Aptasensor for lead(II) based on the use of a quartz crystal microbalance modified with gold nanoparticles

The authors describe a quartz crystal microbalance based aptasensor for the determination of Pb 2+ . In order to enhance its response, oligonucleotide-embellished gold nanoparticles (AuNPs) were used to amplify the frequency changes. The method is based on the use of specific aptamers immobilized on the surface of the quartz crystal microbalance (QCM) and the binding of Pb 2+ , which prevents the self-assembly of the AuNPs on the QCM. Trace concentrations of Pb 2+ can be determined by monitoring the change in the response frequency of the QCM. The method has a 4 nmol∙L −1 detection limit and works in the 5 to 200 nmol∙L −1 Pb 2+ concentration range. This aptasensor also shows adequate selectivity for Pb 2+ over potentially interfering metal ions. Schematic of the assay. The specific aptamer SAP does not readily combine with its partial complementary strand CSAP in the presence of Pb(II) ion. Thus, the mass change on the crystal is inversely proportional to the concentration of Pb(II).