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Au particles are commonly used for deposition on the surface of a bipolar electrode (BPE) in order to amplify electrochemical and electrochemiluminescence (ECL) signal because of their excellent conductivity, biocompatibility, and large surface area. In this work, a closed BPE device was fabricated and Au particles were deposited on the two poles of a BPE via bipolar deposition. Results indicated that the electrochemical stability of Au film on the anode part of the BPE and the reduction of AuCl4– to Au on the cathode part of the BPE depended on the conductivity of the solution. The prepared Au–Au BPE exhibited a remarkable amplification effect on the ECL signal. Then, a specific sensing interface was constructed on one pole of the BPE for the visual detection of prostate-specific antigens (PSA) based on sandwich-type immunoreactions between primary PSA antibodies (Ab1) on the electrode surface, PSA, and SiO2 nanoparticles labeled secondary PSA antibodies (SiO2-Ab2). The designed biosensor exhibited a good linear relationship for the ECL detection of PSA in the range of 1 × 10−6 to 1 × 10−10 g/mL with a correlation coefficient of 0.9866; the limit of detection (LOD) was 1.5 × 10−11 g/mL. Additionally, the biosensor can realize the electrochemical imaging of PSA by regulating the electrochemical oxidation of the Au anode with the immunoreactions on the cathode part of BPE. Therefore, the small, portable and highly sensitive biosensors have great potential for on-site detection. [ABSTRACT FROM AUTHOR]

• Novel BPE-ECL biosensor based on DNA network was developed for S. aureus assay. • Synergic amplification effect based on target-triggered PCR and pMB NPs was used. • Three-dimensional Au-DNA network allows for the loading of plenty pMB NPs. • The electrochemical reduction of pMB NPs could greatly amplify the ECL intensity. A novel bipolar electrode (BPE)-electrochemiluminescence (ECL) device was constructed for the ultra-sensitive detection of Staphylococcus aureus (S. aureus) by combining polymerase chain reaction (PCR) amplification and DNA network-loaded polymethylene blue nanoparticles (pMB NPs). The presence of target triggered the dissociation of double-stranded DNA on Fe 3 O 4 NPs and the release of T strand, which initiated the PCR. The PCR product contains two protruding single-stranded DNA fragments that serve as bridges to connect Au NPs labeled probes. The PCR-Au products were captured by the probes on cathode of BPE to form three-dimensional DNA networks, which offer multiple adsorption sites for pMB NPs, leading to the remarkable enhancement of ECL intensity. Under optimal circumstances, a wide linear range from 10 to 108 CFU/mL and a low detection limit of 0.78 CFU/mL were achieved. This research opens new horizons for the application of PCR-based biosensors for the accurate and sensitive measurement of pathogenic bacteria. [ABSTRACT FROM AUTHOR]

Abstract: An electrochemiluminescent (ECL)-based lactate (LA) biosensor is developed with luminol as signaling species. LA was oxidized under the catalysis of immobilized lactic dehydrogenase (LDH) and pyruvate oxidase (PYOD) with nicotinamide adenine dinucleotide (NAD) as coenzyme. As a result, the reaction yielded the hydrogen peroxide, which enhanced the electrochemiluminescence of luminol, which was acceptable for sensing the LA concentration. The resulting biosensor showed excellent response for lactate. A detection limit of 8.9×10−12 mol/L was obtained with the relative standard deviation (RSD) of 4.13% (C LA 1.34×10−10 mol/L, n =6) and an average recovery of 101.3% for real sweat sample. The research suggests that the ECL-based biosensor was practicable for detecting the LA in sweat samples of athletes during the exercitation for evaluation of exercise degree. [Copyright &y& Elsevier]

Resistance is of great importance for controlling the current flow through bipolar electrodes (BPEs) and the electrochemiluminescence (ECL) signal at the BPE anode. In this work, we firstly studied the effect of the iR drop between the BPE cathode and anode on the electrochemical performance of a closed BPE device. Due to the significant iR loss between the two poles of the BPE, an increased external voltage, applied on the driving electrodes, was required to trigger the redox reactions at the BPE. Accordingly, the peak voltages (forward and reverse scan) shifted to larger values, whereas the current flow through the BPE was remarkably reduced. Moreover, these factors were closely dependent on the concentration of Fe(CN) 6 3−/Fe(CN) 6 4−, the scan rate, and the resistance wired between glassy carbon electrodes (GCEs). Principally, it was proven that the peak-to-peak separation was enlarged as the scan rate and the concentration of Fe(CN) 6 3−/Fe(CN) 6 4− increased, even when the resistance between the two BPE poles was zero, indicating that the ohmic effect of the electrochemical cell is significant. Excellent linear relationships could be observed between the peak voltages and the resistance, enabling the designation of novel biosensors by connecting sensing units with tunable resistance between the GCEs. The noncontact electrochemical measurement could therefore be promising in biosensing applications. [ABSTRACT FROM AUTHOR]

A novel area controllable biosensing interface is designed on glassy carbon bead (GCB) and used for measurement of tetracycline (TET) in closed bipolar electrode-electrochemiluminescence (ECL) device. One face of GCB is modified with Au particles and the covered area is varied from 0 to 45.3% by tuning the external voltage during bipolar electrodeposition process in a home-made open bipolar electrochemical cell. It enables the conjugation of various amounts of biomolecules on Au/GCB. Then DNA walker and methylene blue (MB) labeled DNA (MB-DNA) are conjugated on Au surface for the following combination of aptamer. In the presence of target, aptamer partially hybridized with DNA walker will be released from Au surface, leading to the formation of dsDNA between DNA walker and MB-DNA. As a result, MB-DNA with recognition site for nicking endonuclease (Nb. Bbv CI) in dsDNA is cleft into two segments by Nb. Bbv CI. Meanwhile, the liberated DNA walker is triggered to continue the degradation of many MB-DNA. Due to the excellent electrochemical performance of MB, it is reduced at the cathode of BPE to amplify the ECL signal at the anode of BPE in a closed BPE-ECL platform. When the covered area of GCB by Au particles is enlarged from 10.1 to 45.3%, the change of ECL intensity could be increased 2.7-fold. The linear range for the detection of tetracycline is from 1 × 10−12 to 1 × 10−5 M with the detection limit of 6.0 × 10−13 M. Hence, controllable sensing area on a single glassy carbon bead, the amplification effect of DNA walker and MB make this approach possess many advantages over traditional biosensor. Image 1 • An area controllable sensing interface was fabricated on glassy carbon bead. • DNA walker and electrochemical species induced enhancement were designed to achieve sensitive detection. • Negatively charged ITO electrode was very sensitive to MB-DNA fragment liberated from single bead. • Without the modification of BPE, the biosensor shows great potential in real sample detection. [ABSTRACT FROM AUTHOR]