But these potential advantages require the needle to work as hoped. Lim and his colleagues have experimented with the needle in agarose moulds and live pigs, but they began testing the device and the surgical workflow with real human tissue last week.

The tests were largely successful. The researchers verified that the device can be mounted stably to the skull, and that injections take only a few minutes and go to the anticipated place. There was one hitch: when the device was mounted on the skull, some of its calibration markings were hard to read, but Lim says this will be easy to fix.

Even so, Goldman anticipates that simple, straight needles will still be used for therapies in the next several years. He is part of the Empire State Stem Cell Board, a consortium that received US$12 million last year to bring a stem-cell therapy for multiple sclerosis to clinical trials. Goldman thinks that the cell type he is working with could travel far beyond where they are placed with a needle. “They really zip along quickly,” he says.

Lim’s needle is not the only new brain-injection device being tested for human use. Ivar Mendez, a neurosurgeon at Dalhousie University in Halifax, Canada, has created the Halifax Injector, which delivers cells not by a manually controlled syringe by tiny computer-controlled motors. Up till now, Mendez says, “The way the injection has been done was with very primitive systems."

There's no question delivery will be important, but solving that problem will require better a better understanding of how cell therapies in the brain work, says Gary Steinberg, chair of neurosurgery at Stanford University in Palo Alto, California. “We still don’t know what cell type,” he says. “We don't even know if direct-to-the-brain is the right route of administration.” Each disease, injury, and cell type poses new sets of issues, he says.

But Lim worries that efforts like his are already behind, given the state of advancement in the development of new therapies.  “If we don't do the work now before we think we need it, then it will never be ready.”

Clarified: An earlier version of the article stated, in reference to using the device to treat Pelizaeus–Merzbacher disease, that UCSF and StemCells scientists "hope to get regulatory approval to do so by the end of the year". StemCells is currently not involved in clinical trials needed for approval of device, but the device might be incorporated into future trials, pending US Food and Drug Administration clearance known as 510(k).

This article is reproduced with permission from the magazine Nature. The article was first published on March 4, 2013 and clarified on March 6, 2013.

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