Surface-enhanced electrochemiluminescence combined with resonance energy transfer for sensitive carcinoembryonic antigen detection in exhaled breath condensates.

The detection of biomarkers in exhaled breath condensates (EBCs) is regarded as a promising non-invasive diagnostic approach. However, the ultralow concentration of biomarkers in EBCs is a great challenge. Herein, a sensitive dual signal amplification strategy was developed based on surface-enhanced electrochemiluminescence (SEECL) combined with resonance energy transfer (RET). Gold nanoparticles-functionalized graphite-like carbon nitride nanohybrids (Au-g-CN NHs) could be used as an energy transfer donor because of the good overlap between its emission peak and the absorption peak of tris(2,2'-bipyridine)ruthenium dichloride (Ru(bpy)Cl) at 460 nm. Gold-silicon dioxide core-shell nanoparticles doped with Ru(bpy)(Au@SiO-Ru) were employed as an energy transfer acceptor emitting at 620 nm. Moreover, the signals at 620 nm emitted by Ru (bpy) were enhanced by 5 times, attributed to the localized surface plasmon resonance (LSPR) of gold nanoparticles (Au NPs). The detection of carcinoembryonic antigen (CEA) was performed by using two aptamers as the recognition unit; whereby aptamer 1 (Apt1) was modified on the surface of Au-g-CN NHs, and aptamer 2 (Apt2) was banded on the surface of Au@SiO-Ru. In the presence of CEA, a sandwich structure was formed between Au-g-CN NHs-Apt1-CEA and Apt2-Au@SiO-Ru, which resulted in an ultrasensitive detection of CEA. The proposed electrochemiluminescence sensor showed a wide linear relationship with the CEA concentration in the range from 1.0 pg mL to 5.0 ng mL, with a limit of detection (LOD) of 0.3 pg mL. Finally, the practicality of the proposed sensor was demonstrated to detect CEA in EBCs, and the obtained results were in good agreement with the enzyme-linked immunosorbent assay (ELISA) method.