Homocysteine Solution-Induced Response in Aerosol Jet Printed OECTs by Means of Gold and Platinum Gate Electrodes.

Pasquale D’Angelo,Mario Barra,Antonio Cassinese,Diego Ingrosso,Alessandra F Perna,Davide Vurro,Federico Chianese,Giuseppe Tarabella,Patrizia Lombari,Margherita Borriello,Annapaola Coppola,Simone Luigi Marasso

doi:10.3390/ijms222111507

Abstract

Homocysteine (Hcy) is a non-protein, sulfur-containing amino acid, which is recognized as a possible risk factor for coronary artery and other pathologies when its levels in the blood exceed the normal range of between 5 and 12 μmol/L (hyperhomocysteinemia). At present, standard procedures in laboratory medicine, such as high-performance liquid chromatography (HPLC), are commonly employed for the quantitation of total Hcy (tHcy), i.e., the sum of the protein-bound (oxidized) and free (homocystine plus reduced Hcy) forms, in biological fluids (particularly, serum or plasma). Here, the response of Aerosol Jet-printed organic electrochemical transistors (OECTs), in the presence of either reduced (free) and oxidized Hcy-based solutions, was analyzed. Two different experimental protocols were followed to this end: the former consisting of gold (Au) electrodes’ biothiol-induced thiolation, while the latter simply used bare platinum (Pt) electrodes. Electrochemical impedance spectroscopy (EIS) analysis was performed both to validate the gold thiolation protocol and to gain insights into the reduced Hcy sensing mechanism by the Au-gated OECTs, which provided a final limit of detection (LoD) of 80 nM. For the OECT response based on Platinum gate electrodes, on the other hand, a LoD of 180 nM was found in the presence of albumin-bound Hcy, with this being the most abundant oxidized Hcy-form (i.e., the protein-bound form) in physiological fluids. Despite the lack of any biochemical functionalization supporting the response selectivity, the findings discussed in this work highlight the potential role of OECT in the development of low-cost point-of-care (POC) electronic platforms that are suitable for the evaluation, in humans, of Hcy levels within the physiological range and in cases of hyperhomocysteinemia.

Highlights

organic electrochemical transistors (OECTs) have emerged as versatile tools that are able to implement a Lab on Chip approach
The OECT standard architecture consists of a PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate) channel, filling the gap between two metal electrodes, which is interfaced to an electrolyte containing the third electrode, named the gate
Electrochemical impedance spectroscopy (EIS) measurements were performed in a physiological electrolyte (1× PBS, pH 7.3) upon incubation of the Au working electrode of a screen-printed electrode (SPE) by a Hcy/hydrochloric acid (HCl)/PBS solution

Summary

Introduction

OECTs have emerged as versatile tools that are able to implement a Lab on Chip approach (allowing, for instance, the monitoring of biomolecules’ properties [4] and the properties of cells’ physiology [5], or even of neuromorphic function [6]). OECTs can work in a liquid medium for prolonged time at operating voltages well below 1 V These devices implement an ion-to-electron transduction with a marked amplifying capability, since, during their operation, the ionic species in the electrolyte are reversibly forced, by the gate voltage, towards the PEDOT:PSS channel, producing its charge de-doping and the related decrease in conductivity. The surfaces of the main OECT components, especially the gate, can be bio-functionalized to improve the final selectivity towards the desired analyte (e.g., glucose, dopamine, or DNA) via specific electrochemical or biological interactions [7]

Methods

Results

Conclusion