Inner Ear Delivery of Polyamino Acid Nanohydrogels Loaded with Dexamethasone

Objective To develop a novel polyamino acid-based nanohydrogel drug delivery system for dexamethasone to enhance its delivery efficiency to the inner ear. Methods A fluorescein-labeled polyglutamic acid-based polyamino acid dexamethasone nanohydrogel was synthesized, and its gelation time was measured. The hydrogel was surgically injected into the round window niche of guinea pigs to determine its degradation time in the middle ear cavity in vivo. The safety, pharmacokinetics, and distribution patterns of dexamethasone in the inner ear were evaluated. Results The hydrogel exhibited a gelation time of 80 seconds in a 37℃ water bath. In vivo, the hydrogel was almost completely degraded within 7 days in the middle ear cavity of guinea pigs. Transient hearing loss was observed one day after administration, but hearing gradually returned to normal over time. No significant cytotoxicity, vestibular stimulation signs, or pathological abnormalities in spiral ganglion cells were observed. Histopathological examination revealed no significant inflammatory reactions. Pharmacokinetic analysis demonstrated sustained drug release and prolonged dexamethasone activity. Immunofluorescence staining confirmed the distribution of dexamethasone in both the cochlea and vestibular organs. Conclusion The polyamino acid nanohydrogel exhibits excellent injectability and biodegradability, representing a safe and effective drug delivery system for the inner ear.