Electrochemical Immunosensor for Human IgE Using Ferrocene Self-Assembled Monolayers Modified ITO Electrode

Abstract

The immunoglobulin E (IgE) level in serum is an important factor in the examination of allergy. Ferrocene (Fc)-modified self-assembled monolayers (SAMs) were placed on an indium tin oxide (ITO) electrode as a sensing layer for the detection of human IgE. The Fc moiety in the SAMs facilitated the electron transfer through the organic SAMs layer and electrocatalytic signal amplification. The electrochemical measurement was accomplished after the sandwich type immobilization of the receptor antibody, target human IgE, and enzyme conjugated secondary antibody. The enzyme product, p-aminophenol, was quantitatively analyzed by redox cycling via Fc. In addition, the electrochemical impedance spectroscopy (EIS) was investigated for the detection of IgE. The limit of detection (LOD), limit of quantification (LOQ), and dynamic range of the electrochemical sensor were 3 IU/mL, 10 IU/mL, and from 10 IU/mL to 100 IU/mL, respectively.

Immunosensor for human IgE detection using electrochemical redox cycling with ferrocene‐mixed self‐assembled monolayers modified Au electrode

“…The calculated surface concentration (± standard deviation), Γ c , is 6.7 (± 0.5) × 10 −11 mol/cm 2 . The calculated value is in good agreement with the general surface density of SAMs modification 25,33,34 …”

“…This additional step makes the system complicated and may change the uniformity in the state of the redox mediator. The surface density of the redox mediator has more reproducible values by SAMs on the Au electrode compared to that on the ITO electrode, with percentage relative standard deviations (% RSD) of 7.5% and 24%, respectively 25 …”

“…The human IgE sensors presented in several published papers showed low limit of detection (LOD) of under 0.1 IU/mL 24 . Although EIS has the advantage of not requiring labeled substances, the EIS method showed a higher LOD value of ~10 IU/mL than voltammetric method 25 . Sensors employing QDs or NMs show good performance, but these label materials are expensive and difficult to synthesize.…”

“…An electrode modified with SAMs is an important component of electrochemical immunosensor because the SAMs layer affects the surface density of probe molecules and electron transfer resistance. Indium tin oxide (ITO) 25,28 and Au electrode 29,30 are usually employed for electrochemical biosensors. As well‐known, both substrates are possible to modify with SAMs.…”

“…Previously, we had reported an immunosensor for IgE using an ITO electrode 25 . When using an ITO electrode, steps for introducing the redox mediator molecules on the SAMs were required.…”