Detection Of Dnaand Exosomes Using Electrochemical Method

In recent years,cancer has become one of the major causes endangering human health.Researchers spend a lot of time on sensitive and accurate diagnose of cancer.As a genetic material,DNA molecules participate in the survival and development of various organisms and guide the operation of various life activities.Therefore,the analysis of DNA molecules is of great significance for cancer diagnosis,environmental monitoring and prognosis treatment.It is also a major research topic in modern analytical chemistry.On the other hand,tumor-related exosomes contribute to tumor metastasis,progression,and immune regulation.Exosomes are relatively abundant in body fluids and are less invasive when collecting specimens.This makes exosomes extremely useful in cancer biopsy potential.Therefore,this article mainly explores the electrochemical detection of DNA under the action of exonuclease and the ultra-sensitive detection of exosomes triggered by the target-triggered three-dimensional DNA walker.(1)Accurate and sensitive analysis of DNA is essential for understanding DNA functions and early diagnosis of disease.Here,λ-Exonuclease(λ-Exo)-assisted electrochemical sensor was proposed for the detection of tDNA.In the presence of tDNA,λ-Exo initiated stepwise hydrolysis of the 5′-phosphorylated strand in the direction of 5′ to 3′.Thus,ferrocene labeled strands could be introduced to the surface of gold electrode through hybridization.As a result,electrochemical signal was increased in turn.In this work,the reaction time and the concentration of λ-Exo were optimized.Electrochemical impedance spectroscopy was used to characterize the assemble process.Under optimized condition,0.1 pM to 10 nM tDNA could be detected linearly.(2)Exosomes are membrane-enclosed phospholipid extracellular vesicles.In spite of their great promise as noninvasive biomarkers for cancer diagnosis,sensitive detection of exosomes is still challenging.Herein,the detection of exosomes was changed to the detection of DNA after recognition of exosomes with its aptamers.CD63 aptamer and EpCAM aptamer were used for the detection of MCF-7cell-secreted exosome.The recognition process was amplified through the movements of a three-dimensional DNA walker.And then,Exonuclease III-assisted electrochemical ratiometric sensor was applied for further signal amplification.Under optimal conditions,the detection limit of 1.3 × 104 particles/mL was obtained with excellent selectivity.Furthermore,clinical application test for the detection of exosomes in human plasma was also verified.