Rapidly dissolving fibroin microneedles for transdermal drug delivery

This paper presents rapidly dissolving fibroin microneedles (MNs) for the first time. A reverse PDMS MNs mold was first created and drug-contained fibroin solution was poured into this reverse PDMS MNs mold. Fibroin MNs were successfully fabricated after fan drying and detaching the solidified drug-contained fibroin structure from the PDMS mold. The fibroin serves as a matrix to incorporate drug molecules while maintaining the drug activity. The dimensions of the fabricated fibroin MNs are 500 μm in length, 200 μm in diameter at the base, and 5 μm in radius at the tip. These fibroin MNs can dissolve within minutes under the skin to release the drug molecules and the dissolved fibroin in the skin generates noninflammatory amino acid degradation products usable in cell metabolic functions. The fibroin MNs containing methylene blue as a drug were fabricated and their surface morphology, internal structure, mechanical property, and the dissolving characteristics were analyzed. These rapidly dissolving fibroin MNs provide more benefit than conventional syringes for painless transdermal drug delivery.