Ru(bpy)32+ Incorporated Luminescent Polymer Dots: Double-Enhanced Electrochemiluminescence for Detection of Single-Nucleotide Polymorphism.

Encapsulating a large amount of electrochemiluminescence (ECL) active molecules into one nanoparticle for single-target recognition can greatly improve the sensitivity of the ECL assay. This work used luminescent conjugated polymer as a carrier to synthesize Ru(bpy)32+-doped polymer dots (RuPdots). The RuPdots with an average size of 20 nm and encapsulation of about 1354 Ru(bpy)32+ showed greatly enhanced ECL emission. Using tripropylamine as a coreactant, the resonance energy transfer from the excited polymer dots to the encapsulated Ru(bpy)32+ was demonstrated, which led to a 15.7-fold higher ECL emission than that of Ru(bpy)32+ with the same amount at the gold electrode. By coupling the double-enhanced ECL signal of this nanostructure with the specific ligase detection reaction, a sensitive ECL biosensor was constructed for specific detection of a single-nucleotide polymorphism (SNP). Using mutant KRAS gene as a model target, the ECL SNP detection method showed a linear range from 1 fM to 1 nM and a detection limit of 0.8 fM. The designed RuPdots provided a novel signal amplification strategy and could be used as a universal label for ultrasensitive ECL biodetection.