Nanoconfined Cathodic Electrochemiluminescence for Self-Sensitized Bioimaging of Membrane Protein

Self-enhanced electrochemiluminescence (ECL) can be achieved via the confinement of coreactants and ECL emitters in a single nanostructure. This strategy has been used for the design of anodic ECL systems with amine compounds as coreactants. In this work, a novel confinement system was proposed by codoping positively charged ECL emitter tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺) and negatively charged coreactant peroxydisulfate (S₂O₈^2-) in silica nanoparticles. The codoping process could be performed by introducing S₂O₈^2- in cationic poly(diallyldimethylammonium chloride) (PDDA) to form PDDA@S₂O₈^2- and then encapsulating it and Ru(bpy)₃²⁺ in the Triton X-100 vesicle followed by the hydrolysis of tetraethyl ortosilicate, surface modification, and demulsification. The obtained RuSSNs exhibited good homogeneity, excellent monodispersity, acceptable biocompatibility, and 2.9-fold stronger ECL emission than Ru(bpy)₃²⁺-doped silica nanoparticles at an equal amount of nanoparticles in the presence of 0.1 M K₂S₂O₈. Thus, an in situ self-sensitized cathodic ECL imaging method was designed for the monitoring of glycoprotein on living cell membranes. This work provides a new way for the modification, enhancement, and application of nano-ECL emitters in biological analysis.