Sirolimus-Exuding Core-Shell Nanofibers as an Implantable Carrier for Breast Cancer Therapy: Preparation, Characterization, In Vitro Cell Studies, and In Vivo Anti-Tumor Activity.

Objective Breast cancer accounts for significant mortality worldwide. Here, we develop a localized, sustained-release delivery system for breast cancer therapy. Methods: Sirolimus (SIR) core-shell nanofibers (NFs) are fabricated by coaxial electrospinning with poly(ε-caprolactone) (PCL) for the core and chitosan and PCL for the shell. The NFs were characterized by SEM, AFM, TEM, XRD, FTIR, water uptake, water contact angle, mechanical properties, drug content, and in vitro release. Results: A sustained release behavior is observed during 480 h that is more extended compared to monoaxial NFs. In vitro cytotoxicity and Annexin V/propidium iodide assays indicate that SIR-loaded coaxial NFs are effective in inhibiting proliferation of 4T1 and MCF-7 cells. Implantation of SIR NFs in 4T1 breast tumor-bearing mice inhibits tumor growth significantly compared to free drug. Histopathological examination shows that suppression of tumor growth by SIR NFs is associated with apoptotic cell death. Further, anti-cancer effects are also confirmed by decreased expression levels of Ki-67, MMP-2, and MMP-9. Histological observation of organs, serological analyses, and the lack of body weight changes indicate in vivo safety of SIR NFs. Conclusions: Altogether, we show here that incorporation of SIR into core-shell NFs could act as an effective drug release depot and induce a sustained antitumor response.