A thumbnail-sized chip is mimicking the turbulent conditions a drug experiences on its journey through the body. Franz Gabor, at the University of Vienna, and colleagues in Austria and Germany developed the sound-driven biochip that can be used to study how moving bodily fluids affect cell-particle interactions.

Nanoparticles with tailored properties are promising vehicles for drug delivery. But to develop these systems, researchers need to better understand how the body affects the particles' route to their target. This means that they must simulate the physiological environment in the lab. Gabor's team has developed a fully biocompatible system that mimics a wide range of flow conditions, such as those that would be found in the circulatory system, on a microfluidic chip. 

Bioadhesive proteins help nanoparticles to stick to cells in flow conditions

'At the heart of our flow system is the surface acoustic wave pump which is only as big as pinhead,' says Christian Fillafer, a member of the European team. 'When the pump is activated, it generates a nano-earthquake on the chip surface and liquid can be streamed by placing it into the epicentre.' Using a liquid containing a cell and nanoparticle mixture, the researchers can monitor how stress affects the particles' interactions with the cells. 

'Using this set up we observed that flow completely inhibits nanoparticle binding to cells, unless the particle surface is modified with a bioadhesive protein,' says Fillafer. 'This bears implications for drug delivery with nano- or microparticles, since flow is omnipresent in the body from the urinary tract to the cardiovascular system.' 

Michael Köhler, an expert in miniaturisation biotechnology at the Ilmenau University of Technology, Germany, agrees that the findings may have consequences for drug delivery. He suggests that 'further investigation could address the behaviour of other cell types and classes of particles.' In particular, he adds that 'studying interactions of lymphocytes [key to the immune system] with bacteria, viruses and cancer cells could be of particular interest.'

The pump's small size and lack of tubes and connectors makes it ideal for use in highly miniaturised devices. Gabor's team is now developing a platform that can generate identical flow conditions in several independent microchannels. They suggest that, as well as for fundamental research into cell-particle binding, the device could be used for drug screening studies that are not possible with large scale conventional systems. 

Philippa Ross

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