A highly sensitive electrochemical aptasensor for thrombin detection using functionalized mesoporous silica@multiwalled carbon nanotubes as signal tags and DNAzyme signal amplification

Abstract

In this work, we demonstrated a novel sensitive sandwich-type pseudobienzyme aptasensor for thrombin detection. Greatly amplified sensitivity was based on mesoporous silica-multiwalled carbon nanotube (mSiO₂@MWCNT) nanocomposites as enhanced materials and a pseudobienzyme electrocatalytic system. Firstly, the mSiO₂@MWCNT nanocomposites not only have good biocompatibility and a suitable microenvironment for stabilizing the aptamer assembly, but also can load large amounts of electron mediator thionine (Thi), platinum nanoparticles (PtNPs) and hemin/G-quadruplex bioelectrocatalytic complex. Moreover, in the presence of H₂O₂ in an electrolytic cell, the synergistic reaction of PtNPs and hemin/G-quadruplex bioelectrocatalyzed the reduction of H₂O₂, dramatically amplifying the response signals of electron mediator Thi and improving the sensitivity. Secondly, dendrimer functionalized reduced graphene oxide (PAMAM–rGO) as the biosensor platform enhanced the surface area for the immobilization of abundant primary aptamers as well as facilitated electron transfer from Thi to the electrode, thus amplifying the detection response. Using the above multiple effects, the approach showed a high sensitivity and a wider linearity for the detection of thrombin in the range between 0.0001 nM and 80 nM with a detection limit of 50 fM. This new design avoided the fussy labeling process and the spatial distribution of each sequentially acting enzyme, which provided an ideal candidate for the development of a sensitive and simple bioanalytical platform.