Formation of artificial lipid bilayers using droplet dielectrophoresis
ABSTRACT We describe the formation of artificial bilayer lipid membranes (BLMs) by the controlled, electrical manipulation of aqueous droplets immersed in a lipid-alkane solution. Droplet movement was generated using dielectrophoresis on planar microelectrodes covered in a thin insulator. Droplets, surrounded by lipid monolayers, were brought into contact and spontaneously formed a BLM. The method produced BLMs suitable for single-channel recording of membrane protein activity and the technique can be extended to create programmable BLM arrays and networks.
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ABSTRACT: Basic biophysical studies and pharmacological processes can be investigated by mimicking the intracellular and extracellular environments across an artificial cell membrane construct. The ability to reproduce in vitro simplified scenarios found in live cell membranes in an automated manner has great potential for a variety of synthetic biology and compound screening applications. Here, we present a fully integrated microfluidic system for the production of artificial lipid bilayers based on the miniaturisation of droplet-interface-bilayer (DIB) techniques. The platform uses a microfluidic design that enables the controlled positioning and storage of phospholipid-stabilized water-in-oil droplets, leading successfully to the scalable and automated formation of arrays of DIBs to mimic cell membrane processes. To ensure robustness of operation, we have investigated how lipid concentration, immiscible phase flow velocities and the device geometrical parameters affect the system performance. Finally, we produced proof-of-concept data showing that diffusive transport of molecules and ions across on-chip DIBs can be studied and quantified using fluorescence-based assays. O ver the past two decades, the steady development of microfluidic technologies has provided sophisticated methodologies in many areas of science, including the ability to integrate and multiplex bioassays. The creation of biocompatible environments and the laminar flow properties of microfluidic channel networks offer very exciting prospects for the future development of automated and high-throughput synthetic biology-based platforms. Of particular interest for both drug discovery and biophysical research is the ability to interrogate and characterise the functional behaviour of membrane proteins in a reliable, scalable and miniaturised format. To this end, either live cell systems or a simplified synthetic environment that mimics that of a natural cell membrane can be used. Microfluidic solutions are already commercially available (e.g. from Fluxion, Nanion Technologies, Sophion and Ionera) that use electrophysiology techniques to measure the activity across biological membranes, using either whole live cells 1 or by inserting ion channels in artificial lipid bilayers 2. The latter approach is particularly interesting as it allows the effect of cellular parameters (e.g. membrane composition, pH and ion channel type) to be separately investigated, this having strong implications for carrying out novel types of experiments, for advancing biological knowledge related to membrane proteins and for facilitating the design and testing of more effective drugs. Microfluidic solutions have been proposed to create artificial cell membranes using immiscible fluids in silicon and polymer substrates, where suspended lipid bilayers were formed solely by fluid phase manipulation 3–7. Alternatively, phospholipid stabilised water-in-oil (psW/O) droplets have been used to create artificial cell membranes (known as droplet-interface-bilayers 8-DIBs). DIB formation is achieved when two psW/O droplets come into contact and the lipid molecules at each droplet interface interact spontaneously self-assembling into a lipid bilayer. Initially, DIB based assays have been developed by manually bringing droplets into contact but, in recent years, more efforts have been devoted to establishing similar assays using miniaturised systems that relied on micromanipulators, microgeometries and dielectrophoresis 9–16 or by interfacing psW/O droplets with agarose gel layersScientific Reports 04/2015; 5:9951. DOI:10.1038/srep09951 · 5.08 Impact Factor
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ABSTRACT: Here we present a model and a simulator for a computing architecture that uses excitable chemical droplets, which can be interconnected to form a cal-culating network. The model uses discrete internal states to represent the excitation phase of each droplet, which can influence the states of neighboring droplets if they are connected. Networks can be analyzed in this framework through simulation and by algebraic probability calculus. Furthermore, it is an abstract, phenomenological model and thus applicable to a variety of implementations for compartmentalized excitable chemical media, such as the Belousov-Zhabotinsky reaction with the right parameterization. By staying abstract in respect to the chemical implementation, we are focusing on the signal propagation behavior and its implications for possible signal encoding schemes and computing paradigms.