Typical intramuscular or subcutaneous injections are not ideal for delivering vaccines, therefore requiring a higher dose. Associated pain from needles also reduce patient compliance, especially among children. The intradermal route allows us to use a small dose as our skin has a sophisticated immunological network that can trigger rapid and potent immunogenicity. However, intradermal injection with the Mantoux procedure gives poor reliability and reproducibility, even after training.
Our skin is just 1 mm thick and a great alternative approach is using a skin patch with microneedle arrays (MNAs). A MNA contains hundreds of microneedles made of a dissolvable sugar-based material containing biocargo such as proteins or vaccines into the skin. In this way, the MNA skin patch can deliver the biocargo into the skin within just 15 min. Guess what, no special medical training is needed to self-administer the MNA skin patches.
To make the MNA patch with very sharp tips, diamond micromilling is first used to make a master mold. Silicone (polydimethylsiloxane, PDMS) molds are made from the master mold, then the sugar-based material is spin-coated on the PDMS molds to form the microneedles. Different tip geometries were made with good consistency using this method.
However, the MNA could only carry up to 1 μL of dry-form or dryable biologics initially. Therefore, Prof. Ozdoganlar's group developed Hybrid-MNAs with dissolvable tips and non-dissolvable cannulas (patent pending). The cavities in the microneedles allow various types of biocargo such as vaccines to be carried and delivered into the skin. Furthermore, the Hybrid-MNAs are more easily sterilizable.
Unlike intramuscular or subcutaneous injection-based vaccines requiring cold-chain transport & storage, the MNA materials are not as temperature-sensitive, improving vaccine accessibility and affordability. Needle reuse problems in intramuscular, subcutaneous and Mantoux injections can be avoided. While microneedle arrays have been around for over 15 years, commercialization has been limited. The team is currently working on scaling up. The MNAs hold great promise for future vaccine distribution, we wish them all the best!
Watch the recording of Fundamentals/Therapeutics: F.GI01.11: Live Keynote III & F.GI01.12: Live Panel Discussion III on tackling COVID-19.
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