A Rapid Colorimetric Sensor for Soluble Interleukin‐2 Receptor α, Based on Aptamer‐Adsorbed AuNP

Abstract The soluble interleukin‐2 receptor α (sIL‐2Rα) is a broad indicator of clinical disease activity in various inflammatory diseases. Here we have developed, for the first time, a rapid, washing‐free colorimetric aptasensor based on a sIL‐2Rα aptamer ( K d =1.33 n m ). The aptasensor was fabricated with Au nanoparticles (AuNPs) adsorbing sIL‐2Rα aptamers. On addition of sIL‐2Rα, the aptamers become desorbed from the AuNPs, and this in turn weakens the absorption corresponding to AuNP‐catalyzed oxidation of ortho ‐phenylenediamine ( o PD) with H 2 O 2 . The aptasensor was characterized by TEM imaging, ζ potential measurements, dynamic light scattering (DLS) analysis, and UV/Vis spectrometry, followed by further optimization. The fabricated sensor exhibited great analytical performance, with a linear range of 1 to 100 n m and a detection limit of 1 n m both in buffer and in spiked human serum within 25 min. Other proteins, such as bovine serum albumin (BSA), IL‐17Rα, IL‐5Rα, IL‐13Rα 2 , and CD166, showed negligible effects on the aptasensor. Thanks to the great advantages of the aptamers and AuNPs, this aptasensor provides a rapid, simple, and inexpensive process that might offer insights into various diagnostic applications of sIL‐2Rα.