A test strip for lead(II) based on gold nanoparticles multi-functionalized by DNAzyme and barcode DNA

A simple, rapid, sensitive and selective test strip for the detection of lead(II) in water samples was developed. This method is based on gold nanoparticles multi-functionalized by 17E-17DS duplex and barcode DNA, AuNPs@(17E-17DS duplex & barcode DNA). The complex of 17E and 17DS (duplex) was constructed by the hybridization between 17E DNAzyme and its corresponding 17DS cleavage substrate. Because 17E DNAzyme has high specificity for lead(II), the presence of lead(II) induces 17E DNAzyme to specifically cleave 17DS. A barcode DNA complementary to the capture DNA was employed to reduce the amount of 17E-17DS duplex used and increase the capture probability of cleaved AuNPs@(17E-17DS duplex & barcode DNA) conjugates, and thus effectively improve the detection sensitivity. The test results for lead(II) could be visually obtained within 10 min without any instrument and sample pretreatment, with a detection limit 20 nM. In addition, the selectivity of this sensing system was investigated by challenging the sensor with other divalent metal ions, and no significant interference was found. Therefore, the developed test strip could be a potential on-site screening tool for the rapid detection of lead(II).