Keratin nanoparticles and photodynamic therapy enhance the anticancer stem cells activity of salinomycin

Accepted Manuscript version. The Published Journal Article is available on Materials Science and Engineering: C, Volume 122, Article number 111899 (DOI: https://doi.org/10.1016/j.msec.2021.111899). Supplementary Material available free of charge on the article webpage. © 2021. This Manuscript version is made available under the CC-BY-NC-ND 4.0 license. https://creativecommons.org/licenses/by-nc-nd/4.0/ ABSTRACT The high rates of aggressiveness, drug resistance and relapse of breast cancer (BC) are mainly attributed to the inability of conventional therapies to equally eradicate bulk differentiated cells and cancer stem cells (CSCs). To improve the effectiveness of BC treatments, we report the in-water synthesis of novel keratin-based nanoformulations, loaded with the CSC-specific drug salinomycin (SAL), the photosensitizer chlorin e6 (Ce6) and vitamin E acetate (SAL/Ce6@kVEs), which combine the capability of releasing SAL with the production of singlet oxygen upon light irradiation. In vitro experiments on BC cell lines and CSC-enriched mammospheres exposed to single or combined therapies showed that SAL/Ce6@kVEs determine synergistic cell killing, limit their self-renewal capacity and decrease the stemness potential by eradication of CSCs. In vivo experiments on zebrafish embryos confirmed the capacity of SAL nanoformulations to interfere with the Wnt/β-catenin signaling pathway, which is dysregulated in BC, thus identifying a target for further translation into pre-clinical models