos fiber exposure was mediated by ROS production. Furthermore, combined Fe3+ and H2O2 acted synergistically, producing a membrane effect stronger than that induced by these factors alone. Similar to crocidolite, these changes peaked within 30 minutes of incubation and vanished almost completely after 120 min. However, in the presence of cytochalasin D, which inhibits membrane actin repair mechanisms, crocidolite or applied Fe3+/H2O2 invariably produced oocyte cell death. While the electrophysiological modifications induced by crocidolite suggested a modification of an intrinsic chloride ion channel, the morphological appearance of the treated oocytes also indicated the formation of membrane “pores”; the effects of asbestos exposure may therefore consist of multiple (not necessarily exclusive) underlying mechanisms. In conclusion, using Xenopus oocytes allowed us for the first time, to focus on a specific membrane effect of crocidolite asbestos exposure, which deserves to be tested also on human lung cell lines. Much available evidence suggests that asbestos fibers damage cells through the production of ROS. Our present data confirm that crocidolite fibers can indeed trigger ROS-mediated damaging effects in the oocyte cell membrane, provided iron ions and H2O2 are available for ROS production.

Synthesis, characterization and anticonvulsant activity of new azobenzene-containing VV-hemorphin-5 bio photoswitch.

A novel analog of VV-hemorphin-5 containing azobenzene moiety has been synthesized and investigated for anticonvulsant activity in relation to its E → Z photophysical properties activated by long wavelength light at 365nm. The synthesis was achieved by a modified SPPS by Fmoc-dimerization strategy. The electrochemical behavior before and after UV illumination was investigated using different voltammetric modes. The number of electrons transferred, heterogenic rate constant and diffusion coefficient for E- and Z-isomers were also evaluated. Revealing the governing principles involved in signaling and nerve pulse propagation requires the detailed characterization of the electrical properties of cell membranes. For probing the effect of synthesized azo-peptide on the membrane electrical properties, we measured the specific capacitance of lipid bilayers, representing a basic physical model of biomembranes with their simple reproducibility in laboratory conditions at controlled membrane composition and physicochemical parameters of the surrounding aqueous medium. Our results have shown reduced membrane capacitance in the presence of the azo-peptide, thus providing evidences for possible alterations in the dielectric permittivity of the bilayer. The (Val-Val-Tyr-Pro-Trp-Thr-Gln)2Azo peptide was explored also in vivo for preliminary anticonvulsant activity by using the 6-Hz seizure test and pentylenetetrazol (PTZ) seizure test in mice. The Z-isomer has exhibited higher potency compared to E-isomer most pronouncedly in the 6Hz test for psychomotor seizures where the compound had activity at all three tested doses. It was found that the Z-isomer decrease the latency for onset of clonic seizures induced by PTZ. These results demonstrate that the Z-isomer deserves further evaluation in other screening tests for anticonvulsant activity.

Preparation, characterization and dielectric properties of sodium alginate/titanium dioxide composite membranes

Sodium alginate/titanium dioxide solid polymer composite membranes were prepared by solution casting method. The electrical, optical and thermal properties of these composite membranes are in great demand for advanced electronic device applications. The present study is aimed at the preparation of dioxide membranes to enhance the conductivity of sodium alginate. The diffraction pattern confirmed the change of sodium alginate polymer matrix structure from amorphous to polycrystalline upon dispersing TiO2 powder particles into sodium alginate solution. The surface morphology also evidenced the non-crystalline and polycrystalline (containing grains and grain boundaries) nature of formed films. The infrared spectra showed the presence of various functional groups such as –OH, C=O, O–H, C–H and Na–O. The differential scanning calorimeter (DSC) investigation revealed the existence of exothermic/endothermic peaks, melting and crystallization temperatures. Furthermore, the weight loss of all the films was described as a function of temperature. The dielectric properties highlighted the 5 wt% of TiO2 dispersed in the sodium alginate solution due to its high dielectric constant (e′), dielectric loss (e″) and ac-electrical conductivity (σac).

Changes in physicochemical properties of kidney cells membrane as a consequence of hypertension and treatment of hypertensive rats with FAAH inhibitor

Hypertension is a civilization disease leading to remodeling and damage of blood vessels, impaired renal function and premature death. The aim of this study was to compare the effect of chronic administration of URB597, the FAAH (fatty acid amide hydrolase) inhibitor, to rats with primary (SHRs) and secondary (DOCA-salt hypertensive rats) hypertension on electrical and physicochemical properties of kidney cells membranes. Changes in the electrical charge of the membrane may affect the cell functions. The electrical properties of the kidney cells (surface charge density, zeta potential) were measured by electrophoresis. Qualitative and quantitative composition of the membrane (phospholipids and proteins) was determined by HPLC and lipid peroxidation product (4-hydroxy-2E-hexenal; 4-HHE) level was examined by GCMSMS, while the sialic acid content was measured by resorcinol method. In rats with primary hypertension (SHR) and secondary hypertension (DOCA-salt), changes in electrical properties (increase of electric charge and zeta potential) and membrane composition (increase in sialic acid and protein concentration and decrease in phospholipid level) of kidney cells are observed in comparison to control animals. Greater changes were observed in DOCA-salt hypertensive rats. Changes in membrane properties caused by URB597 depend on the type of hypertension. The administration of URB597 to rats with primary hypertension partially prevents changes in the electrical properties (electrical charge, zeta potential) of the membrane caused by hypertension as well as in the sialic acid and proteins content. However, there is no reduction in oxidative stress, assessed by the level of 4-HHE, which may affect the metabolic function of the kidneys. URB597 administered to rats with DOCA salt does not prevent, but rather intensifies, changes caused by hypertension in the kidney. In conclusion, URB597 given to individuals with hypertension, particularly with secondary hypertension, enhancing some disturbances in electric and physicochemical properties of kidney cells observed in hypertension what may lead to additional kidney disorders. Therefore, further researches are necessary.

Interactions Between Pseudomonas Immunotoxins and the Plasma Membrane: Implications for CAT-8015 Immunotoxin Therapy.

Acute Lymphoblastic Leukemia (ALL) remains the most frequent cause of cancer-related mortality in children and novel therapies are needed for the treatment of relapsed/refractory childhood ALL. One approach is the targeting of ALL blasts with the Pseudomonas immunotoxin CAT-8015. Although CAT-8015 has potent anti-leukemia activity, with a 32% objective response rate in a phase 1 study of childhood ALL, haemolytic-uremic syndrome (HUS) and vascular leak syndrome (VLS), major dose-limiting toxicities, have limited the use of this therapeutic approach in children. Investigations into the pathogenesis of CAT-8015-induced HUS/VLS are hindered by the lack of an adequate model system that replicates clinical manifestations, but damage to vascular endothelial cells (ECs) and blood cells are believed to be major initiating factors in both syndromes. Since there is little evidence that murine models replicate human HUS/VLS, and CAT-8015-induced HUS/VLS predominantly affects children, we developed human models and used novel methodologies to investigate CAT-8015 interactions with red blood cells (RBCs) from pediatric ALL patients and ECs of excised human mesenteric arteries. We provide evidence that CAT-8015 directly interacts with RBCs, mediated by Pseudomonas toxin. We also show correlation between the electrical properties of the RBC membrane and RBC susceptibility to CAT-8015-induced lysis, which may have clinical implication. Finally, we provide evidence that CAT-8015 is directly cytototoxic to ECs of excised human mesenteric arteries. In conclusion, the human models we developed constitutes the first, and very important, step in understanding the origins of HUS/VLS in immunotoxin therapy and will allow further investigations of HUS/VLS pathogenesis.