A team from Zhejiang University in China, through experiments on mice, piglets, and lab-grown human skin models, has demonstrated that a compound combining insulin and a charge-transfer polymer called poly[2-(N-oxide-N,N-dimethylamino)ethyl methacrylate] or OP, can penetrate the tough skin barrier that normally prevents the passage of large, hydrophilic molecules such as insulin.
On the surface of the skin, which is slightly acidic, the polymer carries a positive charge, causing the fats and oils on the skin to adhere, thus ensuring the stability of the compound on the surface.
As it moves to deeper layers where acidity tends to neutralize, the polymer loses its positive charge, its adhesion to fats decreases, and it becomes able to slip between skin cells, reaching the inner layers and releasing insulin inside the body.
When it is linked to insulin to form the OP-I complex, the system becomes able to deliver the hormone into the body efficiently.
During the experiments, the compound successfully restored glucose levels to normal in mice within one hour and maintained its effect for 12 hours, with efficacy similar to injections. Experiments on piglets yielded similar results, with glucose levels decreasing within two hours and remaining stable for 12 hours as well.
Once in the body, the compound concentrates in glucose-regulating tissues—such as the liver, fat, and muscle—to release insulin into cells, activating its pathways and facilitating glucose uptake. Furthermore, trials have not recorded any signs of inflammation or significant side effects, demonstrating its initial safety profile.
Researchers believe this technique could pave the way for delivering other types of large biomolecules through the skin, including proteins, peptides, and nucleic acids, which could expand the horizons of non-invasive treatments (therapeutic methods that do not require penetrating the body with needles or surgery) in the future.
The study was published in he journal Nature.
