An Improved Turn-On Aptasensor for Thrombin Detection Using Split Aptamer Fragments and Graphene Oxide

An improved turn-on aptasensor for thrombin detection using split aptamer fragments and graphene oxide (GO) was reported. The thrombin-binding aptamer (Apt15) was split into two parts for target recognition, an 8-base sequence labeled with fluorescein (FAM-Apt-A) and a 7-base oligonucleotide sequence (Apt-B). In the absence of target protein, the fluorescence of FAM-Apt-A/Apt-B was quenched by GO through pi-pi stacking between GO and single-stranded DNA. However, when thrombin was introduced into the system, a target-induced G-quadruplex forms with two split aptamer fragments and thrombin. The fluorescence recovered due to weak interaction between G-quadruplex and GO. Compared to the strategy using intact aptamer, probe concentration was lowered, and an improved sensitivity was obtained. Moreover, heating process to avoid unfavorable secondary structure was avoided due to the use of shorter split aptamer fragments.