Electrochemiluminescene Resonance Energy Transfer Between Traditional Luminescent Reagents and Nanomaterials and Their Biosensing Application

Abstract

Luminescence resonance energy transfer (LRET) is a powerful technique for probing changes in the distance between energy donors and acceptors, which has often been used in bioassays.1 Electrochemiluminescence (ECL) technique has been widely used in sensing applications, however, it has been seldom reported in LRET due to the difficulty in finding suitable energy donor/acceptor pair. In order to expand its application, it is very important to establish more suitable ECL resonance energy transfer (ECL-RET) pairs. Recently, we found that some traditional ECL reagents, such as luminol, Ru(bpy)3 2+, and lucigenin, can transfer their ECL energy to nanomaterials including semiconductor quantum dots and graphene. The obtained ECL-RET signals are usually stronger than the original ECL signals, which makes the ECL-RET more suitable for biosensing application. Electrochemluminescence resonance energy transfer (ECL-RET) between luminol as a donor and CdSe@ZnS quantum dots (QDs) as an acceptor can be obtained in neutral condition. CdSe@ZnS quantum dots modified on a glassy carbon electrode can catalyze the luminol oxidation to promote the anodic luminol ECL without coreactant. The intensity of anodic luminol ECL (0.60 V) at the CdSe@ZnS/GCE was enhanced more than one magnitude compared with that at the bare GCE. Another strong anodic ECL peak observed at more positive potential (1.10 V) could be assigned to the ECL-RET between the excited state of luminol and the QDs. A label-free ECL aptasensor for the detection of thrombin was fabricated based on the synergic effect of the electrocatalysis and the ECL-RET. The approach showed high sensitivity, good selectivity, and wide linearity for the detection of thrombin in the range of 10 fM-100 pM with a detection limit of 1.4 fM (S/N=3). The energy transfer between lucigenin and CdSe QDs was investigated. Strong anodic ECL can be obtained in neutral lucigenin solution at a CdSe quantum dots modified glassy carbon electrode in the presence of bromide. Electrochemical results suggested that CdSe quantum dots can catalyze the oxidation of lucigenin and bromide, which can generate the anodic ECL. The fluorescence and the ECL spectra revealed that the ECL-RET can occur between lucigenin and CdSe quantum dots. The oxidation product of bromide can promote the ECL-RET and increase the anodic ECL signal significantly. Cytochrome c exhibited apparent inhibiting effect on the anodic ECL emission, based on which a sensitive ECL sensor for the detection of cytochrome c was established.3 The ECL-RET can also occur between Ru(bpy)3 2+ ECL and gold nanoparticles/graphene oxide nanocomposite. Strong anodic Ru(bpy)3 2+ ECL was observed at a graphene oxide modified glassy carbon electrode (GO/GCE) in the absence of coreactants. The catalytical effect of GO on the oxidation of Ru(bpy)3 2+ suggested that GO itself can act as the coreactant of Ru(bpy)3 2+ ECL. Thiol group terminated adenosine triphosphate (ATP) aptamer was immobilized on the GO film via DNA hybridization. When gold nanoparticles/graphene oxide (AuNPs/GO) nanocomposites were modified on the aptamer through S-Au bond to form sandwich-like structure, the ECL-RET could occur between Ru(bpy)3 2+and AuNPs/GO nanocomposites, resulting in apparent decrease of ECL signal. After the ECL sensor was incubated in ATP solution, the AuNPs/GO nanocomposites were released from the electrode due to the specific interaction between aptamer and ATP, leading to the increased ECL signal. Based on these results, an ECL aptasensor was fabricated and could be used in the sensitive and selective detection of ATP in the range of 0.02-200 pM with a detection limit of 6.7 fM (S/N=3). The above results suggested that the ECL-RET between the traditional luminescent reagents and nanomaterials can be used to fabricate different kinds of biosensors for the detection of protein and DNA, which will sufficiently expand the application of ECL technique in biosensing field.