Novel strategy for treatment of inner ears using a biodegradable gel.

Objective: The present study aimed to evaluate the efficacy of a biodegradable hydrogel as a drug-delivery medium for the inner ear. Brain-derived neurotrophic factor (BDNF) was chosen as the agent to be administered. Method: First, we used an enzyme-linked immunosorbent assay to measure BDNF concentrations in the cochlear fluid after placing a hydrogel containing this agent onto the round-window membrane of the ear. Second, the functional and histologic protection of the auditory primary neurons (spiral ganglion neurons [SGNs]) by BDNF applied through the hydrogel was examined using an animal model of SGN degeneration. Results: The results revealed sustained delivery of BDNF into the cochlear fluid by way of the hydrogel. Second, the functional and histologic protection of the auditory primary neurons (SGNs) by BDNF applied through the hydrogel was examined using an animal model of SGN degeneration. The measurement of electrically evoked auditory-brainstem responses demonstrated that BDNF delivered by way of the hydrogel significantly reduced the threshold elevation. Immunohistochemistry for neurofilament 200 kD demonstrated increased survival of SGNs because of BDNF application through the hydrogel. Conclusion: These findings indicate that biodegradable hydrogels can be used for drug delivery to the inner ear.