Co-Administration of Tretinoin Enhances the Anti-Cancer Efficacy of Etoposide via Tumor-Targeted Green Nano-Micelles

Herein we report promoted anti-cancer activity via a combination strategy of synergistic chemotherapy/retinoid-based breast cancer therapy with shell-stabilized micellar green nanomedicine. Amphiphilic zein-chondroitin sulfate (ChS)-based copolymeric micelles (PMs) were successfully developed via carbodiimide coupling for concomitant delivery of etoposide (ETP) and all-trans retinoic acid (ATRA) to breast cancer. The micelles exhibited low critical micellar concentration (CMC) of 0.008 mg/mL with high encapsulation efficiencies of ETP and ATRA (61.2 and 84.29%, respectively). Calcium-mediated crosslinking of the anionic ChS micellar shell resulted in prolonged drug release with small micellar size of 222.7 nm. The micelles exhibited augmented internalization into MCF-7 breast cancer cells by virtue of ChS binding affinity to CD44 receptors overexpressed by cancer cells. Consequently, the ETP/ATRA-loaded micelles exhibited synergistic cytotoxicity against breast cancer cells as revealed by their significantly lower IC50, combination index (CI), and higherdose reduction index (DRI) in comparison to the free ETP and free ATRA or their combination. Micelles displayed superiority in reducing tumor volume, decreasing proliferation, and promoting necrosis in mice bearing Ehrlich Ascites Tumor (EAT) upon comparison to free ETP and free ATRA or their combination. Overall, the developed green zein-ChS micelles offer a promising platform for tumor-targeted delivery of hydrophobic therapeutic agents.