Chemiluminescent and Chemiluminescence Resonance Energy Transfer (CRET) Detection of DNA, Metal Ions, and Aptamer–Substrate Complexes Using Hemin/G-Quadruplexes and CdSe/ZnS Quantum Dots

Abstract

Nucleic acid subunits consisting of fragments of the horseradish peroxidase (HRP)-mimicking DNAzyme and aptamer domains against ATP or sequences recognizing Hg²⁺ ions self-assemble, in the presence of ATP or Hg²⁺, into the active hemin–G-quadruplex DNAzyme structure. The DNAzyme-generated chemiluminescence provides the optical readout for the sensing events. In addition, the DNAzyme-stimulated chemiluminescence resonance energy transfer (CRET) to CdSe/ZnS quantum dots (QDs) is implemented to develop aptamer or DNA sensing platforms. The self-assembly of the ATP-aptamer subunits/hemin-G-quadruplex DNAzyme, where one of the aptamer subunits is functionalized with CdSe/ZnS QDs, leads to the CRET signal. Also, the functionalization of QDs with a hairpin nucleic acid that includes the G-quadruplex sequence in a ‘‘caged’’ configuration is used to analyze DNA. The opening of the hairpin structure by the target DNA assembles the hemin–G-quadruplex DNAzyme that stimulates the CRET signal. By the application of three different sized QDs functionalized with different hairpins, the multiplexed analysis of three different DNA targets is demonstrated by the generation of three different CRET luminescence signals.