Symmetric Exponential Amplification Reaction Based DNA Nanomachine For The Fluorescence Detection Of Nucleic Acids

Nucleic acid is an important genetic material,which plays a key role in the storage,transfer and regulation of genetic information.Moreover,detection of nucleic acids is of great significance in a wide range of fields,such as clinical diagnosis,forensic identification,environmental monitoring and various areas of biomedical research.Thus,it is of great interest to develop an efficient nucleic acid detection method.By introducing palindromic sequences into the classical exponential amplification reaction(EXPAR),we constructed a new palindromic fragment-incorporated multifunctional hairpin probe(P-HP)-mediated symmetric exponential amplification reaction(S-EXPAR)to significantly reduce the background signal caused by its inherent nonspecific amplification.And using G-triplex/ThT complexes as signal reporter to propose a label-free DNA nanomachine for nucleic acid detection.The P-HP consists of five functional regions: a C-rich region(C),a target DNA recognition region(T?),two nicking sites(X?)and a palindromic fragment(P).When target DNA(T)hybridizes with P-HP,the palindromic fragment at 3?end of P-HP is fully exposed.Then the P-HP/T duplexes hybridize with each other through the exposed P,and EXPAR occur automatically and continuously on both sides of P under the synergistic effect of polymerase and nicking endonuclease,which is called S-EXPAR assay.In this system,one T convert to a large number of G-triplex fragments that can combine with ThT within a short time.The formed G-triplex/ThT complexes act as the signal reporter in a label-free and environmental-friendly format.In this way,the dynamic response range of this method is 10 pM to 300 nM.In addition,this method can detect other nucleic acids by simply changing the T? region of P-HP.Thus,the proposed DNA nanomachine is a potential alternative method for nucleic acids detection.