A microfluidic device for the delivery of enzymes into cells by liposome fusion.

Liposomes are versatile carriers of drugs or biomolecules and are ideally suited to transport molecules into cells. However, mechanistic studies to understand and improve the fusion of liposomes with cell membranes and endosomes are difficult. Here, we report a method that allows for stable coimmobilization of liposomes and living cells, thereby bringing the membranes into close contact, which is essential for membrane fusion.

Next generation gene synthesis: From microarrays to genomes.

Similar to the incredible advances in DNA sequencing, the de novo synthesis of DNA is subject to innovations and fast progress in terms of synthesis speed and cost. We will discuss novel techniques that are expected to enable high-throughput synthesis of oligonucleotides on microarrays and the subsequent assembly into longer fragments, up to whole genomes. Especially, the inherent disadvantages of microarray-derived oligonucleotide pools for gene synthesis will be discussed in detail, and also the different approaches to still render these oligonucleotides useful for gene assembly.

A liposomal fluorescence assay to study permeation kinetics of drug-like weak bases across the lipid bilayer.

Lipid bilayer permeation is considered the major route for in vivo barrier passage of drugs. Despite this fact, no technique is currently available to measure the kinetics of permeation across a single lipid bilayer of structurally unrelated drug-like solutes. We developed a liposomal fluorescence assay capable to determine permeation kinetics of basic drug-like solutes across lipid bilayers.

A microfluidic chip for the versatile chemical analysis of single cells.

We present a microfluidic device that enables the quantitative determination of intracellular biomolecules in multiple single cells in parallel. For this purpose, the cells are passively trapped in the middle of a microchamber. Upon activation of the control layer, the cell is isolated from the surrounding volume in a small chamber.

Single-virus fusion experiments reveal proton influx into vaccinia virions and hemifusion lag times.

Recent studies have revealed new insights into the endocytosis of vaccinia virus (VACV). However, the mechanism of fusion between viral and cellular membranes remains unknown. We developed a microfluidic device with a cell-trap array for immobilization of individual cells, with which we analyzed the acid-dependent fusion of single virions.

Bubble-free electrode actuation for micro-preparative scale electrophoresis of RNA.

A microfluidic chip is presented for lysis and one-step RNA purification from bacteria. Bacteria are lysed by joule-heating followed by a gel electrophoresis step for clean-up and subsequent elution of small RNA. Bubble formation during electrophoresis at constant current is suppressed through the use of a silver chloride cathode and a silver anode.

A facile protocol for the immobilisation of vesicles, virus particles, bacteria, and yeast cells.

Immobilisation of liposomes and cells is often a prerequisite for long-term observations. The most common immobilisation approaches rely on surface modifications, encapsulation in porous materials or trapping in microfluidic channels by means of hurdle-like structures. While these approaches are useful for larger mammalian cells, the immobilisation of smaller organisms like bacteria and yeast or membrane model systems such as liposomes typically requires modification of their outer membrane to ensure that they are stably arrested at a defined position.

A microchamber array for single cell isolation and analysis of intracellular biomolecules.

We present a microfluidic device that enables the determination of intracellular biomolecules in multiple single cells. The cells are individually trapped and isolated in a microchamber array. Since the microchambers can be opened and closed reversibly, the cells can be exposed to different solutions sequentially, e.

A microfluidic vesicle screening platform: monitoring the lipid membrane permeability of tetracyclines.

For many drugs including antibiotics such as tetracyclines it is crucial that the molecule has the ability to quickly and passively permeate lipid membranes. Hence, the understanding of the permeability in relation to the molecular structure is an important aspect to rationally design novel pharmaceutically active compounds with high bioavailability. Here, we present a versatile method to study the kinetics of tetracycline permeation across liposome membranes on a microchip.

Tip-enhanced Raman spectroscopic imaging of patterned thiol monolayers.

Full spectroscopic imaging by means of tip-enhanced Raman spectroscopy (TERS) was used to measure the distribution of two isomeric thiols (2-mercaptopyridine (2-PySH) and 4-mercaptopyridine (4-PySH)) in a self-assembled monolayer (SAM) on a gold surface. From a patterned sample created by microcontact printing, an image with full spectral information in every pixel was acquired. The spectroscopic data is in good agreement with the expected molecular distribution on the sample surface due to the microcontact printing process.

Precise electrochemical fabrication of sub-20 nm solid-state nanopores for single-molecule biosensing.

It has recently been shown that solid-state nanometer-scale pores ('nanopores') can be used as highly sensitive single-molecule sensors. For example, electrophoretic translocation of DNA, RNA and proteins through such nanopores has enabled both detection and structural analysis of these complex biomolecules. Control over the nanopore size is critical as the pore must be comparable in size to the analyte molecule in question.

Controlling the length and location of in situ formed nanowires by means of microfluidic tools.

Progress in microelectronics, sensors and optics is strongly dependent on the miniaturization of components, and the integration of nanoscale structures into applicable systems. In this regard, conventional top-down technologies such as lithography have limits concerning the dimensions and the choice of material. Therefore, several bottom-up approaches have been investigated to satisfy the need for structures with large aspect ratios in the nanometre regime.