Dendrimer functionalized reduced graphene oxide as nanocarrier for sensitive pseudobienzyme electrochemical aptasensor

A novel sensitive sandwich-type pseudobienzyme aptasensor was developed by dendrimer functionalized reduced graphene oxide (PAMMA-rGO) as nanocarrier and hemin/G-quadruplex as NADH oxidase and HRP-mimicking DNAzyme. Greatly enhanced sensitivity for the target thrombin was achieved by using a dual signal amplification strategy: first, the PAMMA-rGO not only constructed an effective platform for anchoring larger amounts of electron mediator thionine (TH) and hemin/G-quadruplex bioelectrocatalytic complex with high stability and bioactivity but also accelerated the electron transfer process assisted by the conductive rGO with amplified electrochemical signal output. Second, the hemin/G-quadruplex simultaneously acting as an NADH oxidase and HRP-mimicking DNAzyme for constructing pseudobienzyme amplifying system could in situ biocatalyze formation of H₂O₂ with high local concentrations and low transfer loss that lead to obvious signal enhancements. On the basis of the dual signal amplification strategy of PAMMA-rGO and the pseudobienzyme amplifying, the developed aptasensor could respond to 0.1 pM thrombin with a linear calibration range from 0.0002 to 30.0 nM. Compared with protein enzymes assisted bienzyme aptasensor, this new aptasensor avoided the fussy labeling process and the spatial distribution of each sequentially acting enzyme, which provided ideal candidate for the development of sensitive and simple bioanalytical platform.