Dissertation
Improving cochlear implant and tympanostomy tube surfaces via photografted zwitterionic thin films
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2024
DOI: 10.25820/etd.007419
Abstract
For patients young and old who experience profound deafness or hearing loss, a neural prosthesis known as the cochlear implant can enable the capacity to hear. However, a cochlear implant loses effectiveness and can even harm residual hearing when it causes inflammation in the cochlea through either traumatic insertions or encapsulation in fibrotic tissue. Additionally, tympanostomy tubes can also help prevent hearing loss and infections but sometimes become colonized with bacterial biofilms or plugged with mucus, necessitating removal and replacement. Both tympanostomy tubes and cochlear implants could be greatly improved by changing the biomaterial interactions with surrounding tissue. This work examines photograftable zwitterionic hydrogel thin films to address these shortcomings. Their highly hydrophilic nature is hypothesized to yield reduced biofouling, fibrosis, shear stress, and resistance to mucus flow so long as they are sufficiently durable. To inform potential trade-offs between durability and antifouling properties, the effect of hydrogel cross-linking on these properties is assessed. Fibrinogen, fibroblast, and bacteria adhesion are determined to be reduced by at least an order of magnitude for cross-linked hydrogels where half or more of the thin film mass is zwitterionic. Of these thin films, those with 10% cross-linker or more are found to be sufficiently durable when implanted in cochlear and subcutaneous tissue. The effect of thin film coatings in fibrosis reduction is also demonstrated in vivo using model implants and human cochlear implant electrode arrays, exhibiting a fibrotic capsule thickness reduction of at least 50% regardless of surface geometry, duration of implant (up to one year), or the material coated. Additionally, coatings on these arrays are shown to reduce the force of insertion into cadaveric cochleae. Finally, resistance to mucus flow and unplugging is reduced in coated tube models. These results exhibit the potential of photograftable zwitterionic hydrogel thin films in improving medical implants like cochlear implants and tympanostomy tubes by robustly reducing biofouling, fibrosis, shear stress, and mucus stasis.
Details
- Title: Subtitle
- Improving cochlear implant and tympanostomy tube surfaces via photografted zwitterionic thin films
- Creators
- Ryan Ruben Horne
- Contributors
- C Allan Guymon (Advisor)Marlan Hansen (Committee Member)Jennifer Fiegel (Committee Member)Eric Nuxoll (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Chemical and Biochemical Engineering
- Date degree season
- Spring 2024
- Publisher
- University of Iowa
- DOI
- 10.25820/etd.007419
- Number of pages
- xxiii, 174 pages
- Copyright
- Copyright 2023 Ryan Ruben Horne
- Language
- English
- Date submitted
- 01/10/2024
- Description illustrations
- illustrations, graphs
- Description bibliographic
- Includes bibliographical references (pages 157-165).
- Public Abstract (ETD)
- For the deaf and hard of hearing, a special device known as the cochlear implant can help them be able to perceive sounds again. This device works by taking sound and turning it into an electric signal to simulate the nerves in the inner ear that interpret sound. One problem with this device is that it can cause inflammation in the inner ear. The inflammation can come from the trauma of implanting the device or from the body recognizing foreign material. This inflammation can make the cochlear implant become wrapped in scar tissue. With a thick scar around it, the device does not stimulate the inner ear nerves as well. Ear tubes are another device that can help people who lose hearing temporarily from ear infections. But ear tubes can sometimes get clogged with mucus or get infected by bacteria. This research explores thin coatings that can be placed on devices like cochlear implants and ear tubes to make them resistant to build up of scar tissue, bacteria, and mucus. The coating can also lubricate devices to make them cause less trauma when they are implanted. This project found ways to adjust the chemistry of this coating to make it durable enough to use while still keeping its helpful features. These coatings were shown to reduce the build-up of scar tissue on cochlear implants by 60% after one year. They also reduced the force required to insert a cochlear implant into the inner ear by 50%. The coatings were shown to make 90% fewer bacteria stick to their surfaces. These coatings also make it easier for mucus to flow through tubes so they do not get clogged. They also make it easier to loosen dried mucus if it does get clogged. These results show that coatings can make a difference on cochlear implants by reducing scarring and friction, and on ear tubes by making it ix harder for bacteria and mucus to stick to them. These results have the potential to make the next generation of these devices more effective.
- Academic Unit
- Chemical and Biochemical Engineering
- Record Identifier
- 9984647456002771
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