Lab on a Chip Blog

Cells labelled with magnetic nanoparticles are useful for a number of applications, ranging from MRI to drug delivery and cancer therapy, and being able to sort said cells based on their magnetic nanoparticle loading is obviously necessary. Continuous flow methods currently exist for separating cells based on the extent of their magnetisation, but only for cells where the nanoparticles have been bound to them via specific surface markers.

Photograph of the microfluidic magnetophoresis chip

In this paper Claire Wilhelm (University of Paris Diderot) and Nicole Pamme (University of Hull) make use of the other mechanism of introducing nanoparticles to the cells  – exploiting the natural ability of monocytes and macrophages to engulf molecules. The team produced a free-flow microfluidic chip with an external magnet to separate the cells through five different exits, depending on the loading of magnetic nanoparticles. They demonstrated successful and efficient separation of the monocytes and macrophages, with monocytes displaying a much weaker endocytotic ability than macrophages, at rates of 10 to 100 cells per second.

For the full details download the article – it’s free to access for 4 weeks:

Cell sorting by endocytotic capacity in a microfluidic magnetophoresis device
Damien Robert, Nicole Pamme, Hélène Conjeaud, Florence Gazeau, Alexander Iles and Claire Wilhelm
Lab Chip, 2011, Advance Article
DOI: 10.1039/C0LC00656D

Identifying drugs that have the potential to cause heart dysfunction as early as possible is crucial for preventing the waste of time and money in drug discovery processes.

Cell-based biosensors using living cells have been applied in pharmacological screening, but current technologies encounter difficulties such as small measurement areas, complicated fabrication procedures and high costs.  However, the rapid development of digital consumer technologies has driven down the cost and created compact imaging sensor modules such as CMOS (complementary field oxide semiconductor) imaging senors.  

In this HOT article, Ali Khademhosseini (Harvard Medical School) and colleagues made use of this development, extracting the CMOS sensor from a webcam and using it with an image processing algorithm to measure cardiotoxicity in cardiomyocytes.  They were able to detect beat-to-beat variability in real-time after treatment with drugs iosprenaline and doxorubicin.

The authors hope this neat system may be useful for a range of cell-based biosensing applications.

Download the article for free for 4 weeks:

A cell-based biosensor for real-time detection of cardiotoxicity using lensfree imaging
Sang Bok Kim, Hojae Bae, Jae Min Cha, Sang Jun Moon, Mehmet R. Dokmeci, Donald M. Cropek and Ali Khademhosseini
Lab Chip, 2011, 11, 1801-1807
DOI: 10.1039/C1LC20098D, Paper

Ju-Hee So and Michael Dickey from North Carolina State University present an extremely simple fabrication route for microfluidic electrodes by using metal alloys with low melting point , such as eutectic gallium indium.

The liquid metal injected into the microchannels is inherently aligned and in direct contact with the fluid, but is neatly prevented from mixing with the fluid by posts with spacings that are too small to allow the metal to easily flow through.  The metal also maintains its shape despite being a liquid, due to the spontaneous formation of a thick oxide skin.  The mechanical stability of the electrodes was demonstrated in operating conditions commonly used in microfluidic applications, and as a proof-of-principle, used for electrohydrodynamic mixing, which requires extremely high electric fields.

The authors believe that this technique is significantly simpler and easier to implement than anything that has been published to date in the literature – why not download the article and see for yourself?  The article is free to access for 4 weeks!

Inherently aligned microfluidic electrodes composed of liquid metal
Ju-Hee So and Michael D. Dickey
Lab Chip, 2011, 11, 905-911
DOI: 10.1039/C0LC00501K