Qbd-Guided Development of Ph-Responsive Chitosan–Eudragit Nanoparticles for Controlled Delivery of Tofacitinib Citrate

Objective: The present study aimed to develop and characterise a pH-responsive dual polymeric nanoparticle system of Tofacitinib citrate using chitosan and Eudragit for controlled drug delivery. Methods: Tofacitinib citrate-loaded nanoparticles were prepared by a single emulsion solvent evaporation method and optimised using a Box–Behnken design under a Quality by Design (QbD) framework. The formulations were evaluated for Particle size, Polydispersity Index (PDI), Zeta Potential, Drug Entrapment Efficiency (DEE), and In vitro drug release. Compatibility studies were performed using FTIR, while surface morphology and crystallinity were assessed by SEM and XRD, respectively. Results: The optimised formulation (F14) exhibited a particle size of 191.9±5.81 nm, PDI of 0.3472±0.01, and zeta potential of+34.66±1.57 mV, indicating good stability and uniformity. The drug entrapment efficiency was found to be 93±4.3%. In vitro release studies demonstrated minimal drug release under acidic conditions (6.05±1.10% at 1 h, pH 1.2), followed by sustained drug release reaching 95.6±2.12% at 24 h in phosphate buffer (pH 6.8). XRD analysis indicated a transition of the drug from crystalline to amorphous form, and SEM images confirmed the formation of spherical nanoparticles. Conclusion: The developed chitosan–Eudragit nanoparticle system demonstrated pH-responsive release, providing an in vitro proof-of-concept for the oral delivery of Tofacitinib citrate. However, further in vivo studies are required to confirm its therapeutic performance.