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Zwitterionic Photografted Coatings of Cochlear Implant Biomaterials Reduce Friction and Insertion Forces
Journal article   Peer reviewed

Zwitterionic Photografted Coatings of Cochlear Implant Biomaterials Reduce Friction and Insertion Forces

Douglas M Bennion, Ryan Horne, Adreann Peel, Parker Reineke, Allan Henslee, Christopher Kaufmann, C. Allan Guymon and Marlan R Hansen
Otology & neurotology, Vol.42(10), pp.1476-1483
12/2021
DOI: 10.1097/MAO.0000000000003288
PMCID: PMC8595522
PMID: 34310554

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Abstract

Hypothesis:Application of photografted zwitterionic coatings to cochlear implant (CI) biomaterials will reduce friction and insertion forces.Background:Strategies to minimize intracochlear trauma during implantation of an electrode array are critical to optimize outcomes including preservation of residual hearing. To this end, advances in thin-film zwitterionic hydrogel coatings on relevant biomaterials may show promise, in addition to the potential of these materials for decreasing the intracochlear foreign body response.Methods:Using a recently designed one-step process, thin-film coatings derived from zwitterionic sulfobetaine methacrylate (SBMA) were photopolymerized and photografted to the surface of polydimethylsiloxane (PDMS, silastic) samples and also to CI arrays from two manufacturers. Fluorescein staining and scanning electron microscopy with energy-dispersive X-ray spectroscopy verified and characterized the coatings. Tribometry was used to measure the coefficient of friction between uncoated and coated PDMS and synthetic and biological tissues. Force transducer measurements were obtained during insertion of uncoated (n=9) and coated (n=9) CI electrode arrays into human cadaveric cochleae.Results:SBMA thin-film coating of PDMS resulted in >90% reduction in frictional coefficients with steel, ceramic, and dermal tissue from guinea pigs (p<0.0001). We employed a novel method for applying covalently bonded, durable, and uniform coating in geographically selective areas at the electrode array portion of the implant. Image analysis confirmed uniform coating of PDMS systems and the CI electrode arrays with SBMA polymer films. During insertion of electrode arrays into human cadaveric cochleae, SBMA coatings reduced maximum force by ∼40% during insertion (p<0.001), as well as decreasing force variability and the overall work of insertion.Conclusion:Thin-film SBMA photografted coatings on PDMS and electrode arrays significantly reduce frictional coefficients and insertional forces in cadaveric cochleae. These encouraging findings support that thin-film zwitterionic coating of CI electrode arrays may potentially reduce insertional trauma and thereby promote improved hearing and other long-term outcomes.

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