Dual-signal readout aptasensor for electrochemical and colorimetric assay using a bifunctional Ni-Fe PBA probe

We report a dual-readout, electrochemical (EC) and colorimetric aptasensor for accurate assay of disease biomarkers, based on the Ni-Fe prussian blue analogue (Ni-Fe PBA) as a bifunctional signal probe. Specifically, the redox of plural metal ions in Ni-Fe PBA endows it with excellent redox-activity, providing an obviously welldefined redox current for EC detection. Meanwhile, the peroxidase-like activity of Ni-Fe PBA can catalyze the decomposition of H2O2 and oxidation of chromogenic substrate (TMB), which is beneficial for colorimetric analysis. Based on the excellent redox-activity and peroxidase-like activity of the bifunctional Ni-Fe PBA, we realized dual-readout EC and colorimetric detection of platelet-derived growth factor BB (PDGF-BB). This single probe (Ni-Fe PBA) acting as bifunctional roles depends on two different mechanisms and relatively independent signal transduction, which avoids fussy assembly of diverse probes and decreases the uncontrollable factor in different batches. As a result, an EC-colorimetric dual-readout aptasensor shows two linear responses in the range of 0.0001-5 nM and 0.01-50 nM for PDGF-BB, providing more accurate and reliable results compared with the traditional single-signal readout method. The as-designed dual-readout aptasensor is easy to fabricate, highly accurate and reliable, having promising applications in bioanalysis.