Highly Efficient ECL Immunosensing via a Stimuli-Responsive Luminophore

Electrochemiluminescence (ECL) is the generation of excited states via charge recombination without light excitation. Compared to photoexcitation, it offers lower background, high sensitivity and selectivity [1]. Ruthenium complexes are the most common ECL emitters, though other metal complexes are also being explored recently. While multinuclear systems have been proposed, their performance is limited by self-quenching effects. Stimuli-responsive materials are widely used, but their application in ECL, especially in immunoassays, remains largely unexplored. Here, a new strategy to enhance ECL signals is presented by shifting from the conventional “remote” mechanism to a more efficient homogeneous pathway using cleavable luminophore labels. A [Ru(bpy)₃]²⁺ derivative with a disulfide linker was designed to be cleaved by electrogenerated radicals, releasing the luminophore into solution and boosting emission while reducing quenching. The mechanism was validated using ICP-MS and ECL microscopy, and its performance was tested in a bead-based immunoassay for SARS-CoV-2 Spike protein. This system showed a 40% lower detection limit, doubled sensitivity, and a 72% reduction in TPrA consumption. These results highlight the potential of stimuli-responsive luminophores to significantly enhance ECL biosensor performance [2].