Formulation and Characterisation of Hyaluronic Acid-coated Chitosan Nanoparticles Loaded with Thymoquinone for Targeted Therapy in Rheumatoid Arthritis

Background: Rheumatoid arthritis (RA) is a chronic autoimmune disorder that causes persistent joint inflammation and progressive structural damage, leading to significant disability. Conventional treatments such as DMARDs and biologics improve outcomes but remain constrained by toxicity, immunosuppression, and high cost, creating the need for safer, more efficient strategies. Aim: In this study, thymoquinone (TQ) was encapsulated in hyaluronic acid (HA)–chitosan (Ch) nanoparticles to improve therapeutic delivery. Methods: A Central Composite Design (CCD) was employed to systematically evaluate the effects of HA and Ch concentrations on particle size, polydispersity index (PDI), entrapment efficiency (EE), and drug release. Results: The nanoparticles produced ranged from 121.6–289.4 nm in size, with PDI values of 0.217–0.667, EE between 89.74–98.74%, and cumulative release of 83.67–90% at 49h. The optimised formulation (HA 0.25 mg/mL, Ch 0.75 mg/mL) yielded particles of ~208 nm, PDI 0.387, EE ~98.7%, sustained release of ~86.6%, and a zeta potential of –28.7 mV. FTIR confirmed drug–polymer compatibility, TEM images revealed spherical morphology, and statistical modelling validated robust optimisation. Conclusion: These results establish F6 Ch nanoparticles as a reproducible platform with favourable stability, encapsulation, and controlled release, offering strong potential for targeted RA therapy. Major Findings: Hyaluronic acid–chitosan nanoparticles were successfully optimised for thymoquinone delivery, achieving nanoscale size, uniform distribution, high drug entrapment, and stable surface charge. The formulation exhibited sustained drug release and improved thymoquinone dispersion, enhancing its potential bioavailability. The optimized formulation showed a nanoscale size (~208 nm), good uniformity, high drug entrapment (~98.7%), and a stable negative surface charge. Overall, the system shows strong promise as a controlled delivery platform for rheumatoid arthritis treatment.