Codelivery of metformin and methotrexate with optimized chitosan nanoparticles for synergistic triple-negative breast cancer therapy in vivo

[Display omitted] The development of effective therapeutic strategies for triple-negative breast cancer (TNBC), an aggressive subtype with limited treatment options, remains a critical challenge. This study aimed to design and evaluate a combination therapy using chitosan nanoparticles (Cs NPs) loaded with metformin (Met) and methotrexate (MTX) as a promising approach for TNBC management. The Cs NPs exhibited an average size of 78.8 ± 25.84 nm for blank Cs NPs, 84.50 ± 22.54 nm for Met-Cs NPs, and 86.70 ± 30.90 nm for MTX-Cs NPs, with positive surface charges of 26.40 ± 1.40 mV, 28.20 ± 1.60 mV, and 14.30 ± 2.40 mV, respectively. The drug encapsulation efficiency was 88.56 ± 2.26 % for Met-Cs NPs and 97.03 ± 0.52 % for MTX-Cs NPs. The cellular uptake studies demonstrated a time-dependent increase in the accumulation of Shikonin-labeled Cs NPs in 4T1 cells. The cytotoxicity assays revealed that Met-Cs NPs and MTX-Cs NPs exhibited significantly lower IC50 values (19.85 μg/mL and 103.2 ng/mL, respectively) compared to the plain drugs at 48 h. The combination of Met-/MTX-Cs NPs showed a synergistic cytotoxic effect, inducing 50 % cell death at 15.233 μg/mL of Met and 0.166 μg/mL of MTX. In vivo studies using a 4T1 xenograft mouse model demonstrated that the combination of Met-/MTX-Cs NPs resulted in a 100 % reduction in initial tumor volume, compared to a 40 % decrease with the free drug combination. The tumor growth inhibition was 70.45 % for the Met-/MTX-Cs NPs group, significantly higher than the 33.86 % observed in the free drug combination group. The findings of this study highlight the potential of the Met-/MTX-Cs NPs combination as a novel and effective therapeutic approach for TNBC management. The enhanced therapeutic efficacy, improved safety profile, and the ability to modulate key signaling pathways make this nanoparticle-based combination therapy a promising candidate for further clinical investigation.