The Research On High Sensitivity Detection For Tumor Markers Specific DsDNA Based On Single-color Fluorescence "off-on" Switch System

Tumor is a very serious disease that harms to human life.The blood free DNA increased in the early stage of tumor development,and there are microsatellite changes,genetic and epigenetic inheritances,tumor suppressor gene mutation in cancer patients'blood free DNA,Free DNA as a novel tumor marker is more and more important because it is relatively easy to obtain,non-invasive,easy to operate and can be used for large-scale screening of the population,etc.Researchers attach great importance to establish and develop the fast and sensitive DNA detection method.In this paper,a method based on monochromatic fluorescence"off-on"switch system was used to detect highly sensitive and specific detectable free dsDNA in blood.Firstly,the CdTe quantum dots?GSH-CdTe QDs?with the emission wavelength of 605 nm was prepared and characterized.CdTe quantum dots are in the form of granules with uniform particle size and good dispersion.The particle size is about 2.63 nm and the fluorescence quantum yield is 41.8%.CdTe quantum dots can be completely quenched when the concentration of[Ru?phen?²?dppz?]²⁺:the concentration of CdTe quantum dots is 100:1.[Ru?phen?²?dppz?]²⁺can specifically bind to the double helix structure of dsDNA when the dsDNA is added to the system,and the fluorescence of the complex is at 605 nm,CdTe quantum dots also emit fluorescence at 605 nm.The two fluorescence intensities were superimposed,and the detection limit of dsDNA was 0.06 ng/ml.In order to detect the specific tumors,the specificity of monochromatic fluorescence"off-on"switch system for detecting dsDNA was investigated.According to the literature designed a short single strand form lung cancer susceptible gene,using NaOH,EDTA,urea as a denaturant to explore a suitable denaturant and the concentration of this denaturant,in order to achieve the situation that the normal human blood dsDNA degeneration into a long single Chain,the short single-stranded chain can be designed to be fully integrated with long single-stranded chains in normal human blood while the two long double strands do not bind to each other.And finally select 9mol/L urea as the denaturant.And using the fluorescence"off-on"switch system to detection urine sample,the experimental results show that the urine sample'DNA content is very low,not suitable for this system.Using the fluorescence"off-on"switch system to detection blood sample.In terms of sensitivity,the positive rate of the test results was 50%compared with the result of the hospital.In the specificity,the positive rate was 30%,which was consistent with the mutation probability of the EGFR gene,And there was no specific mutation in the negative control.