Target/aptamer binding-induced inhibition of enzyme activity for amplified electrochemical detection of Sonic Hedgehog protein

Abstract

The high expression of Sonic Hedgehog (SHh) is responsible for the known biological activity of Hedgehog, which closely correlates with cancer metastasis, drug resistance and poor prognosis of hepatocellular carcinoma. In this study, with a new target/aptamer binding-induced inhibition of enzyme activity strategy, we report the construction of an amplified and sensitive electrochemical biosensor for detecting SHh. The analytes bind hairpin aptamer probes to form SHh/aptamer complexes, which inhibit cleavage of aptamers by exonuclease III via the steric hindrance effect not to yield the displacement strands that can displace the biotin-modified signal probes from the sensor electrode. The streptavidin-horseradish peroxidase (STV-HRP) subsequently bind the biotin-probes and are confined on electrode surface through biotin/streptavidin interactions to show highly enhanced catalytic currents with the presence of 3, 3′, 5, 5′-tetramethylbenzidine (TMB)/H2O2 for realizing SHh detection down to 3.34 pM with high selectivity. The interrogation of SHh in diluted serums by this sensor has also been demonstrated. With the verification for SHh assay and the advantages in terms of aptamer recognition, simplicity by electrochemical transduction and sensitivity by catalytic current signal amplification, our strategy can be a convenient aptamer-based approach for detecting different proteins for various biological studies and disease diagnosis purposes.