Detection Of Extracellular Vesicles By Fluorescent Nanospheres-based Lateral Flow Test Strip

Cancer is a serious threat to human life and health,and its early diagnosis is one of the great challenges which clinical medicine has been confronted with.Compared with traditional tissue biopsy,it is important to develop a diagnostic method,which can non-invasively and continuously collect sample from the body fluids of patients.Biomarkers are extremely important for early detection.In recent years,with the rapid development of life sciences,more and more biomarkers have been developed,including free nucleic acids,glycoproteins,circulating tumor cells,and extracellular vesicles et al.Extracellular vesicles(EVs)are particles released by cells and have apparent membrane structure.Compared with other biomarkers in the circulatory system,they are abundant in many body fluids,which high stability,and are rich in various bio-information molecules.These characteristics provides important prerequisite for liquid biopsy,which is expected to become a new type of biomarker with huge application potential.Its clinical value has received extensive attention in recent years,and its accurate detection is of great significance.As a simple and rapid analytical technique,rapid lateral flow assay is cost-effective,hardly requires no specialized technicians and expensive instruments,which shows an obvious advantage in POCT detection.Many nanomaterials have been used as labels to improve the detection sensitivity.Among them,quantum dots fluorescent nanospheres possessed the advantages of high fluorescence intensity,easy operation,and high stability in complex matrices,and have a wide range of applications in the biomedical field.The main research work are as follows:Fluorescent nanospheres(FNs)with high fluorescence intensity and good stability were prepared by embedding method.The surface of the fluorescent nanospheres was rich in functional groups,which facilitated coupling for functionalization.FNs has great application value in the biomedical field.It has obvious advantages for it to work as the label material of rapid lateral flow assay,which could increase the sensitivity by strong fluorescence signal and achieved quantification at the same time.A simple and rapid EVs quantification strategy was established in combination with rapid lateral chromatography and membrane biotinylation strategies.By utilizing biotin-functionalized phosphatidylethanolamine(DSPE-PEG-Biotin),the membrane of EVs could be successfully modified with biotin under strong hydrophobic interactions.Based on the high affinity between streptavidin and biotin,the target particle forms a complex with the functionalized fluorescent nanosphere,and then was separated and captured into the detection zone of the rapid lateral flow test strip.Fluorescence images can be irradiated by the ultraviolet lamp.Qualitative results were obtained by measuring the fluorescence value.Biotinylation of biogenic EVs could be reached to 85%.This strategy does not require complicated pretreatment of the sample and is easy to operate.The whole procedure can be completed within 1 hour.We also validated the feasibility of the method applying to the sensitive detection of extracellular vesicles in saliva,showing great potential for clinical application.