| The development of modern medicine has gradually conquered more and more"incurable diseases".With the extension of human lifespan and the continuous improvement of productivity,a healthy lifestyle and high-quality quality of life have become more commonly pursued goals.Despite the continuous improvement of medical standards,cancer remains the first killer that damages people’s health.So far,except for thyroid cancer,the cure rate of other cancers is still low and the prognosis is still poor,which is closely related to the difficulty of early diagnosis and treatment of cancer.Due to the lack of typical early symptoms and highly invasive biological characteristics,various cancers cannot be detected in a timely manner,leading to many advanced cancer patients miss the golden treatment time.Therefore,how to achieve early screening and diagnosis of cancer has become the key to improving cancer cure rates and improving patient quality of life.At present,cancer diagnosis methods mainly focus on tissue biopsy and imaging examinations,but they also have drawbacks such as high prices,radiation damage,specific site limitations,and difficulty in achieving tumor tissue heterogeneity analysis.This also makes people continue to explore more sensitive,accurate,and minimally invasive cancer early screening strategies.In this context,liquid biopsy has emerged.Liquid biopsy refers to an in vitro diagnostic technique that uses human body fluids as a sample source for detection and analysis.The biomarkers of liquid biopsy mainly include circulating tumor DNA(ctDNA),circulating tumor cells(CTCs),and exosomes.Among them,the commercial development of the kit for tumor diagnosis using CTCs is the most successful,and the exosomes from cancer cells are considered to be the most promising biomarker for minimally invasive liquid biopsy.Compared to CTCs,exosomes have the advantage of providing information from live tumor cells,and have become a hot research field at present.Here,we have developed two detection platforms for tumor liquid biopsy based on CTCs and exosomes.1.An electrochemical aptamer sensor has been developed to achieve sensitive capture and detection of 4T1 cells.Two dimensional MXene nanosheets were prepared as large surface sensing interfaces with excellent electrochemical performance,and amino functionalized Fe3O4 nanoparticles were synthesized as carriers with large surface area and good trapping ability.The carboxyl modified adapter is connected to the Fe3O4 capture carrier through an amide reaction.Furthermore,the specific role between the epithelial cell adhesion factor(EpCAM)aptamer and 4T1 cells is utilized to achieve cell capture.And the detection linear relationship of 4T1 cells was determined by changing the cell concentration to achieve quantitative detection.The designed sensor has a detection range of 102～106 cells/mL,a detection limit of 39 cells/mL,and good stability and reproducibility.2.A novel sandwich structure based electrochemical aptamer sensor was designed to achieve highly sensitive recognition and detection of 4T1 exosomes.Furthermore,we achieved the capture and detection of exosomes at the cellular vesicle level.On the basis of previous research,one adapter was transformed into two aptamers and assembled into a sandwich structure sensor.Amino functionalized Fe3O4 nanoparticles design a sensing interface with large surface area and rapid enrichment capability,while two-dimensional MXene nanosheets serve as signal amplifiers with excellent electrochemistry.Specifically,the Fe3O4 nanoparticles connected to the CD63 aptamers can capture the target exosomes.Then,MXene nanosheets modified with EpCAM aptamers were fixed on the electrode surface to enhance the quantitative detection results of captured exosomes by identifying remaining protein sites.Using this design,the prepared biosensor exhibits a wide linear range(102 particles/μL～107 particles/μL))for 4T1 exosomas sensing,and low detection limit of 43 particles/μL.In addition,this sensing platform can use surface proteins corresponding to aptamers 1 and 2(CD63 and EpCAM)to determine four different tumor cell types(4T1,Hela,HepG2,and A549),and also has good specificity in serum samples.These preliminary results demonstrate the feasibility of establishing a sensitive,accurate,and inexpensive electrochemical sensor to detect the concentration and type of exosomes,and provide important reference value for clinical applications of exosomes in liquid biopsy and early cancer diagnosis. |
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