Bilayered Construct Research Articles

Development of bi-layer vascular constructs by combining polymer biomaterial and cellular self assembly

Development of bi-layer vascular constructs by combining polymer biomaterial and cellular self assembly

Lipid Reconstitution-Enabled Formation of Gold Nanoparticle Clusters for Mimetic Cellular Membrane

Gold nanoparticles (AuNPs) encapsulated within reconstituted phospholipid bilayers have been utilized in various bioapplications due to their improved cellular uptake without compromising their advantages. Studies have proved that clustering AuNPs can enhance the efficacy of theranostic effects, but controllable aggregation or oligomerization of AuNPs within lipid membranes is still challenging. Here, we successfully demonstrate the formation of gold nanoparticle clusters (AuCLs), supported by reconstituted phospholipid bilayers with appropriate sizes for facilitating cellular uptake. Modulation of the lipid membrane curvatures influences not only the stability of the oligomeric state of the AuCLs, but also the rate of cellular uptake. Dynamic light scattering (DLS) data showed that 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), with its relatively small head group, is crucial for establishing an effective membrane curvature to encapsulate the AuCLs. The construction of phospholipid bilayers surrounding AuCLs was confirmed by analyzing the secondary structure of M2 proteins incorporated in the lipid membrane surrounding the AuCLs. When AuCLs were incubated with cells, accumulated clusters were found inside the cells without the lipids being removed or exchanged with the cellular membrane. We expect that our approach of clustering gold nanoparticles within lipid membranes can be further developed to design a versatile nanoplatform.

Fabrication and characterization of nano-fibrous bilayer composite for skin regeneration application

Full thickness wound healing with minimal scarring and complete restoration of normal skin properties still remains as a clinical challenge. In this study, a bilayer skin substitute has been fabricated to biomimic the microstructure of natural extracellular matrix of the skin. Human amniotic membrane (HAM) and silk fibroin nano-fibers were combined to produce bilayer construct, which was further treated and characterized. HAM was obtained from healthy mothers and de-epithelized by means of fine enzymatic method to preserve the extracellular structure. Fibroin protein was extracted from fresh Bombyx mori cocoons and transformed to uniform nano-fiberous structure, which was used as a coating layer on the de-epithelized membrane. Surface modification through oxygen plasma treatment was attempted to further induce hydrophilicity. Subsequently, scaffolds were fully characterized in terms of morphology, mechanical properties, hydrophilicity and cell culture response. Histological and immunohistological staining demonstrated localization of fibronectin, cell denudation and structural integrity of HAM after de-epithelization. Scanning electron microscopy images showed bead-free silk fibroin nano-fibers with the average diameter of 250nm. Water contact angle of bilayer scaffolds reduced dramatically to 26.34° after oxygen plasma treatment, which is correlated with more hydrophilic surface. Due to fibroin nano-fiber coating, mechanical properties of HAM improved significantly. Tensile Young’s modulus and tensile strength increased from 16.14MPa and 68.46MPa to 25.69MPa and 108.03MPa, respectively. 14days in vitro cultivation of mouse embryonic fibroblasts on the scaffolds revealed that bilayer scaffolds are able to support cell attachment and proliferation. Plasma-etched scaffolds provided the best niche for cell-matrix crosstalk by allowing cells to penetrate beneath the pores and to integrate in fibers direction. The obtained results suggest that the presented nano-fibrous bilayer composite based on HAM is a potential substitute for skin regeneration application.

Bilayered construct for simultaneous regeneration of alveolar bone and periodontal ligament.

Periodontitis is an inflammatory disease that causes destruction of tooth-supporting tissues and if left untreated leads to tooth loss. Current treatments have shown limited potential for simultaneous regeneration of the tooth-supporting tissues. To recreate the complex architecture of the periodontium, we developed a bilayered construct consisting of poly(caprolactone) (PCL) multiscale electrospun membrane (to mimic and regenerate periodontal ligament, PDL) and a chitosan/2wt % CaSO4 scaffold (to mimic and regenerate alveolar bone). Scanning electron microscopy results showed the porous nature of the scaffold and formation of beadless electrospun multiscale fibers. The fiber diameter of microfiber and nanofibers was in the range of 10 ± 3 µm and 377 ± 3 nm, respectively. The bilayered construct showed better protein adsorption compared to the control. Osteoblastic differentiation of human dental follicle stem cells (hDFCs) on chitosan/2wt % CaSO4 scaffold showed maximum alkaline phosphatase at seventh day followed by a decline thereafter when compared to chitosan control scaffold. Fibroblastic differentiation of hDFCs was confirmed by the expression of PLAP-1 and COL-1 proteins which were more prominent on PCL multiscale membrane in comparison to control membranes. Overall these results show that the developed bilayered construct might serve as a good candidate for the simultaneous regeneration of the alveolar bone and PDL.

Bi-layered porous constructs of PCL-coated 45S5 bioactive glass and electrospun collagen-PCL fibers

A simple yet promising approach to construct bi-layered scaffolds using bioactive ceramics and biodegradable polymers is presented. This method involves two versatile fabrication techniques used in the field of TE: foam replication process and electrospinning. By the foam replication method, three-dimensional 45S5 bioactive glass (BG)-based scaffolds with high porosity, in the range of 95.8 ± 0.9 %, were produced. To improve the mechanical properties of the BG scaffolds, dip-coating using polycaprolactone (PCL) was performed, which led to a significant increase in the compressive strength of the scaffolds. In order to develop a bi-layered construct, bead-less submicrometric fibers of collagen-PCL were electrospun over the PCL-coated BG scaffolds. Surface morphology, surface properties and mechanical strength of the bi-layered construct were evaluated using scanning electron microscopy analysis, contact angle measurements and compressive strength testing, respectively. In vitro degradation of the collagen-PCL fibers in phosphate buffered saline and in vitro bioactivity of the bi-layered constructs in simulated body fluid were investigated. Formation of hydroxyapatite on the PCL-coated BG and along the morphology of the collagen-PCL fibers was ascertained using different characterization techniques. The bi-layered construct is intended for interface tissue engineering applications where the PCL-coated BG scaffold, which is highly bioactive, can serve as a support for the bone side and the composite collagen-PCL submicrometric fibers are intended for the cartilage side.

Osteogenesis and chondrogenesis of biomimetic integrated porous PVA/gel/V-n-HA/pa6 scaffolds and BMSCs construct in repair of articular osteochondral defect.

A novel bi-layered osteochondral scaffold, including of PVA/Gel/V layer for the cartilage and n-HA/PA6 layer for the subchondral bone, has been proposed to evaluate the potential of the engineered of osteochondral grafts in repairing articular osteochondral defects in rabbits. The two different layers of the scaffolds were seeded with allogenic bone marrow-derived stem cells (BMSCs), which were chondrogenically and osteogenically induced respectively. The critical-size osteochondral defects were created in the knees of adult rabbits. The defects were treated with cell-bi-layered constructs (Group A), bi-layered constructs (Group B) and untreated group C as control group. The adhesion, proliferation and differentiation of BMSCs were demonstrated by immunohistochemical staining and scanning electron microscopy (SEM) in vitro. Cell survival was tracked via fluorescent labeling in vivo. Overall, the porous PVA/Gel/V-n-HA/PA6 scaffold was compatible and had no negative effects on the BMSCs in vitro culture. The cell-bi-layered scaffolds showed superior repair results as compared to the control group using gross examination and histological assessment. With BMSCs implantation, the two different layers of the composite biomimetic scaffolds provided a suitable environment for cells to form respective tissue. Simultaneously, the RT-PCR results confirmed the expression of specific extracellular matrix (ECM) markers for cartilaginous or osteoid tissue. This investigation showed that the porous PVA/Gel/V-n-HA/PA6 scaffold is a potential matrix for treatment of osteochondral defects, and the method of using chondrogenically and osteogenically differentiated BMSCs as seed cells on each layer might be a promising strategy in repair of articular osteochondral defect due to enhanced chondrogenesis and osteogenesis.

Substantial spatial heterogeneity and tunability of glass transition temperature observed with dense polymer brushes prepared by ARGET ATRP

Dense polystyrene (PS) brushes were synthesized on silica wafers via a “grafting from” technique using activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Spectroscopic ellipsometry and fluorescence spectroscopy were used to investigate the effect of nanoscale confinement on the glass transition temperature (Tg) and its distribution in dense PS brushes and bilayer constructs of brushes and freely deposited PS films. Single-layer PS brushes exhibit an overall average Tg that is nearly invariant with thickness down to 11 nm, with Tg values of the dense brushes differing by no more than 2 °C from those of bulk PS of the same molecular weight as that of the brush. These results differ greatly from those obtained with freely deposited PS films that show major Tg reductions with confinement. Distributions of Tgs were also studied by fluorescence in dense, ∼70-nm-thick PS brushes. Relative to Tg,bulk, chain segments within 10 nm of the substrate exhibit a ∼36 °C increase in Tg while segments within 5 nm of the free surface exhibit a 14 °C decrease in Tg. Fluorescence was also used to characterize the tunability of Tg within a single layer of bilayer constructs. As brush thickness increases from 13 to 94 nm, the Tg of a 15-nm-thick PS overlayer film decreases from 100 °C to 87 °C; in contrast, as the overlayer PS film thickness increases from 0 to 101 nm, the Tg of an 11-nm-thick underlayer PS brush increases from 98 °C to 126 °C. These results are compared with the few previous experimental reports of Tg-confinement effects of densely grafted PS brushes and bilayer constructs of brushes and films.

An in vitro priming step increases the expression of numerous epidermal growth and migration mediators in a tissue-engineering construct.

An FDA-approved, prototypic, living, bilayered skin construct (BSC) has been used for non-healing wounds. Using this particular construct as proof of principle, we hypothesized that an in vitro 'priming' step may enhance its repertoire of expression of key mediators and genes. The priming step used here was incubation in Dulbecco's modified Eagle's medium (DMEM) for 24 h at 37°C and 5% CO2 , with or without construct meshing. Microarray and ingenuity pathway analysis (IPA) showed that >1000 genes were overexpressed by the priming step, including interleukin 6 (IL-6), which plays important roles in wound healing. Genes highly overexpressed by priming were those involved in epidermal proliferation and migration. Quantitative real-time PCR (qRT-PCR), immunostaining and western blots verified the results. An epiboly assay (epidermal migration over dermis) showed that BSC epiboly was inhibited by IL-6 neutralizing antibody. Back wounds of nude mice were treated with primed or control BSCs for 3 days prior to harvesting; primed BSCs showed a significantly (p = 0.006) greater level of epidermal migration vs unprimed. Our study demonstrates that an in vitro priming step induces wound healing-related genes in the BSC, leading to a construct that could prove more effective in stimulating wound healing. Copyright © 2014 John Wiley & Sons, Ltd.

Double Layer Porous Structures by an Injection Molding/Particulate Leaching Approach

SummaryScaffolds as a temporary substitute for the extracellular matrix should provide interconnected pores and often require a multilayer design to mimic the geometry and biomechanics of the target tissue. Here, it was explored whether bilayer porous structures can be obtained by a process free of organic solvents and how the individual layers contribute to the overall elastic properties. Porous layers were obtained from polyurethane (PU) blends with polyvinyl alcohol (PVA), which were immersed in water after sequential injection molding. Pore sizes in both layers ranged from 1 μm to 100 μm with an average of 22 ± 1 μm at a porosity of 50 ± 5% in combination with a high interconnectivity. The pore sizes were tailored by applying an annealing treatment, while the porosity was kept constant. Mechanical properties of the individual layers and the double layer constructs as determined by tensile tests suggested that the overall elasticity of the compact bilayer construct and porous bilayer construct was in agreement with the predicted overall elasticity according to the rule of mixtures. The porous bilayer model system will serve as a basis for determining structure‐property relationships with respect to pore size, porosity as well as mechanical properties of individual layers and in this way enable a knowledge‐based design of layered scaffolds.

Factors Influencing Efficacy of Bilayered Cell Therapy.

Objective: Diabetic foot ulcers (DFUs) that fail to heal with standard care should be treated with advanced wound care products. Efficacy of advanced therapies is dependent on many factors. A secondary analysis of pivotal trial data for a bilayered cellular construct used in the treatment of DFU was undertaken to determine if glycemic control and other factors had an effect on time to healing. Approach: We analyzed the effect of age, gender, diabetes type, insulin usage, body mass index, smoking, initial and ending glycohemoglobin (HgbA1c), Charcot deformity, and wound area, duration, and location on likelihood of healing for wounds treated with bilayered cellular construct (BLCC). Results: In those treated with BLCC, initial wound area (cm2), age, and history of Charcot deformity were found to significantly affect healing. Neither initial HgbA1c nor change in HgbA1c was associated with healing. The bilayered product was found to be equally effective regardless of initial or change in HgbA1c levels (p-values 0.94 and 0.44, respectively). In the control group, initial HgbA1c, insulin usage, female gender, and wound location at the toes significantly influenced healing. Innovation: BLCC subgroup analysis to elucidate selection criteria allowing for targeted use of advanced products on those more likely to respond as well as direct further research into prognostic indicators for BLCC-treated patients. Conclusion: The bilayered cellular construct product remains equally effective regardless of initial or change in HgbA1c levels. Further specific research into the effect of glucose control and other factors on the effectiveness of different advanced DFU treatment products is recommended.

Investigation of biofilm formation on polyethylene in a diesel/biodiesel fuel storage environment

Biodiesel usage as in the environment as an alternative to fossil fuels or in biodiesel/diesel blends requires an understanding of the potential effects of its addition on the integrity of the infrastructure used for fuel storage. Polyethylene is one of the most common materials for the manufacturing of fuel storage tanks. Due to the insoluble nature of polyethylene, biofilm formation on its surface boosted by the presence of biodiesel could potentially contribute to its degradation. In this study, the effect of biodiesel concentration on biofilm development on linear low-density polyethylene (LLDPE), cross-linked polyethylene (XLPE) and a bilayer construction of linear-low density polyethylene and polyamide-11 (LLDPE/PA) was studied. Polymers were exposed to biodeterioration conditions during a 200days in a simulated fuel storage tank. Excess of water and blends of diesel/biodiesel (0%, 25%, 50%, 75% and 100%) as a carbon source were employed to simulate the conditions found in the bottom of fuel storage tanks, where the presence of water is common as result of condensation. Microorganisms obtained from a diesel storage facility were used as inoculum. Biofilm growth and viability were quantified by a crystal violet assay and hydrolysis of fluorescein diacetate, respectively. Results show that although there is greater accumulation of biofilm material in pure biodiesel samples metabolic activity is higher in pure diesel ones. Microbial community structure and composition were studied by community level physiological profiling (CLPP) and 16s rDNA sequencing. Principal component analysis of CLPP revealed that both biodiesel concentration and polymer type affect the structure and metabolic capabilities of biofilm communities. These results were confirmed by comparison of libraries of 16s rDNA for different polymers growing at different biodiesel concentrations. Genera isolated in the biofilm were characterized either by their ability to degrade hydrocarbons, produce surfactants or degrade polyethylene or polyamide-11. The results of this study may lead to a better understanding of microbial effects on storage materials for diesel/biodiesel blends.

Thermodynamic Characterization of the Association of Cholesterol with Phospholipids with Varying Degrees of Unsaturation

The preferential association of cholesterol with saturated phospholipids, especially sphingomyelins, is responsible for the formation of coexisting fluid phases in lipid bilayers, and is believed to play a critical role in the existence of more ordered membrane domains in biological systems, sometimes termed lipid rafts. The coexistence of separate fluid phases in model bilayer constructs must be an equilibrium phenomenon, and titration of bilayer cholesterol content allows for thermodynamic characterization of cholesterol partitioning. To achieve a more complete understanding of the parameters governing phase separation, high sensitivity isothermal titration calorimetry was employed to investigate the effects of degree of unsaturation at the sn-2 position of a series of biologically relevant phospholipids. Cholesterol was either extracted from or added to bilayers of a single phospholipid component, allowing determination of a partition constant and enthalpy of transfer. By varying the relative cholesterol content of the bilayer, the non-ideal partitioning behavior was also investigated. It was found that the relative affinity of cholesterol for the bilayer decreased in a generally monotonic manner in response to increasing unsaturation, with the exception that both 20:4n6 and 22:6n3 acyl chains at the sn-2 position showed similar partition constants and enthalpies of transfer. The partitioning of cholesterol was also measured in membranes composed of mixtures of 18:0,22:6 PC and sphingomyelin. Values of both the partition constant and enthalpy of transfer extrapolated to pure sphingomyelin matched those previously reported for mixtures of 16:0,18:1 PC and sphingomyelin. This result suggests that the association of cholesterol and sphingomyelin is largely unaffected by other phospholipids in the bilayer.

Manufacturing and Characterization of Controlled Foaming of Single Layers in Bilayer Constructs Differing in Pore Morphology

SummaryBilayer porous constructs from degradable polymers are considered as scaffold materials with beneficial elastic properties for cell culture application in tissue engineering. Here, we explored whether such bilayer constructs, in which only one layer was porous while the other layer enhanced the compressive mechanical properties, could be created by specific foaming of one layer with supercritical carbon dioxide (scCO2). The bilayer constructs of a poly(L‐lactide) (PLLA) and a poly(ϵ‐caprolactone) (PCL) layer were prepared by sequential injection molding and subsequent specific foaming with scCO2. Foaming conditions of T = 45 °C and P = 100 bar resulted in the formation of a porous PCL layer and a non‐porous PLLA layer. When the time intervals of the foaming process were increased the pore size was increased and the shape of the pores was changed from a circular to an unidirectional lamellar shape, which reduced the compressive elastic modulus of the porous PCL layer. Furthermore, the foaming process increased the adhesion force between the PLLA and PCL layers, which was attributed to a higher degree of diffusion of molten PCL into the PLLA layer. In summary, it was demonstrated that scCO2 foaming is a suitable method for the creation of layered scaffolds with only one foamed layer, in which the compressive elastic modulus and pore morphology of single porous layers can be controlled by the time interval of scCO2 process.

Generation of osteochondral tissue constructs with chondrogenically and osteogenically predifferentiated mesenchymal stem cells encapsulated in bilayered hydrogels

This study investigated the ability of chondrogenic and osteogenic predifferentiation of mesenchymal stem cells (MSCs) to play a role in the development of osteochondral tissue constructs using injectable bilayered oligo(poly(ethylene glycol) fumarate) (OPF) hydrogel composites. We hypothesized that the combinatorial approach of encapsulating cell populations of both chondrogenic and osteogenic lineages in a spatially controlled manner within bilayered constructs would enable these cells to maintain their respective phenotypes via the exchange of biochemical factors even without the influence of external growth factors. During monolayer expansion prior to hydrogel encapsulation, it was found that 7 (CG7) and 14 (CG14) days of MSC exposure to TGF-β3 allowed for the generation of distinct cell populations with corresponding chondrogenic maturities as indicated by increasing aggrecan and type II collagen/type I collagen expression. Chondrogenic and osteogenic cells were then encapsulated within their respective (chondral/subchondral) layers in bilayered hydrogel composites to include four experimental groups. Encapsulated CG7 cells within the chondral layer exhibited enhanced chondrogenic phenotype when compared to other cell populations based on stronger type II collagen and aggrecan gene expression and higher glycosaminoglycan-to-hydroxyproline ratios. Osteogenic cells that were co-cultured with chondrogenic cells (in the chondral layer) showed higher cellularity over time, suggesting that chondrogenic cells stimulated the proliferation of osteogenic cells. Groups with osteogenic cells displayed mineralization in the subchondral layer, confirming the effect of osteogenic predifferentiation. In summary, it was found that MSCs that underwent 7days, but not 14days, of chondrogenic predifferentiation most closely resembled the phenotype of native hyaline cartilage when combined with osteogenic cells in a bilayered OPF hydrogel composite, indicating that the duration of chondrogenic preconditioning is an important factor to control. Furthermore, the respective chondrogenic and osteogenic phenotypes were maintained for 28days in vitro without the need for external growth factors, demonstrating the exciting potential of this novel strategy for the generation of osteochondral tissue constructs for cartilage engineering applications.

Advanced stent coating for drug delivery and in vivo biocompatibility

As an effort to alleviate stent-induced cardiovascular injury including restenosis and thrombosis, advanced drug-eluting stent (ADES) with a bilayer construct composed of a top-coat made of collagen and a base-coat incorporated with N-nitrosomelatonin (NOMela)-loaded PLGA nanoparticles has been developed. NOMela is a hydrophobic prodrug of nitric oxide (NO) that is an endogenous anti-platelet compound. ADES was coated with PLGA nanoparticles via either electrophoretic deposition (EPD) technique or dip-coating technique, and their coating characteristics and efficacies were compared. The drug-loading efficacy and in vitro drug-release profiles from ADES were expressed with various variables including the additives to the collagen layer, the number of layers of the collagen top-coat, the hydrophobicity/hydrophilicity of the loaded drug, the coating technique of nanoparticles, and the concentration of coating emulsions in the EPD method. The morphological status of cross-section and surface of ADES was evaluated by laser scanning confocal microscope and scanning electronic microscope. The real-time release profiles of NO were assessed using the NO-microbiosensor. The anti-platelet activity of ADES was evaluated on the rabbit whole blood using an aggregometer. The intima formation and protein expression in aorta were examined using an in vivo rat model. Both collagen and PLGA used in ADES are biodegradable polymers that fully degrade and consequently produce less inflammation responses. NO released from ADES significantly reduced platelet aggregation in the rabbit blood as compared with those exposed to the control stents. ADES coated with a double layer consisted of collagen and PLGA and containing NOMela was less antigenic at the implanted sites and alleviating intima formation and thrombosis. An external exposure of aorta to NO elicits distinct and specific effects on mitogen-activated protein kinase (MAPK) and Ca2+/calmodulin-dependent protein kinase II (CaMKII) activities which evoke the endoplasmic reticulum (ER) stress response. These findings elucidated that coordinate and reciprocal alterations in the protein kinases followed by the ER stress protein expression are an integral feature of the in-stent-mediated cardiovascular injury.

Microstructure evaluation of Ni–SDC synthesized with an innovative method and Ni–SDC/SDC bi-layer construction

Abstract Nickel oxide and samaria-doped ceria based anode material (NiO–SDC) for high temperature ceramic fuel cells was synthesized via an innovative, simplified method using the reaction of metal acetates and ethylene glycol. Ni content in the final product was 55 vol% while the Ce:Sm molar ratio in the SDC (45 vol%) was 80:20. The influences of preparation conditions including the calcination temperature and morphology characteristics of the prepared powders as well as the influence of the sintering temperature on the final microstructure of sintered bodies were investigated with EGA, BET, XRD, a heating microscope and FE-SEM. After calcination at 500 °C, the one-step synthesis gave powdered products with the specific surface area of 72.5 m 2 g −1 . The optimal sintering temperature that ensured relatively high sintered densities and excellent contact between grains was found at 1250 °C. After sintering at 1250 °C, the prepared bi-layer system electrolyte/anode showed the highest contiguity, excellent contact between phases and proper porosity (31.2%) confirmed from SEM micrographs.

Optical dynamics of MgO/Ga4Se3S interface

Abstract A new p–n interface made of p-type MgO as an optical window to the n-type Ga4Se3S crystals is investigated by means of optical reflectance, transmittance and absorbance in the incident light wavelength ( λ ) range of 200–1100 nm. The reflectivity spectral analysis as a function of angle of incidence for MgO, Ga4Se3S and the Ga4Se3S/MgO layers revealed Brewster angles of 75°, 80° and 70° with the corresponding dielectric constants of 13.93, 32.16 and e MgO = 7.55 e Ga 4 Se 3 S , respectively. To remove Brewster condition of reflection and obtain maximum absorption, the light must be incident from the MgO side. A novel light absorbability is observed. Namely, for all λ λ values, while the crystal absorbance decreases significantly, the bilayer absorbance increased by four times in the visible range and three times in the IR range of spectrum. In the MgO layer, two distinct sets of band tails of the localized states with the widths of 2.30 and 1.26 eV are determined from the absorption spectral analysis. These band tails shift up to 2.32 and 1.44 eV when the interface is constructed. In addition, an indirect energy band gaps (Eg) which are located at 3.10, 2.13 and 1.90 eV for the MgO, Ga4Se3S and the Ga4Se3S/MgO layers, respectively, are determined. The Eg value of the crystal shifts by a 0.23 eV upon bilayer construction. The reflection properties, the band tails, the energy gaps and related shifts make the Ga4Se3S/MgO interface attractive for fabrication of solar cells, narrow barrier resonant tunneling diodes or quantum dots, and as an optical detector for tunable types of lasers.

Novel Ultrathin Membranes Composed of Organic Ions.

Until recently, construction of bilayers was an exclusive mission of nature. It requires careful choice of compounds, whose delicate interplay between head group attraction and chain repulsion engenders a truly unique balance over a narrow temperature range. We report the investigation of artificial bilayers composed of long-chained organic ions, such as dodecyltrimethylammonium (DMA(+)) and perfluorooctaonate (PFO(-)). Various ratios of DMA/PFO surfactants result in bilayers of different stability, thickness, area per molecule, and density profiles. In our quest for water filtration, we incorporated aquaporin protein into the DMA/PFO bilayer but did not observe sufficient stability of the system. We discuss further steps to utilize these surfactant bilayers as highly selective, salt-impermeable membranes.

Molecular Dynamics Simulation of Sorbitan Monooleate Bilayers

the initial structures. The layer was duplicated and inverted to make a bilayer. Packmol, 5 a free software useful for the construction of a solvated bilayer, was used to fill water molecules below and above the bilayer at a thickness of 1.5 nm and density of 10 3 kg/m 3 . The resulting structure was subjected to an energy minimization and subsequently equilibrated for 100 ps at 1 bar and 298 K. A production MD simulation was carried out for 60 ns and the final 20 ns trace was used in the analysis of various physical properties. Particle mesh Ewald method 6 was used in the calculation of Coulomb interactions. Cutoff values for the Coulomb and van der Waals interactions were 1.0 and 1.6 nm, respectively. Bond lengths were constrained by using the LINCS algorithm 7 to allow a 2 fs integration. The temperature of

Balance of Coordination and Hydrophobic Interaction in the Formation of Bilayers in Metal-Coordinated Surfactant Mixtures

Metal-ligand coordination and hydrophobic interaction are two significant driving forces in the aggregation of mixtures of M(n+) surfactants and alkyldimethylamine oxide (CnDMAO) in aqueous solutions. The coordinated systems exhibit rich aggregation behavior. This study investigated the effect of M(n+) ions (Zn(2+), Ca(2+), Ba(2+), Al(3+), Fe(3+), La(3+), Eu(3+), and Tb(3+)) and hydrophobic chains (hydrocarbon and fluorocarbon) on the formation of metal-coordinated bilayers. We found that fluorocarbon chains and branched hydrocarbon chains are preferable to the corresponding linear hydrocarbon chains for the formation of an Lα phase. Moreover, Lα phases formed by fluorocarbon chains exhibited higher viscoelasticity than ones formed by the hydrocarbons, and the bilayers formed by branched chains were rather flexible, revealing obvious undulation. The construction of bilayers was also strongly affected by metal ions due to their variable coordination ability with CnDMAO. Our results contribute to the understanding of the formation of metal-coordinated bilayers, which is driven by the interplay of noncovalent forces.