Revolutionise the DNA transfer to cells

The MEMS (microelectromechanical system) nanoinjector for genetic modification of cells, set up here (top) with a polymer sphere the size of a mouse zygote for demonstration.
Credit: Brigham Young University

This amazing device is not actually new, but we missed Brigham Young University’s announcement when they unveiled it last year. This week, though, it became an internet sensation when someone posted it on Reddit. And well it might – it’s a breathtaking piece of engineering and is an ingenious way to remove the downside from current techniques of introducing genetic material to the nucleus of an egg.

The traditional method, called “microinjection,” involves using a small (for that read very, very, very small) glass pipette to pump a solution containing DNA into the nucleus. But that runs the risk of damaging the egg and the nucleus. The extra fluid can cause the cell to swell and destroy it. The death rate of cells in this way is anywhere between 25 and 40%.

But the researchers at Brigham Young University looked at the problem from a different angle – as engineers are wont to do.

They worked on the fact that DNA is positively charged.

“Essentially, we use electrical forces to attract and repel DNA — allowing injections to occur with a tiny, electrically conductive lance,” explained Brian Jensen, associate professor in the Department of Mechanical Engineering at Brigham Young University.  “DNA is attracted to the outside of the lance using positive voltage, and then the lance is inserted into a cell.”

The nanoinjection process. (A) DNA is put in ambient media with target cell, lance, and constraining arms. (B) A positive voltage is applied to the lance to attract negatively charged DNA. (C) The lance enters the target cell. (D) A negative voltage is applied to the lance to repell DNA into the cell. (E) The lance and constraining arms are retracted to release the cell.
Credit: Brigham Young University

The nanoinjector’s lance is incredibly small and no extra fluid is used, so cells undergo much less stress.

It may also mean that injections can be performed in animals with cloudy or opaque embryos. “Such animals, including many interesting larger ones like pigs, would be attractive for a variety of transgenic technologies,” said Jensen. “We believe nanoinjection may open new fields of discovery in these animals.”

As a next step, Jensen and colleagues are performing injections into cells in a cell culture using an array of lances that can inject hundreds of thousands of cells at once. “We expect the lance array may enable gene therapy using a culture of a patient’s own cells,” he said.

As to how the tiny machine is made, the researchers used MEMSCAP’s proprietary polyMUMPs process – a wafer process – using one polycrystalline silicon substrate layer, two structural layers of polycrystalline silicon and a gold layer for increasing electrical conductivity. The two structural layers are 2.0 micrometres and 1.5 micrometres thick, respectively. (A micrometre is 1,000th of a millimetre and a human hair is about 10 micrometers thick).

The video below, released in May last year when the device was first unveiled, has a great explanation of how the device works.

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