Emerging biomaterials for auditory disorders

The inner ear is a highly specialized sensory organ whose therapeutic inaccessibility arises from its structural sequestration, compartmentalized fluid environment, and the restrictive blood-labyrinth barrier (BLB). These features severely limit drug penetration, spatial precision, and therapeutic durability, thereby constraining the treatment of hearing and balance disorders. Emerging biomaterial platforms have provided promising strategies to overcome these barriers through rationally engineered biomaterials. This review presents a materials-centered framework for emerging biomaterial platforms in auditory disorders, spanning the anatomical and transport foundations of otologic delivery, the major material classes used in ear disorders, and the physicochemical design determinants that govern transport, retention, targeting, biodegradability, and biosafety. We discuss polymer-based, lipid-based, hydrogel-based, exosome-derived, inorganic, composite, and piezoelectric biomaterials, highlighting how structure and property relationships shape therapeutic performance. Beyond serving as delivery carriers, these biomaterial platforms can provide intrinsic or engineered therapeutic and regenerative functions, as well as bioelectronic interfacing capable of redox regulation, anti-inflammatory modulation, synaptic repair, and self-powered auditory sensing or stimulation. We further summarize disease-specific applications and outline major translational barriers, including delivery heterogeneity, incomplete long-term safety evaluation, limited standardization, and manufacturing scalability, together with future directions for precision-guided otologic therapy.