Wireless Electrochemiluminescence Bipolar Electrode Array for Visualized Genotyping of Single Nucleotide Polymorphism

CRISPR/Cas12a-triggered ordered concatemeric DNA probes signal-on/off multifunctional analytical sensing system for ultrasensitive detection of thalassemia

Based on CRISPR/Cas12a triggered ordered concatemeric DNA probes, a "on/off" self-powered biosensor is developed to achieve highly sensitive detection of thalassemia gene CD142 through open-circuit potential-assisted visual signal output. The ingeniously constructed glucose oxidase (GOD)-functionalized ordered concatemeric DNA probe structure can significantly amplify signal output, while the coupled CRISPR/Cas12a system is served as a "signal switch" with excellent signal-transducing capabilities. When the ordered concatemeric DNA probe structure is anchored on electrode, the response signal of the sensing system is in the "signal on" mode. While, the presence of the target activates the non-specific cleavage activity of the CRISPR/Cas12a system, causing the sensing system to switch to the "signal off" mode. In the detection system, GOD catalyzes the oxidation of glucose to produce hydrogen peroxide, which further catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to form a color product, enabling visual signal of the target through naked-eye color contrast. By employing a multifunctional analytical mode combining electrochemical and visual signal outputs, accurate determination of the target is achieved, with linear ranges of 0.0001-100 pM, and detection limits of 48.1 aM (S/N = 3). This work provides a reference method for sensitive detection of thalassemia genes and holds great diagnostic potential in biomedical applications.

Ti3C2 MXene-based nanozyme as coreaction accelerator for enhancing electrochemiluminescence of glucose biosensing

Delamination of the exfoliated multilayer MXenes with electro-catalysts, not only leads to increasing surface area for high electrochemiluminescent (ECL) signal tracer loading but also provides highly sensitive achievements in a coreaction accelerator manner. To this end, herein, we used bromophenol blue (BPB)-delaminated multilayer Ti3C2 MXene as both a coreaction accelerator to promote the electrochemiluminescent (ECL) reaction rate of luminol (LUM) and the co-reactant H2O2 and a substrate for retaining high loading of glucose oxidase (GOx)-conjugated polyethylene imine (PEI) along with luminophore species into more open structure of Ti3C2 MXene for sensitive detection of glucose. In the presence of glucose, in situ generating H2O2 product through a GOx-catalyzed process could produce abundant •OH radicals via the peroxidase-like activity of the BPB@Ti3C2 in the LUM ECL reaction. Moreover, decreasing the distance between the high-content LUM into the BPB@Ti3C2 and the generated •OH, minimizes the decomposition of highly active •OH, providing a superb ECL signal. Last, the proximity of incorporated GOx into the delaminated Ti3C2 MXene near the electrode allows efficient electron transfer between the electrode and enzyme. The integration of such amplifying effects endowed high sensitivity and excellent selectivity for glucose with a low limit of detection of 0.02 μM in the wide range of 0.01 μM-40,000 μM, enabling the feasibility of the glucose analysis in human serum samples. Overall, the enhanced ECL based on the BPB@Ti3C2 opens a new horizon to develop highly sensitive MXene-based ECL toward the field of biosensors.

Flexible Self-Powered Sensing System Based on Novel DNA Circuit Strategy and Graphdiyne for Thalassemia Gene by Rapid Naked-Eye Tracking and Open-Circuit Voltage

Based on the controllable instantaneous self-assembly ability of long-chain branched DNA nanostructures and the synergistic effect between nucleic acid amplification without enzymes, a highly sensitive and highly specific self-powered biosensing platform is developed. Two-dimensional graphdiyne is prepared, modified on flexible carbon cloth, and then functionalized with gold nanoparticles. When DNA mi-tubes are applied on it, target thalassemia gene CD122 triggers a dual-catalytic hairpin assembly reaction. The generated nanoscale DNA is precisely captured by the DNA mi-tube, exposing binding sites and activating the hybridization chain reaction to form long-chain branched DNA. Double-stranded DNA, along with dendritic DNA carrying a large number of guanine bases, precisely captures the signal molecule methylene blue (MB), generating a significant electrochemical signal. The redox reaction of MB also causes a proportional change in the system's color, achieving a colorimetric detection functionality. An efficient dual-mode self-powered sensing platform, therefore, is established for detecting the thalassemia gene CD122. The linear response range of target concentration to open-circuit voltage and RGB Blue value is 0.0001-10,000 pM. The detection limit under electrochemical mode is 36.3 aM (S/N = 3), and under colorimetric mode, it is as low as 12.1 aM (S/N = 3). The new method exhibits high sensitivity, excellent selectivity, and high accuracy, providing a universal strategy for designing novel biosensing platforms that can be extended to the detection of other biomolecules.

Toward Continuous Molecular Testing Using Gold-Coated Threads as Multi-Target Electrochemical Biosensors

Analytical systems based on isothermal nucleic acid amplification tests (NAATs) paired with electroanalytical detection enable cost-effective, sensitive, and specific digital pathogen detection for various in situ applications such as point-of-care medical diagnostics, food safety monitoring, and environmental surveillance. Self-assembled monolayers (SAMs) on gold surfaces are reliable platforms for electroanalytical DNA biosensors. However, the lack of automation and scalability often limits traditional chip-based systems. To address these challenges, we propose a continuous thread-based device that enables multiple electrochemical readings on a functionalized working electrode Au thread with a single connection point. We demonstrate the possibility of rolling the thread on a spool, which enables easy manipulation in a roll-to-roll architecture for high-throughput applications. As a proof of concept, we have demonstrated the detection of recombinase polymerase amplification (RPA) isothermally amplified DNA from the two toxic microalgae species Ostreopsis cf. ovata and Ostreopsis cf. siamensis by performing a sandwich hybridization assay (SHA) with electrochemical readout.

Nanobiosensing Based on Electro-Optically Modulated Technology

At the nanoscale, metals exhibit special electrochemical and optical properties, which play an important role in nanobiosensing. In particular, surface plasmon resonance (SPR) based on precious metal nanoparticles, as a kind of tag-free biosensor technology, has brought high sensitivity, high reliability, and convenient operation to sensor detection. By applying an electrochemical excitation signal to the nanoplasma device, modulating its surface electron density, and realizing electrochemical coupling SPR, it can effectively complete the joint transmission of electrical and optical signals, increase the resonance shift of the spectrum, and further improve the sensitivity of the designed biosensor. In addition, smartphones are playing an increasingly important role in portable mobile sensor detection systems. These systems typically connect sensing devices to smartphones to perceive different types of information, from optical signals to electrochemical signals, providing ideas for the portability and low-cost design of these sensing systems. Among them, electrochemiluminescence (ECL), as a special electrochemically coupled optical technology, has good application prospects in mobile sensing detection due to its strong anti-interference ability, which is not affected by background light. In this review, the SPR is introduced using nanoparticles, and its response process is analyzed theoretically. Then, the mechanism and sensing application of electrochemistry coupled with SPR and ECL are emphatically introduced. Finally, it extends to the relevant research on electrochemically coupled optical sensing on mobile detection platforms.

Closed Bipolar Electrode Array for Optical Reporting Reaction-Coupled Electrochemical Sensing and Imaging

This review centers on a closed bipolar electrode (BPE) array using an electro-fluorochromism (EFC) or electro-chemiluminescence (ECL) reaction as the reporting reaction. Electrochemical signals at one pole of the closed BPE array can be transduced into the EFC or ECL signals at the opposite pole. Therefore, the current signal of a redox reaction can be easily detected and imaged by monitoring the luminescence signal. Recent developments in closed BPE array-based EFC and ECL sensing and imaging are summarized and discussed in detail. Finally, we consider the challenges and opportunities for improving the spatial resolution of closed BPE array-based electrochemical imaging, and emphasize the important application of this technique to the imaging of cellular activities at the single-cell level.

A one-pot rotational DC-bipolar approach for fabricating artistic metallic carpets

This is a brief report on the fabrication of concentric multi-element metallic carpets through a one-pot rotational bipolar electro-engineering procedure. A suspended piece of nickel foam as a bipolar electrode (BPE) is rotated in an aqueous solution containing a ternary mixture of metal ions when sufficient DC potential is applied to driving electrodes. The customizable tools of this art are potential gradient, rotation, and concentration/kinetic polarizations. Creating the multi-element radial gradient is typically tested in a one-pot artistic jewelry electroplating.

Smartphone-Based Electrochemiluminescence for Visual Simultaneous Detection of RASSF1A and SLC5A8 Tumor Suppressor Gene Methylation in Thyroid Cancer Patient Plasma

Visual one-step simultaneous detection of low-abundance methylation is a crucial challenge in early cancer diagnosis in a simple manner. Through the design of a closed split bipolar electrochemistry system (BE), detection of promoter methylation of tumor suppressor genes in papillary thyroid cancer, RASSF1A and SLC5A8, was achieved using electrochemiluminescence. For this purpose, electrochemiluminescence of luminol loaded into the Fe₃O₄@UiO-66 and gold nanorod-functionalized graphite-like carbon nitride nanosheet (AuNRs@C₃N₄ NS), separately, on the anodic and cathodic pole bipolar electrodes (BPEs) in two different chambers of a bipolar cell were recorded on a smartphone camera. To provide the same electric potential (ΔE_elec) through the BPEs to conduct simultaneous light emission, as well as to achieve higher sensitivity, anodic and cathodic poles BPEs were separately connected to ruthenium nanoparticles electrodeposited on nitrogen-doped graphene-coated Cu foam (fCu/N-GN/RuNPs) to provide a hydrogen evolution reaction (HER) and polycatechol-modified reduced graphene oxide/pencil graphite electrode (PC-rGO/PGE) to provide electrooxidation of hydrazine. Moreover, taking advantages of the strong cathodic ECL activity due to the roles of AuNRs, as well as the high density of capture probes on the UiO-66 and Fe₃O₄ roles in improving the signal-to-background ratio (S/B) in complicated plasma media, a sensitive visual ECL immunosensor was developed to detect two different genes as model target analytes in patient plasma samples. The ability of discrimination of methylation levels as low as 0.01% and above 90% clinical sensitivity in thyroid cancer patient plasma implies that the present strategy is able to diagnose cancer early, as well as monitor responses of patients to therapeutic agents.

Gold Nanowires Array-Based Closed Bipolar Nanoelectrode System for Electrochemiluminescence Detection of α-Fetoprotein on Cell Surface

Inspired by the promising applications of a closed bipolar electrodes (c-BPEs) system in electrochemiluminescence (ECL) detection of cell adhesion and disease-related biomarkers, here, a gold nanowires array-based c-BPEs system was constructed for cell surface protein detection. Regular and uniform gold nanowires array were prepared by intermittent potentiostatic deposition. Then, two poly(dimethylsiloxane) (PDMS) chips with a hole diameter of 2 mm as a reservoir were placed at both sides of Au nanowires array to construct c-BPEs system. Thionine-functionalized silicon dioxide nanoparticles conjugated to antibody (Ab2-Th@SiO₂) were used as the electrochemical probe, while [Ru(bpy)₃]²⁺-wrapped SiO₂ nanoparticles (Ru(II)@SiO₂) were employed as the ECL signal readout. Taking α-fetoprotein (AFP) as model, the gold nanowires array-based c-BPEs system allowed sensitive detection of AFP at a linear range from 0.002 to 50.0 ng/mL and at least 6 living cells ascribing to the synergetic amplification effect at both sensing and reporting chambers. Besides, the amount of AFP expressed by HepG2 cells was calculated to be 6.71 pg/cell. The presented strategy with high sensitivity provided a promising and universal platform for the detection of other cancer cells and disease-related biomarkers (such as proteins, glycan, miRNA).

Electrochemiluminescent biosensor for ultrasensitive detection of lymphoma at the early stage using CD20 markers as B cell-specific antigens

Herein, by taking advantage of the special binding of an aptamer to the membrane surface of a B cell and accumulation of the positive charges of a nanocomposite, including luminol-chitosan-platinum nanoparticles (L-Cs-Pt NPs), on the negatively charge of the aptamer phosphate backbone, a sensitive, simple, selective and rapid strategy for the detection of lymphoma cells by a new label-free electrogenerated chemiluminescence (ECL) aptasensor has been introduced. With increasing concentrations of B lymphoma cells, the nanocomposite detaches from the aptamer, leading to a decrease in the ECL of a luminol and H₂O₂ system. With high loading of luminol and Pt NPs on a chitosan, together with the electrocatalytic effect of Pt NPs, enhanced sensitive detection of cancer cells with a limit of detection of 31 cells/mL was achieved. Step-by-step modification and biosensor response to cancer cells was monitored by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and ECL. The aptasensor exhibited excellent specificity for lymphoma cells vs breast cancer (MCF-7) and human embryonic kidney (HEK293) cell lines as potential interferents. Finally, the performance of the aptasensor in blood samples was assessed against a commercial flow cytometric method. Satisfactory results confirmed the applicability of the proposed biosensing platform.

Electrochemiluminescence Biosensors Using Screen-Printed Electrodes

Electrogenerated chemiluminescence (also called electrochemiluminescence (ECL)) has become a great focus of attention in different fields of analysis, mainly as a consequence of the potential remarkably high sensitivity and wide dynamic range. In the particular case of sensing applications, ECL biosensor unites the benefits of the high selectivity of biological recognition elements and the high sensitivity of ECL analysis methods. Hence, it is a powerful analytical device for sensitive detection of different analytes of interest in medical prognosis and diagnosis, food control and environment. These wide range of applications are increased by the introduction of screen-printed electrodes (SPEs). Disposable SPE-based biosensors cover the need to perform in-situ measurements with portable devices quickly and accurately. In this review, we sum up the latest biosensing applications and current progress on ECL bioanalysis combined with disposable SPEs in the field of bio affinity ECL sensors including immunosensors, DNA analysis and catalytic ECL sensors. Furthermore, the integration of nanomaterials with particular physical and chemical properties in the ECL biosensing systems has improved tremendously their sensitivity and overall performance, being one of the most appropriates research fields for the development of highly sensitive ECL biosensor devices.

A label-free and signal-on electrochemiluminescence strategy for sensitive amyloid-beta assay

Development of a simple, cost-effective and sensitive biosensing strategy is highly desirable to advance the applications in Alzheimer's disease diagnosis. In this paper, we present a simple, label-free and signal-on electrochemiluminescence (ECL) aptasensor for the detection of amyloid-beta (Aβ) peptide using luminol as ECL emitter and in-situ generated reactive oxygen species (ROS) as coreactant via catalytic reaction between Cu²⁺-Aβ and the dissolved O₂ in the presence of ascorbic acid (AA). Aβ₁₆, the binding site of Cu²⁺ in the monomeric full-length Aβ, was used as a model in present study. As a result, this signal-on ECL aptasensor has exhibited favorable analytical performance for Aβ₁₆ monomer with a linear range of 1.0 × 10^-13 mol/L-1.0 × 10^-8 mol/L and a limit of detection of 3.5 × 10^-14 mol/L (S/N=3). Furthermore, the proposed biosensor was also able to detect the full length Aβ₄₀ not only in the phosphate buffer saline (PBS) solution but also in human serum. The presented biosensor represents a promising, simple, turn-on and label-free diagnostic tool for blood analysis.

Electrochemiluminescence Imaging for Bioanalysis

Electrochemiluminescence (ECL) is a widely used analytical technique with the advantages of high sensitivity and low background signal. The recent and rapid development of electrochemical materials, luminophores, and optical elements significantly increases the ECL signals and, thus, ECL imaging with enhanced spatial and temporal resolutions is realized. Currently, ECL imaging is successfully applied to high-throughput bioanalysis and to visualize the distribution of molecules at single cells. Compared with other optical bioassays, no optical excitation is involved in imaging, so the approach avoids a background signal from illumination and increases the detection sensitivity. This review highlights some of the most exciting developments in this field, including the mechanisms, electrode designs, and the applications of ECL imaging in bioanalysis and at single cells and particles.

Visual Electrofluorochromic Detection of Cancer Cell Surface Glycoprotein on a Closed Bipolar Electrode Chip

This work reports an electrofluorochromic strategy on the basis of electric field control of fluorescent signal generation on bipolar electrodes (BPEs) for visualizing cancer cell surface glycoprotein (mucin 1). The device included two separate cells: anodic sensing cell and cathodic reporting cell, which were connected by a screen-printing electrode patterned on poly(ethylene terephthalate) (PET) membrane. In the sensing cell, anti-MUC1 antibody immobilized on a chitosan-multiwalled carbon nanotube (CS-MWCNT)-modified anodic BPE channel was used for capturing mucin-1 (MUC1) or MCF-7 cancer cells. Then ferrocene (Fc)-labeled mucin 1 aptamers were introduced through hybridization. Under an applied voltage, the ferrocene was oxidized and the electroactive molecules of 1,4-benzoquinone (BQ) in the cathodic reporting cell were reduced according to electroneutrality. This produced a strongly basic 1,4-benzoquinone anion radical (BQ^•-), which turned on the fluorescence of pH-responsive fluorescent molecules of (2-(2-(4-hydroxystyryl)-6-methyl-4 H-pyran-4-ylidene)malononitrile) (SPM) coexisting in the cathode reporting cell for both spectrophotometric detection and imaging. This strategy allowed sensitive detection of MUC1 at a concentration down to 10 fM and was capable of detecting a minimum of three MCF-7 cells. Furthermore, the amount of MUC1 on MCF-7 cells was calculated to be 6.02 × 10⁴ molecules/cell. Our strategy also had the advantages of high temporal and spatial resolution, short response time, and high luminous contrast and is of great significance for human health and the promotion of life science development.

Film-Spotting chiral miniPEG-γPNA array for BRCA1 gene mutation detection

Peptide nucleic acids array technology is a method of greatly increasing the throughput of laboratory processes to efficiently perform large-scale genetic tests. Diethylene glycol-containing chiral γPNA (miniPEG-γPNA) is considered to be the best PNA derivative and one of the best candidates for gene detection, because it can hybridize DNA with greater affinity and sequence selectivity than DNA and ordinary aminoethylglycyl PNA (aegPNA). Herein, miniPEG-γPNA probes are synthesized by 9-fluorenylmethyloxycarbonyl (Fmoc) solid phase peptide synthesis (SPPS) in a mild condition, and a new biochip fabrication method "Film-Spotting" is invented, by which γPNA arrays with regular pattern, uniform luminance, and very low fluorescence background are obtained easily and cheaply. The miniPEG-γPNA array can effectively distinguish the full matched and mismatched targets in SSarc buffer, serum and urine, and the detection limit of complementary DNA is less than 5.97 nM. A miniPEG-γPNA array for BRCA1 gene mutation (3099delT) detection is also fabricated with a very good detection performance. This work provides an effective avenue for the diagnosis of breast cancer biomarker and expands the application of miniPEG-γPNA in the field of biochip.

Dynamic Bipolar Electrode Array for Visualized Screening of Electrode Materials in Light-Emitting Electrochemical Cells

Charge injection at a metal/semiconductor interface is of paramount importance for many chemical and physical processes. The dual injection of electrons and holes, for example, is necessary for electroluminescence in organic light-emitting devices. In an electrochemical cell, charge transfer across the electrode interface is responsible for redox reactions and Faradic current flow. In this work, we use polymer light-emitting electrochemical cells (PLECs) to visually assess the ability of metals to inject electronic charges into a luminescent polymer. Silver, aluminum, and gold microdisks are deposited between the two driving electrodes of the PLEC in the form of a horizontal array. When the PLEC is polarized, the individual disks functioned as bipolar electrodes (BPEs) to induce redox p- and n-doping reactions at their extremities, which are visualized as strongly photoluminescence-quenched growth in the luminescent polymer. The three metals initially generate highly distinct doping patterns that are consistent with differences in their work function. Over time, the doped regions continue to grow in size. Quantitative analysis of the n/p area ratio reveals an amazing convergence to a single value for all 39 BPEs, regardless of their metal type and large variation in the size of individual doped areas. We introduce the concept of a dynamic BPE, which transforms from an initial metal disk of a fixed size to one that is a composite of p- and n-doped polymer joined by the initial metallic BPE. The internal structure of the dynamic BPE, as measured by the n/p area ratio, reflects the properties of only the mixed conductor of the PLEC active layer itself when the area ratio converges.

Hydrogel electrodeposition based on bipolar electrochemistry

Bipolar electrochemistry has attracted great interest for applications based on sensing, electrografting, and electrodeposition, because the technique enables electrochemical reactions to be induced at multiple bipolar electrodes (BPEs) with only a single power supply. However, there are only a few reports on the biofabrication of hydrogels using BPEs. In this study, we applied bipolar electrochemistry to achieve the electrodeposition of calcium-alginate hydrogels at specified target areas, which is possible because of the use of water electrolysis to obtain acidification at the anodic pole. This scheme was used to successfully fabricate an array of hydrogel deposits at a BPE array. In addition, hydrogels were successfully fabricated either at only the target BPEs or only the target areas of BPEs by repositioning the driving electrodes. Furthermore, a hydrogel was drawn on a large BPE as a canvas by using small driving electrodes. As a demonstration of the electrodeposited hydrogels for bioapplications, mammal cells were cultured in the hydrogels. Because the amount and shape of the hydrogel deposits can be controlled by using the bipolar system, the system we developed can be used for biosensors and cell culture platforms.

Electrochemiluminescence detection of human breast cancer cells using aptamer modified bipolar electrode mounted into 3D printed microchannel

In the present manuscript, a closed bipolar electrode system integrated with electrochemiluminescence (ECL) detection has been introduced for sensitive diagnosis of human breast cancer cells (MCF-7). For sensitive and selective detection, the anodic pole of the bipolar electrode was modified with the AS1411 aptamer, a specific aptamer for the nucleolin, and treated by the secondary aptamer modified gold nanoparticles. The electrochemiluminescence of luminol was followed in the presence of hydrogen peroxide on the anode pole of bipolar electrode (BPE) as an analytical signal. Moreover, 3D printed microchannels were used for the fabrication of BPE systems to minimize the required amounts of sample. The present aptasensor offers low cost, sensitive and selective cancer cell detection with two acceptable linear ranges. The first linear section appears within 10-100 cells and the latter is found to be within 100-700 cells. The limit of detection was about 10 cells.

Laser-Induced Bipolar Electrochemistry-On-Demand Formation of Bipolar Electrodes in a Solid Polymer Light-Emitting Electrochemical Cell

Bipolar electrochemistry (BPEC) is a versatile and powerful technique that has found applications in sensing, chemical synthesis, catalysis, fuel cells, and batteries, among others. In BPEC, the reactions of interest occur at a wireless, bipolar electrode (BPE). BPEC is most commonly carried out in an electrochemical cell that contains an electrolyte solution, in which a metallic BPE is immersed and polarized when the wired driving electrodes are biased. In this article, we demonstrate BPEC in a solid light-emitting electrochemical cell (LEC) that does not initially contain a BPE. Shining a focused laser beam onto the mixed conductor LEC film causes the illuminated spot to function as a BPE from which redox reactions are induced and visualized. Separate experiments using a photosensitizer (widely used in polymer solar cells) confirm that a BPE is formed on-demand via photoabsorption that causes the illuminated spot to have elevated photoconductivity. The simplicity of laser-induced BPEC offers exciting opportunities to explore sciences and applications of BPEC in the new realm of solid-state organic photonic devices.

Visual electrochemiluminescence biosensing of aflatoxin M1 based on luminol-functionalized, silver nanoparticle-decorated graphene oxide

A sensitive electrochemiluminescence (ECL) aptasensor for aflatoxin M1 (AFM1) detection by a closed bipolar electrode (BPE) array has been introduced. The thiolated AFM1 aptamer was immobilized on gold nanoparticle-coated magnetic Fe₃O₄ nanoparticles (Apt-GMNPs). Luminol-functionalized silver nanoparticle-decorated graphene oxide (GO-L-AgNPs) participates in π-π interactions with the unpaired bases of the immobilized aptamer (Apt-GMNPs-GO-L-AgNPs). After the Apt-GMNPs-GO-L-AgNPs were introduced to a gold anodic BPE array, the individual electrodes were subjected to different concentrations of AFM1. Upon the interaction of AFM1 with the aptamers, the GO-L-AgNPs detach from the aptamer; the resulting ECL of luminol and H₂O₂ at the anodic poles is monitored using a photomultiplier tube (PMT) or smartphone, and the images are analyzed using ImageJ software. This process triggers thionine reduction at the cathodic poles. Under the optimal conditions obtained by a face-centered central composite design (FCCD), the PMT-based detection of the BPE-ECL aptasensor exhibit a linear response over a wide dynamic range from 5 to 150ngmL^-1, with a detection limit of 0.01ngmL^-1. Additionally, smartphone-based detection shows a linear relationship between the ECL image gray value and the logarithmic concentration of the AFM1 target over a range of 10-200ngmL^-1, with a detection limit of 0.05ngmL^-1. Furthermore, the BPE-ECL aptasensor was successfully used to detect AFM1 in milk complex media without any serious interferences with reliable reproducibility (average relative standard deviation (RSD = 2.3%)). This smartphone-based detection opens a new horizon for bioanalysis that does not require a trained technician to operate and is a promising technology for point-of-care testing.

Bipolar Electrode Array Embedded in a Polymer Light-Emitting Electrochemical Cell

A linear array of aluminum discs is deposited between the driving electrodes of an extremely large planar polymer light-emitting electrochemical cell (PLEC). The planar PLEC is then operated at a constant bias voltage of 100 V. This promotes in situ electrochemical doping of the luminescent polymer from both the driving electrodes and the aluminum discs. These aluminum discs function as discrete bipolar electrodes (BPEs) that can drive redox reactions at their extremities. Time-lapse fluorescence imaging reveals that p- and n-doping that originated from neighboring BPEs can interact to form multiple light-emitting p-n junctions in series. This provides direct evidence of the working principle of bulk homojunction PLECs. The propagation of p-doping is faster from the BPEs than from the positive driving electrode due to electric field enhancement at the extremities of BPEs. The effect of field enhancement and the fact that the doping fronts only need to travel the distance between the neighboring BPEs to form a light-emitting junction greatly reduce the response time for electroluminescence in the region containing the BPE array. The near simultaneous formation of multiple light-emitting p-n junctions in series causes a measurable increase in cell current. This indicates that the region containing a BPE is much more conductive than the rest of the planar cell despite the latter's greater width. The p- and n-doping originating from the BPEs is initially highly confined. Significant expansion and divergence of doping occurred when the region containing the BPE array became more conductive. The shape and direction of expanded doping strongly suggest that the multiple light-emitting p-n junctions, formed between and connected by the array of metal BPEs, have functioned as a single rod-shaped BPE. This represents a new type of BPE that is formed in situ and as a combination of metal, doped polymers, and forward-biased p-n junctions connected in series.

Sensitive DNA detection using cascade amplification strategy based on conjugated polyelectrolytes and hybridization chain reaction

A novel cascade amplification strategy that combines the molecular wire effects of CPEs with the signal amplification capability of the HCR has been developed for sensitive DNA detection.

A review of electrogenerated chemiluminescent biosensors for assays in biological matrices

Electrogenerated chemiluminescence (ECL) is the production of light via electron transfer reactions between electrochemically produced reagents. ECL-based biosensors use specific biological interactions to recognize an analyte and produce a luminescent signal. Biosensors fabricated with novel biorecognition species have increased the number of analytes detected. Some of these analytes include peptides, cells, enzymes and nucleic acids. ECL biosensors are selective, simple, sensitive and have low detection limits. Traditional methods use ruthenium complexes or luminol to generate ECL. Nanomaterials can be incorporated into ECL biosensors to improve efficiency, but also represent a new class of ECL emitters. This article reviews the application of ruthenium complex, luminol and nanomaterial-based ECL biosensors to making measurements in biological matrices over the past 4 years.

A bipolar electrochemiluminescence sensing platform based on pencil core and paper reservoirs

A very simple, portable and disposable BPE-ECL sensing platform has been investigated using commercial pencil core and paper cells.