Polydopamine assembled stable core-shell nanoworms-DNAzyme probe for selective detection of Pb2+ and in living cells imaging

Lead ion (Pb2+) is a major non-degradable environmental pollutant and poses threat to human health. DNAzymes have proved to be a promising tool for the detection of extracellular metal ions. Owing to cellular uptake, enzymatic degradation and reliable signal output, using DNAzymes to quantitative intracellular sensing of Pb2+ still presents challenges. In this study, we report a core-shell nanoworms-DNAzyme nanoprobe combing hairpin-like DNAzyme (H DNAzyme) with polydopamine-coated Au cores plasmonic "nanoworms" (Au@PDA NWs) for imaging of Pb2+ in living cells. PDA with good biocompatibility, high near-infrared (NIR) fluorescence quenching efficiency, and provides a larger surface for further functionalization of biomolecules. H DNAzyme can loaded onto Au@PDA NWs via coordination interaction and π–π stacking, resulting in significant quenching of their fluorescence by PDA shells and Au cores. In the presence of target Pb2+, the H DNAzyme are activated and release Cy5 fluorophore-labeled short strands from Au@PDA NWs. Therefore, an increased fluorescence signal is observed and allows imaging of Pb2+ in living cells. Moreover, the highly selective of H DNAzyme make the proposed method effectively discriminate against other nonspecific molecules. The Au@PDA NWs-H DNAzyme nanoprobe shows good biocompatibility and obviously decreased background fluorescence, which can monitor Pb2+ levels and biodistribution. The developed nanoprobe holds great potential for further extend to bioimaging of other metal ions.