Researchers at the Imperial College London and the Houston Methodist Research Institute have developed biodegradable, silicon "nanoneedles" that can deliver genetic material to stimulate the growth of blood vessels. They could perhaps even be used to reprogram living cells as needed in a safe, non-invasive manner.

Scientists have been looking for effective ways to stimulate angiogenesis, the body’s ability to grow new blood vessels, to help with organ transplants and medical conditions like myocardial ischemia. Past approaches have ranged from growing vessels in the lab for future transplant, to less invasive injections and bandages.

Dr. Ciro Chiappini and colleagues are one of many teams investigating the approach of directly delivering nucleic acids, the building blocks of all living organisms, to selected cells by injecting them through the cell’s membrane. The exciting aspect of this method is that it could be used not only for regrowing blood vessels (in itself a big achievement), but perhaps also to one day genetically reprogram cells to carry out specific functions.

While this approach isn't new, previous attempts were not able to do deliver genetic material efficiently, at scale, or even safely, because of the toxic materials employed. The team led by Dr. Chiappini, however, claims it has finally managed to solve these issues.

Human cells (green) on the nanoneedles (orange), getting DNA injected into their nuclei (blue) (Image: Imperial College London)

Genetic material is delivered to the cells through "nanoneedles" made of biodegradable silicon. The needles are highly porous, which allows them to can carry a heavier load of nucleic acids than previous structures, and their sharp points can easily penetrate the membrane of the cell to deliver its cargo, but still does not harm it. According to the scientists, the silicon degrades after two days leaving only a small amount of harmless, non-toxic residues.

The researchers tested their method by successfully delivering DNA and siRNA to human cells in vitro. They were then able to use the nanoneedles to deliver nucleic acids to the back muscles of mice. This reportedly increased the formation of blood vessels six-fold after a week, with vessels continuing to grow for a further two weeks without causing detectable side effects.

"Perhaps in the future it may be possible for doctors to apply flexible bandages to severely burnt skin to reprogram the cells to heal that injury with functional tissue instead of forming a scar," says Chiappini. "Alternatively, we may see surgeons first applying the nanoneedle bandages inside the affected region to promote the healthy integration of these new organs and implants in the body. We are a long way off, but our initial trials seem very promising."

The scientists are now looking for ways of using nucleic acids to re-program cells, changing their functions. If this is ever achieved, the medical repercussions could be very significant.

"By gaining direct access to the cytoplasm of the cell we have achieved genetic reprogramming at an incredible high efficiency," says corresponding author Ennio Tasciotti. "This will let us personalize treatments for each patient, giving us endless possibilities in sensing, diagnosis and therapy."

The advance is described in the latest issue of the journal Nature Materials.

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