Rapidly dissolving silk protein microneedles for transdermal drug delivery

This paper presents rapidly dissolving fibroin microneedles for the first time. A reverse PDMS microneedles mold was first created and drug-contained fibroin solution was poured into this reverse PDMS microneedles mold. Fibroin microneedles were successfully fabricated after drying and detaching the solidified fibroin structure from the PDMS mold. These fibroin microneedles serve as a matrix to incorporate drug molecules while maintaining the drug activity. The dimensions of the fabricated fibroin microneedles are 500 μm in length, 200 μm in diameter at the base, and 5 μm in radius at the tip. These fibroin matrix microneedles can dissolve within one minute 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 microneedles containing methylene blue as a drug were fabricated and their surface morphology, internal layered structure, mechanical property, and the dissolving characteristics were examined. These rapidly dissolving fibroin microneedles provide more benefit than conventional syringes for painless transdermal drug delivery.