Immunofluorescence analysis of breast cancer biomarkers using antibody-conjugated microbeads embedded in a microfluidic-based liquid biopsy chip

Early and precise detection of tumors could lead to more effective treatments. Microfluidic technology holds great promise as an emerging tool for the early diagnosis of cancer. However, since the flow in microchannels is usually laminar, the mass transfer efficiency is low, resulting in low biosensing efficiency and sensitivity. In this paper, we employed immunofluorescence analysis in a microfluidic chip to develop a continuous, fast and efficient liquid biopsy chip. We disrupt the laminar flow and improve mass transfer efficiency by filling the chip with antibody-conjugated microbeads. Meanwhile, the microbeads increased the contact area of the immunoaffinity reaction, which greatly enhanced the binding of the antibody to the target protein, amplified the fluorescent signal, and significantly improved the sensitivity and efficiency of detection. This microfluidics-based liquid biopsy device required only a small volume of plasma sample (20-50 μL), realized a low limit of detection (LOD, 0.1 ng/mL), and can detect biomarkers within 55-75 min. We tested plasma from 15 breast cancer (BC) patients and 5 non-cancer controls to demonstrate its clinical application in breast cancer diagnosis, showing that the biomarkers carcinoembryonic antigen (CEA) and cancer antigen 15-3 (CA15-3) reflect the presence of BC, and the method can accurately distinguish cancer patients from non-cancer controls. Receiver operator characteristic (ROC) curves showed that the combined assessment of the two biomarkers provided extremely high sensitivity and specificity. This study provides a new strategy for rapid early diagnosis of cancer and other diseases.