Design Of Au/ITO Hybrid BPE-ECL Biosensors

Electrochemiluminescence(ECL) is a chemiluminescent phenomenon catalyzed by electrode. Because of its inherent advantage such as high sensitivity, wide linear range, simple equipment and easy to operate, ECL has been widely used in bioanalysis and environmental monitoring. Bipolar electrode (BPE) is a single conductor placed in solution, whose faradic reaction at its surface was controlled by electric field in solution. Owing to no direct wire connection, ease of miniaturization and some other characteristics, BPE has been broadly applied in material preparation, substance enrichment, design of sensors etc. In this paper, by changing the structure of microfluidic chip and investigating signal amplification strategy, we have designed new BPE-ECL sensors to achieve rapid and sensitive detection of cancer biomarkers such as cell surface protein. The major contents are described as follows:1. Fabrication of Au/ITO hybrid bipolar electrodeFirstly, we made a bipolar electrode device by using raw materials such as ITO glass, sylgard 184 and Cr plate etc. The device is transparent, miniaturized and easy to operate. Secondly, we deposited Au nanopaticles on cathode ITO surface according to the electric neutrality of BPE. Au nanoparticles (NPs) could enhance its conductivity and surface area, decrease the overpotential of O2 reduction, which would correspondingly increase the oxidation current of Ru(bpy)3+/tripropylamine (TPA) on the anode of BPE and resulting nearly a 4-fold enhancement of ECL intensity. The as-prepared Au/ITO BPE could be used for further fabrication of BPE-ECL sensors.2. Sensitive ECL Biosensor Based on Au/ITO Hybrid BPE Amplification System for Cell Surface Protein DetectionHere we developed a novel BPE-ECL biosensor based on as-prepared Au/ITO bipolar electrode (BPE) for the measurement of cancer cell surface protein using ferrocence (Fc) labeled aptamer as signal recognition and amplification probe. A signal amplification strategy was designed by introducing Fc modified aptamer on the anode surface of BPE through hybridization for detecting the amount of mucin-1 on MCF-7 cells. The presence of Fc could not only inhibit the oxidation of Ru(bpy)32+ because of its lower oxidation potential, its oxidation product Fc+ could also quench the ECL of Ru(bpy)32+/TPA by efficient energy-transfer from the excited-state R.u(bpy)32+* to Fc+, making the ECL intensity greatly quenched. On the basis of the cathodic Au NPs induced ECL enhancing coupled with anodic Fc induced signal quenching amplification, the approach allowed detection of mucin-1 aptamer at a concentration down to 0.5 fM and was capable of detecting a minimum of 20 MCF-7 cells. Besides, the amount of mucin-1 on MCF-7 cells was calculated to be 9041 ± 388 molecules/cell. This approach therefore shows great promise in bioanalysis.