Multi-scale in silico and ex silico mechanics of 3D printed cochlear implants for local drug delivery

Multi-scale in silico and ex silico mechanics of 3D printed cochlear implants for local drug delivery

Isaakidou, A. (TU Delft Biomaterials & Tissue Biomechanics)
Ganjian, M. (TU Delft Biomaterials & Tissue Biomechanics)
van Hoften, R. (Student TU Delft)
Cruz Saldivar, M. (TU Delft Biomaterials & Tissue Biomechanics)
Leeflang, M.A. (TU Delft Biomaterials & Tissue Biomechanics)
Groetsch, A. (Swiss Federal Laboratories for Materials Science and Technology (Empa); University of California)
Wątroba, M. (Swiss Federal Laboratories for Materials Science and Technology (Empa))
Schwiedrzik, J. (Swiss Federal Laboratories for Materials Science and Technology (Empa))
Mirzaali, Mohammad J. (TU Delft Biomaterials & Tissue Biomechanics)
Apachitei, I. (TU Delft Biomaterials & Tissue Biomechanics)
Fratila-Apachitei, E.L. (TU Delft Biomaterials & Tissue Biomechanics)
Zadpoor, A.A. (TU Delft Biomaterials & Tissue Biomechanics)

2024

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 in silico computational models and ex silico 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.

3D printing
two-photon polymerization
stereolithography
Raman spectroscopy
cochlear implant
finite element analysis
mechanical characterization
compression

http://resolver.tudelft.nl/uuid:afda1c8a-079b-4e57-9e08-d2e65b4f87ed

https://doi.org/10.3389/fbioe.2023.1289299

2296-4185

Frontiers in Bioengineering and Biotechnology, 11

Institutional Repository

journal article

© 2024 A. Isaakidou, M. Ganjian, R. van Hoften, M. Cruz Saldivar, M.A. Leeflang, A. Groetsch, M. Wątroba, J. Schwiedrzik, Mohammad J. Mirzaali, I. Apachitei, E.L. Fratila-Apachitei, A.A. Zadpoor