Electrochemiluminescence sensing of HeLa cells labeled with biotinylated ruthenium complex using bipolar electrode based on microwell modified optical fiber

Biotinylated ruthenium complexes exhibit improved photoluminescent (PL) properties when they bind with streptavidin, making them useful labels or probes in bio-related analysis. However, their ECL properties are still unknown to date. Herein, we reported the use of [Ru(bpy)₂(biot-bpy)]²⁺ complexes as a new ECL luminophore, which was functionalized with biotin moiety and exhibited higher ECL efficiency after binding to streptavidin. Moreover, [Ru(bpy)₂(biot-bpy)]²⁺ complexes could be attached to HeLa cells through the biotin-streptavidin binding. A microwell bipolar electrode (MBE) prepared at one end of an optical fiber bundle was applied to produce ECL of the labeled HeLa cells, which was remotely detected at the other end. The [Ru(bpy)₂(biot-bpy)]²⁺-streptavidin binding effect together with the high surface/volume ratio of MBE promoted the ECL generation on HeLa cells, which was applied to sensitively detect HeLa cells with a linear range from 1.56 × 10² to 6.74 × 10⁶ cells/mL and a detection limit of 83 cells/mL. Moreover, ECL images were successfully acquired to resolve the emission on each HeLa cell. Such cytosensor based on [Ru(bpy)₂(biot-bpy)]²⁺ and MBE may extend the applications of ECL for cell detections. Graphical abstract