A PRINTER that spits out ultra-fine droplets of cells instead of ink has been used to print live brain cells without causing them any apparent harm. The technique could open up the possibility of building replacement tissue cell by cell, giving doctors complete control over the tissue they graft.
The device is a variant of a conventional ink-jet printer. Instead of forcing individual droplets of ink through a needle-shaped nozzle and onto the page, the cell printer uses a powerful electric field to produce droplets just a few micrometres in diameter, far smaller than is achievable by other means.
Several research groups have shown that modified ink-jet printers can spray droplets of live cells suspended in a sustaining solution. But these devices have not been able to print droplets smaller than 20 micrometres across, because ultra-fine nozzles are prone to blocking. Now the 鈥渆lectro-spray鈥�, developed by Suwan Jayasinghe of University College London along with Peter Eagles and Amer Qureshi at King鈥檚 College London, has for the first time been able to produce droplets as small as a few micrometres in diameter, each containing only a handful of living cells.
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To make their cell printer, the researchers use a technique called electro-hydrodynamic jetting (Biotechnology Journal, vol 1, p 86). They apply a high voltage to the liquid to give it an electrostatic charge as it flows out of the nozzle, and as this charge interacts with an electric field between the nozzle and the page the liquid flow breaks up into a spray of minute droplets.
To see how the process would affect living cells, the researchers used their device to print human T-cells and mouse brain cells. Though the cells were subjected to an electric field generated by a potential difference of 30 kilovolts over a distance of 15 millimetres, they apparently suffered no harm and continued to behave normally after printing.
鈥淭he printer produces droplets just a few micrometres in diameter鈥�
Further experiments are needed to confirm that the cells suffer no long-term harm. Brian Derby of the University of Manchester, UK, who is using conventional ink-jet technology to print cells, says, 鈥淎 key issue is whether any technique can print three-dimensional structures containing cells that survive for useful periods of time.鈥�
