Bipolar Electrode-electrochemiluminescence Research Articles

Enhanced bipolar electrode electrochemiluminescence biosensor for ultrasensitive monitoring of alkaline phosphatase activity during osteoblast differentiation by integrating electrocatalytic and enzymatic strategies

Alkaline phosphatase (ALP) is an important biomarker that reflects osteoblast activity and bone growth. Accurately detecting ALP activity is of pivotal clinical significance for the diagnosis and differentiation of bone system diseases. In this work, an enhanced bipolar electrode electrochemiluminescence (BPE-ECL) biosensor based on enzyme catalysis and electrocatalysis was proposed for ultrasensitive detection of ALP in osteoblasts. Carbon nitride nanosheets (CNNS) were utilized as electrocatalysts to facilitate the electrochemical reaction of bipyridine ruthenium (Ru(bpy)32+) and tripropylamine (TPrA) in the reporting cell. Meanwhile, in the sensing cell, the target ALP catalyzed the conversion of p-aminophenyl phosphate monohydrate into p-aminophenol (p-AP). The p-AP was subsequently oxidized at the anode of the driving electrode, producing electrons and increasing the Faradaic current of BPE. The dual-signal amplification strategy, combining electrocatalysis and enzyme catalysis, resulted in a 10-fold enhancement of the ECL intensity of Ru(bpy)32+/TPrA. The BPE-ECL biosensor achieved ultrasensitive detection of ALP with a detection limit as low as 1.9×10−6 U/L, and was successfully applied to monitor ALP activity in osteoblast cells. Additionally, a portable smartphone imaging was developed for the visual detection of ALP. This research introduces an innovative BPE-ECL biosensor for the monitoring of ALP activity and point-of-care testing (POCT) in osteoblasts in clinical settings.

Detection of pathogenic gram-negative bacteria using an antimicrobial peptides-modified bipolar electrode-electrochemiluminescence platform.

Real-time, label-free detection of gram-negative bacteria with high selectivity and sensitivity is demonstrated using a bipolar electrode-electrochemiluminescence (BPE-ECL) platform. This platform utilizes anode luminescence and cathode modification of antimicrobial peptides (AMPs) to effectively capture bacteria. Magainin I, basic AMP from Xenopus skin, boasting an α-helix structure, exhibits a preferential affinity for the surface of gram-negative pathogens. The covalent attachment of the peptide's C-terminal carboxylic acid to the free amines of a previously thiolated linker ensures its secure immobilization onto the surface of theinterdigitated gold-plated cathode of BPE. The AMP-modified BPE sensor, when exposed to varying concentrations of gram-negative bacteria, produces reproducible ECL intensities, allowing for the detection of peptide-bacteria interactions within the range 1 to 104CFUmL-1. Furthermore, this AMP-modified BPE sensor demonstrates a selective capacity to detect Escherichia coli O157:H7 amidst other gram-negative strains, even at a concentration of 1-CFU mL-1. This study underscores the high selectivity of Magainin I in bacterial detection, and the AMP-modified BPE-ECL system holds significant promise for rapid detection of gram-negative bacteria in various applications. The AMP-modified BPE sensor generated reproducible ECL intensity that detected peptide-bacteria interactions in the range 1 to 104CFUmL-1. The AMP-modified BPE sensor also selectively detected E. coli O157:H7 from other gram-negative strains at a concentration of 1-CFU mL-1. In this paper, AMP demonstrated high selectivity in bacterial detection. The AMP-modified BPE-ECL system prepared has a great potential for application in the field of rapid detection of gram-negative bacteria.

Confinement Effect Enhanced Bipolar Electrochemistry: Structural Color Coding Coupled with Wireless Electrochemiluminescence Imaging Technology.

In this work, SiO2/CNTs photonic crystal beads were constructed by doping CNTs into SiO2 photonic crystals, which have an angle-independent responsive structural color and can be used as bipolar electrodes due to their good electrical conductivity. In addition, the bipolar electrode-electrochemiluminescence (BPE-ECL) experiments and finite element simulation prove that the low driving voltage can trigger the bipolar electrode electrochemical reactions by confinement effect. Inspired by this, it is the first to combine the SiO2/CNTs structural color coding scheme with low-drive voltage induced wireless BPE-ECL imaging based on the confinement effect of microchannels to achieve simultaneous immune detection of ovarian cancer biomarkers (CA125, CEA, AFP). The detection limits of successfully constructed high-throughput BPE-ECL biosensor for AFP, CEA, and CA125 are 0.72 ng/mL, 0.95 ng/mL, and 1.03 U/mL, respectively, and have good stability and specificity, which expands the application of electrochemiluminescence and lays a foundation for the development of electrochemiluminescence coding technology.

Visual detection of ochratoxin a based on GPE-PET bipolar electrode-electrochemiluminescence platform

A GPE-PET (graphene-polyethylene terephthalate) bipolar electrode-electrochemiluminescence (BPE-ECL) platform was developed for ochratoxin A (OTA) detection. PET served as the electrode sheet substrate, and GPE was drop-coated onto the surface of PET to form a conductive line. On the functional sensing interface, the thiol (-SH) modified OTA aptamer (OTA-Aptamer) are fixed on the surface of the gold-plated cathode through AuS bonds. The efficient electron transfer ability of methylene blue (MB) made the anode ECL signal strong. Due to competition between OTA and MB with OTA-Aptamer, leading to a decrease in ECL intensity of the [Ru(bpy)3]2+/TPA system on the BPE anode. Under optimized conditions, the GPE-PET BPE-ECL biosensor displayed superior sensitivity for OTA with a detection limit of 2 ng mL−1 and a wide linear concentration range of 5–100 ng mL−1. This method could be further applied to detect various toxins and had broad application prospects.

Rapid screening of electrochemically active bacteria based on a biocathode-functional bipolar electrode-electrochemiluminescence platform.

A functional bipolar electrode-electrochemiluminescence (BPE-ECL) platform based on biocathode reducing oxygen was constructed for detecting electrochemically active bacteria (EAB) in this paper. Firstly, thiolated trimethylated chitosan quaternary ammonium salt (TMC-SH) layer was assembled on the gold-plated cathode of BPE. TMC-SH contains quaternary ammonium salt branch chain, which can inhibit the growth of microorganisms on the surface or in the surrounding environment while absorbing bacteria. Then, the peristaltic pump was used to flow all of the samples through the cathode, and the EAB was electrostatically adsorbed on the electrode surface. Finally, applying a constant potential to the BPE, bacteria can catalyze electrochemical reduction of O2, and decrease the overpotential of O2 reduction at the cathode, which in turn generates an ECL reporting intensity change at the anode. In this way, live and dead bacteria can be distinguished, and the influence of complex food substrates on detection can be greatly reduced.

A bipolar Electrode-Electrochemiluminescence sensor for Salmonella typhimurium detection based on β-cyclodextrin Host-Guest recognition

A bipolar electrode electrochemiluminescence (BPE-ECL) with β-cyclodextrin (β-CD) host–guest recognition was constructed for the rapid detection of Salmonella typhimurium (S. typhimurium). Firstly, the sulfhydryl β-CD (SH-β-CD, with inner diameter size: 6.0–6.5 Å) was assembled on the gold-plated cathode of BPE. Ferrocene (Fc, length: 3.5 Å; width: 4.4 Å) labelled signal probe and parts Fc-aptamer complement each other to form a double-stranded DNA (dsDNA). Due to its large size, the dsDNA with a double Fc (width > 8.8 Å) could not be embedded into the cavities of β-CD. In the presence of S. typhimurium, Fc-aptamer bond specifically to S. typhimurium, and the signal probe was shed from the dsDNA. Then, the signal probe (guest) was captured by the SH-β-CD (host) on the surface of the BPE. Due to the principle of spatial matching between Fc and SH-β-CD, a stable inclusion complex could be formed, which made Fc close to the cathode surface of the BPE. When a certain driving voltage was applied, Fc was oxidized to Fc+. The cathode surface of Fc+ would promote electron transfer, causing the [Ru(bpy)3]2+ at the anode emit light, and effectively convert the electrochemical signal into an ECL signal. 101-105 CFU mL−1S. typhimurium was positively correlated with Fc+ and ECL intensity, with a detection limit of 101 CFU mL−1. Therefore, S. typhimurium can be quantitatively detected by the electron transfer rate of the BPE.

Microfluidic Gradient Culture Arrays for Cell Pro-oxidation Analysis Using Bipolar Electrochemiluminescence.

A microfluidic gradient array is a widely used screening and analysis device, which has characteristics of high efficiency, high automation, and low consumption. Bipolar electrode electrochemiluminescence (BPE-ECL) has special value in microfluidic array chips. The combination of the microfluidic gradient and BPE arrays has potential for high-throughput screening. In this article, a microfluidic BPE array chip for gradient culture and conditional screening of cancer cells was designed. The generation of concentration gradients, continuous culture of cancer cells with high throughput, and drug screening through BPE-ECL of the Ru(bpy)32+/TPrA system can be performed in one chip. We tested gradient pro-oxidation of MCF-7 by ascorbic acid and the synergistic effect of pro-oxidation on doxorubicin. The method achieves high analysis efficiency through a BPE array while simplifying the tedious procedures required by cell culture methods.

One-step grain pretreatment for ochratoxin A detection based on bipolar electrode-electrochemiluminescence biosensor

False positives are common and frequently occurring in detection of ochratoxin A (OTA) due to the complexity of the food matrix. In this paper, a novel bipolar electrode-electrochemiluminescence (BPE-ECL) sensing platform for sensitive OTA detection with one-step grain pretreatment was proposed. The biosensor uses cathode of closed BPE as a functional sensing interface and anode as a signal collection interface. On the functional sensing interface, the horseradish peroxidase (HRP) catalyze the polymerization of aniline to form polyaniline (PANI) on nucleic acid backbone which is supplied by DNA tetrahedron-structured aptamer (DTA) and hybrid chain reaction (HCR). In the presence of OTA, PANI is formed and can cause the change of ECL and luminescence voltage of the anode of BPE. On the signal collection interface, the Ru(bpy)32+/TPA system is used as ECL light output. In this way, the analyte does not need to participate the ECL reaction of the anode, which avoids direct contact of photoactive molecules with complex reaction systems and greatly reduce the influence of complex food matrix on signal acquisition. The accuracy of the BPE-ECL biosensor (one-step grain pretreatment) was similar with high performance liquid chromatography (HPLC) analysis (traditional national standard pretreatment method: GB5009.96–2016). Meanwhile, the BPE-ECL biosensor had higher sensitivity (LOD: 3 pg mL−1). Therefore, closed BPE could simplify sample pretreatment and improve detection capability.

A Portable 3-D Printed Electrochemiluminescence Platform With Pencil Graphite Electrodes for Point-of-Care Multiplexed Analysis With Smartphone-Based Read Out

Herein, a portable 3-D printed miniaturized bipolar electrode-electrochemiluminescence (BPE-ECL) platform is presented. The platform has a smartphone-enabled read-out method for ECL signal analysis, a 9-V Hi-watt battery for power supply, and graphitized mesoporous carbon/multiwalled carbon nanotube (GMC/MWCNT) nanomaterial-modified pencil graphite electrodes (PGEs) as bipolar and driving electrodes. The nanomaterial-modified pencil graphite bipolar electrode (PG-BPE) showed great electrocatalytic activity toward luminol–H2O2 and luminol–O2 ECL reactions in neutral medium. The sensitized luminol–O2 and luminol–H2O2 reactions were successfully applied for sensing of H2O2, O2, and CO2. With optimized parameters, the determination of H2O2, O2 and CO2 can be in the linear range of 0.08– $5000~\mu \text{M}$ , 0.3–9 mg/L, and 0.6–9 mg/L with the detection limit of $0.069~\mu \text{M}$ , 0.15 mg/L, and 0.45 mg/L. As a prototype application, quantitative detection of glucose has been carried out with a modified PGE anchored with GOx (GMC/MWCNT at GOx). The prepared electrode was analyzed for physicochemical and microscopic characterizations. The modified PGE showed an excellent ability to detect the glucose in a linear range of $1~\mu \text{M}$ –10 mM with a detection limit of $0.31~\mu \text{M}$ . Finally, the platform was subjected to real sample analysis of H2O2 in clinical H2O2, cosmetic bleach, O2, and CO2 in lake water and tap water and glucose in human blood serum samples. The results indicated that the proposed platform offered excellent reliability, accuracy, and amenable to be used for multiple point-of-care biochemical analysis.

Combination of area controllable sensing surface and bipolar electrode-electrochemiluminescence approach for the detection of tetracycline

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.BbvCI) in dsDNA is cleft into two segments by Nb.BbvCI. 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.

Bipolar electrode-electrochemiluminescence (ECL) biosensor based on a hybridization chain reaction.

A novel electrochemiluminescence (ECL) closed bipolar electrode (BPE) chip was designed based on a hybridization chain reaction (HCR)-induced ECL amplification strategy for the detection of both DNA and H2O2. Without the utilization of a patterned ITO bipolar electrode (BPE), this chip platform consisted of an ITO glass coated with two layers of PDMS slices. The ITO cathode was modified with Au nanoparticles for further functionalization of biomolecules, which could also amplify the ECL signal at the anode of the BPE. Based on the specific hybridization and hybridization chain reaction (HCR), DNA sequences were greatly extended, leading to a significant increase in the resistance of the cathode. The reduction of H2O2 was inhibited on the cathode of the BPE, resulting in a quenching effect on the ECL intensity on the anode of the BPE. The designed biosensor displayed a satisfactory linear relationship for the detection of both DNA and H2O2. Therefore, the biosensor could not only be employed for DNA assays but also used in enzyme reactions based on the generation of H2O2.

Patchy gold coated Fe3O4 nanospheres with enhanced catalytic activity applied for paper-based bipolar electrode-electrochemiluminescence aptasensors

In this work, novel multifunctional patchy gold coated Fe3O4 hybrid nanoparticles (PG-Fe3O4 NPs) have been successfully synthesized in aqueous medium via a facile adsorption-reduction method. A rational formation mechanism has been proposed by monitoring the morphological evolution. The PG-Fe3O4 NPs retained the good magnetic property and exhibited excellent catalytical effeciency towards the electrochemical reduction of hydrogen peroxide. Chronoamperometric and amperometric experiments indicated a relatively high catalytic rate constant of 3.13 × 105 M−1 s−1, a high sensitivity of 578.87 µA mM−1 cm−2 and a low Michaelis-Menten constant of 462 µM. Meanwhile, the introduction of patchy gold could help biofunctionalization via Au-S bond for different biodetection and biosensing purposes. Here, as an example, thiol-terminated aptamers were immobilized onto the patchy gold part as a signal probe to detect carcinoembryonic antigen (CEA). A related paper-based bipolar electrode-electrochemiluminescence (pBPE-ECL) aptasensor was fabricated as the low-cost, disposable and miniature platform. To improve the sensitivity, Au nanodendrites were electrodeposited at the BPE cathode as the matrix for Apt1 immobilization. This aptasensor showed a wide linear range of 0.1 pg mL−1–15 ng mL−1 with a low detection limit of 0.03 pg mL−1, remaining competitive against other ones, and also demonstrating the PG-Fe3O4 NPs have promising potential for catalysis and bioassays.

A novel paperfluidic closed bipolar electrode-electrochemiluminescence sensing platform: Potential for multiplex detection at crossing-channel closed bipolar electrodes

In this work, we for the first time reported a paperfluidic crossing-channel closed-BPE based electrochemiluminescence (P-3C-BPE-ECL) platform where multiple “band”-shaped C-BPEs are situated perpendicular to two parallel channels, and multiplex detection can be achieved in the reporting channel. The paperfluidic devices are easily fabricated by wax and carbon ink-based screen-printing processes. Under optimized conditions, the P-3C-BPE-ECL is applied to the quantitative analysis of hydrogen peroxide (H2O2) and glucose, with corresponding linear ranges of 0.075–10 mM and 0.08–5 mM, and corresponding detection limits of 0.041 mM and 0.03 mM. To our knowledge, this is the first demonstration of paperfluidic C-BPE-ECL method for glucose determination. Based on its acceptable selectivity, the P-3C-BPE-ECL method is used for measurements of glucose in four complex samples (human serum and urine, wine, and glucose injection) and is compared with the traditional methods. The results indicate a good agreement and prove the reliability and accuracy of the proposed platform. Importantly, the proposed method is demonstrated to have the potential for duplex detection of glucose and uric acid, which intensively matches the requirement of those patients simultaneously suffering from diabetes and gout. Therefore, we believe that the P-3C-BPE-ECL could provide a new platform for wide biochemical applications.

Graphite paper-based bipolar electrode electrochemiluminescence sensing platform

In this work, aiming at the construction of a disposable, wireless, low-cost and sensitive system for bioassay, we report a closed bipolar electrode electrochemiluminescence (BPE-ECL) sensing platform based on graphite paper as BPE for the first time. Graphite paper is qualified as BPE due to its unique properties such as excellent electrical conductivity, uniform composition and ease of use. This simple BPE-ECL device was applied to the quantitative analysis of oxidant (H2O2) and biomarker (CEA) respectively, according to the principle of BPE sensing―charge balance. For the H2O2 analysis, Pt NPs were electrodeposited onto the cathode through a bipolar electrodeposition approach to promote the sensing performance. As a result, this BPE-ECL device exhibited a wide linear range of 0.001–15mM with a low detection limit of 0.5µM (S/N=3) for H2O2 determination. For the determination of CEA, chitosan-multi-walled carbon nanotubes (CS-MWCNTs) were employed to supply a hydrophilic interface for immobilizing primary antibody (Ab1); and Au@Pt nanostructures were conjugated with secondary antibody (Ab2) as catalysts for H2O2 reduction. Under the optimal conditions, the BPE-ECL immunodevice showed a wide linear range of 0.01–60ngmL−1 with a detection limit of 5.0pgmL−1 for CEA. Furthermore, it also displayed satisfactory selectivity, excellent stability and good reproducibility. The developed method opened a new avenue to clinical bioassay.

Paper-based bipolar electrode-electrochemiluminescence (BPE-ECL) device with battery energy supply and smartphone read-out: A handheld ECL system for biochemical analysis at the point-of-care level

In this work, a handheld paper-based bipolar electrode-electrochemiluminescence (P-BPE-ECL) system has been proposed. In this system, a rechargeable battery is used for power supply, while a smartphone is applied for read-out of ECL signal. For the P-BPE-ECL, the carbon ink-based BPE and driving electrodes are screen-printed on the paper, and the wax-screen-printing is employed to fabricate microfluidic channels on electrode-patterned paper. Moreover, the luminol/H2O2-based ECL reaction is applied to demonstrate the quantitative ability of the P-BPE-ECL system. Under optimized conditions, H2O2 can be determined over the range of 5–5000μM, with a detection limit of 1.75μM, and relative standard deviations (RSDs) of 7.59%, 3.82% and 4.93% for 10, 100 and 1000μM H2O2 (n=5). Thus, this system has an acceptable sensitivity, dynamic range, stability and reproducibility. Finally, the applicability of the P-BPE-ECL system is demonstrated for detection of glucose in phosphate buffer solution (PBS) and artificial urine (AU) samples, with the detection limits of 0.017mM and 0.030mM, respectively. Moreover, the P-BPE-ECL system has the ability to perform high-throughput detection of glucose. Therefore, the developed system can provide a new platform for many applications such as point-of-care testing, health diagnosis and environmental monitoring.

Open bipolar electrode-electrochemiluminescence imaging sensing using paper-based microfluidics

A novel paper-based open bipolar electrode-electrochemiluminescence (P-o-BPE-ECL) sensing has been developed for visual detection. Wax-screen-printing was employed to make microfluidic channels on filter paper, and the carbon ink-based BPE and driving electrodes were screen-printed on paper. An inexpensive CCD camera was used as a detector for imaging sensing. In this study, two P-o-BPE-ECL imaging sensing platforms were demonstrated. For the first one, a hydrophilic paper channel was used to host a single “band”-shaped BPE. Under optimal conditions, this P-o-BPE-ECL platform successfully fulfilled the imaging sensing of tri-n-propylamine (TPA) with a linear range from 10 to 1000μM with a detection limit of 8.7μM. In addition, the determination of H2O2 using this platform could be performed in the linear range of 50μM to 5000μM with a detection limit of 46.6μM. For the second platform, an open BPE array configuration has been proposed for P-o-BPE-ECL sensing, where eleven BPEs were stridden across the two legs of the “U”-shaped paper channel. On this prototype, a simple screening application has been performed. These results show that the proposed strategy offers great promise in providing a simple, low-cost, rapid and environment-friendly solution for biochemical applications.