A label-free electrochemical genosensor based on maleimide-functionalised polypyrrole

An electropolymerised polypyrrole (PPy) doped with novel, functional poly(styrene sulfonate)-block-poly(ethylene glycol)-maleimide (PSS-b-maleimide) is developed for label-free electrochemical detection of the sxtA4 gene, a biomarker of saxitoxin-producing microalgae. In PSS-b-maleimide, the sulfonate block serves as a dopant for the growing PPy film, while the pendant maleimide functionality covalently anchors a thiolated oligonucleotide probe, specific to the sxtA4 gene, by thiol-maleimide coupling. The developed sensor provides a wide linear detection range spanning seven decades, from 1 fM to 10 nM, a detection limit of 0.83 fM and clear discrimination against non-complementary and single-base-mismatched targets.