The Application Of Strand Displacement Reaction Triggered By Structure Transformation Of Functional Nucleic Acids In Biosensor

DNA nanotechnology has been well developed in the past decades.This is not only because DNA can be used as a genetic material to regulate the functioning of life,but also because Watson–Crick base pairing makes DNA a powerful and versatile material for engineering in molecular recognition and nanostructures.A number of alternative DNA structures acquire the catalysis and recognition because of the structure exchanging through intramolecular hydrogen bonding,metal coordination and so on.Strand displacement is the process through which two strands with partial or full complementarity hybridize to each other,displacing one or more pre-hybridized strands in the process.Strand displacement can be initiated at complementary single-stranded domains(referred to as toeholds)and progresses through a branch migration process that resembles a random walk.Due to the advantages of high sensitivity,high selectivity and simple operation,the developed methods based on strand displacement reaction have well applied in bioanalysis and sensor applications.Based on the molecular bonding of functional nuceic acids and toehold-mediated strand displacement reaction,we construct an universal strategy with some functional DNA structures(DNA hairpin,i-motif,G-quadruplex)to develop an easy to operate,efficient analytical method with high selectivity that can be applied in ATP and ion detecting.Our research works are as follow:1.We have developed an analytical method combining with the functional DNA structure transformation and remote toehold-mediated strand displacement reaction,which can be a universal strategy to detect the small molecules,ions,proteins or viruses.In this work,we introduce the ATP aptamer into the spacer of the probe.Then,a strand will be displaced with the fluorescence intensity changing when the ATP was presented,which can achieve the detecting purpose.This enzyme-free method we constructed has lots of advantages including low cost,high selectivity and high sensitivity and its limit of detection is 1.84 ?M.In addition,we also introduced the i-motif and G-quadruplex structures into the functional domain of the probes to detect pH and K+ ions to prove the versatility of the method.2.Furthermore,we construct a turn-on fluorescent strategy for the analyte detection based on the aptmers and strand displacement amplification-mediated entropy-driven circuit reaction.This is a universal method which can expand the analytes to metal ions,proteins and even viruses through the introduction of the functional nucleic acids introduction.In this work,the DNA sequence of the aptamer and catalyst are cut into two susequences,respectively.After the recombination,the two new DNA strands can form a new catalyst as the ATP presented which can trigger the entropy-driven circuit reaction.Compared with the previous work,this strategy has higher selectivity and sensitivity.The method can detect the ATP within the concentration of 1-20 ?M,and the limit of detection is 0.28 ?M which decreased the limit of detection by almost one order of magnitude.What's more,we have verified that this method can be used for analysis and detection in complex matrices such as serum by standard addition recovery experiments.