Chitosan-PLGA biopolymeric nanogel as a platform for enhanced methotrexate delivery and redox-modulated...

Methotrexate (MTX) is an effective disease-modifying antirheumatic drug for the treatment of chronic inflammatory disorders; however, its clinical application is limited by poor bioavailability, rapid systemic clearance, and dose-dependent adverse effects. In this study, a pH-responsive methotrexate-loaded chitosan/poly(lactic-co-glycolic acid) ((Chit/PLGA)/MTX) nanogel was developed to improve drug delivery and therapeutic performance. The nanogel was fabricated by ionic gelation followed by gamma radiation-induced in situ free-radical polymerization (20 kGy) and subsequently loaded with methotrexate using a pH-triggered swelling-shrinking encapsulation strategy. Physicochemical characterization by TEM, DLS, FTIR, UV-Vis spectroscopy, and zeta potential analysis confirmed the successful formation of spherical nanogel particles with an average hydrodynamic diameter of 125 nm, a polydispersity index of 0.18 ± 0.03, and a zeta potential of -2.5 mV. The nanogel exhibited a high encapsulation efficiency (89.3 ± 2.1%) and drug-loading capacity (15.1 ± 0.8%). In vitro release studies demonstrated pronounced pH-responsive behavior, with cumulative methotrexate release reaching approximately 60% at pH 5.5 compared with 40% at pH 7.4 after 300 s, indicating preferential drug release under acidic inflammatory conditions. Cytotoxicity evaluation showed that the nanogel formulation exhibited improved biocompatibility (IC₅₀ = 422.5 μg/mL) compared with free methotrexate (IC₅₀ = 311.7 μg/mL). The (Chit/PLGA)/MTX nanogel significantly enhanced antioxidant activity, exhibiting 79.1% DPPH radical scavenging, 81.8% membrane stabilization, and 83.3% inhibition of protein denaturation. Furthermore, the formulation effectively suppressed the expression of major inflammatory mediators, including COX-2 (37.2%), iNOS (47.2%), TNF-α (40.3%), and NF-κB (40.9%), while reducing IL-1β (33.5%) and IL-6 (45.0%) production. Collectively, these findings demonstrate that the pH-responsive Chitosan-PLGA nanogel provides efficient methotrexate encapsulation, controlled drug release, enhanced antioxidant activity, and potent anti-inflammatory effects, highlighting its promise as a nanocarrier platform for the treatment of chronic inflammatory diseases.