Determination of dielectric properties of mimicking biological tissues by electrochemical impedance spectroscopy

International audience ; Tissue-mimicking materials are widely developed and used as substitutes in many medical branches, including surgical procedures, medical imaging, machine calibration, training, and simulations. Usually, these materials are fabricated either by chemical synthesis or additive manufacturing (3D printing), to mimic the mechanical, optical or, as in the present work, electrical properties of the targeted tissues.The aim of this work is to fabricate a biomaterial that mimics, as closely as possible, the dielectric properties of bone in the context of spinal surgery, where low-frequency electrical stimulation is performed to verify the correct placement of titanium pedicle screws around the nerve structure [1].To obtain a tissue mimicking the bone of the spine, different mixtures of hydrogels containing chitosan and hydroxyapatite (HAp) were prepared by varying the concentrations and/or the pH of the hydrogels. Electrochemical impedance spectroscopy measurements have been performed within these hydrogels to determine their electrical properties from 1 Hz to 1 MHz. An example of result is shown in Fig.1, where both the conductivity and the relative permittivity of four hydrogels are compared to those of cancellous bone [2].[1] J. Zyss, et al., Neurophysiologie Clinique. 2016, 46(3):234. DOI:10.1016/j.neucli.2016.06.044. [2] C. Gabriel, et al., The dielectric properties of biological tissues: I. Literature survey, Phys. Med. Biol. 1996, 41(11):2231. DOI:10.1088/0031-9155/41/11/001.