Ion‑Responsive in situ Gel of Quercetin‑Loaded PEGylated Liposomes for Anti‑inflammatory Treatment of Dry Eye Disease

Background: Dry eye disease (DED) is a global health burden with limited effective and safe treatments. Quercetin (Qu) possesses potent anti-inflammatory and antioxidant activities, but its poor solubility and short half-life restrict ophthalmic use. Methods: Qu‑loaded PEGylated liposomes (Qu‑PL) were prepared by thin‑film hydration and incorporated into gellan gum to form an ion‑responsive in situ gel (Qu‑PL‑ISG). The formulation was characterized for particle size (PS), zeta potential (ZP), polydispersity index (PDI), encapsulation efficiency (EE), short-stability, in vitro release, cytotoxicity, ocular irritation, mucoadhesion, ocular surface retention, pharmacokinetics, and therapeutic efficacy in a BAC‑induced DED mouse model. Network pharmacology and molecular docking were used to generate testable hypotheses on possible mechanisms of Qu in DED. Results: Qu‑PL‑ISG had a PS of 173.33 ± 1.27 nm, a ZP of − 46.87 ± 0.95 mV, and an EE of 88.85 ± 1.41%. It released 46% of Qu over 72 h and remained stable for 21 days at 4 °C, with no cytotoxicity or irritation. Compared with Qu‑PL, Qu‑PL‑ISG exhibited higher mucoadhesive force (3783.5 ± 125.2 vs. 1986.2 ± 145.7 dyne/cm 2 ) and longer ocular surface retention (45 vs. 20 min). Ocular bioavailability (AUC 0 ‑ 1 80 ) in cornea, conjunctiva, and tears increased 2.79-, 1.47- and 1.44-fold, respectively. In DED mice, 0.2% Qu‑PL-ISG restored tear secretion, reduced corneal staining, repaired epithelial thickness, increased goblet cell density, and lowered corneal IL-1β and TNF-α levels, with efficacy comparable to 0.05% cyclosporine A. Network pharmacology and molecular docking were used as computational tools to predict that Qu may act on DED through multi‑target interactions (TNF, NF‑κB, STAT3, IL-1β, AKT1, IL-6, Src) and pathways (IL-17, PI3K-Akt, TNF signaling), though these findings require experimental validation. Conclusion: Qu‑PL‑ISG is a safe, ion‑activated in situ gel that significantly enhances Qu bioavailability and anti‑inflammatory efficacy, showing promise for DED treatment. The flowchart illustrates the process of quercetin formulation and evaluation. Quercetin is processed using a rotary evaporator to form Qu-PL, which is mixed with gellan gum to create Qu-PL-ISG. Characterization involves PS/PDI/ZP, pH, viscosity test and EE/drug content. Safety evaluation includes CCK8 cell viability assay, sodium fluorescein staining, H&E staining and microscopic observation. Therapeutic efficacy is tested with 0.2 percent BAC twice per day, phenol red thread, slit lamp microscope observation, Elisa and H&E, PAS staining. Mechanism prediction is done through network pharmacology molecular docking. Improved ocular bioavailability is assessed by mucoadhesive force, ocular surface retention and ocular pharmacokinetics.A flowchart illustrating the process of quercetin formulation and evaluation for ocular bioavailability. Keywords: dry eye disease, quercetin, PEGylated liposome, gellan gum, in situ gel