In this work, broad-spectrum aptamers for organophosphorus
pesticides
(OPs) were obtained by alternate target systematic evolution of ligands
by exponential enrichment screening. The secondary and tertiary structure
analyses of the aptamer inferred that the neck-loop structure formed
a G-triplex structure with the target. In addition, optimization of
the sheared aptamer resulted in a stronger affinity (K
d = 86.74 nM), which was increased by 2 orders of magnitude
compared to similar aptamers. A novel electrochemical biosensor was
prepared by modifying an aptamer labeled with an electroactive substance
(methylene blue) on the surface of nanoporous carbon containing Fe–Co
(Fe–Co/NPC). When a target bound to the aptamer, a G-triplex
structure was formed close to the electrode surface. The aptamer phosphate
backbone labeled with methylene blue enhanced the electron-transfer
efficiency and resulted in signal changes. The biosensor exhibited
an excellent sensitivity (7.32 fM) and a wide detection range (1 ×
10–13 to 1 × 10–3 M) for
OPs under optimal conditions, enabling simultaneous detection of multiple
OPs in vegetables.