A novel "on-off-on" electrochemiluminescence strategy based on RNA cleavage propelled signal amplification and resonance energy transfer for Pb2+ detection

Abstract

Background: Lead (Pb) is one of the most toxic heavy-metal pollutants. Additionally, lead ions (Pb²⁺) can accumulate in the human body through the food chain, causing irreversible damage through organ damage and system disorders. In the past few years, the detection of Pb²⁺ has mainly relied on instrumental methods such as atomic absorption spectroscopy (AAS) and inductively coupled plasma mass spectrometry (ICP-MS). Nonetheless, these techniques are complicated in terms of equipment and procedures, along with being time-intensive and expensive in terms of detection. These drawbacks have limited their wide application. Hence, there is a pressing need to develop detection techniques for Pb²⁺ that are not only cost-efficient but also highly sensitive and specific.

Results: A novel "on-off-on" electrochemiluminescence (ECL) sensor for detecting Pb²⁺ was developed based on the resonance energy transfer (RET) effect between AuNPs and boron nitride quantum dots (BN QDs) and the recognition of Pb²⁺ by DNAzyme along with the cleavage reaction of the substrate chain. Poly(6-carboxyindole)/stannic sulfide (P6ICA/SnS₂) nanocomposite was employed as a co-reaction accelerator to consequently facilitate the production of intermediate SO₄^•-. This effective enhancement of the reaction led to an improved ECL intensity of BN QDs and enabled the sensor platform to exhibit a higher original ECL response. Benefiting from the combination of the DNAzyme signal amplification strategy with the "on-off-on" design, the ECL sensor showed satisfactory selectivity, good stability, and high sensitivity. This ECL sensor exhibited a linear detection range (LDR) of 10^-12-10^-5 M and a limit of detection (LOD) of 2.6 × 10^-13 M.

Significance: In the present work, an "on-off-on" ECL sensor is constructed based on RET effect for ultrasensitive detection of Pb²⁺. P6ICA/SnS₂ was investigated as the co-reaction accelerator in this sensor. Moreover, this ECL sensor exhibited excellent analytical capability for detecting Pb²⁺ in actual water samples, providing a method for detecting other heavy metal ions as well.

Keywords: Boron nitride quantum dots; Electrochemiluminescence sensor; Pb(2+)-DNAzyme signal amplification; Poly(6-carboxyindole); Resonance energy transfer.