Silk fibroin double-layer microneedles for the encapsulation and controlled release of triptorelin

A double-layer silk fibroin microneedles (SF-MNs) was proposed for the transdermal delivery of triptorelin. Two-step pouring and centrifugation were employed to prepare SF-MNs. Triptorelin was wrapped in MNs in the form of microcrystals with a size of similar to 1 mu m. beta-sheet nanocrystals (the secondary structure of silk fibroin) were adjusted in content by methanol-vapor treatment to manipulate the characteristics of SF-MNs prepared with two concentrations of silk fibroin. The mechanical strength of MNs was measured and analyzed in proportion to the beta-sheet content. The triptorelin in MNs could be released sustainedly in phosphate-buffered saline for 168 h, and the release amount decreased with increasing beta-sheet content. The Ritger-Peppas equation was employed to fit the release data. A linear decreasing relationship was observed between the diffusion coefficient and increased beta-sheet content. After administration to rats, SF-MNs exhibited long-term testosterone inhibition and maintained castration levels for >= 7 d. Manipulable mechanical properties and release behavior combined with biocompatibility and biodegradability render SF-MNs as viable long-term transdermal delivery devices for triptorelin.

Automated summary

The double-layer silk fibroin microneedles were proposed for transdermal delivery of triptorelin, with the ability to sustainably release the drug in the body and maintain castration levels for an extended period. The mechanical properties and release behavior of the microneedles were controlled by adjusting the concentration of silk fibroin, showcasing their potential as long-term transdermal delivery devices for triptorelin.