Cyclodextrin functionalized graphene-gold nanoparticle hybrids with strong supramolecular capability for electrochemical thrombin aptasensor.

We demonstrate a facile one-pot synthetic strategy for controlled synthesis of thio-β-cyclodextrin functionalized graphene/gold nanoparticles (SH-β-CD-Gr/AuNPs) composites using SH-β-CD as both the dispersant and linker. The obtained SH-β-CD-Gr/AuNPs integrate the excellent electrical properties and large surface area of graphene and AuNPs with supramolecular recognition ability of CD, which show more effective electron transfer and higher enriched ability for the ferrocene probe via the host-guest interaction between CD and ferrocene than SH-β-CD-Gr. In the presence of target, the stronger interaction between aptamer and target makes the ferrocene move closer to the electrode surface, thus facilitating the electron transfer. Based on this sensing mechanism, a new and highly sensitive biosensing concept by the use of SH-β-CD-Gr/AuNPs as enhancing materials is demonstrated for "signal-on" detection of targets (thrombin as a model target). This biosensor exhibits a wide linear range for thrombin from 1.6×10(-17) M to 8.0×10(-15) M and a very low limit of detection 5.2×10(-18) M, which is two-order magnitude better than those of SH-β-CD-Gr (the detection linear range from 1.6×10(-15) M to 8.0×10(-13) M and detection limit of 1.0×10(-15) M). Our proposed electrochemical aptasensor based on SH-β-CD-Gr/AuNPs shows good selectivity against other proteins such as human serum albumin, lysozyme and insulin. To the best of our knowledge, the present SH-β-CD-Gr/AuNPs hybrids are the most efficient graphene-based electrochemical active probes ever reported for biosensors.