A Novel Eosinophilia Diagnostics Using Label-Free Impedimetric Aptasensor for Soluble Interleukin-5 Receptor Alpha

Recently, interleukin-5 receptor alpha (IL-5RA) was reported to be a key surface molecule in the regulation of eosinophil proliferation. In this study, a highly sensitive aptamer for IL-5RA was applied to an electrochemical biosensor. The rod-shaped gold electrodes with circular gold surface were used. The aptasensor specifically detected membrane-bound IL-5RA on human eosinophils according to the number of the eosinophils. We further examined the usability of soluble IL-5RA (sIL-5RA) in the serum as a novel biomarker for the diagnosis of eosinophil-related diseases. When eosinophilic inflammation occurs, the concentration of sIL-5RA in the blood is highly elevated. To diagnose eosinophilic inflammation, the aptasensor was calibrated in phosphate-buffered saline (PBS) to detect sIL-5RA. The detection limit of the aptasensor in PBS was 1.69 pg/mL, which is lower than that of commercially available ELISA kits. The dynamic range of the aptasensor was 10-10,000 pg/mL, with high specificity over other serum proteins and interleukin family members. The aptasensor was capable of distinguishing between patients with eosinophilic asthma (EA) and normal controls (NCs) based on serum sIL-5RA levels. Consequently, the fabricated aptasensor will contribute to the development of novel diagnostic systems for IL-5RA-related diseases.