Impedimetric Detection of Human Interleukin 10 on Diazonium Salt Electroaddressed Gold Microelectrode Surfaces

In this chapter, we describe the development and fabrication of gold microelectrodes based on silicon by silicon technology, for multiplex detection of cytokines. Cytokines have become a crucial biomarker for the identification of end-stage heart failure (ESHF) for patients during early phase of left ventricular assisted device (LVAD) implantation. The microelectrode device consists of three gold working microelectrodes that were activated and 4-aminophenylacetic acid (CMA) was electroaddressed onto individual gold WEs. The carboxylic acid functionalities of the diazotated aromatic amine were activated through carbodiimide chemistry and anti-interleukin-10 monoclonal antibodies (anti-IL-10 mAb) were immobilized onto the transducers surface. The interaction between the antibody-antigen (Ab-Ag) was characterized by electrochemical impedance spectroscopy (EIS). Here, Nyquist plots have shown a stepwise variation due to the charge transfer resistance (Rct) between the Ab activated surfaces with the detection of the human IL-10. For early expression monitoring, commercial proteins of human IL-10 were analyzed between 1 pg/mL and 100 pg/mL. The protein concentrations within the linear range of 1–50 pg/mL were detected and these values formulated a sensitivity of 0.008 (pg/mL)\(^{-1}\) (\(R^2 = 0.9840\)). These preliminary results demonstrated that the developed biosensor was sensitive to the detection of human IL-10 and the calculated limit of detection (LOD) was measured at 0.156 (pg/mL)\(^{-1}\). To validate the biosensors response, the experiment was repeated several times on different gold working WEs by applying the same conditions. The overall relative standard deviation percentage (% R.S.D.) was 4.9% which demonstrates the successful fabrication for the detection of human IL-10 through diazonium salt electroreduction.