In-situ cell extraction by open microfluidics combined with mass spectrometry for EpCAM analysis via DNA-mediated rolling circle amplification.

A sensitive analysis for self-carried biomarkers of tumor cells is of great significance for early tumor diagnosis and following treatment monitoring. In this work, open microfluidics combined with mass spectrometry for Epithelial cell adhesion molecule (EpCAM) analysis using DNA-mediated rolling circle amplification (RCA) was proposed. Following aptamer binding, the EpCAM signal was amplified and hybridized with a short DNA probe, which could be released by extracting with a denaturant agent and detected via mass spectrometry. The open-space microfluidic chip with hydrophilic regions and the regional open microfluidic chip with an extraction chamber provided an effective platform for EpCAM extraction and analysis at both the low-cell population level and even at the single-cell level. Such a strategy converted the analysis of EpCAM to the detection of DNA probes, enabling in-situ detection, as well as overcoming the limitation of cellular component contents and spatial location distribution of biomarkers. EpCAM signal was positively related to the number of tumor cells with a good linear range of 7-210, which could facilitate the evaluation of drug efficiency of 5-fluorouracil (5-FU) in different concentrations. In addition, the EpCAM analysis at a single-cell level could provide a qualitative distinction between tumor cells and normal cells. The two designed open microfluidics provide a new perspective for micro-total analysis and could be promisingly applied in tumor treatment monitoring and tumor identification in real cell samples.