Study On Fluorescent Biosensor Based On G-Quadruplex Conformation Transition

DNA aptamer are a kind of new development in recent years that have high afiinity a nd can some specifity target, some of team using DNA aptamer to identify target material obtained the extensive and in-depth research. Compared with traditional biological sensors b ased on antibody, DNA aptamer can combine to target with high specificity and high selecti vity, it not only synthetic quick and convenient,but also by changing the sequence of aptam er to design different detection scheme, combining with fluorescent and electrochemicalmeth ods to recognition the target of high detection sensitivity, there are a series of biological se nsors in the chemical,biological, environmental detection based on the development,and it pl aysan important role. G-quardruplex is a kind of special single-strand DNA by rich G folde d topology structure, four G hydrogen can bond to form a layer by Hoogsteen, then 2 or 3piece can form a three-dimensional structure, this structure is closely related to the express ion of oncogenes, so the study of G-quardruplex structure is very great significance.This topic research the rich G of adtamer sequence under the G–quadruplex structure tr ansition, the change of DNA structure listed the change of the optical properties, and resulti ng in the change of fluorescent signal.Finally, we implements the high sensitivity detection t o thrombin and Pb²⁺.Molecular brushes is a ong side chain polymer,compared with other linear conjugated p olymer,molecular brushes contain long side chain and high charge density, it have a stronge r electrostatic action with ss-DNA,it also have a stronger FRET with DNA. Once added thr ombin, the aptamer forms a PFNI/G-quardruplex-thrombin complex, G-quardruplex have a la rge space size, and PFNI contain long side chain,it can prevent electrostatic attraction, FRE T decresased due to the diance change between PFNI and G-quardruplex.Compared with oth er conjugate polymer,the molecular brushes can improved the detection limit greatly. The de tection limit reached 0.1 nM.G-quardruplex have many different kinds of structure,for example,parallel quadruplexes,a ntiparallel quadruplex and hybrid quadruplex. Different structures have the different cavity si ze, so some small molecular fluorescent dye binding force is different also, so it can bring some enlightenment to design some biological sensors for us. In this article, we implement sthe unmarked high sensitive detection of thrombin based on the structure transition of the G-quadruplex/ThT.Finally, by comparing the different ion effects on G-quardruplex/ThT, we found Pb²⁺ ca n combine to G–qurdruplex/ ThT and fluorescence intensity is greatly reduced, but the othe r ions is much smaller, and also not cause interference of Hg2+, the result show the linear relationship in 0-100 nM range.