A cochlear implant loaded with dexamethasone and coated with hyaluronic acid to inhibit fibroblast adhesion and proliferation

Inflammation and fibrosis caused by inserting cochlear implants into the inner ear are of great concern in clinical treatment. To address these issues, we studied new cochlear implant electrode analogs, polydimethylsiloxane (PDMS) filaments loaded with anti-inflammation/fibrosis dexamethasone (Dex) and coated with hyaluronic acid (HA) as a surface modifier. The PDMS filaments were prepared by incorporating Dex into PDMS that contained different amounts of poloxamer 188 (P188) as a drug release enhancer. HA coatings were performed to prevent protein adsorption by treating the surfaces of the PDMS filaments with O-2 plasma, 3-aminopropyltriethoxysilane and HA in sequence. The prepared PDMS filaments were investigated by attenuated total reflection Fourier transform infrared spectroscopy, contact angle measurement and atomic force microscopy. Their protein adsorption and drug release behaviors were examined as well. L929 mouse fibroblast cells were used to evaluate the anti-cell adhesion/proliferation effects of the PDMS filaments. The results showed that the prepared PDMS filaments had the expected structure, good surface properties and excellent anti-fibroblast cell proliferation effects. The HA coatings provided filament surfaces that were more hydrophilic, smoother and more protein-repelling. Dex release was significantly facilitated by adding P188 and slightly slowed down by the HA coatings. The PDMS filaments that contained 5% Dex and 5% P188 and that were coated with HA showed a significant decrease in the fibroblast cell number by approximately 51%, with obviously reduced cell adhesion on the surfaces.