Detection Of Circulating Tumor Cells And Exosomes

In recent years,cancer has become an important factor threatening human health and safety.Circulating tumor cells(CTCs)and exosomes can be employed as potential biomarkers for molecular diagnosis and monitoring of tumors processes.This subject developed methods for the detection CTCs and exosomes based on surface-enhanced Raman(SERS)and photoelectrochemical(PEC)technologies.(1)Since Raman probes play an essential role in sensitive SERS assay,here,a novel Raman probe was developed by assembling gold nanoparticles in triangular pyramid DNA(TP-Au NPs).Such probe with intense electromagnetic hot spots can provide dramatically enhanced Raman scattering.Through assembling recognition DNA on one corner of the TP-DNA,the recognition event is definite and designable.The probe was characterized through transmission electron microscope(TEM)and atomic force microscope(AFM).At the same time,its SERS superiority was also investigated.(2)Using the synthesized new probes,CTCs and exosomes were selected as typical targets,respectively.During the detection of CTCs,the EpCAM aptamer was used as the recognition element.Under optimal conditions,5-100000 cells/mL MCF-7cells could be detected in excess HEK-293T cells.The linear range of 3-500 cells/mL CTCs was observed in the peripheral blood of human without enrichment process.During the detection of exosomes,the EpCAM aptamer and cholesterol modified linker DNA were selected for the purpose of enrichment and recognition.Under optimal conditions,the detection limit was 1.1×10~2 particles/μL with good selectivity.(3)A novel photocathode sensor with dual signal reduction using PEC technology was developed.The NiO/BiOI heterojunctions were selected as photoelectrochemically active materials,Au NPs and CdSe quantum dots were used as electron transfer bodies.Exosomes were detected through the recognition of EpCAM aptamer with overexpressed EpCAM protein on tumor cell exosomes.In the absence of the target exosomes,the photocurrent signal was almost unchanged.In the presence of target,due to the specific binding of EpCAM and its aptamer chain,the DNA modified by CdSe quantum dots was removed from the electrode surface,resulting in the reduction of photocurrent signal.At the same time,the existence of exosomes could hinder the process of electron conduction on the electrode surface and caused the further decrease of photocurrent.