Scanometric nanomolar lead (II) detection using DNA-functionalized gold nanoparticles and silver stain enhancement

Based on gold label silver stain method, a facile, sensitive and selective scanometric method for the detection of lead (II) was developed. The main components of the method include “8–17” DNAzyme functionalized gold nanoparticles (AuNP1), capture DNA functionalized gold nanoparticles (AuNP2), and silver staining. In presence of lead (II), AuNP1 was cleaved into different pieces that were captured by AuNP2; and became aggregated and formed network structures. These aggregate structures hindered the exposure of gold particles during the silver staining, resulting in a reduced gray values compared with that in the absence of lead (II). Using the gray value of silver stain signals, the developed scanometric assay realized a semi-quantitative detection of nanomolar levels of lead (II), ranging from 2 to 1000 nmol/L (about 0.4–200 ppb), without significant interference from other metal ions. Results suggested that this scanometric method is a simple, sensitive, selective, and portable tool for the onsite detection of nanomolar levels of lead (II).