Heper Proble-based Enzyme-free Cyclic Amplification Methods For Detection Of Virus DNA

The significance of HIV virus and HBV DNA virus leads it to be the focus of the current reseach.It Is known for its devastating damage to mankind.DNA is the main substance for storing,reproducing and transmitting genetic information.Detection of viral DNA has a crucial role in determining infection,duration surveillance,and exploring endogenous diseases.Therefore,it is very important to establish fast,effective and simple methods of detect virus and HBV DNA virus.HBV carriers can easily lead to hepatitis or liver cancer and spread very fast.exploitation effective detection methods has been put on the agenda.Fluorescence method is widely utilized in nucleic acid detection for its fast,simple and efficient.Signal amplification technology is a very useful technology that makes detection more sensitive.meanwhile.enzyme-free and label-free method can reduce the experimental cost,which can accelerate the process of experiment.In This article,Helper DNA probes also were used for chain replacement reaction,eliminating the trouble of design a number of molecular beacons.So that the experiment become more simple and effective.1?Designed a hairpin molecular beacon MB and two helper probes.With G-quadruplex selected for the signal display platform.When the target DNA is added,the MB is hybridized to the target HIV DNA.The helper probes then undergo chain-substituted reactions with their hybrid products.Then,the replaced DNA continues to react with other MBs for cyclic amplification.THT dye been selected to incorporate G-quadruplex,we can detect the signal enhancement by fluorescence spectrophotometer three times.In the target concentration range(0.1 nM-50 nM),to obtain a good linear effect.The detection limit of proposed method is 50 pm.2?We Designed hairpin molecular beacon MB.with the 2-aminopurine modified in it.When Combining with the single-stranded DNA,2-aminopurine showed fluorescence.while,Combining with double-stranded,2-aminopurine does not show the characteristics of fluorescence.The hybridization reaction was carried out by adding target and molecular beacon,The fluorescence signal produced by 2-aminopurine was measured by fluorescence spectrophotometer.When the target is replaced with Helper probes,the target continues to react with the molecular beacon MB,resulting in a large amount of products,which have the ability to combine with the 2-aminopurine in its Single chain part.This strategy is 3.4 times of magnitude.No fluorescence quenching is required.The detection limit is 80 pm.3?Two kinds of harpin structure(H1 and H2)were designed.The end of the stem part of H1 can form a G-quadruplex structure,which could Incorporate NMM resulting in fluorescence signal.The combination of the target and the molecular beacon H1 causes the molecular beacon to open and the G-quadruplex structure can not be formed.leading to lower Fluorescence value.H2 is subjected to a chain substitution reaction with hybridization products of target DNA-H1.so that the target HBV DNA undergoes a cyclic amplification reaction.in This strategy Fluorescence intensity is reduced by a factor of four.The detection limit is 65 pm.