Polycarbonate Membrane Research Articles

Layer-by-layer assembly of high negatively charged polycarbonate membranes with robust antifouling property for microalgae harvesting

To tailor low-biofouling membranes remains one of the most problematic issues in filtration for microalgae harvesting. The aim of this study is to develop a high negatively charged and hydrophilic membrane to reduce membrane fouling via bioinspired design and Layer-by-layer (LBL) self-assembly technique for the application in microalgae harvesting. Bioinspired adhesive based on the polydopamine and polyethylenimine (PDA/PEI) composite was first linked onto the neutrally charged PC membrane substrates, then the poly-(styrenesulfonate) (PSS)/poly-(diallyldimethylammonium chloride) (PDADMAC) layers were uniformly assembled by electrostatic attraction. The resultant highly negatively charged and hydrophilic PC membranes exhibit a zeta potential of -66.1 mV and a water contact angle of 26°. Moreover, the modified membranes present a high average flux (133.1 L m2 h-1·bar-1) in 1-h microalgae filtration, a high algae retention (~100%) as well as a high flux recovery rate (over 94%). Meanwhile, the resultant membranes exhibit excellent chemical stability in high salty solutions, the low pH solutions and tolerance to long-time running in DI water. The combination of bioinspired construction method and LBL self-assembly technique could be expected to be a universal way to endow neutrally charged materials with highly negative or positive surface charge for various applications.

Structure and Electronic Properties of InSb Nanowires Grown in Flexible Polycarbonate Membranes.

A dense array of vertically aligned indium antimonide (InSb) nanowires with high aspect ratio (diameter 150 nm, length 20 m) were grown in the pores of a track-etched polycarbonate membrane via a one-step electrochemical method. There are several reports on InSb nanowire growth in the pores of a mechanically rigid, nano-channel alumina template (NCA), where nanowire growth occurs in the pores of the NCA. This work on InSb nanowire growth in pores of track-etched polycarbonate (PC) membrane sheds light on the various factors that affect nucleation and nanowire growth. The average length and diameter of the as-grown nanowires was about 10 m and 150 nm, respectively. Two possible mechanisms accounting for two different morphologies of the as-grown nanowires are proposed. The polycrystallinity observed in some of the nanowires is explained using the 3D ‘nucleation-coalescence’ mechanism. On the other hand, single crystal nanowires with a high density of twin defects and stacking faults grow epitaxially by a two-dimensional (2D) nucleation/growth mechanism. To assess the electrical quality of the nanowires, two- and four-terminal devices were fabricated using a single InSb nanowire contacted by two Ni electrodes. It was found that, at low bias, the ohmic current is controlled by charge diffusion from the bulk contacts. On the other hand, at high bias, the effects of space charge limited current (SCLC) are evident in the current–voltage behavior, characteristic of transport through structures with reduced electrostatic screening. A cross-over from ohmic to SCLC occurs at about 0.14 V, yielding a free carrier concentration of the order of cm.

Surface modification of silver nanoparticle (AgNP) by liposomal encapsulation mitigates AgNP-induced inflammation

Silver nanoparticles (AgNP) are widely used in a variety of consumable products as antibacterial to prevent or treat infection. Unfortunately, evidence exits that AgNP induces inflammation which can worsen with repeated human exposure. However, there is little or no research on how to mitigate these adverse effects due to AgNP induced-toxicity. Here, we investigated if surface modification of AgNP by liposomal encapsulation suppresses AgNP-mediated inflammatory responses in THP1 monocytes and THP1 differentiated macrophages (TDM). AgNP was encapsulated in a dipalmitoyl phosphatidyl choline- (DPPC)/cholesterol-based liposome by extrusion through a 100-nm polycarbonate membrane to form Lipo-AgNP. It was found as expected that AgNP induced significant release of IL-1β, IL-6, IL-8 and TNF-α in THP1 monocytes more than the basal level. Interestingly, release of these cytokines was suppressed by Lipo-AgNP. In TDMs, AgNP and Lipo-AgNP induced IL-8 release (p < .0001), but Lipo-AgNP maintained IL-8 release at levels significantly lower than that of AgNP (p < .01). However, both AgNP and Lipo-AgNP suppressed IL-1β and TNF-α release in LPS-stimulated THP1 monocytes and LPS-stimulated or unstimulated TDM respectively. We finally showed that Lipo-AgNP inhibits STAT-3 and this may be responsible for regulating the uncontrolled inflammation induced by AgNP likely mediated STAT-3 protein expression in LPS stimulated THP1 monocytes and TDMs, both LPS-stimulated and unstimulated. This data showed that Lipo-AgNP suppressed AgNP induced inflammation, making Lipo-AgNP particularly useful in treatment of bacteria induced inflammatory diseases and inflammatory cancers.

P7. Moldable allograft bone gel infused with spine-derived exosomes triggers osteogenic induction

BACKGROUND CONTEXT Exosomes are nanoscale vesicles that function as critical mediators of cell-to-cell communication via transportation of molecular cargo from a source cell to a target cell. It has previously been shown that the differentiation fate of primitive cells, such as mesenchymal stem cells (MSCs), can be modified toward an osteogenic path by the uptake of exosomes from defined cell types. Due to these properties, exosomes derived from a bone source such as spine seem an appropriate tool to guide the osteogenic differentiation of progenitor cells. PURPOSE A moldable bone gel was developed to serve as an osteoconductive support in filling bone voids. The effects of processing bone into a gelatinous material inhibits its innate osteoinductive properties. In an effort to restore the osteoinductive capacity of the bone gel product, spine-derived exosomes were added to the gel composition to restore bone graft material osteoinductivity and enhance handling. STUDY DESIGN/SETTING Purified exosomes were characterized by flow cytometry using coating latex beads with the nanoparticles and subsequently labeling these beads with known exosome markers, CD63, CD81 and CD9. Scanning Electron Microscopy (SEM) was performed to verify the size and morphology of the exosomes. Exosome concentration was determined using EXOCET Exosome Quantitation Kit (System Biosciences). PATIENT SAMPLE Exosomes were obtained from qualified cadaveric human spines by ultrafiltration and subsequent differential ultracentrifugation (Beckman Optima XE-90 Ultracentrifuge equipped with a SW32 rotor) of the clarified supernatant. OUTCOME MEASURES Scanning electron microscopy (SEM) was performed to verify the size and morphology of the exosomes. Exosome concentration was determined using EXOCET Exosome Quantitation Kit (System Biosciences). Protein concentration was determined using a Qubit 4.0 Fluorometer (Thermo Fisher), from which the purity of the exosome sample was determined by calculating exosome concentration per microgram of protein. A sensitive, quantitative method to assess the bone forming potential of C2C12 myoblast cell line was used. The expression of alkaline phosphatase, a widely accepted bone marker, was measured following treatment of C2C12 cells with spine-derived exosomes alone or in combination with bone gel using polycarbonate membrane transwells. METHODS Treatment with 50ng of BMP-4 was used as a positive control. Alkaline phosphatase expression was normalized to total protein content, which was measured with Pierce BCA Protein Assay Kit (Thermo Fisher). The osteoinductive (OI) index was calculated by using the following formula: (OI test sample result – OI negative control result)/OI negative control result/protein concentration. An index over 20% of negative baseline was considered as osteoinductive. RESULTS Spine-derived exosomes positively expressed the exosome flow cytometry markers tested. Specifically, they expressed 99 ± % of CD81, 85 ±14% of CD63 and 64 ± 35% of CD9. SEM imaging revealed most of the exosomes were approximately 100 nm in size, consistent with the expected physiological size range of exosomes (30 – 150nm). The mean concentration of the spine-derived exosomes obtained was 1.22 ± 1.09 × 1010 exosomes/mL of supernatant. The mean number of exosomes per microgram of protein was 3.31 ± 2.33 × 108 indicating relatively high purity. Osteoinductive testing was performed using different concentrations of exosomes either alone or in combination with bone gel. The OI index of treatment of C2C12 cells with BMP-4 or 2 × 108, 1 × 109, 2 × 109, 5 × 109 or 1 × 1010 exosomes alone was 28.5, 1.0, 3.7, 7.4, 11.8 and 27.6 respectively. The OI index of treatment with 2 × 108, 1 × 109, 2 × 109, 5 × 109 or 1 × 1010 exosomes, with each dose combined with 0.25cc of bone gel, was 0.9, 4.5, 6.2, 9.3 and 18.5 respectively. These results revealed a dose-dependent effect, with higher doses of exosomes resulting in a greater amount of alkaline phosphatase expression. All doses were 20% above negative baseline indicating an osteoinductive effect at doses ranging from 2 × 108 to 1 × 1010 exosomes alone or with bone gel. All data is expressed as mean ± SEM from 3 separate experiments. Statistical analysis was performed using Student's t-test or one-way ANOVA followed by Bonferroni's post hoc test if multiple group comparisons were performed. CONCLUSIONS In this preliminary study, in vitro osteoinductive effect of spine-derived exosomes alone or infused in bone gel on C2C12 cells was demonstrated. Although different concentrations of exosomes were tested, a single concentration (50ng) of BMP-4 was used as a positive control. Future studies will evaluate in vivo activity in a bone defect rat model. There are specific and key miRNA transcripts involved in the observed osteoinductive regulation to better understand the molecular mechanism of exosome-delivered therapy in the context of bone regeneration. FDA DEVICE/DRUG STATUS Unavailable from authors at time of publication.

Nonbubble-Propelled Biodegradable Microtube Motors Consisting Only of Protein.

This paper describes the synthesis of protein microtube motors having a urease interior surface and highlights their nonbubble-propelled behavior driven by enzymatic reaction (urea→NH3 and CO2 ). The precursor microtubes were prepared by layer-by-layer assembly using a track-etched microporous polycarbonate membrane. Immobilization of a urease on the internal wall was accomplished using avidin-biotin interaction. The tubules swam smoothly in an aqueous media containing a physiological concentration of urea. Each tubule was rotating laterally while moving forward. It is remarkable that the microtubes were digested completely by proteases, demonstrating perfect biodegradability.

Coupled Electrodeposition of Fe-Co-W Alloys: Thin Films and Nanowires.

The electrodeposition of Fe–Co–W alloys was examined using a rotating cylinder Hull (RCH) cell and conditions were determined to create nanowires. The metal ion reduction mechanism was a combination of induced and anomalous codeposition, with water reduction as a gas evolving side reaction, rending deposition into recesses a challenge. In thin film deposition, under kinetic control, the addition of Fe ions into the electrolyte, greatly reduced the Co partial current density, and thus it's content in the deposit. The change of Co partial current density was attributed to an anomalous codeposition behavior, but it had a minimal effect in changing the W wt% in the deposit, despite the expected inducing characteristic of Fe when codeposited with tungsten. Deposition conditions were determined to electrodeposit Fe–Co–W nanowires having similar concentration as the thin films. Nanowires were electrodeposited into polycarbonate membranes under pulsed current at room temperature.

Pb-PbOHCl Composite Nanowires Synthesized by Galvanic Deposition in Template.

In this paper, we report a detailed study on the synthesis of composite nanowires of Pb-PbOHCl via galvanic deposition into the pores of a membrane acting as a template. PbOHCl deposition quantitatively occurs as the solution pH exceeds the value of about 4.12. Simultaneously, owing to the galvanic coupling, electro-deposition of lead occurs, so composite nanowires were formed. The role of different parameters controlling the kinetic evolution of the process, such as oxygen bubbling, solution pH, surface area and type of sacrificial anode were investigated one at a time. The results suggest that every modification accelerating the alkalization of the solution inside the template pores favors growth of composite nanowires richer in PbOHCl. Alumina and polycarbonate membranes were investigated as template, and the best results were obtained for polycarbonate membrane, which can be easily removed by dissolution in CHCl₃ avoiding the collapse and successive loss of the nanowires.

Leaf-inspired multiresponsive MXene-based actuator for programmable smart devices.

Natural leaves, with elaborate architectures and functional components, harvest and convert solar energy into chemical fuels that can be converted into energy based on photosynthesis. The energy produced leads to work done that inspired many autonomous systems such as light-triggered motion. On the basis of this nature-inspired phenomenon, we report an unprecedented bilayer-structured actuator based on MXene (Ti3C2T x )-cellulose composites (MXCC) and polycarbonate membrane, which mimic not only the sophisticated leaf structure but also the energy-harvesting and conversion capabilities. The bilayer actuator features multiresponsiveness, low-power actuation, fast actuation speed, large-shape deformation, programmable adaptability, robust stability, and low-cost facile fabrication, which are highly desirable for modern soft actuator systems. We believe that these adaptive soft systems are attractive in a wide range of revolutionary technologies such as soft robots, smart switch, information encryption, infrared dynamic display, camouflage, and temperature regulation, as well as human-machine interface such as haptics.

Protein Microtube Motors with a Pt Nanoparticle Interior and Avidin Exterior for Self-Propelled Transportation, Separation, and Stirring

This paper describes the synthesis and unique functionalities of protein microtube motors with an exterior surface consisting of avidin (Avi). Using wet-template synthesis with layer-by-layer (LbL) assembly in a track-etched polycarbonate (PC) membrane, we fabricated precursor microtubes having an internal wall composed of Pt nanoparticles (PtNPs). Subsequently, hollow cylinders eliminated from the PC template were dispersed in water and were wrapped electrostatically with Avi by LbL coating. The obtained tubules (1.2 μm outer diameter, 24 μm length) are catalytically self-propelled in aqueous H2O2 solution by jetting O2 bubbles from the open-end terminus. Avidin–biotin complexation allows the swimming microtubes to capture various biotinylated substances. The fluorescent biotin was bound selectively to the tube outer surface, even with the coexistence of other dyes. Biotin-labeled nanoparticles and microparticles were adsorbed tightly and were transported without being shaken off. Furthermore, the self-stirring motion of biotinylated-α-glucosidase-covered microtubes accelerated the enzyme reaction. It is noteworthy that the protease digested the multilayered cylindrical walls. These results demonstrated that the swimming protein microtubes act as ultrasmall transporters, separator, and stirrers with a good biofriendly nature.

Transport characteristics in a novel in vitro release model for testing the performance of intra-articular injectables

There is a need for bio-predictive and well-characterized in vitro release models in the development of intra-articular depot formulations. Here, the commercially-available Scissor system, a membrane-based two-compartment release testing instrument, was applied to characterize the transport and release of the drug diclofenac employing conditions intended to mimic transport in the synovial joint. The fate of hyaluronic acid and human serum albumin, the main bio-relevant components incorporated in the system, was investigated. A promising strategy for providing sustained drug release upon intra-articular administration are lipid-based preformulations forming non-lamellar liquid crystalline phases in situ. The usefulness of the Scissor system for investigating the initial drug release from these delivery systems was evaluated. The diclofenac release rate upon injection of an aqueous solution was influenced by the composition of the injection site matrix, i.e. the hyaluronic acid content. Hyaluronic acid and human serum albumin were found to escape from the donor compartment into the acceptor medium through the employed polycarbonate membrane. Sustained diclofenac release was obtained by formation of highly viscous liquid crystalline phases upon injection of the lipid-based preformulations. The study shows the feasibility and potential of the Scissor system for testing initial release of intra-articular depot formulations of low-molecular-weight drug compounds.

Nanostructured Based Electrochemical Sensors.

In this work, we present some results concerning the electrochemical behavior of nanostructured-based electrochemical sensors. In particular, the attention has been focused on Pd and Cu nanowires for detection of hydrogen peroxide and NiO thin film or Ni@NiO core-shell nanowires for detection of mercury ions. Ordered array of Pd and Cu nanowires was obtained through displacement deposition reaction in a commercial polycarbonate membrane acting as a template. The method leads to stable nanostructured electrodes of Pd and Cu with high surface area. For the detection of mercury ions, we have fabricated a Ni/NiO electrochemical sensor, obtained by mild thermal oxidation of Ni-foil. Some results on Ni@NiO core-shell nanowires were also reported. The effect of oxidation time and temperature was studied in order to compare performances of the Ni@NiO nanowire array with those of NiO thin film. All samples were characterized by XRD, SEM and EDS analysis. Electrochemical tests have been conducted in order to characterize specific electrode performance such as sensibility, selectivity, and accuracy. Highly satisfying results have been obtained.

Perfusion Microfermentor Integrated into a Fiber Optic Quasi-Elastic Light Scattering Sensor for Fast Screening of Microbial Growth Parameters.

This research presents a microfermentor integrated into an optical fiber sensor based on quasi-elastic light scattering (QELS) to monitor and swiftly identify cellular growth kinetic parameters. The system uses a 1310 nm laser light that is guided through single-mode silica optical fibers to the interior of perfusion chambers, which are separated by polycarbonate membranes (470 nm pores) from microchannels, where a culture medium flows in a constant concentration. The system contains four layers, a superior and an inferior layer made of glass, and two intermediate poly(dimethylsiloxane) layers that contain the microchannels and the perfusion chambers, forming a reversible microfluidic device that requires only the sealing of the fibers to the inferior glass cover. The QELS autocorrelation decay rates of the optical signals were correlated to the cells counting in a microscope, and the application of this microsystem to the monitoring of alcoholic fermentation of Saccharomyces cerevisiae resulted in the kinetic parameters of KM = 4.1 g/L and μm = 0.49 h−1. These results agree with both the data reported in the literature and with the control batch test, showing that it is a reliable and efficient biological monitoring system.

Template-Assisted Electrodeposition of Porous Fe-Ni-Co Nanowires with Vigorous Hydrogen Evolution.

A novel method to fabricate porous Fe-Ni-Co nanowires directly by electrodepositing into polycarbonate membranes is reported when the electrolyte pH < 0.5. Hydrogen bubbles are used as a dynamic porous template created by operating in electrolytes with very low pH to drive the proton reduction reaction. The electrolyte pH was adjusted with sulfuric acid, and the added sulfate ions are thought to help reduce bubble coalescence, but not detachment at the electrode surface, to facilitate metal deposition within the nanopores. Porous nanowires were obtained when the electrolyte pH was less than 1.0. The average alloy composition was found to be pH sensitive, which shifted from an Fe-rich porous alloy to a Ni-rich porous alloy as the electrolyte pH decreased.

Evaluation of polymerase chain reaction technique in confirming urinary schistosomiasis among rice farmers in parts of Kaduna State, Nigeria

Schistosomiasis is a prevalent water-based parasitic disease, ranking second to malaria and killing an estimated 280,000 people each year in the African region alone. The application of polymerase chain reaction (PCR) as a technique was evaluated on filtered urine residues of 12 randomly selected rice farmers from some parts of Kaduna State, Nigeria. The urine samples were screened for ova of Schistosoma haematobium by microscopy after filtration using polycarbonate membrane filters (Sterlitech, Kent, WA, USA) of pore size 12 μm and 13 mm in diameter. Microscopy revealed a prevalence of 33.3% (4/12). All samples were further subjected to polymerase chain reaction (PCR) for amplification of the schistosome Dra1 repeat. PCR recorded an overall infectivity rate of 66.7% (8/12) among the rice farmers. Four out of the ova negative samples were confirmed to have the Dra1 repeat hence, making them positive for Schistosoma haematobium. Based on these findings, it can therefore be concluded that PCR can be especially useful in diagnosis of infections in nanograms. This will help in assessing the transmission potential of rice farmers living in low endemic areas and improve the effectiveness of surveillance of mass drug administration (MDA) control programmes as recommended by the World Health Organization.Keywords: PCR technique; schistomosiasis; rice farmers

PolyJet 3D-Printed Enclosed Microfluidic Channels without Photocurable Supports.

Microfluidic devices have historically been prepared using fabrication techniques that often include photolithography and/or etching. Recently, additive manufacturing technologies, commonly known as 3D-printing, have emerged as fabrication tools for microfluidic devices. Unfortunately, PolyJet 3D-printing, which utilizes a photocurable resin that can be accurately printed, requires the use of support material for any designed void space internal to the model. Removing the support material from the printed channels is difficult in small channels with single dimensions of less than ∼200 μm and nearly impossible to remove from designs that contain turns or serpentines. Here, we describe techniques for printing channels ranging in cross sections from 0.6 cm × 1.5 cm to 125 μm × 54 μm utilizing commercially available PolyJet printers that require minimal to no postprocessing to form sealed channels. Specifically, printer software manipulation allows printing of one model with an open channel or void that is sealed with either a viscous liquid or a polycarbonate membrane (no commercially available support material). The printer stage is then adjusted and a second model is printed directly on top of the first model with the selected support system. Both the liquid-fill and the membrane method have enough structural integrity to support the printing resin while it is being cured. Importantly, such complex channel geometries as serpentine and Y-mixers can be designed, printed, and in use in under 2 h. We demonstrate device utility by measuring ATP release from flowing red blood cells using a luciferin/luciferase chemiluminescent assay that involves on-chip mixing and optical detection.

Nanoelectrode ensemble immunosensing for the electrochemical identification of ovalbumin in works of art

This research is aimed to the study and application of an electrochemical immunosensor for the detection of ovalbumin (OVA) from egg white (or albumen) used as a binder in some works of art, such as some historical photographic prints and tempera paintings. The immunosensor takes advantage of the interesting biodetection capabilities offered by nanoelectrode ensembles (NEEs). The NEEs used to this aim are prepared by template deposition of gold nanoelectrodes within the pores of track-etched polycarbonate (PC) membranes. The affinity of polycarbonate for proteins is exploited to capture OVA from the aqueous extract obtained by incubation in phosphate buffer of a small sample fragment (<1 mg). The captured protein is reacted selectively with anti-OVA antibody, labelled with glucose oxidase (GOx). In the case of positive response, the addition of the GOx substrate (i.e. glucose) and a suitable redox mediator (a ferrocenyl derivative) reflects in the up rise of an electrocatalytic oxidation current, which depends on the OVA amount captured on the NEE, this amount correlating with OVA concentration in the extract. After optimization, the sensor is successfully applied to identify OVA in photographic prints dating back to the late 19th century, as well as in ancient tempera paintings from the 15th and 18th centuries.

Advanced assessment of migration and invasion of cancer cells in response to mifepristone therapy using double fluorescence cytochemical labeling

BackgroundPrevious work in our laboratory demonstrated that antiprogestin mifepristone impairs the growth and adhesion of highly metastatic cancer cells, and causes changes in their cellular morphology. In this study, we further assess the anti-metastatic properties of mifepristone, by studying whether cytostatic doses of the drug can inhibit the migration and invasion of various cancer cell lines using a double fluorescence cytochemical labeling approach.MethodsCell lines representing cancers of the ovary (SKOV-3), breast (MDA-MB-231), glia (U87MG), or prostate (LNCaP) were treated with cytostatic concentrations of mifepristone. Wound healing and Boyden chamber assays were utilized to study cellular migration. To study cellular invasion, the Boyden chamber assay was prepared by adding a layer of extracellular matrix over the polycarbonate membrane. We enhanced the assays with the addition of double fluorescence cytochemical staining for fibrillar actin (F-actin) and DNA to observe the patterns of cytoskeletal distribution and nuclear positioning while cells migrate and invade.ResultsWhen exposed to cytostatic concentrations of mifepristone, all cancer cells lines demonstrated a decrease in both migration and invasion capacities measured using standard approaches. Double fluorescence cytochemical labeling validated that mifepristone-treated cancer cells exhibit reduced migration and invasion, and allowed to unveil a distinct migration pattern among the different cell lines, different arrays of nuclear localization during migration, and apparent redistribution of F-actin to the nucleus.ConclusionThis study reports that antiprogestin mifepristone inhibits migration and invasion of highly metastatic cancer cell lines, and that double fluorescence cytochemical labeling increases the value of well-known approaches to study cell movement.

CO2 plasticization effect and selectivity for Pt-Pd alloy coated polycarbonate membrane

The transport of CO2 through variety of polymer membrane has been reported since last few years. CO2 shows plasticizing effect with glassy polymers facilitating molecular motion and increasing free volume which promotes the permeability. In this work, the transport behaviour of CO2 across the metal coated membrane has been studied and compared with that of standard polycarbonate membrane as a function of pressure. Deposition of nanolayer affects the transport properties due to the modification in sorption-diffusion process. As CO2 is a plasticizing agent and at definite pressure it gives plasticizing effect depending on the properties of material. A Platinum-Palladium (Pt-Pd) alloy thin film of around 8–10 nm was coated on thick polycarbonate (PC) substrate using sputtering technique to make layered polymer nanocomposite membrane. The permeability decreases with feed pressure for PC/Pt-Pd. As operating pressure is increased, the diffusion coefficient increases with small change and the solubility decreases. The tests were carried out at different upstream pressures i.e. in the range of 30 psi to 230 psi (2 atm to 16 atm) for PC/Pt-Pd at 35 °C temperature. Further, the selectivity of CO2 over H2, O2 and N2 at various upstream pressures has been reported.

Effect of Formulation Method, Lipid Composition, and PEGylation on Vesicle Lamellarity: A Small-Angle Neutron Scattering Study.

Liposomes are well-established systems for drug delivery and biosensing applications. The design of a liposomal carrier requires careful choice of lipid composition and formulation method. These determine many vesicle properties including lamellarity, which can have a strong effect on both encapsulation efficiency and the efflux rate of encapsulated active compounds. Despite this, a comprehensive study on how the lipid composition and formulation method affect vesicle lamellarity is still lacking. Here, we combine small-angle neutron scattering and cryogenic transmission electron microscopy to study the effect of three different well-established formulation methods followed by extrusion through 100 nm polycarbonate membranes on the resulting vesicle membrane structure. Specifically, we examine vesicles formulated from the commonly used phospholipids 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) via film hydration followed by (i) agitation on a shaker or (ii) freeze–thawing, or (iii) the reverse-phase evaporation vesicle method. After extrusion, up to half of the total lipid content is still assembled into multilamellar structures. However, we achieved unilamellar vesicle populations when as little as 0.1 mol % PEG-modified lipid was included in the vesicle formulation. Interestingly, DPPC with 5 mol % PEGylated lipid produces a combination of cylindrical micelles and vesicles. In conclusion, our results provide important insights into the effect of the formulation method and lipid composition on producing liposomes with a defined membrane structure.

Biomimetic nanochannel membrane for cascade response of borate and cis-hydroxyl compounds: An IMP logic gate device

Biomimetic nanodevice is an important branch to expand the potential applications of artificial nanochannels. Here, we constructed nanochannels for cascade response of borate and cis-hydroxyl compounds by modifying the nanochannels of track-etched polycarbonate (TEPC) membranes with polyvinyl alcohol (PVA). Firstly, borate bound to PVA and increased the negative charge density on the surface of the nanochannels, which obstructed the transport of 1,5-naphthalene disulfonate (NDS2−). Subsequently, the addition of cis-hydroxyl compounds induced leaving of borate due to the stronger binding affinities between borate and cis-hydroxyl compounds, which reduced the negative charge density on nanochannels and then enhanced the transport of NDS2−. The cascade response of the nanochannels also accord with the properties of IMP (implication) logic gate. In addition, such nanochannels showed good reproducibility and reversibility. Therefore, this cascade response model based on nanochannels has the potential to be used as switches in area of actuators and biosensors, and is also expected to be used to understand the interaction of substances in nanoscale and simulate the physiological functions of boron.