Bioactive hydrogels for the reconstruction of sensorineural hearing loss

Sensorineural hearing loss (SNHL) is mainly caused by damage and apoptosis of hair cells in the inner ear and degeneration of spiral ganglion neurons, placing a heavy burden on patients, families, and society. Traditional treatments such as hearing aids and cochlear implants, while effective, have inherent limitations in addressing the underlying pathological causes of SNHL. In contrast, hydrogels offer the attracted alternative as an innovative platform overcoming inner ear delivery barriers. They have emerged as promising bioactive carriers for SNHL therapy owing to their unique advantages, such as the ability to facilitate drug delivery across the inner ear barrier, provide spatiotemporally controlled drug release, and simulate cellular microenvironments. This review highlights diverse hydrogel-based delivery systems, such as nano-hydrogels, microspheres, microneedles, hydrogel films, and amorphous hydrogels. These systems not only enhance drug retention and targeted delivery across barriers such as the tympanic and round window membranes but also enable precise regulation of release kinetics and improve auditory outcomes in animal models. Despite these advances, challenges remain, particularly regarding long-term safety, optimization of drug loading capacity, and controlled degradation rates that match disease progression. Overall, bioactive hydrogels hold significant promise in advancing SNHL treatment, and further research is needed to facilitate their translation into clinical practice.