title: A dual wedge microneedle for sampling of perilymph solution via round window membrane.
abstract: Precision medicine for inner-ear disease is hampered by the absence of a methodology to sample inner-ear fluid atraumatically. The round window membrane (RWM) is an attractive portal for accessing cochlear fluids as it heals spontaneously. In this study, we report on the development of a microneedle for perilymph sampling that minimizes the size of RWM perforation, facilitates quick aspiration, and provides precise volume control. Here, considering the mechanical anisotropy of the RWM and hydrodynamics through a microneedle, a 31G stainless steel pipe was machined into wedge-shaped design via electrical discharge machining. The sharpness of the needle was evaluated via a surface profilometer. Guinea pig RWM was penetrated in vitro, and 1 μL of perilymph was sampled and analyzed via UV-vis spectroscopy. The prototype wedge shaped needle was successfully fabricated with the tip curvature of 4.5 μm and the surface roughness of 3.66 μm in root mean square. The needle created oval perforation with minor and major diameter of 143 and 344 μm (n = 6). The sampling duration and standard deviation of aspirated volume were 3 s and 6.8 % respectively. The protein concentration was 1.74 mg/mL. The prototype needle facilitated precise perforation of RWMs and rapid aspiration of cochlear fluid with precise volume control. The needle design is promising and requires testing in human cadaveric temporal bone and further optimization to become clinically viable.
authors.affiliation: Department of Mechanical Engineering, Columbia University, 220 Mudd Building 500 West 120th Street, New York, NY, 10027, USA. hw2420@columbia.edu.
authors.forename: Hirobumi
authors.initials: H
authors.lastname: Watanabe
authors.affiliation: Department of Biomedical Engineering, The City College of The University of New York, New York, NY, 10031, USA.
authors.forename: Luis
authors.initials: L
authors.lastname: Cardoso
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, Columbia University College of Physicians and Surgeons, New York, NY, 10032, USA.
authors.forename: Anil K
authors.initials: AK
authors.lastname: Lalwani
authors.affiliation: Department of Mechanical Engineering, Columbia University, 220 Mudd Building 500 West 120th Street, New York, NY, 10027, USA.
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Kysar
mesh_terms: D000818:Animals; D003051:Cochlea / Q000166:cytology; D004867:Equipment Design; D006168:Guinea Pigs; D006801:Humans; D055616:Microtechnology / Q000295:instrumentation*; D009339:Needles; D019152:Paracentesis / Q000295:instrumentation*; D010498:Perilymph / Q000378:metabolism; D012996:Solutions; D013997:Time Factors; D014432:Tympanic Membrane / Q000166:cytology*
chemical_list: D012996:Solutions
keywords: Inner ear disease; Microneedle; Minimally invasive sampling; Personalized medicine