Lab on a Chip Blog

Researchers at Philipps-Universität Marburg, Germany, have developed a new technique for the production of polyplexes that produces more regular sized complexes compared to the standard pipetting methods. Polyplexes are the complexes that form by electrostatic interactions of oppositely charged macromolecules – in this case poly(ethylene imine) (PEI) and plasmid DNA, which are used in gene therapy applications.

The group, led by Thomas Kissel, developed a method that produces the complexes using microfluidics on a chip. Over the course of the study, they investigated the factors that could affect the complex size, and discovered that the most important factor was the ratio of PEI to DNA, whilst other factors were not as important. Using the chip method, regular sized complexes (140 nm and 160 nm) were produced, compared to the more irregular pipetting method. The team also showed that different (targeted) PEI-based vectors could be used for the formation of complexes with pDNA and siRNA.

Read the details of the study here:

Optimized preparation of pDNA/poly(ethylene imine) polyplexes using a microfluidic system
Heiko Debus, Moritz Beck-Broichsitter and Thomas Kissel
DOI: 10.1039/C2LC40176B

This HOT article is free to access for the next four weeks following a simple registration for individual users.

Scott Manalis and coworkers at MIT have developed a microfluidic version of the “baby-machine”, a device used to synchronize eukaryotic cells at a specific point in the cell cycle for study of cellular and molecular processes.

The original method which was developed in the 1960s chemically bound cells to a membrane. As they divide one cell remains attached to the membrane and the ‘newborn’ cell is eluted, producing a synchronised population of cells in the G1 phase of the cell cycle.  However, the method of chemically attaching cells to the membrane is not suitable for all cell types.  Manalis et al have modified this procedure to attach cells by applying pressure differences to capture cells on their microfluidic device, thereby avoiding the use of chemicals that can make cells non-viable.

Read more…
A microfluidic “baby machine” for cell synchronization
Josephine Shaw, Kristofor Payer, Sungmin Son, William H. Grover and Scott R. Manalis
DOI: 10.1039/C2LC40277G

Xing-Hua Xia and colleagues at Nanjing University have recently improved on the fluorescent analysis of proteins by utilising the confines of a nanochannel in a microfluidic device.  The nanochannel allows the efficient concentration of proteins and separates labelled proteins from unreacted fluorescent labels due to size.  This removes the need for purification to remove the unreacted dye on an external chromatographic instrument and allows protein concentration, labelling, and purification in continuous manner in one device.

Read more…
Rapid protein concentration, efficient fluorescence labeling and purification on a micro/nanofluidics chip
Chen Wang, Jun Ouyang, De-Kai Ye, Jing-Juan Xu, Hong-Yuan Chen and Xing-Hua Xia
DOI: 10.1039/C2LC20977B

These latest two HOT articles are free to access for 4 weeks following a simple registration for individual users

Measuring the ability of compounds to cross various tissue barriers is of critical importance during drug development, as most drugs will have to cross at least one tissue barrier to reach their target.  Various assays already exist to assess this process, but have shortcomings such as being prone to artefacts or failing to provide information on permeation pathway. Now Joachim Wegener and colleagues have devised a new silicon chip to visualise permeability, with the ability to see defects within the cell layer and details about the permeation route. Read more…

Macroporous silicon chips for laterally resolved, multi-parametric analysis of epithelial barrier function
Stefanie Michaelis,  Christina E. Rommel,  Jan Endell,  Petra Göring,  Ralf Wehrspohn,  Claudia Steinem,  Andreas Janshoff,  Hans-Joachim Galla and Joachim Wegener
DOI: 10.1039/C2LC00026A

On a completely different topic the next HOT article is on acoustofluidics.  Henrik Bruus et al present a simple method based on measuring light intensity to determine the acoustic energy density in microchannel.  This parameter can be used as a measure of acoustophoretic performance, but is typically tricky to measure.  Read how they achieved it:

Measuring acoustic energy density in microchannel acoustophoresis using a simple and rapid light-intensity method
Rune Barnkob,  Ida Iranmanesh,  Martin Wiklund and Henrik Bruus
DOI: 10.1039/C2LC40120G

Remember – these articles are  free (if you have an RSC Publishing account) for the next four weeks!