Colorimetric DNA assay by exploiting the DNA-controlled peroxidase mimicking activity of mesoporous silica loaded with platinum nanoparticles.

A nanozyme composed of mesoporous silica and platinum nanoparticles (MS-PtNPs) was synthesized and is shown to display peroxidase-like activity. Its activity can be controlled by loading with single-stranded DNA. The PtNPs on the MS are homogeneously distributed and act as enzyme mimics. The adsorption of DNA probe on the MS blocks the nucleation sites of PtNPs. This leads to a decrease in the peroxidase-mimicking activity. After introduction of target DNA that is complementary to the DNA probe, the activity of the nanozyme is recovered. By using the 3,3,5,5-tetramethylbenzidine/H2O2 chromogenic system, a rapid method was developed for colorimetric determination of DNA. The assay, best performed at 450 nm, has a linear response in the 5 nM to 100 nM DNA concentration range and a 2.6 nM detection limit. It possesses high selectivity and can distinguish even a single-base mismatch. Graphical abstract The peroxidase-like activity of mesoporous silica and platinum nanoparticles (MS-PtNPs) was depressed when noncovalent ssDNA-MS was in-situ deposited on the PtNPs. After introduction of target DNA, the complementary dsDNA releases from the MS, and then its activity is recovered.