Ceschi P, Bohl A, Sternberg K, Neumeister A, Senz V, Schmitz K P, Kietzmann M, Scheper V, Lenarz T, Stöver T, Paasche G
Hannover Medical School, Department of Otolaryngology, Hannover, Germany; School of Veterinary Medicine Hannover Foundation, Department of Pharmacology, Toxicology and Pharmacy, Hannover, Germany.
J Biomed Mater Res B Appl Biomater. 2014 Aug;102(6):1255-67. doi: 10.1002/jbm.b.33110. Epub 2014 Jan 17.
To improve the electrode-nerve interface of cochlear implants (CI), the role of poly(L-lactide) (PLLA) and poly(4-hydroxybutyrate) (P(4HB)) as potential coating matrices for CI was assessed both in vitro and in vivo in terms of degradation behavior and effects on spiral ganglion neurons, the main target of the electrical stimulation with a CI. Growth rates of fibroblasts on the polymers were investigated and a direct-contact test with freshly isolated spiral ganglion cells (SGC) was performed. In addition, the effects of the polymer degradation inside the inner ear were evaluated in vivo. The polymer degradation was assessed by use of scanning electron microscopy in combination with an energy-dispersive X-ray analysis. In vitro, no influence of the polymers was detected on fibroblasts' viability and on SGC survival rate. In vivo, SGC density was decreased only 6 months after implantation in the basal and middle turns of the cochlea in comparison to normal-hearing animals but not between implanted groups (coated or uncoated). The analysis of the electrode models showed that in vivo P(4HB) is characterized by a gradual degradation completed after 6 months; whereas, the PLLA coatings burst along their longitudinal axis but showed only little degradation within the same time frame. In conclusion, both polymers seem to justify further evaluation as possible coating for CI electrodes. Of the two options, due to its excellent coating adhesion/stability and optimal degradation behavior, P(4HB) may prove to be the more promising biodegradable polymer for designing a drug delivery system from the surface of CI electrodes.
为改善人工耳蜗（CI）的电极 - 神经界面，评估了聚（L - 丙交酯）（PLLA）和聚（4 - 羟基丁酸酯）（P(4HB)）作为CI潜在涂层基质在体外和体内的降解行为以及对螺旋神经节神经元的影响，螺旋神经节神经元是CI电刺激的主要靶点。研究了成纤维细胞在聚合物上的生长速率，并对新鲜分离的螺旋神经节细胞（SGC）进行了直接接触试验。此外，还在体内评估了内耳内聚合物降解的影响。通过扫描电子显微镜结合能量色散X射线分析评估聚合物降解情况。在体外，未检测到聚合物对成纤维细胞活力和SGC存活率有影响。在体内，与听力正常的动物相比，仅在植入6个月后，耳蜗基底转和中转的SGC密度降低，但植入组（涂层或未涂层）之间无差异。电极模型分析表明，在体内P(4HB)的特点是在6个月后逐渐降解完成；而PLLA涂层沿其纵轴破裂，但在同一时间框架内仅显示出少量降解。总之，两种聚合物似乎都值得作为CI电极的可能涂层进行进一步评估。在这两种选择中，由于其优异的涂层附着力/稳定性和最佳的降解行为,P(4HB)可能被证明是从CI电极表面设计药物递送系统更有前景的可生物降解聚合物。
