Disposable inkjet-printed electrochemical platform for detection of clinically relevant HER-2 breast cancer biomarker

Abstract

Rapidly fabricated, disposable sensor platforms hold tremendous promise for point-of-care detection. Here, we present an inexpensive (< $0.25) fully inkjet printed electrochemical sensor with integrated counter, reference, and working electrodes that is easily scalable for commercial fabrication. The electrochemical sensor platform featured an inkjet printed gold working 8-electrode array (WEA) and counter electrode (CE), along with an inkjet -printed silver electrode that was chlorinated with bleach to produce a Ag/AgCl quasi-reference electrode (RE). As proof of concept, the electrochemical sensor was successfully applied for detection of clinically relevant breast cancer biomarker Human Epidermal Growth Factor Receptor 2 (HER-2). Capture antibodies were bound to a chemically modified surface on the WEA and placed into a microfluidic device. A full sandwich immunoassay was constructed following a simultaneous injection of target protein, biotinylated antibody, and polymerized horseradish peroxide labels into the microfluidic device housing the WEA. With an ultra fast assay time, of only 15mins a clinically relevant limit of detection of 12pgmL^-1 was achieved. Excellent reproducibility and sensitivity were observed through recovery assays preformed in human serum with recoveries ranging from 76% to 103%. These easily fabricated and scalable electrochemical sensor platforms can be readily adapted for multiplex detection following this rapid assay protocol for cancer diagnostics.

Keywords: Breast cancer; Human epidermal growth factor receptor 2 (HER-2); Immunoassay; Inkjet printing; Microfluidic; Printed electronics.

Fig. 1

(A) Schematic representation of the fabrication of the fully inkjet printed electrochemical array platform with integrated counter, working and reference electrodes. (B) Picture of the microfluidic system. (C) Schematic representation of the system for electrochemical immunoarray detection of HER-2. (D) Fully developed sandwich immunoassay developed on electrochemical array platform and detection strategy generated by the injection of a hydroquinone and H₂O₂ mixture.

Fig. 2

(A) Simultaneous CVs recorded at 100 mV s⁻¹ on all working electrodes across the inkjet printed array in 0.18 M H₂SO₄. (B) A magnified photograph documented by FireflyPro digital microscope of the electrochemical array platform with a geometric surface area of a working electrode of 0.469 mm². (C) Simultaneous amperometric responses at 0.1 V vs Ag/AgCl in the microfluidic device after a injection of 200 μL of 5 mM Fe(CN)₆ ^3−/4− in 100 mM KCl at 200 μL min⁻¹.

Fig. 3

(A) Amperometric responses for HER-2 in 5X diluted calf serum at −0.15 V vs Ag/AgCl following injection of 1 mM HQ and 0.1 mM H₂O₂. (B) Corresponding calibration curve y= 0.34 + 0.076 log (x); R= 0.99.