Sensitive immunosensor based on high effective resonance energy transfer of lucigenin to the cathodic electrochemiluminescence of tris(bipyridine) Ru(II) complex

Electrochemiluminescence resonance energy transfer (ECL-RET) has been attracting much focus as an effective approach for great ECL enhancement. Here, we found that lucigenin (Luc) could serve as a new energy transfer donor and greatly improve the cathodic ECL of bis(2,2′-bipyridyl)(4′-methyl-[2,2′]bipyridinyl-4-carboxylicacid) ruthenium(II) (Ru(Bpy)2(Mcbpy)2+, acceptor). Then, both Luc and Ru(Bpy)2(Mcbpy)2+ were largely co-immobilized onto the PdCu nanocrystals and polyethyleneimine (PEI) modified single-walled carbon nanohorns (SWCNHs-PdCuNCs-PEI) through π-π stacking and crosslinking reaction, respectively. By this way, the excellent electrocatalytic behavior and high loading capability for both Luc and Ru(Bpy)2(Mcbpy)2+ of SWCNHs-PdCuNCs-PEI effectively facilitated the ECL reaction. Particularly, the co-immobilization strategy making the donor (Luc)/acceptor (Ru(Bpy)2(Mcbpy)2+) pairs co-exist in the same nano-composite could obviously increase the ECL-RET efficiency by shortening the electron-transfer path and reducing energy loss, further significantly improving the ECL signal. Combining the obtained nano-composite (Luc-SWCNHs-PdCuNCs-PEI-Ru(Bpy)2(Mcbpy)2+) with sandwiched immunoreaction, an ECL immunosensor was constructed for β2-microglobulin (β2-M) measurement. And as a result, it exhibited excellent performance in sensitivity, stability and selectivity. The establishment of the new effective donor/acceptor pairs for ECL-RET and the co-immobilization strategy of making those donor/acceptor pairs largely co-exist in the same nano-composite would greatly improve the ECL efficiency and motivate the wider application of ECL technology.