An electrochemical aptasensor for lead ion detection based on catalytic hairpin assembly and porous carbon supported platinum as signal amplification

Abstract

An electrochemical aptasensor is fabricated for lead ion (Pb²⁺) detection based on catalytic hairpin assembly as signal amplification. Biomass porous carbon derived from soybean straw (PCs) is used to load platinum nanoparticles (PtNPs), which are introduced as mimetic enzymes to catalyze the hydroquinone–H₂O₂ system. In the presence of Pb²⁺, the complementary DNA (cDNA) releases from aptamer-cDNA and hybridizes with hairpin DNA1 (HP1) on the electrode surface. After bio-hairpin DNA2 (bio-HP2) is added, hybridization between HP1 and bio-HP2 further releases cDNA, which participates in the next cycle and triggers amplification, eventually forming a large number of bio-HP2/HP1 on the electrode surface. Then PtNPs@PCs immobilize on the electrode surface by specific binding of streptavidin with biotin, and catalyze the oxidation of hydroquinone in the presence of H₂O₂. The produced electrochemical signal depends on the concentration of Pb²⁺. The developed biosensor exhibits a wide linear range from 50 pM to 1000 nM with a detection limit of 18 pM, and high selectivity for Pb²⁺ over other environmentally relevant metal ions at concentration ratios of 100. The recoveries of Pb²⁺ in real samples were 93.5–108%. Thus, the proposed biosensor can provide an efficient method for sensitive and selective detection of Pb²⁺ in real samples.