Label-free competitive time-resolved fluorescent aptasensor for the detection of Pb 2+ using ssDNA-sensitized fluorescence of Tb 3+ ions.

Lead (Pb ²⁺ ) is one of the most toxic heavy metals, and its environmental pollution and serious damages is a global concern. Therefore, it is necessary to develop effective sensing methods. This study describes a new strategy for the design of label-free competitive time-resolved fluorescent (TRF) aptasensor for detecting Pb ²⁺ ions. The sensing principle of this aptasensor is the competition between Pb ²⁺ and Tb ³⁺ ions to bind to the guanine/thymine-rich sequence (lead aptamer) and the sensitized luminescence of Tb ³⁺ by this sequence. The developed TRF aptasensor demonstrated a good linear detection range from 2.5 nM to 150 nM and a limit of detection (LOD) of 645 pM. In addition, the proposed TRF aptasensor has a high selectivity towards Pb ²⁺ , and it has also been successfully utilized to detect this ion in milk and human serum samples. This TRF aptasensor offers advantages such as short analysis time, simple operation, low cost, being label-free, and surpassing the interference of background fluorescence of biological samples due to its TRF characteristic. In this paper, we propose a Tb ³⁺ /guanine/thymine-rich sequence system for designing different aptasensors against diverse targets by applying a proper guanine-rich sequence.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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