Multiplex detection of cell surface markers using Surface Plasmon Resonance Imaging

Surface Plasmon Resonance (SPR) is an established technique for detection of molecular binding. More recently, new experimental set ups transformed SPR in a label-free and real-time detector of specific cell binding to an immobilized ligand. In this work, Surface Plasmon Resonance Imaging (SPRi) was employed to investigate the feasibility of a multiplex sensor to detect simultaneously 44 different cell surface antigens. For this purpose, a total of 5 cancer cell lines KG1a, MCF7, MG-63, NCI-H460 and SK-BR-3 and peripheral blood cells from healthy donors were used to illustrate the potential of this sensor. For cancer cells, SPR curves showed a variety of responses to each one of the targeted antigens, proving the ability of this sensor to characterize multiple cell surface molecules. Regarding the peripheral blood cell measurements, frequent leukocytes populations such as T-cells and Granulocytes were easily identified. Furthermore, measurements performed on samples spiked with cancer cells showed that based on specific cancer antigens response, cancer detection in a complex sample is possible. Exploring the factors behind the detected SPR signals, a comparison with flow cytometry showed a relation between the response intensity and the number of antigens on the cell surface. A study of the number of cells binding to the sensor and the cell area effect on the signal also demonstrated a proportional relation with intensity. Also, single-cell image based analysis indicated that individual cell binding can be monitored by reflectivity variation. In conclusion, here it was illustrated that SPRi allows the simultaneous observation of cell binding to multiple markers and suggests that antigen quantification can be achieved.