Characterization of silk fibroin-based microneedles and in vitro study of stromal cell-derived factor-1-loaded microneedles on adipose stem cell recruitment

Silk fibroin (SF) has good biocompatibility, degradability and mechanical properties. In this study, SF-based microneedle (MN) patches were fabricated as stromal cell-derived factor-1 (SDF-1) carriers that may be used for adipose stem cell (ASC) recruitment. Therefore, SF was chosen as the main MN material to achieve sustained drug release. In addition, the variations in SF-based MN crystallinity after water annealing treatment were also determined. The results indicated that SF-based MN patches were successfully fabricated with a 3M™ commercial template and Polydimethylsiloxane mold. Through optical coherence tomography, it was found that all of the SF-based MN patches prepared in this study had sufficient strength to penetrate the skin to a depth of approximately 400 μm. Sustained release of the model drug-dextran from the SF-based MNs was demonstrated. Although SF-based MNs release SDF-1 in a sustained manner, the quantity released can be regulated and improved. Subsequently, dual-layer SDF-1-loaded MNs fabricated with a gelatin tip and SF body were prepared to enhance SDF-1 release for ASC recruitment. SF-based MNs can show good penetration ability and provide good sustained release while dual-layer MNs can regulate the amount of drug released, which could present an alternative for stem cell therapy.