Smart Composite Reagent Composed of Double-Stranded DNA-Templated Copper Nanoparticle and SYBR Green I for Hydrogen Peroxide Related Biosensing

On the basis of an interesting experimental phenomenon, a novel and smart composite reagent consisting of double-stranded DNA-templated copper nanoparticles (dsDNA–CuNPs) and DNA intercalator (SYBR Green I) was developed and exploited for hydrogen peroxide (H 2 O 2 ) detection as well as oxidase-based biosensing. The study found that, within the composite reagent, the small molecule SYBR Green I was easily adsorbed on the surfaces of CuNPs, instead of intercalating into the dsDNA. So the composite reagent only exhibited the red fluorescence generated from dsDNA–CuNPs. However, when the solution of H 2 O 2 was added into the composite reagent, the CuNPs were deconstructed and their fluorescence was quenched; meanwhile, the inhibition of SYBR Green I binding with dsDNA was eliminated. As a result, the mixed solution of the composite reagent with H 2 O 2 exhibited green fluorescence generated from the intercalation of SYBR Green I into dsDNA. Since H 2 O 2 is an important molecule and involved in various research fields, this developed composite reagent could be employed for many applications in biological analysis. As a proof-of-application demonstration, the sensitive detection of glucose was conducted. Moreover, the method was also extended to the detection of other biomolecules, such as cholesterol and horseradish peroxidase, which indicated the broad applications of the proposed sensing strategy in biomedical analysis.