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 (Pb(2+)). The specific binding between avidin and biotinylated DNAzymes was used to cap the pore of dye-trapped silica nanoparticles. In the presence of Pb(2+), 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 Pb(2+)-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 Pb(2+). 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.