Sophia Chen of MRS Bulletin interviews Stephen Balmert of the University of PIttsburgh about a patch delivery method of a vaccine to counter COVID-19. Read the article in EBioMedicine.
CHEN: To prevent the spread of Covid-19 in the long term, we will almost certainly need a vaccine against the disease. Stephen Balmert, a biomedical engineer from the University of Pittsburgh, is part of an international collaboration that has made such a candidate vaccine for Covid-19. They’ve tested their vaccine in mice and gotten promising results.
BALMERT: I think everybody really wants to know, when is this going to be in humans? We’re putting together [a form] to get approval from the FDA to begin a clinical trial.
SC: Under the microscope, the pathogen resembles a sphere adorned with spikes, known as spike proteins. Balmert’s vaccine is made of these spike proteins. To produce the spike, they introduce the genetic instructions for making the proteins into human embryonic kidney cell lines. These cells make the proteins. Then, the idea is to introduce the spike proteins into the human body, which teaches the immune system to recognize these proteins and produce antibodies that neutralize the virus. Their Covid-19 vaccine piggybacks off previous research on a similar coronavirus. Balmert’s colleague, Andrea Gambotto, had previously studied the MERS virus in his lab.
SB: They had already identified at that point there’s a particular part of the virus, which is called the S protein or the spike protein, they’d identified that was a good target for vaccines.
SC: Targeting the spike protein is a popular approach. But Balmert’s team uses a distinctive delivery method. Instead of injecting the vaccine via the traditional needle, they package their vaccine as a small, fingertip-sized patch covered in very small, short needles. The needles are made of a material called carboxymethyl cellulose, a hydrogel that dissolves in the skin. Each one is 225 µm in width, 750 µm in length, with a pointy tip shaped like a tiny Washington monument.
SB: Each of those needles has the vaccine in the tips, so in the pyramidal part at top, and there’s a flat backing underneath that you use for the application. We say the application of the microneedle feels a little bit like Velcro, the hook part of the Velcro. So you can feel the pressure, but it’s not painful in the sense of a traditional injection is.
SC: In addition, the patch deposits the spike proteins into the skin, as opposed to muscle like many traditional vaccines. This offers potential benefits as well. The skin contains a high concentration of immune cells because it protects the body from foreign particles.
SB: So you have potentially somewhat of a dose sparing effect, where you get a stronger immune response with the same dose. Or you can use less dose for the same immune response than a regular injection. In that sense, it requires potentially less vaccine.
SC: They could also be easier and cheaper to store compared to other vaccines.
SB: With these microneedle arrays, the carboxymethyl cellulose in the hydrogel material around the vaccine itself kind of maintains the structure of the vaccine. It maintains its bioactivity so you don’t have to keep them refrigerated. You don’t have to have refrigerated shipping or store them in a refrigerator necessarily, so that’s another potential advantage.
SC: They’ve published peer-reviewed results indicating the vaccine produces antibodies in mice. Now, they’re running tests to confirm that their results are reproducible and are working to gain approval from the Food and Drug Administration to begin clinical trials in humans.