A sensitive electrochemical aptasensor based on palladium nanoparticles decorated graphene–molybdenum disulfide flower-like nanocomposites and enzymatic signal amplification

• PDDA–G–MoS2 nanoflowers were firstly used for the fabrication of thrombin aptasensor.
• MoS2 was adopted to enhance the surface area of graphene and accelerate the electron transfer.
• GOD, PdNPs and hemin/G-quadruplex could amplify the electrochemical signal through synergetic catalysis.
• The proposed aptasensor displayed an improved sensitivity.

In the present study, with the aggregated advantages of graphene and molybdenum disulfide (MoS2), we prepared poly(diallyldimethylammonium chloride)–graphene/molybdenum disulfide (PDDA–G–MoS2) nanocomposites with flower-like structure, large surface area and excellent conductivity. Furthermore, an advanced sandwich-type electrochemical assay for sensitive detection of thrombin (TB) was fabricated using palladium nanoparticles decorated PDDA–G–MoS2 (PdNPs/PDDA–G–MoS2) as nanocarriers, which were functionalized by hemin/G-quadruplex, glucose oxidase (GOD), and toluidine blue (Tb) as redox probes. The signal amplification strategy was achieved as follows: Firstly, the immobilized GOD could effectively catalyze the oxidation of glucose to gluconolactone, coupling with the reduction of the dissolved oxygen to H2O2. Then, both PdNPs and hemin/G-quadruplex acting as hydrogen peroxide (HRP)-mimicking enzyme could further catalyze the reduction of H2O2, resulting in significant electrochemical signal amplification. So the proposed aptasensor showed high sensitivity with a wide dynamic linear range of 0.0001 to 40 nM and a relatively low detection limit of 0.062 pM for TB determination. The strategy showed huge potential of application in protein detection and disease diagnosis.

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