Carcinoembryonic antigen (CEA) is recognized as a disease biomarker to reflect the existence of various cancers and tumors in the human body. Sensitive detection of CEA in body fluid is valuable for clinical diagnosis and treatment assessment of cancers. Herein, we present a new approach for ultrasensitive determination of CEA in human serum based on localized surface plasmon resonance (LSPR) enhanced electrochemiluminescence (ECL) of Ru(bpy)3(2+). In this surface-enhanced ECL (SEECL) sensing scheme, Ru(bpy)3(2+)-doped SiO2 nanoparticles (Ru@SiO2) act as ECL luminophores, and AuNPs are used as LSPR source to enhance the ECL signal. Two different kinds of aptamers specific to CEA are modified on the surface of Ru@SiO2 and AuNPs, respectively. In the presence of CEA, a multilayer of Ru@SiO2-AuNPs nanoarchitectures would be formed. Our investigation reveals that the ECL signal of Ru@SiO2 can be effectively enhanced by AuNPs. One layer of Ru@SiO2-AuNPs nanoarchitectures would generate about 3-fold ECL enhancement compared with the ECL of the nanoarchitectures without the presence of AuNPs. As much as 30-fold ECL enhancement could be obtained by a multilayer of Ru@SiO2-AuNPs nanoarchitectures. Under the optimal conditions, a detection limit of 1.52 × 10(-6) ng/mL of CEA in human serum was achieved. To the best of our knowledge, CEA assays with such a low LOD have never been reported for an ECL sensor.

Surface enhanced spectroscopy such as surface enhanced Raman spectrum (SERS) and surface enhanced fluorescence have been investigated extensively in the past two decades. Herein, we present experimental evidence to demonstrate the existence of a new surface enhanced spectroscopy, namely, surface enhanced electrochemiluminescence (SEECL). Our investigation indicates that the electrochemiluminescence (ECL) response of the Ru(bpy)32+-tri-n-propylamine (TPrA) system could be significantly enhanced when the working electrode is modified with gold nanoparticle-SiO2 core-shell nanocomposites (AuNP@SiO2). It is worth noting that comparing with a working electrode modified with pure SiO2 nanoparticles, the electrochemical responses of the two electrodes were quite similar, but the ECL signal of the AuNP@SiO2 modified electrode was ~5 times higher than that of the SiO2 nanoparticles modified electrode. Thus we infer that the localized surface plasmon resonance (LSPR) of the AuNPs could be a major contribution to the ECL enhancement. Our investigations also demonstrate that the ECL enhancement is closely related to the thickness of the SiO2 layer. As much as 10 times ECL enhancement (comparing with the ECL intensity of bare electrode) is observed under the optimal conditions. The possible mechanism of the SEECL phenomenon is also discussed.

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We demonstrate the first colorimetric aptasensor for sensitive detection of ochratoxin A based on disassembly of aggregates of oriented AuNP dimers.