Research On Electrochemical Aptamer Sensor Based On MXene And Target Cycle Amplification Strategy

Today,cancer has already become one of the killers of people’s lives.The effective analysis of cancer markers is beneficial to the early diagnosis and treatment of diseases,and can significantly improve the cure rate of cancer patients.Therefore,the development of sensitive and rapid marker detection has shown important research significance.Electrochemical aptasensors（ECAS）have the advantages of low cost,simple operation,fast response,high sensitivity and high selectivity.MXene is more and more used in the field of electrochemical sensing due to its large specific surface area,good electrical and thermal conductivity,high thermal stability,and good catalytic performance.More importantly,MXene’s surface is rich in various functional groups and can be directly connected to biomolecules such as aptamers（Apt）,making it applicable to the construction of ECAS.The large surface area of MXene can provide a large number of binding sites for aptamers Apt,enzymes and other biomolecules to form bioprobes.The bioprobes formed play an important role in the signal amplification strategy.In order to further improve the sensitivity of ECAS.We apply nucleic acid signal amplification strategies using technologies such as nucleic acid recognition and enzyme-assisted target cycling to the construction of sensors.The application of this amplification strategy is conducive to improving the sensitivity and selectivity of target detection.Based on the signal amplification function of MXene as a biological probe carrier and nucleic acid signal amplification strategy,this research has carried out the following research work:1.Competitive electrochemical aptasensor based on cDNA-ferrocene/MXene probe for detection of breast cancer marker mucin1Gold nanoparticles（AuNPs）were used as the base material,and then mucin1（MUC1）Apt were grafted onto the surface of the AuNPs.The ferrocene-labeled Apt partially complementary DNA（cDNA-Fc）is connected to the surface of MXene to form a probe,and the probe captures the aptamer binding to the electrode surface.The initial signal of ferrocene was obtained by square wave voltammetry（SWV）.Competitive testing of MUC1was then performed.Due to the high affinity of MUC1 and Apt,the probe was detached from the electrode surface,and a significantly reduced Fc signal was detected by SWV.We quantitatively detect MUC1 by changing the signal before and after competition.The research results show that the method has a wide detection range and low detection limit.This is mainly because the large surface area of MXene provides a large number of binding sites for the probe,which makes the signal change significantly before and after competition.Thus,the function of signal amplification and sensitivity improvement is achieved.2.MXene/Au-CNTs complex constructs dual aptamer sandwich electrochemical biosensor for detecting breast cancer marker mucin1Apt and horseradish peroxidase（HRP）are loaded on the surface of MXene to constitute a probe.The synthesized gold nanoparticle-carbon nanotube（Au-CNTs）composite was used as the substrate.The Apt was grafted onto the surface of the Au nanoparticle,and then the Apt captured MUC1 to the electrode surface.The electrode and probe were incubated for SWV in a hydrogen peroxide/hydroquinone（H₂O₂/HQ）solution.HRP on the surface of MXene and MXene itself can catalyze the H₂O₂/HQ reaction to produce a detectable electrochemical signal that increases with increasing MUC1concentration.In this study,Au-CNTs composites were used as the substrate,which could not only improve the conductivity of electrodes,but also combine more aptamer molecules to improve detection sensitivity.More importantly,MXene as a probe carrier can support a large number of enzymes and Apt,can accelerate the reaction process of H₂O₂/HQ in the same time,enhance the signal intensity and improve detection sensitivity.3.miRNA-155 electrochemical biosensor based on nucleic acid recognition-induced multiple DNA release and Exo Ⅲ assisted target cyclingmiRNA-155 Apt are grafted onto carboxylated magnetic beads.The two DNAs modified by methylene blue（mDNAs-MB）were linked to the surface of the magnetic beads by complementation with the Apt part and then incubated with the mi RNA-155solution.Due to the high affinity between the target and the Apt,two types of mDNAs-MB were released from the surface of the magnetic beads and released into the solution.After magnetic separation,only the two types of mDNAs-MB remained in the solution.Then,the Au electrode modified by capturing DNA（P1）was incubated with the above solution,and then the SWV was used to detect the electric signal of MB.The results show that the sensor has high sensitivity and high selectivity.This result is mainly due to the fact that the Apt can bind two kinds of mDNAs-MB at the same time,which will cause double release of mDNAs-MB after recognition with the target.And the Apt-target double strand formed will start the Exo Ⅲ cleavage process to achieve the target cycle and release more mDNAs-MB.So as to play the role of dual signal amplification.After that,both types of mDNAs-MB are captured to the electrode surface at the same time,which further provides detection sensitivity.