Membrane Charge Density Research Articles

Preparation and characterization of polyvinyl chloride based nickel phosphate ion selective membrane and its application for removal of ions through water bodies

Polyvinyl chloride based nickel phosphate (PVC–NP) composite membrane was prepared by cast die method of membrane fabrication. The nickel phosphate (NP) inorganic material has been prepared by the novel sol-gel method which is qualitative method of material synthesis. The composite membrane has been designed by a uniform mixing of the NP and polyvinyl chloride (PVC) materials into 1:3 ratio of percentage. This novel PVC supported NP composite membrane is used as a barrier for transporting the electrolytes and heavy metal ions due their charge characteristic. By this nature composite membrane governs to adsorb and absorb characteristics of cations and anions present in water body. The structural, thermal and electrochemical characterizations were done by using different sophisticated techniques like FTIR, XRD, TGA/DTA as well as SEM-EDX, LCR and potentiometer. The characterizations of material as well as membrane indicated the information of functional groups, material nature, thermal stability, surface structure, porosity, elemental percentages, dielectric nature, ionic transportation etc. Teorell-Meyer-Sievers (TMS) theoretical method is used to determine the charge density of membrane which is an important theory to analyze the performance of designed membrane. The other important parameters of membrane can also be determined very easily by the help of calculated values of membrane charge densities.

Charge controlled switchable CO2/N2 separation for g-C10N9 membrane: Insights from molecular dynamics simulations

Using molecular dynamics simulations, we theoretically demonstrate that the CO2/N2 separation performance of g-C10N9 membrane can be controlled by introducing different charges into this membrane. It is found that neutrally charged g-C10N9 membrane is non-selective for CO2/N2 separation resulting from its large pore size. However, positively charged g-C10N9 membrane with charge density of 88 × 1013 e/cm2 exhibits 100% N2/CO2 selectivity, and the CO2/N2 selectivity of negatively charged g-C10N9 membrane with charge density of -60 × 1013 e/cm2 is more than four times higher than that of neutrally charged g-C10N9 membrane. Furthermore, it is shown that the CO2/N2 separation performance of charged g-C10N9 membrane is influenced by the number of CO2 molecules blocking at the pores and the binding energy between CO2 molecules and charged g-C10N9 membrane, which are determined by positive or negative membrane charge and charge density. Our results manifest that charge control is an excellent method for g-C10N9 membrane to realize switchable CO2/N2 separation.

Water and ion sorption in a series of cross-linked AMPS/PEGDA hydrogel membranes

Charge density of ion exchange membranes (IEMs) profoundly influences water and ion sorption. However, fundamental studies of water and ion sorption in charged membranes over a wide range of charge densities are not widely available, which makes it difficult to establish fundamental structure/property relations in such materials. In this study, a series of homogeneous cross-linked uncharged and sulfonated hydrogel membranes were prepared using poly(ethylene glycol diacrylate) (PEGDA) copolymerized with 2-acrylamido-2-methylpropanesulfonic acid (AMPS). Equilibrium water uptake and ion content (Na+, Cl−) in the membranes were determined as a function of external NaCl concentration (0.01–1.0 mol/L). As polymer fixed charge density increased, both water and counter-ion (Na+) sorption increased. Co-ion (Cl−) sorption decreased markedly with only modest increases in polymer fixed charge density, suggesting that even low levels of fixed charges exclude co-ions significantly. However, Cl− sorption became independent of charge density at higher levels of charge density. Experimental values for sorbed Cl− concentrations deviated from those obtained via ideal Donnan model due to thermodynamic non-idealities of ions in the solution and membrane phases.

Surface charges promote nonspecific nanoparticle adhesion to stiffer membranes

This letter establishes the manner in which the electric double layer induced by the surface charges of the plasma membrane (PM) enhances the nonspecific adhesion (NSA) of a metal nanoparticle (NP) to stiffer PMs (i.e., PMs with larger bending moduli). The NSA is characterized by the physical attachment of the NP to the membrane and occurs when the decrease in the surface energy (or any other mechanism) associated with the attachment process provides the energy for bending the membrane. Such an attachment does not involve receptor-ligand interactions that characterize the specific membrane-NP adhesion. Here, we demonstrate that a significant decrease in the electrostatic energy caused by the NP-attachment-induced destruction of the charged-membrane-electrolyte interface is responsible for providing the additional energy needed for bending the membrane during the NP adhesion to stiffer membranes. A smaller salt concentration and a larger membrane charge density augment this effect, which can help to design drug delivery to cells with stiffer membranes due to pathological conditions, fabricate NPs with biomimetic cholesterol-rich lipid bilayer encapsulation, etc.

Synthesis, Characterization, Electrochemical and Antibacterial Studies of Synthesized PVC Supported CP Composite

The copper phosphate {Co3 (PO4 )2 } inorganic material has been synthesized by the sol gel method. The PVC supported CP membrane was designed by the mixing of inorganic CP and organic polyvinyl chloride (PVC) materials in 1:3 ratios of percentage. This membrane is used as a barrier for transportation of electrolyte and heavy metal ions due the charged particles on it. Due to this nature of membrane, it governs to adsorb as well as absorb characteristics of cations and anions. The structural, thermal and electrochemical characterizations were done by using different sophisticated techniques like FTIR, XRD, TGA/DTA as well as SEM-EDX, LCR and potentiometer analysis. The characterizations of material and membrane indicated the information of functional groups, material nature, thermal stability, surface structure, porosity, elemental percentages, dielectric nature, ionic transportation etc. Teorell-Meyer-Sievers (TMS) theoretical method is used to determine the charge density of membrane which is an important theory is used to analyze the performance of membrane. The other important parameters of membrane have also been determined easily by the help of obtained values of charge densities.

Induction of spontaneous curvature and endocytosis: Unwanted consequences of cholesterol extraction using methyl-β-Cyclodextrin

ABSTRACTMembrane curvature is a property of biological membranes essential for organelle morphology and the formation of tubulovesicular carriers. Curvature generation is influenced by the lipid composition of the membrane and protein-mediated processes. Lipids with small headgroups, such as phosphatidic acid, are conical and impose negative curvature on a monolayer. Conversely, lipids with large headgroups relative to the hydrophobic tail(s), such as lysophosphatidylcholine, have an inverted conical shape and impose positive curvature. Due to its abundance and high rates of spontaneous flip-flop between membrane leaflets cholesterol is proposed to buffer the formation of membrane curvature. Recently, we demonstrated that cholesterol is also crucial for maintaining the proper spacing of anionic phospholipids. Upon extraction of cholesterol with cyclodextrin there is a sharp increase in the negative surface charge density of the plasma membrane, which promotes electrostatic repulsion between anionic headgroups, the generation of spontaneous positive curvature and rapid membrane internalization.

Competition of charge-mediated and specific binding by peptide-tagged cationic liposome–DNA nanoparticles in vitro and in vivo

Cationic liposome–nucleic acid (CL–NA) complexes, which form spontaneously, are a highly modular gene delivery system. These complexes can be sterically stabilized via PEGylation [PEG: poly (ethylene glycol)] into nanoparticles (NPs) and targeted to specific tissues and cell types via the conjugation of an affinity ligand. However, there are currently no guidelines on how to effectively navigate the large space of compositional parameters that modulate the specific and nonspecific binding interactions of peptide-targeted NPs with cells. Such guidelines are desirable to accelerate the optimization of formulations with novel peptides. Using PEG-lipids functionalized with a library of prototypical tumor-homing peptides, we varied the peptide density and other parameters (binding motif, peptide charge, CL/DNA charge ratio) to study their effect on the binding and uptake of the corresponding NPs. We used flow cytometry to quantitatively assess binding as well as internalization of NPs by cultured cancer cells. Surprisingly, full peptide coverage resulted in less binding and internalization than intermediate coverage, with the optimum coverage varying between cell lines. In, addition, our data revealed that great care must be taken to prevent nonspecific electrostatic interactions from interfering with the desired specific binding and internalization. Importantly, such considerations must take into account the charge of the peptide ligand as well as the membrane charge density and the CL/DNA charge ratio. To test our guidelines, we evaluated the in vivo tumor selectivity of selected NP formulations in a mouse model of peritoneally disseminated human gastric cancer. Intraperitoneally administered peptide-tagged CL–DNA NPs showed tumor binding, minimal accumulation in healthy control tissues, and preferential penetration of smaller tumor nodules, a highly clinically relevant target known to drive recurrence of the peritoneal cancer.

Effect of bilayer charge on lipoprotein lipid exchange.

Lipoproteins play a key role in the onset and development of atherosclerosis, the formation of lipid plaques at blood vessel walls. The plaque formation, as well as subsequent calcification, involves not only endothelial cells but also connective tissue, and is closely related to a wide range of cardiovascular syndromes, that together constitute the number one cause of death in the Western World. High (HDL) and low (LDL) density lipoproteins are of particular interest in relation to atherosclerosis, due to their protective and harmful effects, respectively. In an effort to elucidate the molecular mechanisms underlying this, and to identify factors determining lipid deposition and exchange at lipid membranes, we here employ neutron reflection (NR) and quartz crystal microbalance with dissipation (QCM-D) to study the effect of membrane charge on lipoprotein deposition and lipid exchange. Dimyristoylphosphatidylcholine (DMPC) bilayers containing varying amounts of negatively charged dimyristoylphosphatidylserine (DMPS) were used to vary membrane charge. It was found that the amount of hydrogenous material deposited from either HDL or LDL to the bilayer depends only weakly on membrane charge density. In contrast, increasing membrane charge resulted in an increase in the amount of lipids removed from the supported lipid bilayer, an effect particularly pronounced for LDL. The latter effects are in line with previously reported observations on atherosclerotic plaque prone regions of long-term hyperlipidaemia and type 2 diabetic patients, and may also provide some molecular clues into the relation between oxidative stress and atherosclerosis.

Emulsion Electrospinning of Polytetrafluoroethylene (PTFE) Nanofibrous Membranes for High-Performance Triboelectric Nanogenerators.

Electrospinning is a simple, versatile technique for fabricating fibrous nanomaterials with the desirable features of extremely high porosities and large surface areas. Using emulsion electrospinning, polytetrafluoroethylene/polyethene oxide (PTFE/PEO) membranes were fabricated, followed by a sintering process to obtain pure PTFE fibrous membranes, which were further utilized against a polyamide 6 (PA6) membrane for vertical contact-mode triboelectric nanogenerators (TENGs). Electrostatic force microscopy (EFM) measurements of the sintered electrospun PTFE membranes revealed the presence of both positive and negative surface charges owing to the transfer of positive charge from PEO which was further corroborated by FTIR measurements. To enhance the ensuing triboelectric surface charge, a facile negative charge-injection process was carried out onto the electrospun (ES) PTFE subsequently. The fabricated TENG gave a stabilized peak-to-peak open-circuit voltage (Voc) of up to ∼900 V, a short-circuit current density (Jsc) of ∼20 mA m-2, and a corresponding charge density of ∼149 μC m-2, which are ∼12, 14, and 11 times higher than the corresponding values prior to the ion-injection treatment. This increase in the surface charge density is caused by the inversion of positive surface charges with the simultaneous increase in the negative surface charge on the PTFE surface, which was confirmed by using EFM measurements. The negative charge injection led to an enhanced power output density of ∼9 W m-2 with high stability as confirmed from the continuous operation of the ion-injected PTFE/PA6 TENG for 30 000 operation cycles, without any significant reduction in the output. The work thus introduces a relatively simple, cost-effective, and environmentally friendly technique for fabricating fibrous fluoropolymer polymer membranes with high thermal/chemical resistance in TENG field and a direct ion-injection method which is able to dramatically improve the surface negative charge density of the PTFE fibrous membranes.

Direct measurement of surface charge distribution in phase separating supported lipid bilayers.

The local surface charge density of the cell membrane influences regulation and localization of membrane proteins. The local surface charge density could, until recently, not be measured directly under physiological conditions, and it was largely a hypothetical yet very important parameter. Here we use unsaturated lipids of a distinct charge (DOTAP, DOPC, and DOPG) and a neutral fully saturated lipid (DPPC) to create model membranes with phase separating domains of a defined charge. We then apply quantitative surface charge microscopy (QSCM) to investigate the local surface charge density; this is a technique based on a scanning ion conductance microscope (SICM) capable of measuring surface charge density with nanoscale lateral resolution. We are able to clearly distinguish lipid domains from charge and topography in all three model membranes. The measured surface charge densities furthermore reveal that disordered domains formed by charged lipids are in fact not only impure, but also incorporate uncharged saturated lipids. We estimate that at least 30% of disordered domains in DOPG : DPPC and DOTAP : DPPC will be DPPC. These ratios could present a limit for the formation of charged domains in lipid membranes.

Electrochemical Properties and Antibacterial Activity of Polyvinyl Chloride Supported Silver Molybdate Ion-Exchange Composite Membrane

Polyvinyl chloride supported silver molybdate composite material is used to develop by solution casting method. This membrane was characterized by various instrumental techniques such as Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) analyses. These characterizations are used to understand the functional groups,thermal stability, surface morphology, porosity, ion transportation etc. The electrochemical study of membrane showed that the ionic potentials decrease by increasing the concentration of electrolyte solutions while the surface charge density of membrane followed the reverse order. It indicated that the membrane is showing negative charge property. Electrochemical parameters of membrane like surface charge density, transport number, mobility ratio, charge effectiveness etc are determined by TMS and Nernst theoretical equations.

Selective ion-permeation through strained and charged graphene membranes

By means of molecular dynamics simulations and density functional theory calculations, we demonstrate that stretched and charged graphene can act as ion sieve membranes. It is observed that loading 30% strain on graphene can induce pores in the dense electron cloud to allow ions to pass through the aromatic rings. Meanwhile, a charged surface is helpful to peel the hydration layers from the ions and decrease the energy barrier for ion translocation through nanopores. Our results suggest that with a membrane charge density of 6.80 e nm−2, Li+ can be highly purified from the mixed solution including Li+, K+, Na+ and Cl− ions. Further increasing the charge density to 15.78 e nm−2 can obtain excellent Na+/K+ selectivity. The potential of mean force profiles of ion permeation reveal that the potential for each ion is quite different. By fine tuning membrane charge density, pristine monolayer graphene can act as ion sieves with both high permeability and high selectivity.

Impedance spectroscopy and membrane potential analysis of microfiltration membranes. The influence of surface fractality

In this work, the proper charge density of a microfiltration membrane has been determined by using two different methods. Firstly, the ionic transport of a KCl solution has been investigated by simultaneous measurements of saline flux and membrane potential (MP) resulting from a concentration gradient through the membrane. A simple model, including all the relevant contributions to the global electrical potential drop, allowed a calculation of transport numbers and membrane charge density.The response of ions inside the membrane to an oscillating electrical potential has been analyzed by impedance spectroscopy (or electrical impedance spectroscopy EIS). A quite simple experimental EIS design allowed, by taking into account MP measurements too, an easy assignation of an equivalent circuit. After a careful analysis of EIS results, it was possible to evaluate the electrical conductivity inside the pores and the charge density. Both were found to be quite similar to the values obtained from MP alone. This agreement of EIS results with the MP ones, that are much simpler to deal with, confirms the accuracy of EIS to study the electrical properties of microfiltration membranes.The influence of electrode roughness and, in our EIS cell, the membrane roughness, on the constant phase element (CPE) of the equivalent circuit has been proved. Within this frame, the roughness fractal dimension of the membrane surface could be determined from EIS measurements. It resulted in fair agreement with the atomic force microscopy (AFM) determination.

Super-swelled lyotropic single crystals

Lipids self-assemble into diverse supramolecular structures that exhibit thermotropic and/or lyotropic behavior. Lyotropic mesophases, where membranes conform to periodic minimal surfaces dividing two nonpenetrating aqueous subspaces, are arguably one of the most intriguing phases of lipid materials. Traditional 3D bicontinuous cubic lipid materials appear as a polycrystal of varying degrees of order. When exposed to water, the properties of the molecular building blocks of the membrane determine specific swelling limits setting the lattice dimensions at about 15 nm. This limited swelling severely impairs their application as delivery vehicles of large drugs or as matrices for guiding protein crystallization. We report the discovery of self-assembly strategies leading to the emergence of lipid bicontinuous single crystals with unprecedented swelling capacity. The conventional strategy to increase unit cell size is tweaking membrane composition to include charged building blocks, a process to achieve electrostatic-driven swelling. In this paper, we demonstrate that controlling self-assembly external conditions when coupled to membrane composition yields 3D bicontinuous cubic phases that swell up to lattice dimensions of 68 nm. Importantly, and contrary to what is perceived for soft lyotropic materials in general, the self-assembly methodology enables the development of large super-swelled monocrystals. Utilizing small-angle X-ray scattering and cryoelectron microscopy, we underpin three crucial factors dictating the stabilization of super-swelled lipid bicontinuous cubic single crystals: (i) organic solvent drying speed, (ii) membrane charge density, and (iii) polyethylene glycol-conjugated lipids amount.

Synthesis and electrochemical behaviour of polyvinyl chloride based Tin (IV) TungstoArsenate composite membrane for purification of aqueous contaminated electrolyte solutions

Polyvinyl chloride (PVC) based Tin-Tungusto-Arsenate (TTA) composite membrane was designed through the important die casting process. The used inorganic material was synthesized by sol-gel method of material synthesis. The synthesized composite membrane has the combination of PVC polymer and TTA inorganic material that shows novel and better chemical plus mechanical stabilities. The synthesized membrane is differentiated and characterized by their chemical composition, ion exchange capacity, x-ray diffraction (XRD), fourier transform infrared (FTIR) spectroscopy, thermo gravimetric (TGA), differential thermal (DTA) analysis and scanning electron microscopy (SEM). These characterizations verified the functional groups, material nature, thermal stability, surface structure, porosity, elemental percentage, ion transportation etc. Membrane shows good ion-exchange capacity, high stability, reproducibility and selectivity for salts and heavy metal ions. To observe the electrochemical studies of membrane KCl, NaCl and LiCl electrolyte solutions are experimentally analyzed and the obtaining data has been theoretically applied. The charge density of membrane shows KCl > NaCl > LiCl order whereas observed potential, transport number and mobility ratio follows KCl < NaCl < LiCl order.

Osmotic Stress Induced Desorption of Calcium Ions from Dipolar Lipid Membranes.

The interaction between multivalent ions and lipid membranes with saturated tails and dipolar (net neutral) headgroups can lead to adsorption of the ions onto the membrane. The ions charge the membranes and contribute to electrostatic repulsion between them, in a similar manner to membranes containing charged lipids. Using solution X-ray scattering and the osmotic stress method, we measured and modeled the pressure-distance curves between partially charged membranes containing mixtures of charged (1,2-dilauroyl-sn-glycero-3-phospho-l-serine, DLPS) and dipolar (1,2-dilauroyl-sn-glycero-3-phosphocholine, DLPC) lipids over a wide range of membrane charge densities. We then compared these pressure-distance curves with those of DLPC membranes in the presence of 10 mM CaCl2. Our data and modeling show that when low osmotic stress is applied to the DLPC bilayers, the membrane charge density is equivalent to that of a charged membrane containing ca. 4 mol % DLPS and 96 mol % DLPC. As the osmotic stress increased, the charge density of the DLPC membrane decreased and resembled that of a membrane containing ca. 1 mol % DLPS. These data are consistent with desorption of the calcium ions from the DLPC membrane with increasing osmotic stress.

Synthesis of Fe-Ag/f-MWCNT/PES nanostructured-hybrid membranes for removal of Cr(VI) from water

Abstract This work describes the synthesis of Fe-Ag/functionalized-multiwalled carbon nanotube (f-MWCNT)/polyethersulphone (PES) nanostructured-hybrid membranes via a modified phase inversion method and its permeability properties. As-synthesized MWCNTs were first treated with acid and then Fe and Ag nanoparticles (Fe-Ag NPs) were uniformly dispersed on the surface of the f-MWCNTs using a microwave-assisted polyol method prior to addition to the PES polymer matrix. The addition of Fe-Ag/f-MWCNTs into the PES polymer increased the surface roughness of PES membranes and resulted to a higher hydrophilicity. Thermal stability and crystallinity properties of PES were significantly improved. The Fe-Ag/f-MWCNTs enhanced the surface charge density of the PES membranes and were found not to leach from PES. Performance evaluation studies revealed that the addition of Fe-Ag/f-MWCNTs into the PES polymer matrix increased water flux from 26.5 to 36.9 L/m 2 h and improved the rejection of Cr 6+ ions (up to 94%) in a cross-flow system. Furthermore, the addition of Fe-Ag/f-MWCNTs improved fouling resistance of PES membranes. The improved properties of these hybrid membranes make the ideal for use as either point-of-use or end-of-use water purification system for production of potable water.

Electron Transport Between an Electrode and Red Blood Cells

It is well known that red blood cell (RBC) membranes are charged negatively and surrounded by an electric double layer (EDL). The electrochemical nature of blood cell interaction with foreign materials that are electrical conductors is due to the interaction of blood cell EDL with the foreign material. Numerous investigations of the above systems have led to a hypothesis of charge transfer occurring between the cell and the electrode [1]; however, there has been no experimental corroboration of this phenomenon to date. The present work attempted to bridge this gap by investigating the electrochemical behavior in the Pt/RBC system in isotonic (physiologic) saline solution (aqueous 0.15 M NaCl), where the above solution served as the background electrolyte. Erythrocyte suspension for experiments was prepared from donor whole blood by centrifugation using a CR 3.12 (Jouan, France) centrifuge at 4-6 °C and 1500 g. The erythrocytes were subsequently washed with isotonic physiologic saline to remove residual blood plasma. Erythrocyte counts in suspensions were measured using a Beckman Coulter AcT Diff 2 hematology analyzer. Erythrocyte counts in suspensions used in the electrochemical cell were 4.0×1012 L–1. Polarization and microcoulometric measurements were performed with an IPC Pro L potentiostat (ZAO «Kronas») in a three-electrode electrochemical cell, with the cathodic and anodic chambers separated by a polypropylene porous membrane. A platinum microelectrode and platinum wire mesh were used as the working and counter electrode, respectively. Potentials were measured against a saturated silver/silver chloride reference electrode. For microcoulometric measurements, the electrochemical cell was filled with the above background electrolyte, and the platinum electrode was polarized to a set potential for 30 min; subsequently, the erythrocyte suspension was added to the background electrolyte, and microcoulometric data were recorded for 30 min. Oxygen was removed from the background electrolyte by the addition of Na2SO3 to a final sulfite concentration of 0.02 M in the electrochemical cell. The residual quantity of Na2SO3 was monitored in the cell via the sulfite/sulfate anode oxidation peak. A considerable difference in the charge Q was found to be required to maintain the same cathode potential of Pt electrode in the background electrolyte and in the background electrolyte containing the RBC suspension, with the difference between those measured values (ΔQ= Q saline – Q saline+RBC) varying depending on the working electrode potential (Fig. 1(a)). It turned out that a similar phenomenon occurs in the anodic range (Fig. 1(a)). Thus, electrochemical activity of erythrocytes in isotonic saline was shown at the platinum electrode for cathode potentials more negative than E = –150 mV, and for anode potentials more positive than E= +200 mV. This observation is very important because it provides the first experimental corroboration of electron transport between the electrode and erythrocytes. It should also be emphasized that electrochemical processes were not observed between –150 mV and +200 mV (no changes of charge Q), which indicates relative indifference of the electrode material with respect to the erythrocytes. Additionally, electron transport without polarization was observed on the Pt electrode. It was observed that open-circuit potential (OCP) values of Pt in isotonic saline changed with the addition of RBC suspension to saline. These data for the Pt electrode are shown in Fig. 1(b). Negative shifts of OCP for Pt electrode were observed after a addition of RBC suspension to saline with ∆E= 106 mV. This phenomenon can be rationalized by the leveling of charge densities of erythrocyte membranes and electrode surface in the electrostatic field of the [electrode/erythrocyte] system. Thus, electron transport occurred from the erythrocyte membrane to the electrode. Reference [1] Sawyer P. N. et al. Electrochemical Aspects of Thrombogenesis-Bioelectrochemistry Old and New // Journal of The Electrochemical Society. – 1974. – V. 121. – №. 7. – P. 221C-234C. Figure 1

Determining Interactions of Cationic Membrane Nanoparticles with Hydrophobic Drug Cargo and their Mechanisms of Drug Delivery to Cells

Paclitaxel (PTXL), a member of the taxane family of mitotic inhibitors, is a widely used cancer drug. The first PTXL clinical incarnation (Taxol®) employs the non-ionic surfactant, Cremophor® EL—which itself causes hypersensitivity reactions—to solubilize hydrophobic PTXL. Second generation alternatives to deliver PTXL include Abraxane® and EndoTAG® (a liposomal formulation), which achieve limited passive tumor targeting and are still associated with typical chemotherapy side effects. In order to make a substantial therapeutic improvement, delivery vehicles must concentrate more PTXL in tumors and interact less with healthy tissue (Int J Pharm Sci Rev Res 2015, 31, 205; J Cont Release 2012, 163, 322; Chem Rev 2016, 116, 3883). Lipid nanoparticles have many advantages as drug delivery agents including a diverse set of lipid building blocks to tune physical and chemical properties, as well as their ease of modular fabrication. We demonstrate the ability to alter the drug-loading capacity of liposomes and the nanoparticle-cell interactions by changing the lipid composition to affect membrane charge density, steric stabilization, hydrophobic domain disorder, and lipid shape (which determines membrane curvature). Here, we present results that indicate the importance of tail structure for hydrophobic drug loading and retention. We have also observed a non-monotonic drug delivery dependence on the amount of PTXL incorporated into liposomes. Preliminary results reveal a significant divergence from the known tenets governing liposome-based gene delivery to those that determine small molecule hydrophobic drug delivery. In order to develop a set of design principles for the latter, a systematic understanding of how liposome formulation dictates the nanoparticle's subsequent path in vitro and in vivo is essential. Novel liposome formulations achieve in vitro outcomes equal to and better than the stage III formula EndoTAG®.

In situ electrical monitoring of cancer cells invading vascular endothelial cells with semiconductor‐based biosensor

Cellular dynamics is very closely related to ionic behaviors, most of which have been hardly monitored in real time, whereas semiconductor-based biosensors have the unique advantage of direct detection of ionic charges in a real-time and noninvasive manner. In this study, we monitored the invasion process of cancer cells into the vascular endothelial layer in real time by a label-free method using a field-effect transistor (FET) biosensor. Endothelial cells were cultured on the sensing surface of the FET gate, to form a basement membrane between the endothelial cells and the sensing surface. When invasive cancer cells (HeLa cells) approached the endothelial cell-coated gate FET biosensor, a change in the surface potential was clearly detected using the FET biosensor. This is because HeLa cells, which invaded the endothelial cell layer, reduced the molecular charge density in the basement membrane by decomposing it. A platform based on the cell-coated gate FET biosensor is suitable for real-time and noninvasive monitoring of cellular dynamics based on intrinsic ionic charges.