Construction Of Fluorescent Biosensor Based On DNA Nano Walkers Signal Amplification Strategy

High sensitivity detection of tumor cells is an important topic in the early diagnosis and treatment of cancer.The DNA nanowalker is based on the basic structure of the DNA chain and drives the chain molecules to migrate along a specific track to achieve signal amplification.Based on DNA,quantum dots（QDs）and polystyrene microspheres,an entropy-driven DNA nano-3D walking fluorescence sensor with a bipedal fuel hairpin structure is constructed in this paper,which improves the efficiency of signal amplification and should be used for tumor cell detection.（1）Water soluble DNA functionalized quantum dots（DNA-QDs）had been synthesized by one-pot method,and had self-assembled with DNA and aptamer DNA as a tracing tetrahedral capture probe;The structure and characteristics of the prepared DNA tetrahedron had been characterized by electrophoresis,atomic force microscope and transmission electron microscope,and then the phagocytosis of the tetrahedral DNA-aptamer and single-stranded aptamer and He La cells had been used to characterize the superiority and functionality of its structure;The 3D orbit of the DNA walker had been constructed by combining the DNA-QDs modified with amino group and the carboxyl-modified polystyrene microspheres;By base complementary pairing,the DNA chain of the modified fluorescence quenching group BHQ2 was combined with the orbital chain of the modified quantum dots,thus causing fluorescence quenching of the quantum dots.By discussing the effect of monopodia or biped fuel chain in the entropy-driven cycle amplification process and the influence of reaction conditions on the construction of the entropy-driven DNA nano-3D walking fluorescence sensor,the optimal preparation conditions of the walker were determined.（2）By adding different concentrations of He La cells to the prepared amplification system,the He La cells have a recovery effect on the fluorescence of the entire entropy-driven DNA nano-3D walking fluorescence sensor,and the recovery of fluorescence intensity has a linear relationship with the cell concentration.In the linear concentration interval of 10²-10⁶ cell·m L^-1,the equation of linear regression is:ΔF=-0.2229+0.5547lg C（C is the concentration of He La cells）,the linear correlation coefficient is 0.997,and the theoretical limit of detection is 7 cells·m L^-1（S/N=3）.The prepared entropy-driven DNA nano-3D walking fluorescence sensor has high selectivity,specificity and stability.The entropy-driven DNA nano-3D walking fluorescence sensor designed in this research provides a new direction for the early diagnosis and treatment of tumor cells in high clinical cancer.