•Controllable electroporation of cells was achieved using microcavity electrodes.•An optimized microcavity electrode for cell electroporation/electro-fusion was obtained.•A cell electroporation model was developed and validated.•High-yield electro-fusion in a microfluidic device with microcavity electrodes was achieved.Cell electro-fusion includes four steps, cell alignment, cell electroporation, reconstruction of cytomembrane and cytoplasm exchange. The cell alignment and electroporation steps are highly related to the intensity and distribution of the electric field, which depend on the applied voltage as well as the microelectrode structure. The microelectrode structures were first evaluated based on the numerical analysis of the electric field and the transmembrane potential induced on biological cells when the cell electroporation and electro-fusion were performed based on different designs of microelectrodes. Microelectrodes in a micro-cavity geometry can induce electroporation around the contact area of the paired cells for high-yield electro-fusion. Microfluidic chips with co-planar microelectrodes and microelectrodes within micro-cavities have been fabricated and tested for electro-fusion of Myoblast cells, and the experimental results confirmed the numerical analysis.Download high-res image (128KB)Download full-size imageControllable cell electroporation is successfully achieved by microcavity electrodes.

•The effect of ion concentration on vesicle formation was investigated on a designed miniaturized reactor.•Na+ and Cl− would bind with the lipid head and act a much strong hydrophobic repulsion on the lipid tail.•High salt concentration enhanced hydrophobic repulsion on lipids increasingly, and forced lipids attached firmly on the substrate.•Much larger external disturbance would be needed for vesicle formation in salt solutions than that in pure water.Lipid vesicle formation is known to be suppressed in salt solutions, but the mechanism of this phenomenon remains unclear. In order to better understand this issue, the effect of salt concentrations (0–800 mM) of sodium chloride on the behavior of L-α-phosphatidylcholine (PC) in aqueous solution was investigated in this work. The results showed that fusion among vesicles, micelles and bilayers may be essential for vesicle formation. With addition of ions and an increase in ion concentration, the lipids became constrained in lateral movement and packed increasingly tightly. The resulted hard supported phospholipid bilayers (SPBs) were thus more difficult to detach from the substrate to form vesicles. These phenomena were tried to be explained at molecular level. Hydrophobic effect is the original cause of lipid vesicle formation, which in fact is absence of attraction between the involved substances. That is to say, the stronger the 3D network was bounded in the medium, the stronger the hydrophobic repulsion on the lipids would be. This might be one reason for the suppression of vesicle formation in salt solution.Download high-res image (108KB)Download full-size image

•Surface morphology of lipid films is accurately and rapidly characterized.•A SPR imaging device based on an angle interrogation manner is constructed.•Mathematical model is developed to describe the shift of the light path.Surface topographies of lipid films have an important significance in the analysis of the preparation of giant unilamellar vesicles (GUVs). In order to achieve accurately high-throughput and rapidly analysis of surface topographies of lipid films, a homemade SPR imaging device is constructed based on the classical Kretschmann configuration and an angle interrogation manner. A mathematical model is developed to accurately describe the shift including the light path in different conditions and the change of the illumination point on the CCD camera, and thus a SPR curve for each sampling point can also be achieved, based on this calculation method. The experiment results show that the topographies of lipid films formed in distinct experimental conditions can be accurately characterized, and the measuring resolution of the thickness lipid film may reach 0.05 nm. Compared with existing SPRi devices, which realize detection by monitoring the change of the reflective-light intensity, this new SPRi system can achieve the change of the resonance angle on the entire sensing surface. Thus, it has higher detection accuracy as the traditional angle-interrogation SPR sensor, with much wider detectable range of refractive index.