A ‘smart’ insulin patch that can detect increases in blood sugar levels and secrete doses of insulin into the bloodstream could replace painful injections for diabetics, scientists say.
Researchers at the University of North Carolina and NC State University, developed the patch – a thin square no bigger than a penny – which is covered with more than one hundred tiny needles, each about the size of an eyelash.
The study, which is published in the Proceedings of the National Academy of Sciences, found that the new, painless patch could lower blood glucose in a mouse model of type 1 diabetes for up to nine hours.
“We have designed a patch for diabetes that works fast, is easy to use, and is made from nontoxic, biocompatible materials,” said co-senior author Zhen Gu, a professor in the Joint UNC/NC State Department of Biomedical Engineering.
“The whole system can be personalised to account for a diabetic’s weight and sensitivity to insulin so we could make the smart patch even smarter,” Gu said.
For the study, Gu and his colleagues chose to emulate the body’s natural insulin generators known as beta cells. These versatile cells act both as factories and warehouses, making and storing insulin in tiny sacs called vesicles.
“We constructed artificial vesicles to perform these same functions by using two materials that could easily be found in nature,” said Jiching Yu, a PhD student in Gu’s lab.
The first was hyaluronic acid or HA, a natural substance found in many cosmetics. The second was 2-nitroimidazole or NI, an organic compound used in diagnostics.
The researchers connected the two to create a new molecule, with one end that was water-loving or hydrophilic and one that was water-fearing or hydrophobic.
A mixture of these molecules self-assembled into a vesicle, much like the coalescing of oil droplets in water, with the hydrophobic ends pointing inward and the hydrophilic ends pointing outward.
The result was millions of bubble-like structures, each 100 times smaller than the width of a human hair. Into each of these vesicles, the researchers inserted a core of solid insulin and enzymes specially designed to sense glucose.
In lab experiments, when blood sugar levels increased, the excess glucose crowded into the artificial vesicles. The enzymes then converted the glucose into gluconic acid, consuming oxygen all the while.
The resulting lack of oxygen or “hypoxia” made the hydrophobic NI molecules turn hydrophilic, causing the vesicles to rapidly fall apart and send insulin into the bloodstream.
The researchers then decided to incorporate these balls of sugar-sensing, insulin-releasing material into an array of tiny needles.
Gu created these “microneedles” using the same hyaluronic acid that was a chief ingredient of the nanoparticles, only in a more rigid form.
Researchers then arranged more than one hundred of these microneedles on a thin silicon strip to create what looks like a tiny, painless version of a bed of nails.