We present a micropipet-assisted writing technique for formation of two-dimensional networks of phospholipid vesicles and nanotubes on functionalized and patterned substrates. The substrates are patterned with vesicle-adhesive circular spots (5−7.5 μm in diameter) consisting of a basal layer of biotin on gold and an apical coating of NeutrAvidin in a sandwich manner. The area surrounding the adhesive spots is coated with a phosphatidylcholine bilayer membrane, preventing protein and liposome adhesion. Networks were formed by aspirating a biotin-functionalized giant unilamellar or multilamellar liposome (5−50 μm in diameter) into a ∼3 μm inner diameter borosilicate glass micropipet. By using a pressurized-air microejection system, a portion of the liposome is then ejected back into the solution while forming a first vesicle ∼3 μm in diameter. This vesicle is placed on an adhesive spot. When the micropipet is moved, a nanotube connection is formed from the first vesicle and is pulled to the next adhesive spot where a second vesicle is ejected. This procedure can then be repeated until the lipid material is consumed in the pipet. The method allows for formation of networks with a large number of nodes and vertexes with well-defined geometry and surface adhesion, and represents a first step toward very large scale integration of nanotube−vesicle networks in, for example, nanofluidic applications.
A simple and low-cost pulling device for fused-silica capillaries was developed. By using a tantalum heating filament and the self-tension in a bent capillary, tips and constricted regions with outer diameters of approximately 1 microm and inner diameters of a few hundred nanometers could be reproducibly pulled from 50-microm-i.d., 375-microm-o.d. capillaries. The tips can be used in different applications such as microinjection, micromanipulation, and single-channel patch-clamp, injection ends for CE or as electrospray tips. Constricted capillaries with optimized dimensions to minimize cylindrical lensing effects and to match the size of a diffraction-limited laser focus can be used as optical detection windows in CE and micro-HPLC. Fused silica has several advantages over other glasses such as high melting temperature and superior optical and mechanical properties.
Ion channels are transm embrane proteins, found in virtually all cell types throughout the human body. Ion channels underlie neural communication, memory, behavior, every movement and heartbeat, and are as such prone to cause disease if malfunctioning. Therefore ion channels are very important targets in drug discovery. The gold standard technique for obtaining information on ion channel function with high information content and temporal resolution is patch-clamp. The technique measures the minute currents originating from the movement of ions across the cellular membrane, and enables determination of the potency and efficacy of a drug. However, patch-clamp suffers from serious throughput restrictions due to its laborious nature. To address the throughput problems we have developed a microfluidic chip containing 48 microchannels for an extremely rapid, sequential delivery of a large number of completely controlled solution environments to a lifted, patch-clamped cell. In this way, throughput is increased drastically compared to classical patch-clamp perfusion set-ups, with uncompromised data quality. The 48-microchannel chip has been used for the characterization of drugs affecting ligand-gated ion channels including agonists, antagonists and positive modulators with positive effects on both throughput and data quality.
Abstract Structured magnetic surfaces enabling programmable motion of single micrometer‐sized magnetic particles are reported on p. 1730 by Gunnarsson and co‐workers. Patterns of thin‐film magnetic elements are tailored to form transport lines with junctions for the separation of individual particles. This method has the potential to improve and generate new applications in biotechnology. The cover shows a schematic of the transportation and separation of magnetic particles functionalized with antibodies capable of selectively capturing the corresponding analytes from a sample.
Around one percent of the Swedish population is defined as visually impaired and ten percent of them are classified as blind (Funka, n.d.; SRF, 2017a). A study shows that the prevalence of nearsigh ...
We report that GABAA receptors in a patch-clamped biological cell form a short-term memory circuit when integrated with a scanning-probe microfluidic device. Laminar patterns of receptor activators (agonists) provided by the microfluidic device define and periodically update the data input which is read and stored by the receptors as state distributions (based on intrinsic multistate kinetics). The memory is discharged over time and lasts for seconds to minutes depending on the input function. The function of the memory can be represented by an equivalent electronic circuit with striking similarity in function to a dynamic random access memory (DRAM) used in electronic computers. Multiplexed biohybrid memories may form the basis of large-scale integrated biocomputational/sensor devices with the curious ability to use chemical signals including odorants, neurotransmitters, chemical and biological warfare agents, and many more as input signals.
Microfluidic systems are powerful tools in chemistry, physics, and biology. The behavior of confined fluids differs from macroscopic systems and allows precise control of the chemical composition of fluids, as well as the temporal and spatial patterns of microscopic fluid elements. Cell-based assays can benefit when adapted to microfluidic formats, since microscale systems can offer low sample consumption, rapid application of well-defined solutions, generation of complex chemical waveforms, and significantly reduced analysis or experiment time.
Primary neurons in culture are considered to be a highly relevant model in the study of neuronal development and activity. They can be cultivated and differentiated in vitro but are difficult to transfect using conventional methods. To address this problem, a capillary electroporation system called Cellaxess Elektra was developed for efficient and reproducible transfection of primary cortical and hippocampal neurons without significant impact on cell morphology and viability. The cells are transfected in any stage of differentiation and development, directly in cell culture plates. Genetic material is delivered in situ to as many as 384 samples at a time, which enables both high-throughput and high-quality screening for hard-to-transfect primary cells, meaning that gene function can be studied on a genome-wide scale in cells previously inaccessible to genetic manipulation.
