A novel colorimetric lead ion detection method using lead-2′3-dimercaptosuccinic acid chelates to catalyze etching of gold nanostars

Lead ions are an environmental pollutant and a threat to human health. Traditional methods for detecting lead ions suffer disadvantages such as being time-consuming and expensive, therefore there is a need to develop simpler and faster methods. We developed an optimized spectroscopic method to detect lead ions by first identifying a lead-specific chelator 2,3-dimercaptosuccinic acid (DMSA) which was screened using a novel biological screening system and verified by metal chromophore assays. Synthetic gold nanostars (GNSs) were explored for use as probes and we found that DMSA-Pb chelates catalyzed the etching of GNSs in solution resulting in a color change. We observed a change in the longitudinal local surface plasmon resonance (LSPR) peak of GNSs in the presence of DMSA-Pb which could be measured in subsequent experiments. The optimized etching reaction displayed strong sensitivity and selectivity for Pb²⁺ and achieved a detection limit of 2 nM less than 2 min, which is well below the safety threshold of Pb²⁺ in environmental water and food. The Pb²⁺ contents of rice, beans, milk, grapes, peaches, and cabbage were detected by the DMSA-Pb GNSs method and were consistent with those of inductively coupled plasma mass spectrometry (ICP-MS). Our study provides a novel and practical approach for rapid, safe, and cost-effective detection of lead ions.