Yesterday I wrote about the use of microfluidics chips for imaging neuronal activity and the behaviour correlated with it in the nematode worm C. elegans, without going into too much detail about exactly what microfluidics is.
Microfluidics is a multidisciplinary field – a combination of chemistry, physics, engineering and biotechnology – which involves the manufacture of devices that contain sub-millimeter-sized channels and which can be used to control the movements of miniscule amounts of fluids (nano-, or even picoliters).
Starting in the 1990s, microfluidics began to revolutionize molecular biology, and the technology is today applied widely, in, for example, the manufacture of DNA microarrays. Microfluidics-based devices are now being used to diagnose diseases and to detect toxins or pathogens in both biological and non-biological samples.
And, because these chips can be to used manipulate such tiny amounts of fluids, they are now beginning to transform neuroscience too.
For example, microfluidic chips seem ideal for investigating processes such as cell migration and axon guidance, which involve concentration gradients of diffusible and substrate-bound chemical signals. (See Dan Rhoads‘s Ph.D. thesis; he links to a PDF of the introduction in this post.)
Larry Millet and his colleagues, of the University of Illinois at Urbana-Champaign, now report that they have used microfluidics devices to culture nerve cells. The devices consist of cell-sized chambers in which individual neurons can be grown in isolation. They therefore enabled the researchers to define and closely control the local environment in which the neurons were kept.
The image at the top shows a hippocampal neuron from a newborn rat growing on such a device. Towards the top left, the dendrites of the cell can be seen aligning themselves along the edges of the channels in the chip.
Cultured cells need to be kept immersed in a medium containing growth factors and other substances. The cells take up these substances, so, with conventional cell culture techniques, the medium needs to be replaced regularly so that the cells remain alive.
Using the microfluidics chips they developed, Millet and his colleagues provided their cells with a continuous supply of growth medium. The cells therefore remained viable for much longer than they could have been if cultered by conventional means. They were also able to differentiate further, so that they more closely resembled mature neurons.
The cells cultured in these devices were completely isolated. Chips in which each cell is isolated in its own chamber, but is in close proximity to the cells in adjacent chambers, would enable researchers to investigate cell-to-cell signalling, and other neuronal processes, in unprecedented detail.
Millet, L. J., et al. (2007). Microfluidics devices for culturing primary mammalian neurons at low densities. Lab Chip 7: 987-994. [Full text]