Biofilm surface proximity-induced branched hybridization chain reaction strategy based on microchip electrophoresis...

The exosome surface contains various cancer markers that can be suitable candidates for early cancer diagnosis and therapeutic efficacy evaluation. However, due to the very small size of exosomes, major challenges remain to detect tumor markers on their surface. To circumvent these challenges, a signal amplification strategy based on microchip electrophoresis-assisted biofilm surface proximity-induced branched hybridization chain reaction (bHCR) is proposed to distinguish exosomes from different cancer types. It uses an aptamer to identify the epithelial cell adhesion molecule (EpCAM) protein on the exosome surface by adjacent hybridization reaction on the biofilm surface. The multistage bHCR is designed for signal amplification, inducing a detection limit of 250 exosomes/μL in MCF-7 cells. When applied to distinguish exosomes from different cancer cell types, the results show that exosomes from MCF-7 cells contain a large number of EpCAM protein molecules on their membrane surface, while exosomes from A549 and HeLa cells contain relatively few EpCAM protein molecules. This finding indicates that EpCAM protein is highly expressed on the surface of exosomes secreted from breast cancer cells, and the expression of EpCAM protein from different types of cancer cells are also varies. The developed method has important application potential in terms of exosome analysis, and is expected to provide a new technical platform for breast cancer screening and prognosis assessment.