Improvement of Cochlear Implants By Controlling and Quantifying Material Properties for Directing Neurite Growth

One cause of deafness is the loss of hair cells within the cochlea. This particular type of deafness can be partially remedied with a cochlear implant. Although these implants can reproduce the basic sensation of hearing, they deliver little tonal information due to poor spatial resolution. The distance between the transmitting electrode and the receiving hearing elements allows the signal to spread and electrically stimulate multiple regions of the nerve cells within the cochlea. One solution to deal with the poor spatial resolution may be to regenerate and guide spiral ganglion neurites to decrease the distance or even contact the electrode. Accordingly, we use photopolymerization to synthesize materials with surface physical and mechanical cues to orient the growth of regenerative neurites. Mechanical properties ware controlled by varying cross linking density in hexyl methyl methacrylate (HMA) with 1,6 hexanediol dimethacrylate (HDDMA) and polyethylene glycol dimethacrylate (PEGDMA) with ethylene glycol dimethacrylate (EGDMA) co-polymers. Each co-polymer system can be controlled by varying each components concentration to manipulate the elastic modulus while maintaining a relatively constant surface polarity.