Using Electrospinning Technique for Rapid Preparation of BDNF-Releasing Electrode Array of Cochlear Implant: An In Vitro Study

Cochlear implantation (CI) remains the primary intervention for individuals with severe-to-profound sensorineural hearing loss, and its clinical outcomes can be influenced by the preservation and functional integrity of spiral ganglion neurons (SGNs). While brain-derived neurotrophic factor (BDNF) shows promising neuroprotective effects on SGNs, its clinical translation remains limited by current drug delivery methods. We present a clinically adaptable electrospinning technique using polycaprolactone/poly(ethylene oxide) (PCL/PEO) nanofibers to fabricate customizable BDNF-eluting coatings for CI electrode arrays. To enable flexible dosage adjustment tailored to surgical requirements, three modular loading protocols were developed: spray (S), spray-immersion (SI), and spray-immersion-spray (SIS). Among them, the SIS protocol demonstrated superior performance, achieving: (1) sustained BDNF release over 5 days, (2) maintenance of electrode impedance within functional ranges (2.20 ± 0.67 kΩ, n = 23), and (3) significantly enhanced SGN proliferation (p < 0.001 at 5 μg/mL) and adhesion in vitro. Importantly, our rapid electrospinning technique supports flexible customization of drug type and concentration, enabling patient-specific therapeutic loading. This method allows ultrafast coating of CI electrodes (<3 min), offering controlled drug release and consistent safety, with promising clinical translation prospects.