DNA-Tethered Lipid Membrane Formation via Solvent-Assisted Self-Assembly.

DNA-tethered lipid bilayers have been used in many studies, based on the controllable and well-defined properties of DNA tethers. However, their application has been limited, because it is difficult to cover a wide range of surfaces and achieve electrical insulation. We implemented an existing method, where a DNA hybrid chip on a silica or glass surface supports a lipid membrane using solvent-assisted self-assembly.

Enhanced electrochemical biosensing on gold electrodes with a ferri/ferrocyanide redox couple.

Detection of specific DNA is important in many fields. Label-free DNA sensing performed by electrochemical impedance spectroscopy (EIS) or using a quartz crystal microbalance (QCM) is widely employed for this purpose. Gold electrodes are mainly used for these techniques due to their chemical stability.

Capacitively coupled contactless conductivity detection for microfluidic capillary isoelectric focusing.

We report capacitively coupled contactless conductivity detection (C4D) of proteins separated by microfluidic capillary isoelectric focusing (μCIEF). To elucidate the evolution of negative conductivity peaks during focusing and seek IEF conditions for sensitive conductivity detection, numerical simulation was performed using a model protein GFP (green fluorescence protein) and hypothetical carrier ampholytes (CAs). C4D was successfully applied to the μCIEF by optimizing assay conditions using a simple and effective pressure-mobilization approach.

Influence of natural organic matter (NOM) coatings on nanoparticle adsorption onto supported lipid bilayers.

As the worldwide usage of nanoparticles in commercial products continues to increase, there is growing concern about the environmental risks that nanoparticles pose to biological systems, including potential damage to cellular membranes. A detailed understanding of how different types of nanoparticles behave in environmentally relevant conditions is imperative for predicting and mitigating potential membrane-associated toxicities. Herein, we investigated the adsorption of two popular nanoparticles (silver and buckminsterfullerene) onto biomimetic supported lipid bilayers of varying membrane charge (positive and negative).

A Simple and Fast Aqueous-Phase Synthesis of Ultra-Highly Concentrated Silver Nanoparticles and Their Catalytic Properties.

A simple and fast synthetic route to ultra-highly concentrated silver nanoparticles with long-term stability by reducing AgNO3 with ascorbic acid in the presence of polyethyleneimine (PEI) as a stabilizer in an aqueous phase is reported. The concentration of silver precursor was as high as 2000 mm (200 g of Ag nanoparticle per liter of water) and the reaction time was less than 10 min. The resulting silver nanoparticles show long-term stability after two months of storage at room temperature without any signs of particle aggregation or precipitation in an aqueous phase.

Note: A microfluidic freezer based on evaporative cooling of atomized aqueous microdroplets.

We report for the first time water-based evaporative cooling integrated into a microfluidic chip for temperature control and freezing of biological solution. We opt for water as a nontoxic, effective refrigerant. Aqueous solutions are atomized in our device and evaporation of microdroplets under vacuum removes heat effectively.

Polymer sieving matrices in microanalytical electrophoresis.

Microfluidic design has advanced existing protein separation capabilities and supported novel assays. Key metrics for successful protein separations include fast, robust, and sensitive analysis of complex mixtures of bio-macromolecules. Attaining high separation resolution is a chief concern.

Microchamber Western blotting using poly-L-lysine conjugated polyacrylamide gel for blotting of sodium dodecyl sulfate coated proteins.

We report a novel strategy to immobilize sodium dodecyl sulfate (SDS)-coated proteins for fully integrated microfluidic Western blotting. Polyacrylamide gel copolymerized with a cationic polymer, poly-L-lysine, effectively immobilizes all sized proteins after sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and enables SDS-PAGE and subsequent immuno-probing in an automated microfluidic chip. Design of a poly-l-lysine conjugated polyacrylamide gel allows optimization of SDS-protein immobilization strength in the blotting gel region of the microchamber.

Formation and analysis of topographical domains between lipid membranes tethered by DNA hybrids of different lengths.

We recently described a strategy to prepare DNA-tethered lipid membranes either to fixed DNA on a surface or to DNA displayed on a supported bilayer [Boxer et al., J. Struct.

Vesicle fusion observed by content transfer across a tethered lipid bilayer.

Synaptic transmission is achieved by exocytosis of small, synaptic vesicles containing neurotransmitters across the plasma membrane. Here, we use a DNA-tethered freestanding bilayer as a target architecture that allows observation of content transfer of individual vesicles across the tethered planar bilayer. Tethering and fusion are mediated by hybridization of complementary DNA-lipid conjugates inserted into the two membranes, and content transfer is monitored by the dequenching of an aqueous content dye.

Stability of DNA-tethered lipid membranes with mobile tethers.

We recently introduced two approaches for tethering planar lipid bilayers as membrane patches to either a supported lipid bilayer or DNA-functionalized surface using DNA hybridization (Chung, M.; Lowe, R. D.

DNA-tethered membranes formed by giant vesicle rupture.

We have developed a strategy for preparing tethered lipid bilayer membrane patches on solid surfaces by DNA hybridization. In this way, the tethered membrane patch is held at a controllable distance from the surface by varying the length of the DNA used. Two basic strategies are described.

Use of monoclonal antibodies that recognize p60 for identification of Listeria monocytogenes.

Listeria monocytogenes causes major food-borne outbreaks of disease worldwide. Specific identification of this microorganism is of utmost importance to public health and industry. Listeria species are known to secrete a 60-kDa protein collectively termed p60, which is encoded by the iap (invasion-associated protein) gene and secreted in large quantities into the growth media.