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.Artificial BLM techniques are of great importance in membrane protein research. Electrophysiological studies of proteins reconstituted into BLMs can generate detailed information at the single molecule level on protein activity, ligand-binding and kinetics. 1 Classical BLM techniques have been in use for over 40 years, but are not amenable to applications where high-throughput processes and reproducibility are required (e.g. drug screening and biosensing applications). 2 New labon-chip technologies are being developed which allow for ever greater integration of complex functions with precise control of fluids on the micro-scale. 3 This technology can be exploited to combine parallelization, achieved through microfluidics, with the sensitivity and selectivity of BLM approaches. Although various miniaturized devices have been reported, only a few BLM formation methods 4-7 have been developed on-chip that are reproducible, potentially automatable and suitable for singlechannel recording.An alternative technique was recently described by Holden et al.,[8][9][10][11][12] which uses an alkane-lipid solution as the bulk phase, as opposed to an aqueous electrolyte. Droplets of buffer are immersed in the organic solution and at the interface between the two phases lipid monolayers form. When two droplets are brought into contact, a BLM forms at the interface between the droplets. As well as forming single BLMs, this approach allows for the creation of BLM networks. However, the method required manual manipulation of the droplets using micromanipulators.Electrical methods for droplet manipulation exist, based on electrodynamic techniques, such as dielectrophoresis (DEP) and electro-wetting on dielectric (EWOD).

Direct contact of nanoparticles with the plasma membrane is essential for biomedical applications such as intracellular drug delivery and imaging, but the effect of nanoparticle association on membrane structure and function is largely unknown. Here we employ a sensitive electrophysiological method to assess the stability of protein-free membranes in the presence of silica nanospheres of different size and surface chemistry. It is shown that all the silica nanospheres permeabilize the lipid bilayers already at femtomolar concentrations, below reported cytotoxic values. Surprisingly, it is observed that a proportion of the nanospheres is able to translocate over the pure-lipid bilayer. Confocal fluorescence imaging of fluorescent nanosphere analogues also enables estimation of the particle density at the membrane surface; a significant increase in bilayer permeability is already apparent when less than 1% of the bilayer area is occupied by silica nanospheres. It can be envisaged that higher concentrations of nanoparticles lead to an increased surface coverage and a concomitant decrease in bilayer stability, which may contribute to the plasma membrane damage, inferred from lactate dehydrogenase release, that is regularly observed in nanotoxicity studies with cell cultures. This biophysical approach gives quantitative insight into nanosphere–bilayer interactions and suggests that nanoparticle–lipid interactions alone can compromise the barrier function of the plasma membrane.

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