When describing skin structure, the “brick and mortar” model is frequently used. This is because the structure of a mortar (lipids, sebum) firmly connecting aligned bricks (skin cells) into a wall is similar to the skin. Due to this, hydrophilic(lipophobic) substances, especially bigger particles, can hardly pass through the skin than hydrophobic(lipophilic) substances.
No matter how potent they are, medicines prove its efficacy once absorbed into the body. In particular, the transdermal drug delivery system (delivering a drug through the skin) can minimize whole-body side effects and abdominal discomfort. Also, the drug directly activates without metabolization; thus, it is applicable even if one has liver or kidney problems.
These advantages allow the transdermal drug delivery system to be applied in a wide range including various skin disease treatments, vaccination, genes or exosome delivery, cosmetics penetration, etc. However, it is not easy for hydrophilic medicines to be absorbed through lipophilic skin without using special techniques.
The most common and traditional method of transdermal drug delivery is a patch (like the nicotine patch), where delivery is made according to its concentration differences. But other methods using physical modification, electrical differences, and pressure are emerging.
First, a method using physical modification is known as the “microneedling,” making tiny holes on the skin in which drugs can penetrate through. Needles made of iron are usually used traditionally, but soluble needles, which contain drugs within themselves, are being developed recently.
As an electrical method, electrophoresis is generally applied. Using the principle of pushing away the same electrical polarity (like negative and negative) from each other, an electric plate or stick with the same polarity of a liquid state of the drug is applied to penetrate the skin. The most common usage of it is “vitamin C iontophoresis” for melasma.
A relatively new delivery method of using pressure is a device that shoots drugs into the skin like an air gun, utilizing instantly increased pressure. Classical devices are gas or air injectors, but control of the fine pressure is difficult, resulting in too much of drugs injected at a time with an uneven amount. Also, it is much painful, and the injection speed is not so fast, shooting once every 1-2 seconds.
The need for a transdermal drug delivery system with painless, fine adjusting of drug amount, and fast injection drives the development of new technology, and finally, “Mirajet”, a brand-new technology has come out and is grabbing attention. I had been involved in the development and research of the technology at the beginning and presented the world’s first patient live demonstration in Frankfurt, Germany in 2018.
As JSK Biomed’s “Mirajet” is a medical device with the world's first technology invented in Korea, it had quite a lot of difficulties from classification to approval. But finally, it obtained approval from the Korea Ministry of Food and Drug Safety and CE marking from Europe this year. It is planning on applying for permission to the U.S. FDA soon.
The principle of “Mirajet” is similar to the other pressure-based transdermal drug delivery system, but its generation of pressure is created by the laser, not by air or gas. Therefore, it can be administrated more precisely and repetitively with faster speed because the pressure is made at every shot of the laser.
The interior of the Mirajet nozzle consists of two chambers. When the laser focuses on the upper room filled with water and explodes, the generated pressure pushes down the membrane in the middle. That pressure, then, pushes the drugs in the lower room to be administered through the skin (refer to the image).
“Mirajet” is developed as an add-on device for most commercial lasers, and it is also called a “needle-free injector” for injecting precise amounts in microliters with the rate of 10 to 40 shots per second and most importantly without pain. In fact, I remember how surprised the executives of a European big Pharma, who received the procedure without anesthesia at my live demonstration, for feeling no pain.
It is confirmed that the ink successfully penetrates the skin with a constant interval and depth through a pigskin and gelatin in an experiment. I injected botulinum toxin into my forehead by myself with a prototype device and I can guarantee that the effect is similar to using a syringe. It is expected that the transdermal drug delivery system using new technologies will continue to develop further in the future.
