In this work, a novel “on-off” electrochemiluminescence (ECL) biosensor was successfully constructed for ultrasensitive detection of concanavalin A (ConA). The “signal-on” state with strong initial ECL signal was obtained by Ag-doped graphitic carbon nitride nanosheet (Ag-g-C3N4), which was modified onto the glassy carbon electrode (GCE) for immobilizing phenoxy dextran (DexP) through π-π interaction. Then, the target ConA was anchored onto the DexP/Ag-g-C3N4 modified film via the specific carbohydrate-ConA interaction. Successively, polyaniline-3,4,9,10-perylenetetracarboxylic acid-DexP conjugate (denoted as PANI-PTCA-DexP), as the ECL signal quenching probe, was incubated onto the electrode through the carbohydrate-ConA interaction to achieve the “signal-off” state. Here, PTCA was used as a matrix for the high loading of PANI and DexP, PANI served as the quencher towards Ag-g-C3N4 system, and DexP as the recognition element for bounding ConA. With the formation of the sandwiched structure of DexP, ConA and PANI-PTCA-DexP, a desirable quenching ECL signal was measured with S2O82− as the co-reactant of Ag-g-C3N4. The quenching effect of PANI towards Ag-g-C3N4 is positively correlated with the concentration of ConA. With such an “on-off” system, the detection of ConA was achieved with a wide linear range from 0.001 ng/mL to 50 ng/mL as well as a low detection limit down to 0.0003 ng/mL.

•A novel signal-on electrochemiluminescence (ECL) biosensor with sandwich type for detecting concanavalin A (Con A) was fabricated.•The signal probe of AgNCs–PAMAM–luminol–GOx was prepared, achieving the solid-state model of luminol and improving the ECL efficiencies of luminol.•Both AgNCs and MoS2 could catalyze H2O2 to generate abundant reactive oxygen species (ROSs), further enhancing the ECL intensity of luminol.•This enhanced ECL biosensor shows a lower detection limit for detecting Con A.A sandwich-configuration electrochemiluminescence (ECL) biosensor was constructed with Ag nanocubes–polyamidoamine dendrimer–luminol–glucose oxidase (AgNCs–PAMAM–luminol–GOx) as the signal probe for detecting concanavalin A (Con A). In brief, three-dimensional molybdenum disulfide–polyaniline (3D-MoS2–PANI) nanoflowers were prepared as the matrix for combining phenoxy functionalized dextran (DexP) via π–π interaction. Here, DexP served as a recognition element for binding Con A. Then, AgNCs–PAMAM–luminol–GOx nanocomposite was bound to the bind site of Con A through specific carbohydrate–Con A interaction, thus achieving a solid-state luminol biosensor. Herein, DexP, Con A and AgNCs–PAMAM–luminol–GOx formed a sandwich-type configuration. AgNCs–PAMAM could immobilize large amounts of luminescence reagent luminol. Importantly, AgNCs and MoS2 could catalyze H2O2 to generate abundant reactive oxygen species (ROSs), further enhancing the ECL intensity. As a result, such a sandwiched ECL biosensor exhibited two wide linear response ranges from 0.005 to 0.1 ng/mL and 0.1 to 20 ng/mL for Con A detection.

A sensitive cathodic luminol-based electrochemiluminescence (ECL) biosensor for detecting cholesterol was fabricated with three-dimensional MoS2–polyaniline (3D-MoS2–PANI) nanoflowers and Ag nanocubes (AgNCs) for signal enhancement. In this study, the synthesized 3D-MoS2–PANI–AgNCs nanocomposites with a large surface area were used as a matrix for loading a high amount of cholesterol oxidase (ChOx). Subsequently, the loaded ChOx efficiently catalyzed the oxidation of cholesterol to produce H2O2 in situ, which could promote the oxidation of luminol to generate a cathodic ECL signal. In addition, 3D-MoS2–PANI–AgNCs nanocomposites accelerate the decomposition of H2O2 into reactive oxygen species (ROSs), which increase the ECL intensity. Due to the integration of the properties of 3D-MoS2–PANI nanoflowers and AgNCs, the proposed cholesterol biosensor exhibits a wide linear response range from 3.3 nM to 0.45 mM with a low detection limit of 1.1 nM.

A novel electrode based on 3,4,9,10-perylenetetracarboxylic acid (PTCA) and overoxidized dopamine polymer (PDAox) was developed for the simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA), xanthine (XN) and hypoxanthine (HXN). The developed sensors exhibited an excellent catalytic activity, high sensitivity and good selectivity toward the oxidation of AA, DA, UA, XN and HXN. Scanning electron microscopy (SEM), cyclic voltammetry (CV), different pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the sensor. The peak separations between AA–DA, DA–UA, UA–XN and XN–HXN were large, up to 0.15, 0.18, 0.37 and 0.4 V, respectively. The calibration curves for AA, DA, UA, XN and HXN were obtained in the ranges of 76 μM to 3.9 mM, 0.60 to 253 μM, 1.8 to 238 μM, 5.1 to 289 μM and 3.8 to 293 μM with detection limits (S/N = 3) of 25.3 μM, 0.20 μM, 0.60 μM, 1.7 μM and 1.3 μM, respectively. The integration of PDAox and PTCA in the sensor opens up a facile and promising method for the simultaneous determination of above five substances.

A sensitive electrochemiluminescence (ECL) biosensor was fabricated for detection of cholesterol based on an anodic ECL of luminol at low potential. First, C60 was functionalized with L-cysteine (L-cys) to obtain an L-cys–C60 composite, which was modified onto the surface of glassy carbon electrodes for adsorbing gold colloidal nanoparticles (AuNPs). Subsequently, cholesterol oxidase (ChOx) was dropped onto the surface of modified electrode to fabricate a cholesterol biosensor. The assembly process was characterized with atomic force microscopy (AFM), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and ECL. Under the optimal conditions, the proposed biosensor exhibited a sensitive response to cholesterol in the concentration range from 1.7 × 10−5 mM to 0.30 mM with the detection limit of 5.7 × 10−6 mM (S/N = 3). Furthermore, the proposed biosensor has good reproducibility, stability and anti-interferent ability.

•Overoxidized polyimidazole/graphene oxide copolymer was used to modify the electrode.•Simultaneous detection of five substances was achieved using an electrochemical sensor.•The sensor demonstrates a good stability, selectivity and high sensitivity.•The proposed method is simple, rapid, and cost-effective.In the present work, a novel strategy based on overoxidized polyimidazole (PImox) and graphene oxide (GO) copolymer modified electrode was proposed for the simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA), guanine (G) and adenine (A). The copolymer was characterized by the scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effects between PImox and GO, the proposed electrode exhibited excellent electrochemical catalytic activities and high selectivity and sensitivity toward the oxidation of AA, DA, UA, G and A. The peak separations between AA and DA, AA and UA, UA and G, and G and A were 140 mV, 200 mV, 380 mV and 300 mV, respectively. The linear response ranges for AA, DA, UA, G and A were 75–2275 μM, 12–278 μM, 3.6–249.6 μM, 3.3–103.3 μM and 9.6–215 μM, respectively, and corresponding detection limits were 18 μM, 0.63 μM, 0.59 μM, 0.48 μM and 1.28 μM.

In this paper, graphene-multiwall carbon nanotube-gold nanocluster (GP-MWCNT-AuNC) composites were synthesized and used as modifier to fabricate a sensor for simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The electrochemical behavior of the sensor was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The combination of GP, MWCNTs, and AuNCs endowed the electrode with a large surface area, good catalytic activity, and high selectivity and sensitivity. The linear response range for simultaneous detection of AA, DA, and UA at the sensor were 120–1,701, 2–213, and 0.7–88.3 μM, correspondingly, and the detection limits were 40, 0.67, and 0.23 μM (S/N = 3), respectively. The proposed method offers a promise for simple, rapid, selective, and cost-effective analysis of small biomolecules.

A sensitive electrochemiluminescence (ECL) biosensor was fabricated for detection of cholesterol based on an anodic ECL of luminol at low potential. First, C60 was functionalized with L-cysteine (L-cys) to obtain an L-cys–C60 composite, which was modified onto the surface of glassy carbon electrodes for adsorbing gold colloidal nanoparticles (AuNPs). Subsequently, cholesterol oxidase (ChOx) was dropped onto the surface of modified electrode to fabricate a cholesterol biosensor. The assembly process was characterized with atomic force microscopy (AFM), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and ECL. Under the optimal conditions, the proposed biosensor exhibited a sensitive response to cholesterol in the concentration range from 1.7 × 10−5 mM to 0.30 mM with the detection limit of 5.7 × 10−6 mM (S/N = 3). Furthermore, the proposed biosensor has good reproducibility, stability and anti-interferent ability.