Isaakidou A, Ganjian M, van Hoften R, Saldivar M C, Leeflang M A, Groetsch A, Wątroba M, Schwiedrzik J, Mirzaali M J, Apachitei I, Fratila-Apachitei L E, Zadpoor A A
Department of Biomechanical Engineering, Faculty of Mechanical Engineering, Delft University of Technology (TU Delft), Delft, Netherlands.
Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory of Mechanics of Materials and Nanostructures, Thun, Switzerland.
Front Bioeng Biotechnol. 2024 Jan 31;11:1289299. doi: 10.3389/fbioe.2023.1289299. eCollection 2023.
The currently available treatments for inner ear disorders often involve systemic drug administration, leading to suboptimal drug concentrations and side effects. Cochlear implants offer a potential solution by providing localized and sustained drug delivery to the cochlea. While the mechanical characterization of both the implants and their constituent material is crucial to ensure functional performance and structural integrity during implantation, this aspect has been mostly overlooked. This study proposes a novel methodology for the mechanical characterization of our recently developed cochlear implant design, namely, rectangular and cylindrical, fabricated using two-photon polymerization (2 PP) with a novel photosensitive resin (IP-Q™). We used computational models and experiments to study the mechanics of our newly designed implants when subjected to torsion mimicking the foreseeable implantation procedure. Torsion testing on the actual-sized implants was not feasible due to their small size (0.6 × 0.6 × 2.4 mm³). Therefore, scaled-up rectangular cochlear implants (5 × 5 × 20 mm³, 10 × 10 × 40 mm³, and 20 × 20 × 80 mm³) were fabricated using stereolithography and subjected to torsion testing. Finite element analysis (FEA) accurately represented the linear behavior observed in the torsion experiments. We then used the validated Finite element analysis models to study the mechanical behavior of real-sized implants fabricated from the IP-Q resin. Mechanical characterization of both implant designs, with different inner porous structures (pore size: 20 μm and 60 μm) and a hollow version, revealed that the cylindrical implants exhibited approximately three times higher stiffness and mechanical strength as compared to the rectangular ones. The influence of the pore sizes on the mechanical behavior of these implant designs was found to be small. Based on these findings, the cylindrical design, regardless of the pore size, is recommended for further research and development efforts.
目前用于内耳疾病的治疗方法通常涉及全身给药，导致药物浓度不理想且会产生副作用。人工耳蜗通过向耳蜗提供局部和持续的药物递送提供了一种潜在的解决方案。虽然人工耳蜗及其组成材料的力学特性对于确保植入过程中的功能性能和结构完整性至关重要，但这方面大多被忽视了。本研究提出了一种新颖的方法，用于对我们最近开发的人工耳蜗设计进行力学特性表征，即使用新型光敏树脂（IP-Q™）通过双光子聚合（2PP）制造的矩形和圆柱形人工耳蜗。我们使用计算模型和实验来研究我们新设计的人工耳蜗在模拟可预见植入过程的扭转作用下的力学性能。由于实际尺寸的人工耳蜗尺寸较小（0.6×0.6×2.4mm³），对其进行扭转测试不可行。因此，使用立体光刻技术制造了放大尺寸的矩形人工耳蜗（5×5×20mm³、10×10×40mm³和20×20×80mm³）并进行扭转测试。有限元分析（FEA）准确地反映了扭转实验中观察到的线性行为。然后，我们使用经过验证的有限元分析模型来研究由IP-Q树脂制造的实际尺寸人工耳蜗的力学行为。对具有不同内部多孔结构（孔径：20μm和60μm）和空心版本的两种人工耳蜗设计进行力学特性表征，结果表明，与矩形人工耳蜗相比，圆柱形人工耳蜗的刚度和机械强度高出约三倍。发现孔径对这些人工耳蜗设计的力学行为影响较小。基于这些发现，建议对圆柱形设计进行进一步的研发工作，无论孔径大小如何。
