3D-Printed Microneedles Create Precise Perforations in Human Round Window Membrane in Situ

Area of Science:

• Biomedical Engineering
• Otolaryngology
• Drug Delivery Systems

Background:

• The human round window membrane (HRWM) acts as a barrier to inner ear drug and diagnostic agent delivery.
• Previous studies showed microperforation of the guinea pig round window membrane enhances diffusion 35-fold.
• Precisely perforating the thicker human HRWM without damage presents a significant challenge.

Purpose of the Study:

• To design and evaluate 3D-printed microneedles for precise perforation of the human round window membrane (HRWM).
• To assess the force, displacement, and structural integrity of microneedles during HRWM perforation.
• To determine the safety of microneedle use concerning intracochlear structures.

Main Methods:

• Two microneedle designs were 3D-printed based on HRWM thickness and mechanical properties.
• Perforation tests were conducted on fresh frozen human temporal bones.
• Force, displacement, perforation morphology (confocal microscopy), and microneedle integrity (scanning electron microscopy) were analyzed.

Main Results:

• The average HRWM thickness was measured at 60.1 ± 14.6 μm.
• Microneedles created slit-shaped perforations by separating collagen fibers.
• Minimal displacement was required for complete perforation, avoiding damage to intracochlear structures.
• The 3D-printed microneedles demonstrated durability and remained intact post-procedure.

Conclusions:

• 3D-printed microneedles can create precise HRWM perforations safely, without damaging intracochlear structures.
• These microneedles have potential applications in inner ear fluid aspiration for diagnostics.
• They can also serve as portals for targeted therapeutic agent delivery into the inner ear.