Development of piperine/HPβCD-loaded PVA-coated iron oxide nanoparticles in in situ gel for enhanced retinal delivery and anti-VEGF activity

Piperine (PIP) is a potential therapeutic agent for retinal diseases; however, its poor aqueous solubility limits its ocular bioavailability. To overcome this limitation, a novel nanocarrier system was fabricated through the adsorption of PIP/hydroxypropyl-β-cyclodextrin (HPβCD) inclusion complexes onto the surface of polymer-stabilized iron oxide nanoparticles (IONs), which were then incorporated into an in situ gelling formulation. Three hydrophilic polymers, i.e., polyethylene glycol, poloxamer 407, and polyvinyl alcohol (PVA) were used as surface coatings. Among these, PIP/HPβCD/PVA-IONs exhibited the highest percent entrapment efficiency (77.38 ± 2.17 %) and superior mucoadhesive properties. Ocular safety was evaluated using the hen's egg test on chorioallantoic membrane (HET-CAM), which indicated no irritation. To further enhance ocular retention and retinal delivery, the PIP/HPβCD/PVA-IONs were incorporated into an in situ gel. Upon contact with simulated tear fluid, the formulation underwent a sol-to-gel transition with excellent gelling capacity and improved ex vivo permeation across excised porcine cornea (0.85 ± 0.07 × 10^-6 cm⋅s⁻¹) and sclera (3.16 ± 0.29 × 10^-6 cm⋅s⁻¹). In vitro studies on ARPE-19 retinal cells demonstrated the formulation was non-toxic at concentrations up to 50 µg/mL (>70 % cell viability). Furthermore, in vitro and in vivo evaluations revealed that the formulation effectively suppressed vascular endothelial growth factor A at both the protein and mRNA levels. It also exhibited significant anti-inflammatory and anti-angiogenic effects. These findings suggest that the PIP/HPβCD-loaded IONs incorporated in in situ gel system offers a promising nanocarrier platform for targeted ocular drug delivery in the treatment of retinal diseases.