Thermosensitive in situ–gelling chitosan–hyaluronic acid hydrogel for sustained levofloxacin release and improved corneal wound healing in a rabbit corneal chemical-burn model

BACKGROUND: Topical eye drops are rapidly cleared from the tear film, limiting drug efficacy. We developed a thermosensitive in situ–gelling chitosan–hyaluronic acid (CH–HA) hydrogel for sustained levofloxacin delivery and evaluated its effects in a rabbit corneal chemical-burn model. METHODS: A chitosan/β-glycerophosphate/HA solution was optimized for sol–gel transition at physiological temperature. Physicochemical properties, in vitro release, cytocompatibility (human MSCs), and antibacterial activity were assessed. Rabbits (n = 16) with corneal burns received levofloxacin drops (control) or hydrogels twice daily for 5 days. On day-10, corneal oxidative stress markers (TOC, TAC, OSI), semi-quantitative histology, and quantitative epithelial thickness were examined. RESULTS: The optimized formulation (30% β-glycerophosphate) gelled within ~ 15 min at 37 °C and displayed a porous, biodegradable network. In vitro, it showed biphasic levofloxacin release (~ 50% over 25 h) and maintained high MSC viability. The drug-loaded hydrogel exhibited significantly larger antibacterial inhibition zones against S. aureus and S. epidermidis than the drug-free hydrogels. In vivo, all hydrogel-treated groups showed significantly lower oxidative stress index (OSI) values than the levofloxacin-drop control. Histological scoring and quantitative morphometry demonstrated that the HA-containing hydrogels improved epithelial integrity and reduced inflammation, while significant stromal-edema reduction was observed in the CH–HA–D group. CONCLUSIONS: The thermosensitive CH–HA hydrogel provided sustained in vitro levofloxacin release and, in this rabbit corneal burn model, was associated with lower day-10 corneal oxidative stress and improved selected histologic repair indices versus levofloxacin eye drops. These findings support further pharmacokinetic and longer-term studies of this platform as a potential ocular drug-delivery system. TRIAL REGISTRATION: Not applicable; this preclinical animal study was not registered in a clinical trial registry.