- A novel polymer helps insulin cross the skin without needles or skin damage
- In animal studies, insulin delivered through the skin worked as well as injections
- The approach may open the door to non invasive delivery of other large medicines
Transdermal drug delivery is well established for small molecules, offering convenience and good adherence.
The outer layers of the skin, however, form an effective barrier against larger molecules, including proteins and peptides such as insulin.
Existing methods to increase skin permeability, including microneedles, ultrasound and chemical enhancers, tend to be invasive or can damage skin structure, which limits long term use.
Researchers have been searching for a way to deliver insulin through intact skin without compromising its protective role.
A fast skin permeable polymer
Rongjun Chen, Youqing Shen, Jiajia Xiang, Ruhong Zhou and colleagues report a polymer called poly[2 (N oxide N,N dimethylamino)ethyl methacrylate], referred to as OP. This polymer can move rapidly through different layers of the skin by interacting with the skin’s natural pH gradient.
When OP is combined with insulin, it acts as a carrier, enabling insulin to cross the skin barrier and enter the bloodstream. Once in circulation, the insulin accumulates in tissues that are central to blood glucose control, including the liver and skeletal muscles.
Results in mice and minipigs
In diabetic mice and minipigs, applying an OP insulin formulation to the skin lowered blood glucose into the normal range within one to two hours. The effect was similar to that achieved with injected insulin and lasted for up to twelve hours.
Importantly:
- The polymer did not disrupt skin architecture
- There were no observed adverse effects on skin cells, blood cells or major organs such as the liver and kidneys
- Insulin retained its biological activity after transport with OP
Molecular dynamics simulations suggested that insulin, once delivered, can still bind effectively to insulin receptors, supporting the idea that its function is preserved.
What needs to happen before clinical use
The study suggests that OP can achieve meaningful skin permeation without physically breaching the skin. If confirmed in humans, this could provide a needle free alternative for insulin delivery and potentially a platform for other large biomolecules.
However, several questions remain. Further work must examine:
- Long term safety of repeated application
- Precise dose control with transdermal delivery
- Effects on different skin types and in varied clinical settings
- Practicalities of patch or cream design for everyday use
