The present study aimed to develop, optimize, and evaluate methotrexate-loaded polymeric nanoparticles coated with poloxamer 407 to enhance drug delivery to the brain. Methotrexate-loaded nanoparticles were prepared using the emulsification solvent evaporation technique.

A full 3² factorial design was employed to investigate the effects of polymer and surfactant concentrations, which were considered as independent variables at three levels, on various formulation characteristics. The prepared nanoparticles were optimized and characterized based on particle size, polydispersity index (PDI), zeta potential, entrapment efficiency, percentage yield, scanning electron microscopy (SEM), in vitro drug release, and sterilization parameters.

To facilitate efficient brain delivery, the nanoparticles were coated with poloxamer 407 (1–2% of the total suspension volume). The optimized formulations exhibited particle sizes within the nanometer range, with low PDI values indicating uniform size distribution. Among all formulations, the F5 formulation demonstrated optimal characteristics, with a particle size of 192.2 nm and a zeta potential of −19.10 mV, indicating sufficient electrostatic repulsion and stability.

The maximum entrapment efficiency (72.4%) was observed in the F5 formulation. The percentage yield ranged from 58.3% to 76.7% across different formulations (F1–F9), while drug content remained approximately 72%. Statistical analysis revealed that the model was significant, with p-values ≤ 0.05 for all evaluated responses.

The results demonstrated that the developed PLGA-based polymeric nanoparticles provided sustained release of methotrexate over an extended period. Furthermore, the coated nanoparticles showed potential for enhanced drug delivery to the brain. Overall, the study indicates that poloxamer 407-coated polymeric nanoparticles are a promising carrier system for improving the therapeutic efficacy of methotrexate.