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.