Microfluidic Generation, Encapsulation and Characterization of Asymmetric Droplet Interface Bilayers

2016 ◽  
Author(s):  
Mary-Anne Nguyen ◽  
Stephen A. Sarles
Keyword(s):  
Lipid Bilayers ◽  
Smart Materials ◽  
Electrical Measurements ◽  
Synthetic Cell ◽  
Versus Bias Voltage ◽  
Voltage Dependent ◽  
Droplet Interface Bilayer ◽  
Emergent Behaviors ◽  
First Time

Our research focuses on creating smart materials that utilize synthetic cell membranes assembled at liquid interfaces for autonomic sensing, actuation, and energy conversion. Unlike single membrane assemblies, systems featuring many membranes have the potential to offer multi-functionality, greater transduction sensitivity, and even emergent behaviors in response to environmental stimuli, similar to living tissue, which utilizes networks of highly packed cells to accomplish tasks. Here, we present for the first time a novel microfluidic platform capable of generating a stream of alternating droplet compositions, i.e. A-B-A-B, and sequentially capturing these droplets in precise locations to enable the spontaneous formation of synthetic lipid bilayers between droplets of different compositions (i.e. A and B) in an enclosed substrate. This platform preserves a key feature of the droplet interface bilayer (DIB) method, which allows asymmetric conditions within and across the membrane to be prescribed by simply using droplets containing different species. In this work, we demonstrate the ability to assemble bilayers consisting of asymmetric lipid compositions and, separately, show that alternating droplets containing the same lipid type can also be used to control the direction of ion channel insertion. In the first study, A and B droplet types contain liposomes comprised of different lipid types, which are used to establish an asymmetric composition of the leaflets that make up the lipid bilayer. This asymmetry results in a dc, non-zero membrane potential, which we measure via membrane capacitance versus bias voltage. In the second study, alamethicin peptides are included in only one of the droplet types, which enable voltage-dependent insertion to occur only at one polarity. Cyclic voltammetry measurements are performed to confirm the direction of insertion of alamethicin channels in bilayers. Also, these results show the ability to perform simultaneously electrical measurements on multiple DIB, which increases the experimental capacity and efficiency of a microfluidic approach. The ability to produce alternating droplets in a high throughput manner with electrical access provides a system to investigate the effects of lipid asymmetry on the function of membrane proteins in a controlled model system.

Calcium-activated potassium channels from coronary smooth muscle reconstituted in lipid bilayers

1991 ◽  
Vol 260 (6) ◽  
pp. H1779-H1789 ◽  
Author(s):  
L. Toro ◽  
L. Vaca ◽  
E. Stefani
Keyword(s):  
Smooth Muscle ◽  
Lipid Bilayers ◽  
Surface Membrane ◽  
Dependent Manner ◽  
Coronary Smooth Muscle ◽  
Voltage Sensors ◽  
Kca Channels ◽  
Voltage Dependent ◽  
Calcium Activated Potassium Channels

This work is the initial characterization of Ca(2+)-activated K+ (KCa) channels from coronary smooth muscle reconstituted into lipid bilayers. The channels were obtained from a surface membrane preparation of porcine coronary smooth muscle. KCa channels were the predominant K+ channels in this preparation. The conductance histogram (n = 137 channels) revealed two main populations of “maxi” KCa channels with conductances of 245 and 295 pS. Each population could be subdivided in two “isoforms” or “isochannels” with different functional properties (voltage and Ca2+ sensitivities and kinetics). The analysis of “burst” probability of opening showed that at pCa 4 the two isochannels of 245 pS (KCa-1 and KCa-1') had half-activation potentials (V1/2) of -80 and 6 mV, respectively. The isochannels of 295 pS (KCa-2 and KCa-2') had V1/2 of -28 and -66 mV, respectively. KCa-1 had the highest Ca2+ sensitivity; at -60 mV, the concentration of half-activation value for Ca2+ was 1.2 +/- 0.3 microM (n = 5). External tetraethylammonium reduced channel amplitude in a voltage-dependent manner; dissociation constant was 180 +/- 6 and 466 +/- 41 microM at -40 and +80 mV, respectively (n = 5). Charybdotoxin (5-50 nM) produced typical long closings. These effects were similar in all the channels. We conclude that coronary smooth muscle possesses isoforms of maxi KCa channels with Ca2+ and voltage sensors with different properties, which may confer to each channel a specific functional role.

Interrogation of Bilayers in a Multi-Droplet Cluster for Membrane-Based Sensing

2015 ◽  
Author(s):  
Mary-Anne Nguyen ◽  
Nima Tamaddoni ◽  
Stephen A. Sarles
Keyword(s):  
Hair Cell ◽  
Lipid Bilayers ◽  
Experimental Studies ◽  
Membrane Structures ◽  
Electrical Measurements ◽  
Membrane Area ◽  
Sensing Applications ◽  
Synthetic Cell ◽  
Droplet Cluster ◽  
Living Tissues

The long-term vision of our work is to create a new class of smart material that utilizes networks of active, synthetic cell membranes for sensing, actuation, and energy harvesting. Having multiple membrane structures is specifically targeted because a higher density of functional membranes is expected to enable amplification and collective utility, similar to how living tissues and organisms utilize networks of highly connected cells to accomplish large tasks. While there are several known methods for assembling droplet-based networks of synthetic lipid bilayers, there has been much less effort to develop methods for electrically characterizing each interface in a multi-bilayer-droplet network. This paper specifically focuses on a strategy for using electrical measurements to independently record transmembrane currents occurring at each bilayer in multi-bilayer networks where the number of bilayers present is equal to or greater than the number of droplets in the system. Using a multichannel patch clamp amplifier, we develop a measurement technique for sequentially assigning sensing electrodes to apply a non-zero voltage or function as virtual ground (V=0). Experimental studies on a three-droplet cluster containing three bilayers confirm the validity of the proposed approach for independently interrogating each membrane, and the results allow extension of the method to networks with 4–7 droplets. Furthermore, alamethicin peptide gating is monitored using the measurement cycle in order to interrogate all interfaces. Due to high total membrane area, highly packed systems can provide an increase in the magnitude of sensing current generated by a stimulus. Such amplification could feasibly be employed in droplet-based hair cell sensing applications in which airflow or vibration acts as the perturbation source, and the proposed approach and challenges for interrogating the transduction response in a multi-membrane hair cell sensor are discussed herein.

Robust Sensing and Reversible Actuation Using Triblock Copolymer Stabilized Intradroplet Interfaces

2015 ◽  
Author(s):  
Nima Tamaddoni ◽  
Graham J. Taylor ◽  
Stephen A. Sarles
Keyword(s):  
Hair Cell ◽  
Smart Materials ◽  
Triblock Copolymer ◽  
Shape Change ◽  
Interfacial Area ◽  
Electrical Measurements ◽  
Voltage Dependent ◽  
Oil Mixtures ◽  
Induce Change ◽  
Robust Sensing

In this work, a recently developed method for forming copolymer-stabilized interfaces (CSI) between aqueous droplets is pursued to as a means to construct smart materials and systems. The ABA type copolymer employed consists of two hydrophilic (PEO) groups sandwiching a hydrophobic PDMS core. Aqueous droplets submerged in triblock copolymer (PEO-PDMS-PEO)-oil mixtures are rapidly coated in copolymer monolayers, however, unlike phospholipid-stabilized droplet interface bilayers (DIBs), electrical measurements reveal that there is no spontaneous formation of a “thinned” interface with droplet contact alone. The capacitance of the interface begins increasing significantly only upon application of sufficient voltage (>100mV), and capacitance then stabilizes within minutes. Further, the interfacial capacitance and area decreases when applied voltage is reduced back to 0mV, and droplets eventually return to their initial separated state. The fact that droplet adhesion and formation of the interface is voltage dependent and completely reversible clearly distinguishes a CSI from a DIB, and the novel polymer based interface is significantly more robust with average rupture potential of ≥ 800mV compared to 200–300mV with DIBs. Durable and stable CSIs could feasibly be used in applications ranging from sensing and energy harvesting to mechanical actuation. To demonstrate, this work introduces a new version of the DIB based hair cell sensor, now replacing lipids with block copolymers to provide greater durability, stability, and resistance to rupture when subjected to airflow. We calculate the current generated by the vibrating membranes in DIBs and CSIs to study the influence of surfactant selection on the hair cell durability and the related airflow operation range. We conclude that the hair cell constructed using triblock copolymer, as opposed to a DIB, withstands higher nominal airflow speeds (45m/s) and higher applied bias voltages (i.e. 0.1–1V) without rupturing. The ability to apply higher voltages provides a means of tuning the hair-cell sensitivity. Separately, the results of initial trials demonstrate the possibility for voltage-controlled shape change using networks of droplets and CSIs. The ability to apply large voltages and induce change in interfacial area leads to rearrangement of the droplet networks due to conservation of volume. Several embodiments of possible actuators based on this mechanism are discussed. In concert, the various aspects of this work highlight the potential use of CSIs in developing novel, reliable smart materials for sensing and actuation.

Characterization of a voltage-dependent potassium channel in quid Schwann cells reconstituted in planar lipid bilayers

Glia ◽  
1995 ◽  
Vol 15 (1) ◽  
pp. 33-42 ◽  
Author(s):  
F. Noceti ◽  
A. N. Ramírez ◽  
L. D. Possani ◽  
G. Prestipino
Keyword(s):  
Potassium Channel ◽  
Schwann Cells ◽  
Lipid Bilayers ◽  
Planar Lipid Bilayers ◽  
Voltage Dependent

Hall Factor Calculation for the Characterization of Transport Properties in N-Channel 4H-SiC MOSFETs

2014 ◽  
Vol 778-780 ◽  
pp. 483-486 ◽  
Author(s):  
Viktoryia Uhnevionak ◽  
Alex Burenkov ◽  
Christian Strenger ◽  
Vincent Mortet ◽  
Elena Bedel-Pereira ◽  
...  
Keyword(s):  
Hall Effect ◽  
Gate Voltage ◽  
Strong Dependence ◽  
Relaxation Times ◽  
Hall Factor ◽  
Current Voltage ◽  
Voltage Dependent ◽  
Hall Effect Measurements ◽  
First Time

For the characterization ofn-channel 4H-SiC MOSFETs, current-voltage and Hall-effect measurements were carried out at room temperature. To interpret the Hall-effect measurements, the Hall factor for the electron transport in the channel of SiC MOSFETs was evaluated, for the first time. The method of the Hall factor calculation is based on the interdependence with mobility components via the respective scattering relaxation times. The results of the calculation reveal a strong dependence of the Hall factor on the gate voltage. Depending on the gate voltage applied, the values of the Hall factor vary between 1.3 and 1.5. Sheet carrier density and drift mobility values derived from the Hall-effect measurements using our new gate-voltage-dependent Hall factor show very good agreement with simulations performed with Sentaurus Device of Synopsys.

TBE in Sweden

2020 ◽  
Keyword(s):  
Genetic Characterization ◽  
Immunoglobulin M ◽  
Enzyme Linked Immunosorbent Assay ◽  
Second Phase ◽  
Serum Samples ◽  
Tick Borne Encephalitis ◽  
Specific Immunoglobulin ◽  
Tick Borne Encephalitis Virus ◽  
First Time

Tick-borne encephalitis virus (TBEV) was isolated for the first time in Sweden in 1958 (from ticks and from 1 tick-borne encephalitis [TBE] patient).1 In 2003, Haglund and colleagues reported the isolation and antigenic and genetic characterization of 14 TBEV strains from Swedish patients (samples collected 1991–1994).2 The first serum sample, from which TBEV was isolated, was obtained 2–10 days after onset of disease and found to be negative for anti-TBEV immunoglobulin M (IgM) by enzyme-linked immunosorbent assay (ELISA), whereas TBEV-specific IgM (and TBEV-specific immunoglobulin G/cerebrospinal fluid [IgG/CSF] activity) was demonstrated in later serum samples taken during the second phase of the disease.

Chemical Constituents and Antibacterial Activity of Cissus Aralioides.

2020 ◽  
Vol 17 ◽  
Author(s):  
Balogun Olaoye Solomon ◽  
Ajayi Olukayode Solomon ◽  
Owolabi Temitayo Abidemi ◽  
Oladimeji Abdulkarbir Oladele ◽  
Liu Zhiqiang
Keyword(s):  
Plant Extract ◽  
Chemical Constituents ◽  
Ethyl Acetate Fraction ◽  
Antibacterial Activities ◽  
Sub Saharan Africa ◽  
Chromatographic Purification ◽  
Whole Plant ◽  
Sub Saharan ◽  
First Time

: Cissus aralioides is a medicinal plant used in sub-Saharan Africa for treatment of infectious diseases; however the chemical constituents of the plant have not been investigated. Thus, in this study, attempt was made at identifying predominant phytochemical constituents of the plant through chromatographic purification and silylation of the plant extract, and subsequent characterization using spectroscopic and GC-MS techniques. The minimum inhibitory concentration (MICs) for the antibacterial activities of the plant extract, chromatographic fractions and isolated compounds were also examined. Chromatographic purification of the ethyl acetate fraction from the whole plant afforded three compounds: β-sitosterol (1), stigmasterol (2) and friedelin (3). The phytosterols (1 and 2) were obtained together as a mixture. The GC-MS analysis of silylated extract indicated alcohols, fatty acids and sugars as predominant classes, with composition of 24.62, 36.90 and 26.52% respectively. Results of MICs indicated that friedelin and other chromatographic fractions had values (0.0626-1.0 mg/mL) comparable with the standard antibiotics used. Characterization of natural products from C. aralioides is being reported for the first time in this study.

Green Synthesis and Spectroscopic Studies of Ag-rGO Nanocomposites for Highly Selective Mercury (II) Sensing

2018 ◽  
Vol 9 (1) ◽  
pp. 101-108 ◽  
Author(s):  
Shubhangi J. Mane-Gavade ◽  
Sandip R. Sabale ◽  
Xiao-Ying Yu ◽  
Gurunath H. Nikam ◽  
Bhaskar V. Tamhankar
Keyword(s):  
Green Synthesis ◽  
Color Change ◽  
Limit Of Detection ◽  
Aqueous Media ◽  
Suitable Condition ◽  
Cost Effective ◽  
Spectroscopic Studies ◽  
Calibration Plot ◽  
First Time

Introduction: Herein we report the green synthesis and characterization of silverreduced graphene oxide nanocomposites (Ag-rGO) using Acacia nilotica gum for the first time. Experimental: We demonstrate the Hg2+ ions sensing ability of the Ag-rGO nanocomposites form aqueous medium. The developed colorimetric sensor method is simple, fast and selective for the detection of Hg2+ ions in aqueous media in presence of other associated ions. A significant color change was noticed with naked eye upon Hg2+ addition. The color change was not observed for cations including Sr2+, Ni2+, Cd2+, Pb2+, Mg2+, Ca2+, Fe2+, Ba2+ and Mn2+indicating that only Hg2+ shows a strong interaction with Ag-rGO nanocomposites. Under the most suitable condition, the calibration plot (A0-A) against concentration of Hg2+ was linear in the range of 0.1-1.0 ppm with a correlation coefficient (R2) value 0.9998. Results & Conclusion The concentration of Hg2+ was quantitatively determined with the Limit of Detection (LOD) of 0.85 ppm. Also, this method shows excellent selectivity towards Hg2+ over nine other cations tested. Moreover, the method offers a new cost effective, rapid and simple approach for the detection of Hg2+ in water samples.

Sign in / Sign up

Export Citation Format

Share Document