Fluorescence Detection Of Telomerase Activity Based On The Substitution Reaction Of Spherical Nucleic Acid DNA Strands

Telomere is an important biological structure.It exists at the end of the chromosome,and protects our genetic information in the chromosome.But the defect of DNA copy is resulting in shortened telomeres.End-to-end chromosome fusions and the nuclease will be degraded when the length of telomere is shortening to a limit value.The final result is that cell may die.Thus,unrestrained cancer cell proliferation is only achieved by telomere elongation.But telomere elongation needs a specialized DNA polymerase,telomerase.Therefore,telomerase can avoid the shorten problem of telomere in cell division.Telomerase is present in all kind cells.It is regulated in normal cell.But,telomerase activity is unregulated in many kinds of tumor cells.Herein,telomerase is an important biomarker for cancer detection and therapy.Now,TARP is a traditional method for detection of telomerase activity.But,the drawback of this method is hindering it application.Thus,we design two scheme for detect telomerase activity based on SNA structure.1.We design a SNA probe based AuNP that can detect telomerase activity,and this probe can delivery drug for cancer therapy.This SNA is made up of sgc8c aptamer,a fluorescent DNA complex and a gold core.We use sgc8c as aptamer,which target PTK7 protein in cell membrane.This SNA probe is highly sensitive to detect telomerase activity from HeLa cells extracts equivalent to 38-50000 cells.Meanwhile,SNA probe could be applied for imaging different telomerase activity intracellular.Furthermore,Gluttonous snake SNA probe is a better drug carrier.The probe has the characteristics of good specificity,better stability and good biocompatibility.2.Silver-nanocluster(AgNC),a new type of fluorescent material,has the wide range of applications and the most stable properties.The mechanism of Turn ON that the G-base-rich sequence is proximal or hybrid to AgNC/DNA can significantly increase the fluorescence intensity of AgNC.So,we combine the SNA structure of magnetic bead and this mechanism together to measure telomerase activity.Firstly,we link Telomerase prime DNA on the surface of magnetic bead.After SNA react with telomerase and dNTPs,TSP on surface of SNA will extend telomere repeat sequence.Then,SNA will hybrid with S1 sequence.Hereafter,we use magnetic iron to separate None-hybrid S1 DNA.Afterthat,we use AgNC-DNA to hybrid S1 anchored SNA.Finally,we measure the fluorescence of AgNC.In this paper,we are tested these sequence that own the mechanism about "turn on" fluorescence.Sencondly,we optimized the synthesis ratio,synthesis time and synthesis temperature of AgNC.Lastly,we use this method to detect telomerase activity.