Can vaccines and other drug solutions be delivered without an intramuscular injection?
If you said yes, you’re correct! Transdermal and microneedle patches deliver medications through adhesive skin contact.
As a flexible material converter, Strouse helps build skin adhesive products that hold medical devices, like the patches that press microneedles up against the skin (albeit not the needles themselves).
Creating a safe bond between the adhesive and the skin is crucial for the long-term contact needed for the drug solution to take effect. That’s why today, we’re explaining how microneedle patches work and how they’re manufactured.
What Are Microneedle Patches?
Microneedle patches are a type of transdermal patch that has been embedded with an array of tiny needles to deliver the drug solution.
Every microneedle patch has an adhesive layer that sticks to the skin and needles that puncture the skin to facilitate drug delivery. Some microneedle patches contain the drug solution meant to enter the body, but others are used in tandem with transdermal patches for solution application.
There are many potential use cases for microneedle patches, including: drug or vaccine delivery, disease diagnostics, cosmetics, and patient health monitoring.
Microneedle patches are a safe and easy alternative to certain shots or oral medications, ideal for patients at a greater risk of infections or having trouble ingesting oral medicine.
Occasionally, microneedle patches are used for purposes other than drug delivery, such as storing a patient’s vaccine history under the skin using nanocrystals.
How Do Microneedle Patches Work?
Microneedle patches rely on prolonged skin contact and pressure to deliver their drug solution effectively. An adhesive backing holds a strip of microneedles loaded with the drug solution against the skin.
- Users can apply the patch directly onto the body, where microneedles painlessly puncture a patient’s topmost layer of skin.
- The drug solution then travels through the tiny tunnels created by the needles through the layers of skin until it reaches the dermis, where it enters a patient’s bloodstream through their capillaries.
Microneedle patches can distribute drug solutions consistently over a longer period. Because they reach farther into the skin, microneedle patches can deliver certain prescribed medications that transdermal patches cannot.
WHAT MATERIALS ARE MICRONEEDLE PATCHES MADE OF?
Microneedle patches are created using stick-to-skin tapes with enough strength to carry a small device.
The inside of the patch is often covered with a ring of skin-safe adhesive silicone, meaning that the microneedle array needs a bare spot in the middle of the patch or some type of adhesive to attach it since it’s challenging to adhere silicone to anything but itself.
Before you finalize your design, consult a manufacturer or skin adhesive resources to seek the right materials for your microneedle patch.
What are the Different Types of Microneedles?
Depending on the patch’s purpose, physical location, manufacturability, and drug solution delivery rate, different types of microneedles are attached to the patches. These designs ultimately fulfill the same purpose of spreading a drug through the dermis but are constructed with different layers and materials depending on the ideal delivery method.
1. SOLID MICRONEEDLES
Solid microneedles function using a two-step application process where the needles puncture the skin and are then removed so the indents can be covered with a transdermal patch. These tiny punctures, imperceptible to the eye, allow the drug solution to seep deeper into the skin.
While solid microneedles are among the easiest to manufacture, their tiny microincisions can still lead to infections. They are most often used for drug delivery and cosmetic purposes.
2. COATED MICRONEEDLES
Coated microneedles are embedded in the skin for extended periods so the outer coating dissolves into the epidermis. Once the solution has had enough time to seep through the epidermis, the coated microneedle patch is removed and disposed of.
While coated microneedles reduce the application into a single process, they are limited in how much solution they can deliver based on the thin coating and the amount retained during the initial puncture.
3. HOLLOW MICRONEEDLES
Hollow microneedles can puncture the skin and deliver drugs from a drug reservoir. Because of their empty insides, hollow microneedles facilitate the flow of the drug solution down through the needle and into the skin. Like coated microneedles, they simplify the application into a simple, one-step process but are eventually removed from the body.
The disadvantage of using hollow microneedles is that they can cause leakage and clogging. Yet, they are highly applicable to disease diagnosis practices and can deliver large doses of drug solutions.
4. DISSOLVABLE MICRONEEDLES
Dissolvable microneedles dissipate once lodged inside the moist inner skin of the human body.
Unlike solid or coated microneedles, often made of silicone or stainless steel, dissolvable microneedles are made of sugar and hydrophilic crosslinked polymers. These are also applied using an adhesive patch, but the needles dissolve in the skin while distributing the solution.
Dissolving microneedles are used for drug or vaccine delivery and cosmetic purposes. They can be more challenging to manufacture and might take longer to dissolve, leading to more extended wear.
5. HYDROGEL-FORMING MICRONEEDLES
Hydrogel-forming microneedles penetrate the skin and swell when they encounter the body's natural fluids, allowing them to expand and release drugs.
Unlike the dissolvable variety, hydrogel-forming microneedles are removed along with the adhesive patch once the drug solution has been distributed. They are most commonly used to deliver hydrophilic drugs like caffeine and high-dose drugs like ibuprofen.
How Are Microneedle Patches Manufactured?
Microneedle patches can be manufactured in various ways, but the patches are often produced separately from the needles.
For instance, a flexible material converter can rapidly produce adhesive patches, but needles are often assembled separately and loaded with drug solutions.
Strouse builds adhesive patches to carry medical devices such as microneedles, but we don’t manufacture the needles themselves. Instead, many manufacturers use automatic placement to stick the strip of needles, preloaded with the drug solution, onto the patch.
Additionally, patches or bandages must remain free of biological waste or excess particles, which is why they’re processed in an area known as a manufacturing Clean Room.
Clean Rooms are certified to match a high standard of particle control, which is why they’re often used to build medical devices. Because they significantly reduce biological contamination, Clean Rooms can also save you money in sterilizing your products later.
When you’re creating your microneedle patches, you’ll want to know how you can combine the different elements of your patch, like the skin adhesive and needle array, in the most effective way possible. Partnering with a manufacturer early in the design process will ensure your production is time and cost-efficient.
If you enjoyed this article and want to learn more about skin-friendly adhesives or medical applications, visit our Learning Center.
Originally published: June 26, 2023
