Photoelectrochemical Aptasensor for the Sensitive Detection of Microcystin-LR Based on Graphene Functionalized Vertically-aligned TiO2 Nanotubes

In this work, a visible-light driven photoelectrochemical (PEC) aptasensor with high sensitivity and selectivity for cyanobacterial toxin Microcystin-LR (MC-LR) has been developed. MC-LR aptamers, serving as the specific recognition element, were conveniently immobilized onto vertically-aligned titanium dioxide nanotubes (TiO2 NTs) photoanode substrate with the aid of graphene via - stacking interactions between the graphene hexagonal cells and the nucleobases of the DNA. The functionalization of graphene further endowed the constructed aptasensor visible-light response activity. The aptasensor was used for the label-free analysis of MC-LR by monitoring the increase in photocurrent that resulted from the binding of MC-LR and its aptamers. Results showed that the photocurrent increment had a linear relationship with logarithm of MC-LR concentration in the range from 1.0 to 500fM and the limit of detection reached as low as 0.5fM. Furthermore, the aptasensor exhibited high selectivity while used to detect 100-fold concentration other several potential coexisting interferents. A promising PEC aptasensing platform for highly sensitive and selective monitoring of MC-LR has thus been established.