Enhanced Anti-inflammatory Effects of Diclofenac Delivered Orally via Polyvinylpyrrolidone K30/Silk Fibroin Nanoparticles in a Murine Model of Carrageenan-Induced Paw Edema

Diclofenac has a relatively low oral bioavailability (50-60%) and is quickly metabolized with a half-life of less than 1 h. Therefore, the oral therapeutic effect of diclofenac is not optimal. This research developed polyvinylpyrrolidone K30-functionalized silk fibroin nanoparticles as an effective delivery system for diclofenac (FNPs-PVP-DC). The FNPs-DC and FNPs-PVP-DC were formulated by two methods of adsorption and solvent exchange. Depending on the formulation factors, the obtained particles exhibited different properties of nano-scale sizes (400-800 nm), narrow size distribution, negatively charged surfaces (-17 to -19 mV), high PVP K30 incorporation (23%-50%), pHpzc of ~6.6, and appropriate chemical interactions. Interestingly, particles formulated by the adsorption method showed low drug encapsulation efficiencies of < 15%, whereas the solvent exchange method yielded moderate results of ~40%. The FNPs-DC possessed aggregated patterns, while the FNPs-PVP-DC were more uniformly distributed. All formulations limited diclofenac release (< 20%) under gastric conditions and sustained its release in the intestinal environment. In in-vivo carrageenan-induced paw edema mice model, the FNPs-PVP-DC demonstrated a 20-30% higher anti-inflammatory effect and a faster onset of action (within 1 h) compared to pure diclofenac at the same dose (5 mg/kg). These findings suggest that FNPs-PVP-DC have promising potential as novel oral anti-inflammatory products.