Last week, a paper titled "A skin-permeable polymer for non-invasive transdermal insulin delivery" was published in Nature.
Until now, the ability to "administer drugs through the skin"—like compresses or patches—has been limited to drugs with a molecular weight of 500 or less. While anti-inflammatory analgesic compresses are the most commonly used, patches containing isosorbide dinitrate or nitroglycerin (which have coronary vasodilating effects) also slowly release ingredients through the skin. However, for peptides and proteins with large molecular weights like insulin (approx. 5,800), the skin acts as a formidable barrier preventing entry, leaving injection as the only option. Theoretically, the idea that applying collagen (molecular weight approx. 300,000; collagen peptides are in the thousands) makes the skin "plump" is actually impossible.
In this paper, the authors discovered a special material called "poly[2-(N-oxide-N,N-dimethylamino)ethyl methacrylate] (OP)" (a homopolymer; the "poly[ ]" notation indicates that many molecules named [2-(N-oxide-N,N-dimethylamino)ethyl methacrylate] are linked together). This functions as a drug "carrier," enabling the uptake of insulin into the body. This OP breaks through the skin barrier by changing its properties depending on the location. On and in the skin (which is acidic), it takes on a "positive charge" to pass between the lipids on the surface. Once it enters beneath the skin (a neutral-pH environment), the OP loses its electrical charge and appears to move by "hopping" across cell membranes, thereby allowing it to reach blood and lymph vessels.
When insulin was attached to this OP and applied to the skin of diabetic mice and mini-pigs, blood glucose levels dropped to a normal range, just as they would with an injection. It would be wonderful if this can be used without issues in humans. If this technology is practically applied, diabetic patients might no longer need to endure painful daily injections. Expectations are also rising: perhaps cancer vaccines could also be utilized without painful experiences?
However... however.
When applying a compress for lower back pain or stiff shoulders, I feel there is a significant sensory difference between when the body is warmed up after a bath and when it is not. What happens during times of heavy sweating, such as during sports? What about for people like me—faint-hearted types whose sweat glands fly open when nervous, causing sweat to seep out? There are already large individual differences in drug absorption from the intestinal tract... Am I the only one concerned about such seemingly trivial matters?
