High Sensitivity DNA Biosensor Based On Fluorescence Signal Amplification

When biologically analytes are present in trace amounts,the detection method is particularly required to have ultra-high sensitivity characteristics,which can avoid time-consuming and expensive concentration steps.When detecting the interaction between the sensor and the target,high sensitivity is required to provide the recorded fluorescence,the necessary dynamic range for parameter changes.Fluorescent biosensors can achieve ultra-high sensitivity required for detection by amplifying the target DNA or detecting the signal generated by the target molecule.Therefore,the construction of new highly sensitive biosensors in the detection of biomedical compounds,food quality control,detection environment and screening of drug compounds is expected to revolutionize healthcare,especially in the field of molecular diagnosis.This paper includes three experimental contents:In the first part,double-cycle fluorescence signal amplification was realized by nucleic acid Exonuclease III（Exo III）.A new fluorescence detection platform with go as a quenching agent and labeled DNA as a recognition element was used to determine insulin concentration.The detection range is 0.048-2.15 U/ml,and multiple amplification of target fluorescence signal is achieved,providing a feasible method for biological insulin detection.In the second part,double fluorescence signal amplification was realized by Exonuclease III（Exo III）and Rolling Circle Amplification reaction（RCA）,and a new fluorescence detection platform was constructed by using a labeled detection probe to determine the concentration of micro RNA.The detection limit can be as low as 4.1 pmol L^-1.This platform provides a highly sensitive and selective feasible method for the measurement of micro RNA in biological detection,and is expected to become a general platform for the analysis of micro RNA.In the third part,the target induced Rolling Circle Amplification reaction（RCA）was used to obtain DNA fragments containing specific sequences,which were complementary with self-cutting DNAzyme bases and could emit fluorescence under the action of Mg²⁺.According to the fluctuation of fluorescence,a fluorescent DNA sensor for micro RNA detection is constructed.This detection platform has a fast response and the detection limit can be as low as 0.49 pmol L^-1.The biosensors constructed in the above three experiments all realize multiple fluorescence signal amplification,which is simple to operate,can detect targets quickly and sensitively,and has the prospect of detecting small molecules in the experiment of living cells.It provides a new idea in the field of biomolecule detection,and realizes high sensitivity detection,which has potential advantages in the feasibility,disease prevention,treatment and drug discovery of trace analytes.