Construction And Application Of Electrochemical Sensor Based On Carbon Nanomaterials And DNA Amplification

Electrochemical sensing technology detects target by detecting changes in signals such as current,potential,resistance,and capacitance.Electrochemical sensing technology has a wide range of applications in biomedical,environmental monitoring,food testing,industry.Due to its advantages such as simple instrumentation,good selectivity to target detection materials,fast analysis speed,low detection cost,and easy miniaturization,has broad application prospects in biomedicine,environmental monitoring,food testing,industry and other fields.How to use electrochemical sensing technology for fast and sensitive detection is one of the current hot research topics.In recent years,the use of carbon nanomaterials has provided new ideas for solving these problems.Carbon nanomaterials include:fullerenes,carbon nanotubes,graphene,carbon dots,etc.Carbon nanomaterials not only exist stably,but also have good electrical conductivity,fast electron transport speed,large specific surface area,high reactivity,and biocompatibility,so it has received extensive attention in the field of electrochemistry.A nucleic acid aptamer is an oligonucleotide sequence fragment?DNA or RNA?obtained by screening in vitro by exponential enrichment fitting phylogenetic technology,and can specifically bind to a specific target.Nucleic acid aptamers have the advantages of in vitro synthesis,short cycle,high specificity,high affinity,and good stability.Biomagnification technology is widely used in electroanalytical chemistry due to its stability,sensitivity,biocompatibility and high specificity.Some biomagnification technologies such as enzymatic amplification,target cycle amplification,and DNA amplification techniques are widely used in the construction of electrochemical biosensors.Therefore,based on carbon nanomaterials,nucleic acid aptamers and DNA amplification technologies,this paper has carried out the following work:1.A novel lead???electrochemical sensor using carbon dots as signal amps and thionine?THi?as signal probes was constructed.First,the thiol-modified aptamer is modified to the electrode by the interaction of gold-sulfur bonds,and the carbon dots are further modified to the electrode by?-?stacking interaction,and the electrochemical probe is further modified to the electrode by?-?stacking in lead.When the ions are present,the aptamer specifically binds to the lead ions and transforms from a single chain to a G-quadruplex,causing the carbon dots and thionine to leave the surface of the electrode,and the electrochemical signal is reduced,thereby achieving the purpose of detecting lead ions.The linear range of detection under optimal conditions is:0.01-10 nM,and the detection limit is 3.8 pM.The sensor can be used to add lead in the water sample to recover the recovery rate:95.0%-104.3%.2.The electrochemical detection of human immunodeficiency virus?HIV?gene based on aminated redox graphene?NH₂-rGO?was constructed.After culturing NH₂-rGO on glassy carbon electrode,?-?stacking was used.The capture DNA is modified to the electrode,and Methylene blue?MB?can specifically bind to the G base in the DNA molecule to modify the MB to the electrode.In the presence of the HIV gene,HIV can be combined with the capture DNA base.Complementary pairing to form double-stranded DNA,because NH₂-rGO adsorbs single-stranded DNA stronger than double-stranded DNA,causing double-stranded DNA to detach from the electrode surface,reducing the current signal,achieving the purpose of detection,and detecting linearity under optimal conditions.The range is:0.05-1 pM,and the detection limit is 33 fM.The sensor can achieve the recovery rate of blood sample HIV addition and recovery:96.0%-106.6%.The sensor has the advantages of high selectivity and sensitivity,low detection limit and wide linear range,strong anti-interference ability,and detection of actual samples.3.A ratio-type electrochemical sensor based on triple helix structure was constructed to detect Adenosine triphosphate?ATP?.First,the methylene blue-modified DNA?MB-DNA?was modified to the surface of the gold electrode by a gold-sulfur bond,and the non-specific site of the 6-mercaptohexanol?MCH?blocking electrode was passed through Watson-Crick and Hoogsteen base.The base pairing principle modifies the ferrocene-modified DNA?Fc-DNA?onto the electrode to form a triple helix structure.At this time,the Fc is close to the electrode surface,the current signal is the largest,the MB is far away from the electrode surface,and the current signal is the smallest,and the target detection ATP is added.After that,ATP specifically binds to the surface of the electrode with Fc-DNA,the Fc signal decreases,the triple helix structure cleaves,the MB-DNA re-forms the hairpin structure,and the MB signal increases to form a ratio signal for ATP detection.Detection range:0.05-100 pM,detection limit:5.2 fM.It has high selectivity and sensitivity,low detection limit and wide linear range,strong anti-interference ability,and realizes the detection of actual samples.4.Based on target circular amplification and Rolling circle amplification?RCA?for the detection of K-ras gene.First,the Fc-modified hairpin DNA?Fc-DNA?is modified to the electrode.When K-ras is present,the hairpin architecture is opened.Exonuclease ??Exo ??can cleave the Fc-DNA and the Fc is cleaved off.On the surface of the electrode,the signal is reduced;the K-ras release cycle,the single-stranded DNA of the remaining Fc-DNA after enzymatic cleavage is used as the RCA primer DNA to generate a large amount of G-base-rich DNA.Hemin is capable of binding to the DNA of the G base to form a G-quadruplex/hemin complex as an electrochemical signal output.Within a certain range,the larger the K-ras concentration,the smaller the Fc,and the larger the G-quadruplex/hemin signal,forming a ratio type electrochemical sensor.Detection range:0.5-10000 fM,detection limit:0.286 fM.