Breaking the Sensitivity-Sustainability Trade-Off in Heavy Metal Sensing: A DNA Breathing-Actuated Nanoprobe.

Currently established heavy metal sensors based on plasmonic nanoparticles often face an intractable trade-off between high sensitivity and sustainability, a dilemma that impedes their real-world application, particularly in resource-limited settings. Here, we report a dynamic DNA interface strategy that breaks this trade-off in Hg(II) ion detection by leveraging the programmable, thermally responsive DNA breathing on gold nanorods (AuNRs). Hg(II) ion binding to terminal T-T mismatches triggers base pair stacking assembly of the DNA-AuNRs, while mild heating induces controlled DNA unpairing to disassemble the DNA-AuNRs and partially reset the interface. Unlike conventional "one-and-done" designs, our system achieves fully reversible assembly through mild thermal cycling (25-35 °C), enabling multiple detection cycles. Strikingly, the retention of T-HgII-T complexes during thermal resetting progressively lowers the activation threshold for subsequent reassembly and colorimetric responses, which boosts the sensitivity of the probe to 3.3 nM by a factor of ∼6 after two regeneration cycles, much lower than the stringent limits set by international environmental and food safety regulations. The probe further demonstrates excellent selectivity against competing ions and robust performance in complex matrices, including seafood digests. Our strategy establishes a versatile route to break the traditional trade-offs that have long constrained reusable sensor development.