Aerosol-Jet Printed, Molecularly Imprinted Polymer-Based Wearable Sensors for Lactate and Glucose Monitoring in Human Sweat

Molecularly Imprinted Polymer (MIP) materials can perform as chemical recognition elements for targeted biomarker detection. These materials are employed in small wearable devices to analyze biofluids, such as human sweat, and extract useful bioinformation, contributing significantly to disease diagnosis and healthcare monitoring applications [1], [2].<br/><br/>In this work, a selective lactate MIP sensor was developed. The sensor prototype consists of a polydimethylsiloxane (PDMS) microfluidic channel for the biofluids control and a MIP-modified electrode substrate for lactate sensing. The initial electrode substrate is aerosol-jet printed using the carbon nanotubes ink as the first layer, providing the deposition sites, while a metallic layer, such as silver and gold, is printed on top, functioning as the detecting probes [3], [4]. The electrodes are designed as interdigitated electrodes to form a capacitor for electrical signal detection. The selective MIP layer is polymerized using aniline with target analyte, lactate acid, and crosslinkers such as 3- or 4-Aminophenylboronic acid (3-APBA/4-APBA). The advantage of the MIP polymerized APBA over simple polyaniline chains is that it shows a response to glucose due to its reaction with boronic acid, while retaining sensitivity to lactate [5], [6]. The relationship between the conductivity, MIP polymerization efficiency, sensitivity, and accuracy was evaluated using Cyclic Voltammetry (CV), Differential Pulse Voltammetry (DPV), and particularly, Electrochemical Impedance Spectroscopy (EIS). The impedance frequency sweeping results demonstrate significant differential features of lactate, glucose, and other interfering analytes, showcasing the sensor's sensitivity and specificity.<br/><br/>References:<br/>[1] Y. L. Mustafa and H. S. Leese, “Fabrication of a Lactate-Specific Molecularly Imprinted Polymer toward Disease Detection,” <i>ACS Omega</i>, vol. 8, no. 9, pp. 8732–8742, Feb. 2023, doi: 10.1021/acsomega.2c08127.<br/>[2] R. D. Crapnell, N. C. Dempsey-Hibbert, M. Peeters, A. Tridente, and C. E. Banks, “Molecularly imprinted polymer based electrochemical biosensors: Overcoming the challenges of detecting vital biomarkers and speeding up diagnosis,” <i>Talanta Open</i>, vol. 2, p. 100018, Dec. 2020, doi: 10.1016/j.talo.2020.100018.<br/>[3] P. Kanokpaka <i>et al.</i>, “Self-powered molecular imprinted polymers-based triboelectric sensor for noninvasive monitoring lactate levels in human sweat,” <i>Nano Energy</i>, vol. 100, p. 107464, Sep. 2022, doi: 10.1016/j.nanoen.2022.107464.<br/>[4] G. Dykstra, I. Chapa, and Y. Liu, “Reagent-Free Lactate Detection Using Prussian Blue and Electropolymerized-Molecularly Imprinted Polymers-Based Electrochemical Biosensors,” <i>ACS Appl. Mater. Interfaces</i>, May 2024, doi: 10.1021/acsami.3c19448.<br/>[5] D. Yang <i>et al.</i>, “Polyaniline-Based Biological and Chemical Sensors: Sensing Mechanism, Configuration Design, and Perspective,” <i>ACS Appl. Electron. Mater.</i>, Jan. 2023, doi: 10.1021/acsaelm.2c01405.<br/>[6] M. Thiruppathi, N. Thiyagarajan, M. Gopinathan, J.-L. Chang, and J.-M. Zen, “A dually functional 4-aminophenylboronic acid dimer for voltammetric detection of hypochlorite, glucose and fructose,” <i>Microchim. Acta</i>, vol. 184, no. 10, pp. 4073–4080, Oct. 2017, doi: 10.1007/s00604-017-2440-8.