Avidin–biotin capped mesoporous silica nanoparticles as an ion-responsive release system to determine lead(II)

We have developed DNAzyme-functionalized silica nanoparticles for the rapid, sensitive, and selective detection of lead ion (Pb2+). The specific binding between avidin and biotinylated DNAzymes was used to cap the pore of dye-trapped silica nanoparticles. In the presence of Pb2+, DNAzymes were catalytically cleaved to uncap the pore, releasing the dye cargo with detectable enhancements of fluorescence signal. This method enables rapid (15 min) and sensitive (limit of detection = 8.0 nM) detection. Moreover, the Pb2+-responsive behavior shows high selectivity with other metal ions. The superior properties of the as-designed DNAzyme-functionalized silica nanoparticles can be attributed to the large loading capacity and highly ordered pore structure of mesoporous silica nanoparticles as well as the catalytical cleaving of DNAzymes with Pb2+. The recoveries obtained by standard Pb(II) addition to real samples—tap water, commercial mineral water, and lake water—were all from 98 to 101%. Our design serves as a new prototype for metal–ion sensing systems, and it also has promising potential for detection of various targets in stimulus–release systems.