Are Microneedles Revolutionizing the Way Vaccines Are Delivered?

The novel coronavirus pandemic has put the entire world in crisis mode. While health care and other essential workers risk their lives to keep the U.S. running, scientists are working equally as hard trying to develop a vaccine to stop the virus in its tracks.

Recently, the University of Pittsburgh School of Medicine announced a potential vaccine against COVID-19. They are using a microneedle array as the delivery method for the drug, something of which Harvinder Gill, the Whitacre Endowed Chair of Science and Engineering and an associate professor of chemical engineering in Texas Tech University’s Edward E. Whitacre Jr. College of Engineering, is keenly aware.

Gill explains what microneedles are, what makes them ideal for vaccine delivery and their potential in other medical areas.

What is a microneedle array?
A microneedle array is a small, flat device the size of a dime. One side of the device contains tens of tiny sharp projections, which are called microneedles. To put the tininess of the microneedles into perspective, each microneedle is about half the thickness of the dime, which is the thinnest U.S. coin. Because of their tiny size, microneedles are painless. The microneedles are arranged in a grid-like pattern, so the entire device is often called a microneedle array, or sometimes a microneedle patch. The array is a new way of delivering vaccines and drugs. Often the target area is the skin, however, other areas such as the mouth can also be targeted.

Microneedles are unique because they are not only painless, but they can be used in ways that a regular hypodermic needle is not. While a regular hypodermic needle is hollow and used to inject liquid, microneedles can be used to not just inject liquid, but to also carry a solid form of the vaccine/drug. For example, if the microneedle is made as a solid structure rather than a hollow one, the solid structure can be ‘coated’ with a film of vaccine or medication just like paint. The coated vaccine film, however, is water soluble, which dissolves inside the skin tissue when the microneedle gets inserted into the skin. The film is designed to stay attached to the microneedles so it does not get removed during insertion. Another way the microneedle can deliver a solid vaccine/drug is by packing the drug into the microneedle structure. The microneedle is fabricated from a water-soluble material, and the vaccine/drug is dispersed in this solid matrix. When the microneedle is inserted into the skin, the solid matrix dissolves and release the vaccine/drug. These types are often called “dissolvable microneedles.”

What is your experience with microneedles?
I have been working in the microneedle field since their invention about 20 years ago. My doctoral degree was in the field of ‘coated’ microneedles, and I invented a microprecision process to coat the microneedles with vaccines and drugs. At Texas Tech, I have continued to develop the microneedle technology. I have expanded the use of microneedles into the mouth for delivery of vaccines and anti-tumor drugs for treatment of oral cancers.

A new direction that I have given the microneedle research is to use them for allergy immunotherapy. Patients are used to taking allergy shots for seasonal allergies. Instead of the allergy shots, my lab is developing microneedles for allergy treatment, which will be painless and perhaps can be self-administered by the patient. An exciting advancement of the microneedle technology I am pushing is their use in the treatment of peanut and other food allergies. In preclinical studies, we have found that coated microneedle arrays are able to show therapeutic effect against peanut allergies. We have filed a patent through the Texas Tech Office of Research Commercialization. A startup company called Moonlight Therapeutics is commercializing this technology. As a disclaimer, I am one of the co-founders of this startup company.

What makes a microneedle array the ideal delivery method for the potential COVID-19 (or any) vaccine?
Microneedles have been extensively tested in preclinical studies for vaccine delivery. Recently, microneedles were tested in humans for flu vaccination and were found to be well-tolerated and as effective as regular flu shots. Microneedles are attractive for vaccine delivery of COVID-19 or other diseases because they offer multiple advantages. Microneedles are painless and have the potential to be self-administered, making them ideal for vaccine distribution to the public in scenarios such as the current COVID-19 pandemic where social contact needs to be limited.

In addition, it has been shown that a solid form of the vaccine often is more stable than its liquid counterpart. This means that microneedles “coated” with a vaccine or with vaccine in their core can be stable at room or even elevated temperatures, and they won’t require the “cold chain,” which is required for storage and transportation of traditional hypodermic needle-based vaccines. This could open the possibility of even mailing out the vaccines to the public and transporting them across the world without worrying about lack of “cold” transportation services in some developing countries. The health care could be made equally available to all people.

Another reason to consider microneedles is that, in preclinical studies, they outcompeted the intramuscular vaccine shots; microneedles were able to generate the same immune response as the intramuscular shots but at much lower doses. This means that, with microneedles, a given vaccine batch could go along much farther in vaccinating more people than the conventional shots.

Is there a known vaccine that would not benefit from the use of microneedles?
To my knowledge, there is no vaccine that would not benefit from the use of microneedles.

Is there anything else you’d like to add or mention?
As a side note, microneedles have received some popularity as devices for cosmetic treatment, such as for reducing wrinkles on the face. I would like to note that microneedles are not approved by the Food and Drug Administration for such applications.

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