Biosensing Application Research Based On DNA Nanostructures And Graphene

At present,research on life sciences has received more and more attention,and the choice of materials was often involved in scientific researching.Since Turberfield first assembled four DNA strands into a DNA tetrahedral structure,due to its unique properties,the application of DNA tetrahedrons in life sciences has become more and more popular among researchers.In addition,DNA tetrahedras also have the advantages of easy synthesis and high yield.Graphene oxide(GO)has excellent optical,electrical,mechanical and chemical properties and was easy to synthesize,so it was widely used in DNA-based sensors.This paper mainly used the special functions of DNA nanostructure and GO to developed several biosensors based on fluorescence for detecting lead ions,thrombin(K+),adenosine triphosphate(ATP)and single nucleotide polymorphism(SNP),etc.,The main research contents are as follows:(1)FRET fluorescence fingerprint analysed biomolecules and ions based on DNA tetrahedra self-assembled.Synthesized a DNA tetrahedron,then,several fluorescent molecules were modified on the vertices or edges of the tetrahedron.When the target biomolecules(or ions)were added to the solution,the corresponding nucleic acid aptamer recognized the target molecules(or ions),changed the structure of the nucleic acid aptamer or the shape of the tetrahedron,thereby caused a FRET effect between adjacent two fluorescent molecules.The ratio of the emission peak IExcitation peak of the second fluorescent molecule/(Excitation peak of the first fluorescent molecule is calculated to analyze the concentration of the target molecule(or ion).The synthesized tetrahedron was separated by high performance liquid chromatography(HPLC)with high yield and high purity.The linear correlation coefficient was 0.98 when ATP was analyzed,and the lowest detection value was 0.1?M.The linear correlation coefficient was 0.99 when DNA was analyzed,and the lowest detection value was 0.1 ?M.The linear correlation coefficient was 0.98 when K+was analyzed,and the lowest detection value was 1 mM.The sensor has high sensitivity and immunity to interference.(2)A highly sensitive sensor for Lead ion based on thioflavin T-induced G-quadruplex formation was developed.First,we detected that the fluorescence value of ThT in the buffer was very low.Then,when we added the G-rich DNA sequence,the DNA sequence specifically bound to the lead ion,and we detected a significant increase in fluorescence.Finally,in the presence of lead ions,the DNA sequence specifically bound to lead ions and detached from ThT,resulting in a decrease in fluorescence value,thereby detected lead ions.The linear range of the fluorescence signal of the biosensor for lead ion concentration ranges from 20 nM to 1000 nM,the detection limit is 1 nM.The proposed biosensor was highly selective and specific for rapid detection of lead ions by the "on/off" mode.(3)The graphene-based fluorescent intercalating dye SYBR Green I was used to detect single nucleotide polymorphisms.SG could specifically insert double-stranded DNA(dsDNA),and fluorescence could be detected at 525 nm by excitation at 497 nm.However the binding ability of SG to single-stranded DNA(ssDNA)was much weaker,so ssDNA has a lower fluorescence value at 525 nm than dsDNA.GO has been shown to quench fluorescence by energy transfer,so we used GO-specific adsorption of ssDNA to quench the fluorescence,so that the fluorescence value decreased rapidly,while the fluorescence value of the fully complementary oligonucleotide group was still high,the signal to noise ratio was high.The detection method requires no labeling,low cost,simple operation,high sensitivity,high SNP discrimination,and SNP discrimination at room temperature.