Traffic Lights Of Quantum Dots-based Paper Analytical Devices For Visualized Detection Of G-quadruplex DNA

G-quadruplex DNA(G4-DNA)is a nucleic acid sequence rich in guanine which can form a four-stranded helical structure through intramolecular hydrogen bonds.There are many G4-DNA sequences in varying regions of the eukaryotic genome.The presence of abundant G4-DNA at the end of the chromosome is closely related to the regulation of gene expression and the occurrence and development of cancer.Small molecule compounds capable of inducing or stabilizing telomeric G-quadruplex structures have become a hotspot in the study of new anticancer drugs.Therefore,the detection of G4-DNA and its interaction with small molecule compounds have important biological significance.Paper-based analytical devices(PADs)show significant advantages in terms of low cost,wide range of sources,light and portable,easy to save.In recent years,PADs have realized the detection of protein,nucleic acid and metabolites,showing great prospects.Based on the unique characteristics,a variety of nanoparticles can be vised for PADs research.Among them,quantum dots(QDs)have unique optical properties such as high fluorescence quantum yield,size dependent narrow band emission,continuous emission peak emission,good anti-bleaching and bleaching,and can be applied to PADs to construct visual detection platform.In this paper,a novel QDs-based PAD(Q-PADs)is constructed.By competitive reaction,visualized detection of G4-DNA is realized,and the interaction between G4-DNA and small molecule compound is studied.The main contents of the paper are as follows:1.The surface of cellulose paper is modified with PEG-biotin molecule.Green-emitting quantum dots are coated with silica and modified with streptavidin.gQDs@SiO2-strAV is then immobilized onto the surface of cellulose paper by the specific biotin-streptavidin binding.Biotin-labeled probe is further immobilized on the surface of gQDs@SiO2-strAV,constructing the Q-PADs platform.Red-emitting InP/ZnS quantum dots modified with report DNA and PEG are used as fluorescent reporter for our Q-PADs.2.The target DNA competes with the reporter DNA to hybridize with the probe on the surface of the silica nanosphere.When the target DNA is randomly coiled,the red-emitting InP/ZnS quantum dots that modified with reporter DNA can not be bound to the gQDs@SiO2 surface due to the shorter chain length than the target DNA.Q-PADs remain green under UV lamp.In the presence of a stabilizer,the target DNA forms G-quadruplex structure,and is difficult to hybridize with the probe.Therefore,the reporter DNA is preferentially hybridized with the probe.Accordingly,the fluorescence of Q-PADs changes from green to red.By the presence of a G4 stabilizer(ZnPc),we implement visualized recognition of telo,telo-mut,bcl-2 and linear ssDNA using Q-PADs in the way of "traffic light".3.In the absence of ZnPc,telo can preferentially hybridize with the probe and cause change of the amout of InP/ZnS quantum dots on gQDs@SiO2.Based on the competitive reaction,we implement visualized detection of high concentration,medium concentration and low concentration of telo using Q-PADs in the way of "traffic light".The stability of G-quadruplex structure of telo varies with small molecule compounds.Based on the competitive reaction,we use the Q-PADs to screen out the strongly interacting ligands(ZnPc),weakly interacting ligands(hemin)and non-ligand compounds(TSPP)in the way of "traffic light",providing a new way for screening G-quadruplex ligands.