Selection of a DNA Aptamer for the Development of an Electrochemical Aptasensor for the Detection of Pb²⁺

Abstract

In order to develop a simple, highly sensitive and cost-effective electrochemical sensor with high specificity for lead ion (Pb2+), a method of modified magnetic beads-systematic evolution of ligands by exponential enrichment (Capture-SELEX) was employed to isolate the Pb2+-specific aptamers. After 9 rounds of screening, the aptamer (APTP-3) with high binding affinity and excellent specificity for Pb2+ was obtained, exhibiting a dissociation constant (Kd) of 535 ± 59 nM. Subsequently, an electrochemical aptasensor for Pb2+ detection was designed, utilizing a black phosphorus/poly-L-lysine (PLL/BP) nanocomposite film and AuNPs in conjunction with the APTP-3. The aptasensor demonstrated a significant linear relationship between the change in DPV peak current and the logarithm of Pb²⁺ concentration, ranging from 0.01 nM to 1 µM, with a detection limit as low as 8.3 pM and good selectivity in the presence of various interfering metal ions. Furthermore, the electrochemical aptasensor exhibited satisfactory performance for Pb2+ detection in tap water.