Photoinduced electron transfer from polymer-templated Ag nanoclusters to G-quadruplex-hemin complexes for the construction of versatile biosensors and logic gate applications.

Abstract

In this paper, fluorescent Ag nanoclusters (Ag NCs) templated by hyperbranched polyethyleneimine (PEI) are utilized as a versatile probe through the photoinduced electron transfer (PET) between PEI-Ag NCs and G-quadruplex-hemin complexes. In the presence of hemin and target molecule, the specific conjugation with its aptamer induces the conformational change of the DNA sequence, releasing the G-quadruplex sequence part. Once the G-quadruplex-hemin complexes are introduced, electron transfer from the PEI-Ag NCs to G-quadruplex-hemin complexes occurs, resulting in fluorescence quenching. Through changing the sensing DNA sequence, this novel PET system enables the specific detection of target DNA and adenosine triphosphate (ATP) with the wide linear range of 1-200nM and 5-500nM, respectively, and the corresponding limit of detection as low as 0.3nM for target DNA and 1.5nM for ATP. In addition, the proposed method is successfully applied to the determination of ATP in human serum samples with satisfactory recoveries, and a logic gate is fabricated using target molecules and hemin as inputs and the fluorescence signal of PEI-Ag NCs as an output.