Discrimination of colorectal cancer cell lines using microwave biosensors

This paper illustrates the potential of microwave frequencies for biological analysis and cell discrimination. Microwave electric fields have the capability to penetrate inside cells and interact with their intracellular content. Hence, measuring cell electrical properties in the Gigahertz frequency spectrum may allow distinguishing intracellular differences between cells without requiring any labeling or denaturation. Here, we present how microwave resonators can be used as biosensors to measure individual cell dielectric permittivity and obtain characteristic electromagnetic signatures as a function of the cell type considered, in particular their cancer cell stage (i.e. aggressiveness level). Five cell lines, all derived from low to high grade human colorectal tumors, were cultured on-chip or simply deposited in water droplets on microwave biosensors. For this preliminary study, the sensors only operated in air for frequencies ranging from 5 GHz to 14 GHz, allowing establishing a representative electromagnetic signature. During our experiments, sensors were fully dried, and a fixation step allowed the reproducible characterization of cells outside their culture medium, in ambient air, while maintaining their intracellular content unmodified. Results showed significant electromagnetic signature differences between cell lines, especially between cells with low and high aggressiveness levels. We also show that a correlation might be envisioned between the measured electromagnetic signatures and the potential aggressiveness stage. At this level, we stand at the proof-of-concept stage, and a clinical investigation will be required to establish from several patients both the reliability and the reproducibility of the potentially existing relationship between electromagnetic signatures identified in this study and actual cancer progression.