In this study, we developed injectable intratympanic hyaluronic acid (HA) depots for the treatment of hearing loss. We prepared an injectable click-crosslinking formulation by modifying HA with tetrazine (HA-TET) and trans-cyclooctene (HA-TCO), which crosslinked to form an HA depot (Cx-HA). Preparation of the click-crosslinking HA formulation was facile, and Cx-HA depot formation was reproducible. Additionally, the Cx-HA hydrogel was significantly stiffer than HA hydrogel. To monitor the degradation pattern of hydrogels, we mixed a zwitterionic near-infrared (NIR) fluorophore (e.g., ZW800-1C) in the click-crosslinking HA formulation. Then, HA-TET and HA-TCO solutions containing ZW800-1C were loaded separately into the compartments of a dual-barrel syringe for intratympanic injection. The Cx-HA depots formed quickly, and an extended residence time in the tympanic cavity was confirmed by performing NIR fluorescence imaging. We have successfully prepared an injectable click-crosslinking HA formulation that has promise as an intratympanic drug depot.
Keywords: click-crosslinking; depot; hyaluronic acid; intratympanic injection; near-infrared fluorescence.