In-vitro perforation of the round window membrane via direct 3-D printed microneedles

  • Aykut Aksit
  • Daniel N. Arteaga
  • Miguel Arriaga
  • Xun Wang
  • Hirobumi Watanabe
  • Karen E. Kasza
  • Anil K. Lalwani
  • Jeffrey W. KysarEmail author


The cochlea, or inner ear, is a space fully enclosed within the temporal bone of the skull, except for two membrane-covered portals connecting it to the middle ear space. One of these portals is the round window, which is covered by the Round Window Membrane (RWM). A longstanding clinical goal is to reliably and precisely deliver therapeutics into the cochlea to treat a plethora of auditory and vestibular disorders. Standard of care for several difficult-to-treat diseases calls for injection of a therapeutic substance through the tympanic membrane into the middle ear space, after which a portion of the substance diffuses across the RWM into the cochlea. The efficacy of this technique is limited by an inconsistent rate of molecular transport across the RWM. A solution to this problem involves the introduction of one or more microscopic perforations through the RWM to enhance the rate and reliability of diffusive transport. This paper reports the use of direct 3D printing via Two-Photon Polymerization (2PP) lithography to fabricate ultra-sharp polymer microneedles specifically designed to perforate the RWM. The microneedle has tip radius of 500 nm and shank radius of 50 μ m, and perforates the guinea pig RWM with a mean force of 1.19 mN. The resulting perforations performed in vitro are lens-shaped with major axis equal to the microneedle shank diameter and minor axis about 25% of the major axis, with mean area 1670 μ m2. The major axis is aligned with the direction of the connective fibers within the RWM. The fibers were separated along their axes without ripping or tearing of the RWM suggesting the main failure mechanism to be fiber-to-fiber decohesion. The small perforation area along with fiber-to-fiber decohesion are promising indicators that the perforations would heal readily following in vivo experiments. These results establish a foundation for the use of Two-Photon Polymerization lithography as a means to fabricate microneedles to perforate the RWM and other similar membranes.


Inner ear delivery Round window membrane 3-D laser printing Microneedles Nanoscribe 



The authors gratefully acknowledge Professor Elizabeth Olson, Charlotte Prevoteau, Wenbin Wang, Dimitrios Fafalis, and Arnuparp Santimetaneedol for helpful discussions. Dr. Charles Emala, M.D. generously provided euthanized guinea pigs with intact temporal bones through a tissue sharing program at the Institute of Comparative Medicine at Columbia University Medical Center. KEK holds a Career Award at the Scientific Interface from the Burroughs Wellcome Fund and a Clare Boothe Luce Professorship from the Henry Luce Foundation. This work was performed in part at the Advanced Science Research Center NanoFabrication Facility of the Graduate Center at the City University of New York. This research was supported by NIH National Institute on Deafness and Other Communication Disorders of the National Institutes of Health under award number R01DC014547.


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  • Aykut Aksit
    • 1
  • Daniel N. Arteaga
    • 2
  • Miguel Arriaga
    • 1
  • Xun Wang
    • 1
  • Hirobumi Watanabe
    • 1
  • Karen E. Kasza
    • 1
  • Anil K. Lalwani
    • 1
    • 2
  • Jeffrey W. Kysar
    • 1
    • 2
    Email author
  1. 1.Department of Mechanical EngineeringColumbia UniversityNew YorkUSA
  2. 2.Department of Otolaryngology - Head, Neck SurgeryColumbia University College of Physicians and SurgeonsNew YorkUSA

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