Our recent work obtained the X-ray crystallography structures of the Pb2+ binding DNA aptamer sequence, revealing that Pb2+ binds to the DNA strand when folded into a tetraplex structure. We designed a reporter probe of a guanine-rich sequence that can respond to Pb2+ ions in solution. To confirm that the Pb2+ binding previous findings is also valid in solution, we tested the binding of Pb2+ ions to DNA aptamer sequence in solution using circular dichroism (CD). Compared to the CD spectrum of the DNA probe, the addition of Pb2+ ions caused the appearance of a robust positive peak at 312 nm, which is characteristic of Pb2+-stabilized quadruplexes. This result indicated that the DNA aptamer sequence could be used for sensing Pb2+ ions based on a conformational change. (Figure 1) For the readout of this conformational change, we modified the oligonucleotide with a fluorophore (FAM) at the 3'-end and a quencher (Iowa black) at the 5' end (/5IABkFQ/-5-GGTTGGTGTGGTTGGT-3'/6-FAM/). We monitored the fluorescent signal change to check the probe's response to different metal ions and the assay assay showed high selectivity to Pb2+ ions. To demonstrate the potential utility of our assay with real samples, we tested the efficiency of the aptamer probe to detect Pb2+ in various complex fluids such as FBS, human urine, saliva, and the results showed that even in the presence of these complex fluids, our detection worked well which was seen by the increase in signal in the presence of Pb2+ions. In the future, such metal ion responsive sequences can be incorporated into nucleic acid nanostructures for dynamic reconfigurations for biosensing and therapeutic delivery applications.

Fluorescent aptaswitch for detection of lead ions

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ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.