Investigation of Optimal Silk Film Thickness in Silk Microneedle Fabrication

Abstract

Injection is one of the most commonly used methods for delivering drugs or vaccines into human bodies. It is rapid, low-cost and compatible with almost any drugs. However, the major drawbacks of the injection by hypodermic needles are the pain associated with the injection and the disposal of used needles. Microneedles have then received wide attention since they can overcome such drawbacks, especially dissolving microneedles. Recently, silk fibroin has been used to fabricate dissolving silk microneedles for transdermal drug delivery at low temperature. In the fabrication process, the quality of the silk microneedles relies on the solidification of silk fibroin solution. This research aims to study the role of silk fibroin concentration (silk film thickness) in the formation of silk microneedles. In the experiment, silk microneedles were fabricated using various concentrations of silk fibroin solution from 3 to 7% while the volume of the silk fibroin solution was fixed. According to the experimental resuls, it was found that the concentrations of 4-5% were suitable for producing silk microneedles (silk film thickness of 470 μm) while the concentrations of 6-7% caused wrinkles on microneedle patch due to mismatch of upper and lower layers of microneedles. Furthermore, the concentration of 3% had a problem with the demolding step of microneedles since it caused mold damage due to strong adhesion force between microneedles and mold.