The Application Of Graphene-based Electrochemical Aptamer Sensors In The Detection Of Cancer Markers

With the progress and development of nanotechnology,the application of nanomaterials has reached a new level.On account of the unique physical and chemical properties and the excellent function of nanomaterials,they have been widely used in many fields.Graphene(GN)and graphene oxide(GO)as the new emerging carbon nanomaterials,based on its high mechanical strength,large surface area,good electrical and thermal conductivity,high thermal stability,high transmittance,good biocompatibility and other excellent properties,they have shown a good development trend and application potential in a large number of research fields such as energy,photoelectricity,catalysis,sensor,machinery,environmental protection,drug delivery and biomedical imaging etcetera.At present,graphene based nanomaterials have been widely used in the field of electrochemistry.Electrochemical technology has many advantages,such as low cost,easy operation,low pollution,high sensitivity and fast response.It has developed into an important technology that intersecting and interpenetrating with biology,energy,catalysis,medicine and other disciplines.Presently,cancer has been one of the most serious diseases that threaten people’s health.The effective and sensitive detection of cancer markers is beneficial for early diagnosis and timely treatment of cancer.In this study,graphene and graphene oxide were used as support materials.On the base of full utilization of their unique physical and chemical properties,we further modified the carbon nanomaterials with aptamer molecules,nanoparticles and electroactive materials to fabricate the graphene and graphene oxide based aptasensors.Then the aptasensors were employed to capture cancer markers and subsequently undergone electrochemical analysis.Based on the aim of constructing electrochemical aptasensors with high sensitivity,good selectivity and strong stability for cancer markers detection,we have carried out the following two research works.1.Graphene oxide-based label-free electrochemical aptasensor for alpha-fetoprotein detectionThe GO was undergone carboxylation treatment.After the activation of carboxyl groups(-COOH)on GO surface,the amino(-NH2)functionalized alpha-fetoprotein(AFP)aptamer was covalently immobilized on GO support.When the nonspecific adsorption sites on the sensing interface were fully covered,the sensor was used for the capture of AFP,and then cyclic voltammetry(CV)measurement was carried out.Under the optimized experimental conditions,a series of AFP solution were detected by the sensor.The results showed that the method had a wide linear range,a low detection limit and good selectivity.The test results were satisfactory mainly owing to the following advantages: carboxylated GO had a large surface area and plenty of-COOH,which could be covalently linked with large number of-NH2 functionalized AFP aptamer;the sensor was constructed with aptamer which could enhance the sensitivity and maintain high stability toward interference conditions;the label free method for constructing sensor had the advantages of simple procedures,which was conducive to the maintenance of more active sites.2.Three dimensional graphene-based ratiometric signal amplification electrochemical aptasensor for mucin1 detectionA three dimensional graphene substrate supporting with gold nanoparticles(Au-RGO)was synthesized by hydrothermal reaction and freeze-drying treatment.Then the ferrocene labeled sulfhydrylation mucin1 aptamer(Fc-Apt)was grafted on the surface of Au nanoparticles.When the nonspecific adsorption sites on the sensing interface were fully covered,the sensor was used for mucin1 capture.After Fc-Apt capturing mucin1 onto the electrode surface,the sensor was incubated with methyl blue(MB)labeled sulfhydrylation mucin1 aptamer modifing Au nano-composite(MB-Apt@Au)and then used for alternating current voltammetry(ACV)test.In this research,the Au-RGO composite was used as substrate,which could not only enhance the conductivity of the electrode,but also facilitate grafting of more aptamer molecules to improve the sensitivity of detection.The adoption of aptamer for constructing sensing interface was conducive to enhancing the stability and selectivity of the sensor.At the same time,two kinds of electroactive substances,Fc and MB,were introduced into the sensing system,in which Fc played as a reference role and MB was used as signal amplification element.After using this method to detect mucin1,it obtained a wide linear range,a low detection limit and a good selectivity.The ratiometric signal amplification aptsensor has the application potential for mucin1 detection.