Silk Devices for Tympanic Membrane Repair Show No Ototoxicity in a Rat Model

Hypothesis Implantation of ClearDrum^®, a biodegradable silk fibroin device, into the middle ear (ME) cavity in a rat model will not affect hearing thresholds as measured by auditory brainstem response. Background Chronic otitis media (COM) is a recurrent middle ear infection often accompanied by tympanic membrane perforation. Our laboratory has developed a biodegradable silk fibroin device (ClearDrum®) designed to treat tympanic membrane perforations in COM. ClearDrum^® acts as a prosthetic eardrum, providing a substrate on which tympanic membrane cells can grow and acts as a long-lasting implant. Methods Two formulations were tested based on silk/glycerol and silk/polyurethane blends. Animals were anesthetized, and either a ClearDrum^® formulation or an autologous cartilage graft was surgically implanted into the middle ear. Thresholds of the auditory brainstem response (ABR) were measured at the time of implantation and at 4 and 12 weeks post-implantation to assess hearing after the implantation. After the final measurements at 12 weeks, middle ear and cochlea were harvested for histological assessment. Results No significant differences in ABR thresholds between male and female animals were found at any timepoint. Results showed that there were no detrimental effects of either Cleardrum^® formulation on ABR thresholds as compared with implantation of autologous cartilage and no presence of inflammation within the middle ear or cochlea. Conclusion Our ABR data suggest no substantial ototoxic effects on outer or inner hair cells and provides some support toward clinical translation of ClearDrum devices.