In the U.S., approximately 6 million people use insulin to help control their diabetes and prevent their bodies from going into diabetic shock. They do this by injecting themselves with pens or syringes, or have insulin pumps implanted in their body.
While effective, those options are uncomfortable, invasive and, in the case of needles, require biohazard disposal. Researchers have explored other ways to deliver insulin, such as a gel-like lotion spread on the arm or stomach. However, the skin has always proved too tough a barrier for drugs to easily pass through to enter the bloodstream.
But, not all skin is made equal. Skin, with a total thickness of about 2 mm is an adequate barrier for drugs. The membrane lining the inside of your mouth, however, is only about 500 μm—1/4 of the thickness of skin found on other parts of the body. Additionally, it has characteristic pore sizes of ∼20 to 200 nm, further opening the door to easy drug delivery.
With that in mind, Sabine Szunerits, a professor of chemistry at University of Lille (France), and her colleagues wanted to see if a material they had previously developed could attach to the inside of a cheek’s lining to deliver insulin.
In the study, the researchers soaked the nanofiber mat—made from electrospun fibers of polyacrylic acid, β-cyclodextrin and reduced graphene oxide, in a solution with insulin for three hours. Then, the team applied the insulin-loaded patches onto cheek linings and corneas of pigs.
Heating the patch to 122 F with a near-infrared laser for 10 minutes activated the polymer material and released insulin into the two types of membranes several times faster than through skin. As soon as the material was activated, the pig’s blood sugar levels declined. Simultaneously, the animals’ plasma insulin levels increased, which the researchers say is proof-of-concept that this unconventional platform is effective at getting insulin into the bloodstream.
Additionally, the pigs’ cheek linings showed no irritation or visual changes from the laser’s heat, so the researchers placed a placebo version of the patch inside the cheeks of six human volunteers. All volunteers rated the patch as excellent, with most feeling comfortable. None of the volunteers reported interference with speech nor effects on saliva production and swallowing. The volunteers wore the patch for 120 minutes, in which adhesion was excellent with no movement of the patch.
In their study published in ACS Applied Bio Materials, Szunerits and her research team says the mucoadhesive patch could be especially suited to treat type 2 diabetes, the most common form of the disease. For people with type 2 diabetes, oral medication is often supplemented by basal insulin therapy, which involves taking a low dose of slow-acting insulin to moderate blood glucose when not actively eating.
“The quantity of insulin released from the mucoadhesive patches could be in line with their use in basal therapy,” the authors write in their paper. “Compared with multiple insulin injection, this mode of delivery offers a huge advantage by increasing the compliance of patients to treatment, as it is resilient and can be easily self-administrated.”
The researchers say their next step is to conduct further preclinical studies of the prototype on animal models.
Photo: A prototype patch comfortably sticks inside the cheek to deliver insulin. Credit: Adapted from ACS Applied Bio Materials 2022, DOI: 10.1021/acsabm.1c01161