Study On Luminol And Carbon Nitride-Based Electrochemiluminescence Biosensor For Detecting Cholesterol And Concanavalin A

The electrochemiluminescence(ECL) biosensor combines the merits of electrochemical and chemiluminescent techniques. Due to the remarkable properties concluding simplified optical setup, low background signal, versatility and high sensitivity, the ECL biosensor has been applied in various fields, such as clinical diagnostics, biology, chemistry analysis, food, industry and environmental monitoring.With the rapid development of nanotechnology, nanomaterials have been applied in the biosensor field. Moreover, nanomaterials possess lots of charming advantages, such as exceptional physical and chemical properties, good biocompatibility and large surface area. With the integration of virtues of nanomaterials, the biosensor could perform high sensitivity. Combining the advantages of ECL biosensor and nanomaterials, a series of ECL biosensors were constructed for detecting cholesterol and concanavalin A in this study. Three-dimensional MoS2-polyaniline nanoflowers, Ag nanocubes,three-dimensional graphene, gold nanoparticles and Ag nanocubes-polyamidoamine dendrimer nanocomposites were synthesized and applied in these biosensors. The detailed researches are listed as follows.1. A cathodic luminol-based electrochemiluminescence biosensor for detecting cholesterol using 3D-MoS2-PANI nanoflowers and Ag nanocubes for signal enhancementA 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 work, the synthesized 3D-MoS2-PANI-AgNCs nanocomposites with large surface area were used as matrix for high loading of cholesterol oxidase(ChOx). Subsequently,the loaded ChOx efficiently catalyzed cholesterol to in situ produce H2O2, which could promote the oxidation of luminol to generate cathodic ECL signal. In addition,3D-MoS2-PANI-AgNCs nanocomposites hasten the decomposition of H2O2 into reactive oxygen species(ROSs), amplifying the ECL intensity. Due to the integration of the virtues of 3D-MoS2-PANI nanoflowers and AgNCs, the proposed cholesterol biosensor performed a wide linear response range from 3.3 nmol·L-1 to 0.45 mmol·L-1,with a low detection limit of 1.1 nmol·L-1(S/N=3).2. A signal-on electrochemiluminescence biosensor for detecting Con A using phenoxy dextran-graphite-like carbon nitride as signal probeA novel signal-on electrochemiluminescence(ECL) biosensor for detecting concanavalin A(Con A) was fabricated with phenoxy dextran-graphite-like carbon nitride(Dex P-g-C3N4) as signal probe. In this construction strategy, the nanocomposites of three-dimensional graphene and gold nanoparticles(3D-GR-AuNPs) were used as matrix for high loading of glucose oxidase(GOx), which served as recognition element for bounding Con A. Con A further interacted with DexP-g-C3N4 through a specific carbohydrate-Con A interaction to achieve a sandwiched scheme. With the increase of Con A incubated onto the electrode, the ECL signal resulted from DexP-g-C3N4 would enhance, thus achieving a signal-on ECL biosensor for Con A detection. Due to the integration of the virtues of 3D-GR-AuNPs and the excellent ECL performance of Dex P-g-C3N4, the prepared biosensor exhibits a wide linear response range from 0.05ng·mL-1 to 100 ng·mL-1 and a low detection limit of 17 pg·mL-1(S/N=3).3. Sandwich-configuration electrochemiluminescence biosensor based on Ag nanocubes-polyamidoamine dendrimer-luminol nanocomposite for Con A detectionA 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(Dex P) via π-π interaction. Here, Dex P 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-stateluminol biosensor. Herein, Dex P, 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 ng·mL-1 to 0.1 ng·mL-1 and 0.1 ng·mL-1 to 20 ng·mL-1 for Con A detection.