Spatial-resolved electrochemiluminescence ratiometry based on bipolar electrode for bioanalysis.

Herein, a spatial-resolved electrochemiluminescene (ECL) ratiometry based on a closed biopolar electrode (BPE) is reported for the highly sensitive detection of prostate specific antigen (PSA). Au@g-C3N4 NCs as one ECL emitter were firstly coated on the cathode of BPE, while the anode of the BPE served for calibration via another ECL substance, Ru(bpy)3(2+). The electroneutrality across the BPE makes the reactions on each pole of BPE electrically coupled. Thus one electrochemical sensing reaction at one pole of BPE could be quantified at both ends. A composite, Pt-PAMAM-DNAzyme was assembled on the surface of cathode via DNA hybridization between probe DNA and PSA aptamer. It acted as an ECL quencher of g-C3N4 via resonance energy transfer (RET) and catalyzing the reduction of O2, the co-reactant of g-C3N4. Meanwhile, it could promote the ECL of Ru(bpy)3(2+) at anode, since the catalytic reduction of O2 at the cathode increased the faradiac current flowing through the BPE. Based on this signal composite, an ECL "off-on" phenomenon was observed at the cathode, after Pt-PAMAM-DNAzyme was "peeled off" by PSA. Conversely, at the anode, an "on-off" ECL changing was obtained. Therefore, a sensitive ratiometry for PSA detection was achieved with a linear range from 0.10 to 200ng/mL. Since the two ECL emitters were physically separated, the ratiometric system was relatively simple and neither optical filters nor spectrometer were required. The strategy combining the ECL ratiometry and BPE broadens the applications of BPE-ECL and shows good perspective in clinical application.