Self-Enhanced Electrochemiluminescence Nanorods of Tris(bipyridine) Ruthenium(II) Derivative and Its Sensing Application for Detection of N-Acetyl-β-d-glucosaminidase

A self-enhanced electrochemiluminescence (ECL) reagent, synthesized by covalently linking bis(2,2'-bipyridyl)(4'-methyl-[2,2']bipyridinyl-4-carboxylicacid) ruthenium(II) (Ru(bpy)2(mcbpy)(2+)) with tris(3-aminopropyl)amine (TAPA), has been chosen as precursor to prepare nanorods ([Ru(bpy)2(mcbpy)(2+)-TAPA]NRs) with high luminous efficiency via a solvent-evaporation-induced self-assembly procedure. Due to the shorter electron-transfer path and less energy loss, the intramolecular reaction between the luminescent Ru(bpy)2(mcbpy)(2+) and coreactive tertiary amine group in TAPA has shown improved luminous efficiency compared with the common intermolecular ECL reactions. Moreover, using the electrochemiluminescent Ru(II)-based complex as precursor to directly prepare a nanostructure with high electro-active surface area is a more effective and convenient method for enhancing the immobilized amount of Ru(II)-based complex in the construction of biosensors compared with the traditional immobilized methods. Meanwhile, the obtained nanorods could be further functionalized easily, owing to their positive electrical property and the amino group on the surface. Here, Pt nanoparticles functionalized [Ru(bpy)2(mcbpy)(2+)-TAPA]NRs are used to load the detection antibody (Ab2). In addition, the Au/Pd dendrimers (DRs) with hierarchically branched structures are synthesized to immobilize capture antibody (Ab1) with increased amount. Based on sandwiched immunoreactions, a simple and sensitive "signal-on" immunosensor is constructed for the detection of N-acetyl-β-d-glucosaminidase (NAG), a biomarker of diabetic nephropathy, with excellent linearity in concentrations from 1 ng mL(-1) to 0.5 pg mL(-1) and a detection limit of 0.17 pg mL(-1).