Hypothesis: Silver-plated microneedles can be used to confirm penetration of semi-permeable membranes such as the round window membrane (RWM) by detection of voltage change at the moment of perforation.
Background: The introduction of microperforations in the RWM can significantly enhance intracochlear delivery of therapeutics. However, the moment of needle penetration through the RWM cannot be reliably detected by visualization or sensation alone. We explore the ability of electrochemical detection of penetration in defining the precise instant a microneedle enters the inner ear.
Methods: 0.2 mm diameter stainless steel Minutien pins were electroplated with copper, then silver. Pins were then soaked in bleach for 24 h to complete Ag/AgCl plating. Experiments were performed using a 3 mL Franz cell diffusion system with 1%, 2%, 3%, 4%, and 5% saline solution in the donor chamber and artificial perilymph solution in the receptor chamber separated by 5-μm pore synthetic membrane. Continuous voltage measurements were made throughout the process of membrane penetration by the microneedle (N = 6 for each saline concentration).
Results: Silver-plated needles were able to detect an instantaneous change in voltage when traversing the membrane from saline solution into artificial perilymph. As calculated, the magnitude of the change in voltage upon penetration increased with increasing saline concentration and was stable across trials.
Conclusion: Ag/AgCl coated microneedles are effective in detecting the moment of penetration across semi-permeable membranes. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 307-311, 2017.
Keywords: electrochemical detection; electrochemical plating; inner ear therapeutics; microneedle; round window membrane.
© 2015 Wiley Periodicals, Inc.