Aptamer-based and highly sensitive electrochemical label-free gliotoxin biosensor via a dual recycling signal...

Gliotoxin (GT), a mycotoxin produced by Aspergillus fumigatus, exerts immunosuppressive and pro-apoptotic effects on mammalian cells, posing severe health threat upon human. Ultrasensitively and selectively detecting GT is therefore of great significance. In this work, on the basis of a new GT-specific aptamer, we describe construction of electrochemical label-free biosensor for GT with high sensitivity via exonuclease III (Exo III)-aided dual recycling signal amplification strategy. Target GT analyte combines with the aptamer recognition probe in the aptamer/ssDNA duplex to liberate the ssDNA, which hybridizes with the assistant hairpin to trigger the dual recycling cleavage of the G-quadruplex strand-containing signal hairpin on the electrode with the presence of Exo III. As a result, a substantial number of free G-quadruplex strands are generated. Consequently, aided by K⁺ ions, these G-quadruplexes bind and confine many hemin molecules on the electrode, which are subjected by electro-reduction for the generation of highly amplified current for label-free GT assay with 3.14 pM detection limit. In addition, such aptamer biosensor is also demonstrated with high selectivity and amenable for detecting GT in diluted human serums, highlighting its promising potentials for the convenient diagnosis of GT-associated diseases.