Green-synthesized selenium nanoparticles overcoming methotrexate resistance in colorectal cancer

Colorectal cancer (CRC) therapy with methotrexate (MTX) is limited by toxicity and resistance. This study developed eco-friendly selenium nanoparticles (SeNPs) to enhance MTX delivery and overcome resistance. SeNPs were synthesized using a green reduction method and optimized via a Box–Behnken design. Characterization confirmed spherical nanoparticles with an average size of 20–30 nm. MTX loading efficiency (LE%) and release behavior were measured, and biological evaluation was conducted in HCT116 colorectal cancer cells through cytotoxicity, apoptosis (Annexin V/7-AAD), and efflux-transporter assays. Optimized SeNPs achieved an MTX loading efficiency of ≈48–52 %, with controlled early-phase release. MTX–SeNPs markedly enhanced cytotoxicity, reducing the IC₅₀ to 62.4 µg/mL, compared with 186.6 µg/mL for MTX alone—representing a ∼67 % reduction in required dose. Docking analysis showed selenium interacting with human glutathione reductase, supporting the observed increase in ROS and apoptosis. Green-synthesized SeNPs significantly improve MTX efficacy by enhancing drug retention, suppressing efflux activity, and reducing resistance. These findings highlight MTX–SeNPs as a promising strategy for CRC treatment and justify further in vivo investigation.