DNA-grafted hemin with preferable catalytic properties than G-quadruplex/hemin for fluorescent miRNA biosensing

Nucleic acids-based hemin mimetic enzymes have attracted substantial attention as catalysts in extensive biosensing applications. But the reformative modes and their catalytic properties are still vigorously needed to be explored and characterized in detail. In this work, we proposed a conceptual analogy analysis to clarify the catalytic properties and kinetics of novel DNA-grafted Hemin (DGH) and classical G-quadruplex/hemin (G4/hemin) DNAzyme. Two similar biosensing systems based on target-triggered switch of catalytic activity were further designed to compare their analytical performance as probes and catalysts for enzyme-free fluorescent biosensing. The results revealed that DGH had lower background, higher catalytic rate, better oxidation tolerance and higher efficiency for target-triggered conformational switch than G4/hemin, though G4/hemin displayed greater catalytic capacity. Moreover, when using miRNA-21 as model analyte, the limit of detection (LOD) of DGH system was calculated to be 0.17 nM which was approximately 20 fold than that of G4/hemin, highlighting higher sensitivity and better dose-response ability of DGH for fluorescent biosensing. So, DGH present an excellent alternative artificial enzyme mimetics for enzyme-free signal transduction and would become a potential tool for universal biosensing application.