A reusable aptasensor of thrombin based on DNA machine employing resonance light scattering technique

The design of molecular nanodevices attracted great interest in these years. Herein, a reusable, sensitive and specific aptasensor was constructed based on an extension-contraction movement of DNA interconversion for the application of human thrombin detection. The present biosensor was based on resonance light scattering (RLS) using magnetic nanoparticles (MNPs) as the RLS probe. MNPs coated with streptavidin can combine with biotin labeled thrombin aptamers. The combined nanoparticles composite is monodispersed in aqueous medium. When thrombin was added a sandwich structure can form on the surface of MNPs, which induced MNPs aggregation. RLS signal was therefore enhanced, and there is a linear relationship between RLS increment and thrombin concentration in the range of 60pM-6.0nM with a limit of detection at 3.5pM (3.29S_B/m, according to the recent recommendation of IUPAC). The present aptasensor can be repeatedly used for at least 6 cycling times by heat to transfer G-quadruplex conformation to single strand of DNA sequence and release thrombin. MNPs can be captured by applying the external magnetic field. Furthermore, the proposed biosensor was successfully applied to detect thrombin in human plasma.