Peroxidase deoxyribozyme-based biosensors for the detection of nucleic acids and proteins

Abstract

Sensors are devices at least comprising of two components: target recognition and signal transduction, which respond to physical or chemical stimuli and produce readout signals. The development of highly sensitive and selective sensors to recognize important analytes has long been a focus of research of many areas, including environment monitoring, industrial quality control, and medical diagnostics. Since a large number of deoxyribozymes (DNAzymes) have been selected in vitro, various biosensors have been developed by utilizing DNAzymes as the signal transduction components owning to their catalytic activity, and many unique advantages over the protein enzymes, such as great flexibility, high stability, cost-effectiveness, easy synthesis, and facile modification. An interesting DNAzyme is horseradish peroxidase-mimicking DNAzyme that is a complex of guanine-rich DNA strand and hemin catalyzing H2O2-mediated oxidation of substrate producing colorimetric or chemiluminescens readout signals. By combining these peroxidase-mimicking DNAzymes with nanoparticles, DNA probes, molecular beacons, and aptamers, we have developed various novel biosensors for the detection of nucleic acids, small molecules, and proteins. In the first strategy, we constructed two types of oligonucleotide-modified nanoparticles, one being a gold nanoparticles (AuNPs) modified with both capture DNAs and peroxidase DNAzymes and the other a magnetic nanoparticles (MNPs) modified with another capture DNA for the ultrasensitive detection of the target DNA. In presence of the target DNA, AuNPs associate with the MNPs by forming sandwich complexes. After magnetic separation, the result complexes were separated from the unreacted nanoparticles, and subsequently the peroxidase DNAzymes on the AuNPs catalyze the oxidation of ABTS generating a green colorimetric signal. This DNAzyme-based colorimetric assay allowed the highly sensitive detection and separation of nucleic acids down to femtomolar leve...